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Flores hominidNew species or microcephalic dwarf.

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THE ANATOMICAL RECORD PART A 288A:1123–1145 (2006)
Flores Hominid: New Species or
Microcephalic Dwarf ?
ROBERT D. MARTIN,1* ANN M. MACLARNON,2 JAMES L. PHILLIPS,3
4
AND WILLIAM B. DOBYNS
1
Academic Affairs, Field Museum, Chicago, Illinois
2
School of Human and Life Sciences, Roehampton University, London, United Kingdom
3
Department of Anthropology, University of Illinois at Chicago and the Field Museum,
Chicago, Illinois
4
Department of Human Genetics, University of Chicago, Chicago, Illinois
ABSTRACT
The proposed new hominid ‘‘Homo floresiensis’’ is based on specimens
from cave deposits on the Indonesian island Flores. The primary evidence, dated at 18,000 y, is a skull and partial skeleton of a very small
but dentally adult individual (LB1). Incomplete specimens are attributed
to eight additional individuals. Stone tools at the site are also attributed
to H. floresiensis. The discoverers interpreted H. floresiensis as an insular
dwarf derived from Homo erectus, but others see LB1 as a small-bodied
microcephalic Homo sapiens. Study of virtual endocasts, including LB1
and a European microcephalic, purportedly excluded microcephaly, but
reconsideration reveals several problems. The cranial capacity of LB1
( 400 cc) is smaller than in any other known hominid < 3.5 Ma and is
far too small to derive from Homo erectus by normal dwarfing. By contrast, some associated tools were generated with a prepared-core technique previously unknown for H. erectus, including bladelets otherwise
associated exclusively with H. sapiens. The single European microcephalic skull used in comparing virtual endocasts was particularly unsuitable. The specimen was a cast, not the original skull (traced to Stuttgart),
from a 10-year-old child with massive pathology. Moreover, the calotte
does not fit well with the rest of the cast, probably being a later addition
of unknown history. Consideration of various forms of human microcephaly and of two adult specimens indicates that LB1 could well be a
microcephalic Homo sapiens. This is the most likely explanation for the incongruous association of a small-brained recent hominid with advanced
stone tools. Anat Rec Part A, 288A:1123–1145, 2006. Ó 2006 Wiley-Liss, Inc.
Key words: brain size; cranial capacity; hominid evolution;
Homo; microcephaly; stone tools; prepared core;
Flores; insular dwarfism
Brown et al. (2004) recently recognized a new hominid
species, ‘‘Homo floresiensis,’’ on the basis of skeletal
remains recovered from the limestone cave of Liang Bua
on the Indonesian island of Flores. In a companion paper, Morwood et al. (2004) reported on associated stone
tools and faunal remains, providing dates bracketed
between 38,000 and 18,000 years ago for the relevant
sediments. The time depth for H. floresiensis and associated stone artifacts was extended to 74,000–95,000 years
ago by Morwood et al. (2005a). The primary specimen
(LB1), from an uppermost level dated at about 18,000
Ó 2006 WILEY-LISS, INC.
years ago, is an associated skull and partial skeleton
from a dentally adult individual. The most immediately
*Correspondence to: Dr. Robert Martin, The Field Museum –
Academic Affairs, 1400 S. Lake Shore Drive, Chicago, Illinois
60605. Fax: 312-665-7806. E-mail: rdmartin@fieldmuseum.org
Received 26 April 2006; Accepted 1 August 2006
DOI 10.1002/ar.a.20389
Published online 9 October 2006 in Wiley InterScience
(www.interscience.wiley.com).
1124
MARTIN ET AL.
striking feature of the LB1 skeleton is its small size.
Maximum length of the femur is 280 mm, slightly less
than the minimum value of 281 mm recorded for Australopithecus afarensis (AL-288-1) and equal to the minimal estimate for the Homo habilis skeleton (OH62). Taking maximum femur length, stature of the LB1 skeleton
was estimated at 106 cm using formulae derived from
human pygmies (Jungers, 1988), and a body mass of
16.0–28.7 kg was then inferred from this stature. (For
comparative purposes below, a mid-range value of 23 kg
is taken.) One key feature, which gives the visual
impression of primitive morphology in LB1, is the absence of a chin in the mandible. An even more striking,
and certainly unexpected, feature of the skull of the
main specimen is its very small cranial capacity. Brown
et al. (2004) reported a value of only 380 cc measured
with mustard seed. Indeed, because of the small cranial
height associated with the small brain size of this individual, Brown et al. (2004) stated that their inferred
stature of 106 cm was likely to be an overestimation. Despite this very small cranial capacity, a follow-up study
of a virtual endocast derived from the LB1 skull concluded that the brain shows a number of similarities to
that of Homo and is closest to that of Homo erectus (Falk
et al., 2005a).
In addition to the main skeleton LB1, fragments of
two other individuals were reported in the initial publications. Brown et al. (2004) referred to Homo floresiensis
an isolated mandibular premolar (left P3) dating back at
least 37.7 kyr and stated that ‘‘additional evidence of a
small-bodied adult hominin is provided by an unassociated left radius shaft, without the articular ends, from
an older section of the deposit (74–95 kyr).’’ Morwood
et al. (2004) gave a body height estimate of about 1 m
based on that radius shaft. Additional elements of the
LB1 skeleton and further remains attributed to six additional individuals were subsequently reviewed by Morwood et al. (2005a). The only substantial new specimens
reported are a second mandible (LB6) that resembles
the LB1 mandible in lacking a chin and a second right
tibia (LB8).
The overall conclusion initially derived from all of the
skeletal material from an inferred total of nine individuals is that Homo floresiensis was a dwarf form derived
from Homo erectus. Dwarfing was interpreted as a result
of isolation on the island of Flores, paralleling known
cases of evolutionary dwarfing in certain island-living
mammals (e.g., elephants). In fact, dwarf elephants (genus Stegodon) are found in the same deposits, and it
was concluded that Homo floresiensis not only made the
stone tools found in the deposits but also hunted juvenile Stegodon and possibly even used fire for cooking, in
view of the presence of charred animal bones (Morwood
et al., 2005a). This scenario was reiterated in a popular
account by Morwood et al. (2005b). Among other things,
it has been suggested that the Flores hominid shows
that a large brain size is not a prerequisite for the production of advanced stone tools (Wong, 2005). Given
such far-reaching interpretations, the finds have naturally attracted considerable attention.
Because the Flores finds involve such a strikingly incongruous combination of a tiny-brained hominid with
advanced stone tools, it is surely advisable to give serious consideration to alternative explanations (Henneberg and Thorne, 2004; Jacob et al., 2006; Martin et al.,
2006; Richards, 2006). One possibility is that the individual represented by the main skeleton LB1 suffered
some kind of pathology, exhibiting a form of microcephaly. For the time being, only a single skull is known
for Homo floresiensis and that skull happens to have a
very small cranial capacity. In this sense, it is undoubtedly microcephalic, i.e., small-headed (see also Richards,
2006). It is important to note at once that small brain
size and small body size are to some extent separable
issues. It is perfectly possible that Flores was inhabited
by a small-bodied hominid species between 100,000 and
18,000 years ago. It is well established that human body
size tends to decrease with decreasing latitude, accompanied by increasing average annual temperature, and is
particularly small in warm, humid climates at low latitudes (Roberts, 1953; Ruff, 1994; Katzmarzyk and Leonard,
1998). Furthermore, a skeleton from an adult human
‘‘pygmoid’’ with an estimated age of about 30 years and
a height of only 146 cm has been reported from the separate cave site of Liang Toge on Flores (Verhoeven, 1958;
Jacob, 1967). Richards (2006) provides an extensive discussion of reduced stature in various modern human
pygmy populations. LB1 could be a pathological, tinybrained individual from such a population of very short
stature.
Rejection of the possibility of pathological microcephaly in LB1 by Brown et al. (2004) was seemingly supported by a subsequent publication by Falk et al.
(2005a), which compared virtual endocasts of LB1, modern human, Homo erectus, chimpanzee, and ‘‘a European
microcephalic.’’ It was concluded that the endocast of
LB1 was distinctly different from the single microcephalic included in that comparison. Later on, however, a
study of 19 human microcephalic skulls revealed considerable variation in external brain morphology, with the
endocast of one individual seemingly showing overall
similarity to that of LB1 (Weber et al., 2005), although
that conclusion was questioned (Falk et al., 2005a).
CRANIAL CAPACITY
As Brown et al. (2004) themselves noted, the value of
380 cc they reported for the cranial capacity of LB1 is
comparable to the lowest values recorded for Australopithecus and lies well within the range for great apes
(e.g., chimpanzees). In fact, the volume of the virtual
endocast subsequently reported for LB1 by Falk et al.
(2005a) is appreciably larger, at 417 cc. The discrepancy
of 37 cc between these two reported values for cranial
capacity, almost 10%, is disconcertingly large. Nevertheless, even the higher value of 417 cc is strikingly small
in comparison to all other known hominids. The initially
reported value (380 cc) is smaller than in any other
known undoubted hominid apart from two individual
Australopithecus afarensis (343 cc in AL 333-105; 375 cc
in AL 162-28), although the higher value of 417 cc also
exceeds that reported for more recent Paranthropus
aethiopicus (410 cc for WT 17000). In fact, the volume of
a computer-generated endocast of LB1 has since been
reported to be 400 cc (Holloway et al., 2006), and that
value (close to the mean of the two previously reported
values) will be taken for purposes of further discussion
here. Accordingly, it is necessary to go back about 3.5
million years (my) to find a hominid cranial capacity as
small as that of the Flores hominid (Fig. 1). All values
FLORES HOMINID
1125
Fig. 1. Cranial capacities recorded for 118 fossil hominids plotted
against time, extending back almost 3.5 Ma (data from Stanyon et al.,
1993). The arrow indicates the highly incongruous value (red circle)
reported for Homo floresiensis at only 18,000 years ago. The recently
reported values for the four Dmanisi skulls (magenta circles) fall well
within the range for hominids dated at around 1.7 mya and fit the general trend, in striking contrast to the value for H. floresiensis.
reported for the Flores hominid (380–417 cc) are also
smaller than in most gorillas and fall well within the
range for common chimpanzees (Fig. 2). Hence, it is
unquestionable that brain size in the LB1 skeleton of
Homo floresiensis, dating back only 18,000 years, was
tiny by any standard.
At first sight, it might be thought that the diminutive
cranial capacity of LB1 could be attributable to evolutionary dwarfism, as suggested by Brown et al. (2004),
although Argue et al. (2006) note that ‘‘insular dwarfism
is unknown for Homo to date.’’ However, it is well established that reduction of body size within a mammal species (including Homo sapiens) is usually associated with
only moderate reduction in brain size. Whereas the
exponent value for scaling of brain mass size to body
mass in comprehensive interspecific comparisons across
placental mammals is close to 0.75 (Martin, 1981; Martin et al., 2005), there is a progressive decline with
decreasing taxonomic rank and the value for intraspecific scaling among adults of a single species is typically
about 0.25 (Martin and Harvey, 1985; Kruska, 2005).
One of the best-documented cases is that of the domestic
dog, with an exponent value of 0.27 determined for 26
breeds covering a 21-fold range of body sizes generated
by artificial selection (Bronson, 1979). In fact, in modern
humans and other primates examined, the exponent
value is generally lower than 0.25 and approaches zero
if males and females are considered separately (Martin
and Harvey, 1985). Even with an intraspecific scaling
exponent value of 0.25, halving of body mass would only
be expected to result in reduction of brain mass to 84%
of its original value. In modern human pygmies, for
example, cranial capacity is not greatly different from
that in populations of larger body size. Falk et al.
(2005a) note that human pygmy skulls typically have
cranial capacities exceeding 1,000 cc (compared to a
worldwide mean value for all modern humans of 1,349
cc) (Beals et al., 1984). The adult female pygmy skull
used in their comparison in fact had a cranial capacity
of 1,249 cc, while modern Rampasasa pygmies on Flores
have an average cranial capacity of 1,270 cc (Jacob
et al., 2006), similar to the value of 1,204 cc reported by
Jacob (1967) for the Flores ‘‘pygmoid’’ described by Verhoeven (1958).
Brown et al. (2004) explicitly suggested that Homo
floresiensis was derived from Homo erectus through a
process of insular dwarfing (see also Morwood et al.,
2005b), although Morwood et al. (2005a) state that ‘‘H.
floresiensis is not just an allometrically scaled-down version of H. erectus.’’ Examination of this proposal is complicated by considerable divergence in the definition of
Homo erectus. Here, a very broad view with no geographical restriction will be taken, as this effectively
covers all options for comparison. In one general survey
using such a broad definition (Stanyon et al., 1993),
mean cranial capacity for 28 Homo erectus was 991 cc
(range, 727–1,251 cc). If brain size scales to body size
with an exponent value of 0.25, the body size of Homo
erectus would have to be reduced to one-eighth of the
original value for a cranial capacity of 400 cc to be
included at the lower end of the range. In fact, for a cranial capacity of 400 cc to correspond to the mean value
of dwarfed Homo erectus, body size would have to be
reduced to 1/32 of its original value (Martin et al., 2006).
Fig. 2. Histograms showing cranial capacities for African great
apes (Gorilla gorilla; n ¼ 48; Pan troglodytes; n ¼ 95) and various fossil hominids (Australopithecus spp., n ¼ 10; Paranthropus spp., n ¼ 8;
Homo habilis, n ¼ 7; Homo erectus, n ¼ 28; archaic Homo, n ¼ 17;
Homo neanderthalensis, n ¼ 22; Homo sapiens, n ¼ 26). Data for the
African great apes are taken from the records of Adolph Schultz (Anthropological Institute, University of Zurich); data for fossil hominids
are from Stanyon et al. (1993). The pink vertical bar indicates the
range covered by the reported values for Homo floresiensis (380–
417 cc).
In other words, an original body size of 60 kg for Homo
erectus (Kappelman, 1996) would have to be reduced to
just 2 kg for the mean cranial capacity to be reduced
from 991 cc to an average value of 420 cc. A more recent
survey of cranial capacity in broadly defined Homo erectus, with an increased sample size of 38 (Krantz, 1995),
reported a higher mean value of 1,045 cc (range, 780–
1,360 cc). This would correspond to an even greater body
FLORES HOMINID
mass reduction required to attain the cranial capacity of
LB1 in a dwarf form.
It could be argued that some individuals included in
the broadly defined taxon Homo erectus have quite
small brains, and that the cranial capacity reported for
Homo floresiensis would be more likely to result from
dwarfing of such small-brained individuals. A case in
point is provided by four skulls from the Dmanisi
deposits in Georgia, dated at about 1.7 mya. Although
these specimens have in fact been referred to the taxon
Homo ergaster, for geographical reasons they could conceivably be relevant to the origin of the Flores hominid.
The four skulls from Dmanisi have a mean cranial
capacity of only 664 cc (range, 600–775 cc) (Gabunia
et al., 2000; Vekua et al., 2002; Rightmire et al., 2006).
It has been suggested that the Flores hominid
descended from such a small-brained population, but
this proposal is also unconvincing. First, with an intraspecific scaling exponent of 0.25, body size would still
have to be reduced to one-eighth of the average for
Homo erectus (from 60 to 7.5 kg) to decrease mean cranial capacity from 664 to 400 cc. In fact, taking the
smaller body mass of 50 kg estimated for the Dmanisi
fossils (Gabunia et al., 2001), body size would have to
be reduced to around 6 kg to reach a mean cranial
capacity of 400 cc. Contrary to the impression that has
been given, cranial capacities of the Dmanisi hominids
are not unusually small, given their antiquity. The four
values recorded fall within the range previously found
for hominids at 1.7 mya (Fig. 1). Indeed, the antiquity
of the Dmanisi hominids renders any direct comparison
with the Flores hominid inappropriate because cranial
capacity shows a general trend to increase over time
within the broadly defined taxon Homo erectus and
among hominids generally. Taking the sample of 28 values for Homo erectus given by Stanyon et al. (1993), a
trend line indicates that average cranial capacity
increased by about 200 cc over the period covered. As
Homo floresiensis is only 18,000 years old and has been
identified as a remarkably late-surviving evolutionary
dwarf form of Homo erectus, it seems more likely that
dwarfing would have taken place from a relatively
large-brained late representative. It should also be
noted that in one of the cranial comparisons conducted
by Argue et al. (2006), including a single skull from
Dmanisi (D2280), there was no indication of any morphometric affinity with the LB1 skull.
In both temporal and geographical terms, the representatives of the taxon Homo erectus that are closest to
the Flores hominid are the Ngandong specimens from
the Solo River in Java. Dating of those specimens has
been subject to much uncertainty. They were originally
thought to date back around 200,000 years or more.
However, preliminary radiometric dating indicated an
age of 50,000–100,000 years (Bartstra et al., 1988), and
subsequent dating using a combination of radiometric
measurement and electron spin resonance yielded an
even younger age of 27,000–53,000 years (Swisher et al.,
1996). Hence, the Ngandong specimens may possibly be
only 9,000–35,000 years older than the LB1 skeleton.
The average cranial capacity for six skulls from Ngandong is 1,149 cc (Stanyon et al., 1993), almost three
times larger than that of the Flores hominid.
This all leads to the conclusion that it is simply unrealistic to explain the tiny cranial capacity of 380–417 cc
1127
recorded for Homo floresiensis as an outcome of evolutionary dwarfism affecting an insular population of latesurviving Homo erectus (Martin et al., 2006).
Several instances of evolutionary dwarfism in mammalian lineages are known from the fossil record as well
as from recent species, ranging from squirrels and sloths
to hippopotami and mammoths. Pleistocene dwarf elephants, for example, are known from a number of Mediterranean islands. The presumed ancestral mainland
species, Elephas antiquus (Caloi et al., 1996), had an average estimated body mass of 10,000–15,000 kg, while
the comparatively tiny island dwarf form, E. falconeri,
from Malta-Sicily, had an estimated mass of only 100 kg
(Roth, 1992). The difference in brain size between these
two species was much less marked than the hundredfold difference in body size. The cranial capacity of E.
antiquus was approximately 9,000 cc, whereas that of E.
falconeri was 1,800 cc (Accordi and Palombo, 1971). The
slope of the line joining these two sets of values corresponds to an exponent value of 0.32–0.35, much closer to
the typical intraspecific scaling value of 0.25 than to the
interspecific scaling value of about 0.75 for mammals
generally. Brain size dwarfing in elephants therefore
resembles the scaling pattern determined across wide
body size ranges for domestic dogs (scaling exponent ¼
0.27) (Bronson, 1979), sheep (0.29) (Bronson, 1979), horses
(0.25) (Bronson, 1979), and wild boar (0.24) (Kruska,
1970). The time taken for the dwarfing of Mediterranean
elephants is unknown, but could be up to several hundred thousand years (Ambrosetti, 1968; Caloi et al.,
1996; Lister, 1996). However, the dwarfing process can
occur very quickly. This is shown by the case of red deer
on the island of Jersey, which became dwarfed to about
one-sixth of their original size (estimated body mass of
about 36 kg for dwarf adult males compared with about
200 kg for the ancestral mainland species) over a period
of 6000–11,000 years (Lister, 1996).
A special case explicitly invoked by Brown et al.
(2004), Brown and Morwood (2004), and Argue et al.
(2006) to account for the remarkably small cranial
capacity of LB1 is a report on unexpectedly small brain
size in a dwarfed insular bovid by Köhler and Moyà-Solà
(2004). It was found that six chronologically successive
species of the extinct genus Myotragus found in Pliocene
and Pleistocene deposits of Majorca had relatively small
brains compared to other living and fossil bovids.
Because the inferred sister genus (the Pliocene rupicaprine Gallogoral) resembles the other bovids in its relative brain size, it was concluded that a marked decrease
in relative brain size (by about 50%) had taken place following the isolation of Myotragus on Majorca by 5.2
mya. Despite the apparent parallels to the case of the
Flores hominid, however, there are crucial differences.
Most importantly, investigation of relative brain size in
Myotragus was initiated because of the strikingly small
size of the orbits, suggesting marked reduction in size of
the eyes. No such reduction in orbit size has been suggested for the Flores hominid, and there is indeed no
evidence thereof. Furthermore, the time scale concerned
is one or two orders of magnitude greater and involves a
distinction at the generic level (between Myotragus and
other bovids) rather than at the intraspecific level (if
LB1 is interpreted as a dwarfed Homo erectus). In fact,
a comparative study of a short DNA sequence extracted
from Myotragus (Lalueza-Fox et al., 2002) indicates that
1128
MARTIN ET AL.
this genus is not closely related to rupicaprines after all
(hence ruling out Gallogoral as the sister genus) and is
most closely related to Ovis, which was not included in
the comparative sample studied by Köhler and MoyàSolà (2004). The ancestry of Myotragus is at present
undetermined, so we have no direct information about
relative brain size at the outset. Inferred reduction in
relative brain size in Myotragus thus has little or no
relevance to the tiny brain of the Flores hominid.
STONE TOOLS
Some scholars believe that the archaeological history
of the Island of Flores begins during the Lower Pleistocene/Middle Pleistocene transition, based on equivocal
evidence from the site of Mata Menge (dated to ca.
800,000 BP). At that site, 14 stone tools out of a total of
54 artifacts were identified originally (Morwood et al.,
1998, 1999), while an additional 507 artifacts were found
in recent excavations (Brumm et al., 2006). The objects
concerned were found in river gravels in association
with a Stegodon, although there is some question
whether all of them are actually artifacts, rather than
accidents of nature.
Brumm et al. (2006) suggest that there are ‘‘similarities, and apparent technological continuity’’ between
the flakes produced at Mata Mange and Liang Bua, the
site where remains of H. floresiensis was recovered.
There are, however, real questions concerning the association of the artifacts with the fission track dates
because Brumm et al. (2006) mention ‘‘hydraulic transportation and size sorting.’’ Furthermore, the suggestion
that there is cultural continuity over a period of almost
800,000 years is quite surprising and represents a view
of lithic technology that is at odds with our understanding of production and use of stone tools. Because flakes
were produced at Mata Menge does not mean they represent a ‘‘tradition’’ (see Clarke, 1968). Instead, they
may be just flakes, as one would find in any assemblage
at any time and anywhere in prehistory. Additionally,
the few cores from Mata Menge are not of types ever
found with an Acheulean or Mousterian assemblage, but
are recorded from the Upper Paleolithic period onward.
Further, Brumm et al. (2006: Fig. 4) consider the relationship between two perforators found at Liang Bua
and several pieces they claim are the same type from
Mata Menge. In this instance, we have to consider the
fact that perforators have never been recovered from
Acheulean or Mousterian sites on any continent where
these technocomplexes have been found. If the flakes
and tools from Mate Menge do indeed have any relationship with those recovered at Liang Bua, it is far more
likely that that they are from the same time period (ca.
18,000 BP) and must have been transported either by
the movement of Homo sapiens or by water.
The presumption of Morwood and colleagues is that
the maker of the Mate Menge implements was Homo
erectus, remains of which had been found on the island
of Java early in the 20th century, but never on Flores.
Although artifacts of Middle Pleistocene age are attributed to fossil hominid finds on Java (Bartstra, 1992;
Keates and Bartstra, 2000), the exact association is
equivocal (Corvinus, 2004), and there is some question
of whether some are artifacts at all, whether on Java or
Flores. Thus, stone artifact production earlier than
30,000 or so on Flores, and therefore the presence of
Homo erectus, is not confirmed.
The belief stated by Morwood and colleagues is that
Homo erectus remained isolated on Flores for the remainder of the Pleistocene. It is proposed that, along
with other mammals, Homo erectus became progressively smaller, until dwarf mammals and giant reptiles
(e.g., Komodo dragons) were the main animal species on
Flores ca. 18,000 BP (but see Allen, 1991). Morwood
et al. (2004) also hypothesize that their supposed dwarf
form of Homo erectus developed hunting practices—together with evolved artifacts—that replicate artifact assemblages (and, presumably, hunting patterns) of modern
Homo sapiens in other parts of Indonesia (e.g., East
Timor) (O’Connor et al., 2002). This leads on to a particularly incongruous feature of the proposed interpretation of the recently discovered Flores material from
Liang Bua cave: All of the stone tools (n ¼ 32) reported
from the level of section VII containing the LB1 skeleton
by Morwood et al. (2004), as well as those described
from section IV (which are even more advanced than
those in section VII), clearly belong to types that are
consistently associated with Homo sapiens and have not
previously been associated with H. erectus or any other
early hominid. The artifact assemblage clearly involved
a tradition using the prepared-core technique, which is
confined to Homo neanderthalensis and Homo sapiens.
Furthermore, the explicitly noted presence of bladelets
is a hallmark of Homo sapiens, found in Africa, Asia,
Europe, and after ca. 40,000 BP. Yet Morwood et al.
(2004) concluded that ‘‘H. floresiensis made the associated stone artifacts.’’
In fact, two anomalous features of the section VII
assemblage are evident in Figure 5 of Morwood et al.
(2004): 5g is a Levallois core (not a burin core for producing microblades; the small bladelet-like removals are
features of the core preparation); and 5c, the bipolar
core, like the Levallois core, produced flakes, not blade
or bladelet blanks. In other words, the blanks in the
assemblage are blades and bladelets, while the cores correspond to production of flakes. The most likely interpretation is that these blade and bladelet blanks, although
found near the cores, are not actually associated with
them. For section IV, stratigraphically partially above
the section VII material and located toward the center
of the cave, the authors mention the finding of thousands of artifacts, ‘‘up to 5,500 per cubic meter,’’ mainly
flakes produced from radial cores (i.e., Levallois). However, they also mention a ‘‘more formal component . . .
including . . . blades and microblades,’’ thus reinforcing
the interpretation that there are at least two sets of
assemblages in the cave, both seemingly associated with
their hominid.
It is inherently unlikely that the reported complex of
Upper Paleolithic blanks and tools would have been
developed independently by an unusually small-brained
dwarf evolutionary descendant of H. erectus. Any alternative explanation invoking secondary acquisition by
Homo floresiensis of tools or tool-making techniques
from Homo sapiens would raise a host of additional
unanswered questions. The normal expectation would be
that any hominid dated at 18,000 years ago associated
with tools typical of Homo sapiens would be a member
of that species. The anomalies in the archaeological data
most likely indicate the presence of fully modern compe-
FLORES HOMINID
tent Homo sapiens utilizing the Liang Bua cave many
times after their arrival on Flores.
SKULL IN HUMAN MICROCEPHALICS
Given that the brain size is so unusually small in the
LB1 hominid despite its remarkable young geological
age (Fig. 1), the possibility of a pathological disorder,
specifically some form of microcephaly, must be considered (Henneberg and Thorne, 2004; Jacob et al., 2006;
Martin et al., 2006; Richards, 2006). This possibility was
mentioned briefly in the original report (Brown et al.,
2004), but then rejected. The main authors of the original reports on the LB1 skeleton also defended this position in dismissing the proposal by Henneberg and
Thorne (2004) that LB1 might be a pathological specimen (Brown and Morwood, 2004). That proposal was explicitly addressed in a subsequent paper comparing a
virtual endocast of the LB1 skull with endocasts from
an adult female chimpanzee, an adult female H. erectus
(specimen ZKD XI from Zhoukoudian), a modern human
female, and a single ‘‘European microcephalic’’ (Falk
et al., 2005a). The origin of the European microcephalic
skull was not otherwise described, but the authors
reported that ‘‘its shape conforms to features of its corresponding skull that typify primary microcephaly (microcephalia vera): small cranial vault relative to face, sloping forehead, and pointed vertex.’’
On closer examination, the single microcephalic skull
of unstated provenance taken by Falk et al. (2005a) for
their comparison has proved to be an inappropriate
choice for several reasons (Martin et al., 2006; Richards,
2006). The published account provides no details of the
skull that was investigated. It was particularly important
to establish whether the skull concerned was that of an
adult as in the case of LB1 or derived from an immature
individual suffering from a pronounced pathology resulting in early death. Another cause for concern is that the
cranial capacity of this microcephalic skull, which is not
explicitly stated by the authors, is exceedingly small.
Although its remarkably small size is not obvious from
the illustrations provided by Falk et al. (2005a), which
were all scaled to a standardized volume (rather than
scaled in proportion), it is evident from the diminutive
linear dimensions provided in the accompanying table.
In response to our enquiry, Falk reported that the
microcephalic specimen examined had been obtained
from the collections of the American Museum of Natural
History (AMNH) in New York. Falk also noted that the
specimen’s skull shape typifies that associated with
microcephalia vera and stated that the specimen had
anomalous teeth. For that reason, the specimen’s age at
death was not estimated, although it was believed to be
a juvenile. In fact, it is simply impossible to take any
single skull as typical of ‘‘true microcephalics.’’ The term
‘‘primary microcephaly’’ (microcephalia vera) is a general
descriptor applied to individuals that have an unusually
small brain size at birth, recently defined as 3 standard deviations at birth (Dobyns, 2002) or 4 standard
deviations at older ages (Woods et al., 2005), reflecting
impairment of brain development attributable to a great
variety of syndromes (Gilbert et al., 2005). As noted by
Mochida and Walsh (2001), ‘‘the condition is clearly genetically and clinically heterogeneous.’’ The key point is
that the microcephalic skull examined by Falk et al.
1129
(2005a) was used for a comparison with adult representatives of all other taxa despite the fact that it was
thought to come from an immature individual. Although
brain size reaches adult dimensions early in development (typically 6–7 years in normally developing
humans), early death of the microcephalic individual
studied renders direct comparison with the adult LB1
inappropriate.
Direct measurement of the cranial capacity of the
AMNH specimen using glass beads yielded a cranial
capacity of only 260 cc (K. Mowbray, personal communication). Hence, the apparent brain size of this specimen
was remarkably small not only in comparison to that of
LB1 (about 65% of the value) but also in comparison to
the usual range of modern human microcephalics. In
fact, the published images of the microcephalic endocast
in the supplementary data provided by Falk et al.
(2005a) also exhibit several unusual features that are
not seen in humans with the more common forms of
microcephaly. Few gyral indentations are apparent in
comparison to all of the other endocasts, and the frontal
pole is pointed. The cerebellum is small, although it is
not as drastically reduced as the cerebrum. Also, both
the occipital lobes and the cerebellum appear to hang
down further and at a sharper angle than observed in
most hominid brains. Finally, the foramen magnum is
seemingly greatly enlarged, a defect known to be associated with cerebellar malformations. These rare anomalies, combined with the extremely small cranial volume,
suggest that the individual suffered from a severe brain
malformation and not isolated or primary microcephaly.
Examination of the microcephalic skull studied by
Falk et al. (2005a), housed in the collections of the
AMNH (Fig. 5), revealed the surprising fact that it is
not an original specimen but a plaster-based cast. It
bears the accession number 2792a and is contained in a
box bearing an inscription indicating that it came from
Cannstatt, Germany. However, the catalogue entry
states ‘‘Casts of microcephalus skull from Plattenhardt
and fragments from Cannstatt, Germany (Wurtemberg).’’
The cast itself bears the inscription ‘‘Plattenhardt.
Tausch mit Stuttgart 1907’’ (‘‘Plattenhardt. Exchange
with Stuttgart 1907’’). Available records provide no further information concerning this specimen, other than
the fact that it was included in a large collection purchased from Felix von Luschan by the AMNH in 1924.
The teeth on the cast (eight in the upper jaws and nine
in the mandible) are highly unusual. They are small,
widely separated, and peg-like, with apparent signs of
heavy wear on the crowns. It is indeed virtually impossible to determine a reliable age from the cast of this individual using standard dental criteria. One reasonable
interpretation would be that only one molar is present,
on the right side of the lower jaw, and that this is the
skull of a child.
Further enquiries revealed that the original skull from
which the AMNH cast had been made almost a century
ago is in fact still included in the collection of the Staatliches Museum für Naturkunde, Stuttgart (Dr. Elmar
Heizmann, personal communication; Fig. 3). The skull
has two accession numbers: 5297 (former registration
system) and 25523 (new registration system). Using
standard criteria, the age of this individual at death was
estimated to be 12–13 years (Dr. Doris Morike, personal
communication).
1130
MARTIN ET AL.
Fig. 3. Comparison of the original microcephalic skull in Stuttgart (left; Staatliches Museum für Naturkunde, 5297/25523) with the cast held in the collections of the American Museum of Natural History, New
York (right; AMNH No. 2792a). Note the clear difference in coloration of the calotte compared to the rest
of the skull in the AMNH cast.
A remarkable feature of the AMNH cast 2792a is
that the calotte (a separate element) is cream-colored,
whereas the rest of the cranium and the mandible are
dark brown (Fig. 3), suggesting that the latter parts
were varnished at some time. Furthermore, the calotte
does not fit properly onto the rest of the skull and the
profile of the cut line deviates in several respects
between the two. Whereas sutures are clearly apparent
on the calotte, their continuation cannot be traced down
into the lower part of the cranium. These disparities,
taken together, raised the distinct possibility that the
calotte was not in fact part of the original cast and had
been manufactured subsequently. In order to check this,
small samples were taken from the two separate parts
of the cranium and subjected to chemical analysis using
an inductively coupled plasma-mass spectrometer (ICPMS) in the Department of Anthropology at the Field Museum in Chicago. It emerged that there are striking
chemical differences between the two parts (Table 1).
The level of calcium, effectively serving as a control, is
virtually identical in the two samples, but there are
major differences in other elements. The level of lead is
approximately 50 times higher in the lower part of the
skull (compatible with the interpretation that there had
been previous treatment with a lead-based varnish),
whereas the calotte shows markedly higher levels of
manganese (2.73), barium (3.53), lanthium (14.63), and
cerium (14.43). By contrast, tin—a major component in
the elemental profile—is three times higher in the lower
part of the skull cast than in the calotte. Other notable
differences in that part of the cast are seen in boron
(53), sodium (2.73), and potassium (2.43). These major
differences in elemental composition demonstrate beyond
reasonable doubt that the calotte was created from a different batch of plaster and has a questionable connection with the rest of the cast. This would directly con-
cern any impressions of gyri on the dorsal surface of the
virtual endocast generated from this specimen by Falk
et al. (2005a). The dangers of studying a cast instead of
the original skull are further illustrated by the fact that
the cross-sectional area of the foramen magnum is in
fact about 17% greater in the AMNH cast than in the
original skull. This increase exaggerates the marked
pathological appearance of the foramen magnum and adjacent features of the endocast. Furthermore, there are
discrepancies between the cast and the original skull
with respect to volumetric measurements. Measurement
by one of us (R.D.M.) of the cranial capacities of the
original skull and the AMNH cast, using fine lead shot,
yielded values of 269 and 268 cc, respectively. Although
these values are almost identical, the volume of the ventral part of the cranial cavity is larger in the original
skull than in the AMNH cast (139 vs. 130 cc), whereas
the volume of the calotte is smaller (130 vs. 138 cc).
It was also discovered that the Stuttgart skull was
included in an early discussion of human primary microcephaly by Vogt (1867). That survey covered 10 skulls
from Germany in considerable detail, including descriptions of endocasts for 9 of them, and also incorporated
information from 19 other cases. Only 6 of the overall
sample of 29 cases (i.e., 21%) involved adult individuals
aged 21 years or more. In a more extensive review conducted much later by Hofman (1984), the proportion of
adult individuals aged 21 years or more was higher (31
out of 68; i.e., 46%; Fig. 4), but it is nevertheless clear
that many microcephalics represented in collections and
surveys died before reaching adulthood. On the other
hand, survival into adulthood is not uncommon, and
Hofman’s survey included one woman with a height of
1.34 m who survived to the age of 74 with a brain mass
of only 277 g. The average cranial capacity reported for
nine of the skulls examined by Vogt was 410 cc (393 cc
1131
FLORES HOMINID
TABLE 1. Results from chemical analysis of the two parts (calotte and remaining cranium) of the
cast of a microcephalic skull (AMNH 2792a). (Results generated using an inductively coupled
plasma-mass spectrometer (ICP-MS) by Laure Dussubieux and P. Ryan Williams.)
Isotope
Calotte
Skull
Isotope
Calotte
Skull
Isotope
Calotte
Skull
Li7
Be9
B11
Na23
Mg24
Al27
Si29
P31
Cl35
K39
Ca44
Sc45
Ti49
V51
Cr53
Mn55
Fe57
Co59
115
4
3418
311505
237809
31002
20895
4340
<lod
578559
10794102
283
1677
<lod
<lod
404493
22892
3706
346
6
16959
833007
518235
104554
20447
10108
10097084
1424824
10749608
437
2830
<lod
<lod
148028
28713
5850
Ni60
Cu65
Zn66
Rb85
Sr88
Y89
Zr90
Nb93
Mo98
Pd105
Ag107
Sn118
Sb121
Cs133
Ba137
La139
Ce140
Pr141
2732
43161
18741
1196
1726897
4740
1130
35
136
76
1489
1926023
<lod
42
11603
8153
14009
1431
2667
35435
8617
2402
1453091
943
770
31
156
46
935
5812254
<lod
146
3279
557
974
152
Nd146
Sm147
Eu153
Gd157
Tb159
Dy163
Ho165
Er166
Tm169
Yb172
Lu175
Hf178
W182
Au197
Pb...
Bi209
Th232
U238
800
108
94
117
76
110
81
59
16
28
8
10
<lod
96365
238506
111
18
47
88
27
37
33
24
24
10
11
<lod
3
<lod
5
61
161942
11191181
799
43
23
lod ¼ limit of detection
N.B. The value for chlorine (Cl35) must be discounted because hydrochloric acid was used to dissolve the samples.
Fig. 4. Age distribution for 68 cases of human primary microcephaly surveyed by Hofman (1984). Note that most cases (ca. 54%) are
from individuals that died before exceeding the age of 21 years. Data
set from Hofman (1984), kindly provided by the author. [Color figure
can be viewed in the online issue, which is available at www.
interscience.wiley.com.]
for the four adult individuals aged 21 years or above).
Comparable figures are indicated by the sample examined by Hofman (1984) (Fig. 5), with a mean brain mass
of 421 g for adult females (n ¼ 16) and a mean of 433 g
for adult males (n ¼ 17). All of these values match well
with the observation from clinical experience that the
brain volume of human primary microcephalics is about
400 cc, an estimate consistent with typical adult head
circumferences of 40–45 cm in living human cases personally examined by one of us (W.B.D.). The full range
Fig. 5. Histograms showing brain mass in adult microcephalics
(n ¼ 16 female; n ¼ 17 male), with an overall average vale of 427 g.
Data set from Hofman (1984), kindly provided by the author. [Color
figure can be viewed in the online issue, which is available at www.
interscience.wiley.com.]
1132
MARTIN ET AL.
Fig. 6. Virtual reconstructions from CT scans of the right hemiskull and endocast of the Stuttgart
microcephalic specimen. Note the highly unusual dentition and the downward-hanging occipital lobes
and cerebellum. Images prepared by Jonathan Brown.
of postnatal head circumferences in human microcephalics lies between 4 and 12 SD (Woods et al.,
2005).
The skull in the collection of the Staatliches Museum
für Naturkunde in Stuttgart is undoubtedly that of an
individual named Jakob Moegele from the village of
Plattenhardt, who died at the age of 10 years and
1 month. Vogt (1867) recorded the cranial capacity of
that individual as 272 cc, the smallest value determined
in his survey. Interestingly, 3 of the 10 individual skulls
examined by Vogt came from closely related individuals;
in addition to the skull of Jakob Moegele, he also examined that of his brother Johann Georg Moegele (who
died at 5 years of age) and that of his cousin Johann
Moegele (who died at 15 years of age). Jakob Moegele
was the 8th of 11 children born in a single family. In
addition to his elder brother Johann Georg (the 6th
child), the 2nd child (also named Jakob) and the 11th
child (Barbara) were likewise microcephalic, giving a
total of 4 microcephalic individuals among the 11 siblings. Even more intriguingly, a total of seven microcephalic children were born to four couples (two of them
unrelated to the two Moegele families) in the village of
Plattenhardt within the space of a few years. This
aroused sufficient attention for a special report to be
commissioned from the court physician (Vogt, 1867).
The extreme pathological nature of Jakob Moegele’s
skull is clearly revealed by CT scans. Both the endocranial cavity and the virtual endocast (which has a calculated volume of 268 cc) show the unusual shape of the
brain, with both the occipital lobes and the cerebellum
hanging down conspicuously (Fig. 6). The teeth, aptly
described as ‘‘mushroom-like’’ by Vogt (1867), are highly
unusual in shape and position, and the developing
replacement teeth that would be expected in a 10-yearold child are completely lacking in both upper and lower
jaws (Fig. 7).
In contrast to the aberrant skull of Jakob Moegele,
microcephalic skulls and endocasts that are much closer
in morphology to the Flores LB1 specimen most certainly do exist. One hemiskull of a dentally adult male
microcephalic that is held in the collections at the Hunterian Museum in London (RCSHM/Osteo 95.1) is quite
similar in size and external appearance (Fig. 8). The
museum catalogue indicates that this specimen came
from India, and it is described in a note by Shortt (1874)
in which he states that the individual concerned was 5
ft. 6 in. tall and weighed 89 lb (40.3 kg). Further information is provided in a review of 19 microcephalic skulls
by Humphry (1895), who included an illustration of the
Hunterian skull (his Fig. 1 of skull 1) confirming its origin in India. Doubling of the endocranial volume measured from the Hunterian hemiskull yields a cranial
capacity of 432 cc, very close to the value recorded for
LB1. The anthropological collections of the Field Museum in Chicago also include plaster casts of a dentally
adult human microcephalic skull (accession number
A219679) and an accompanying endocast (accession
number A219680). The catalogue entry indicates that
the skull and endocast (Fig. 9) are from a ‘‘microcephalic
idiot’’ from Basutoland (now Lesotho). The specimens
were acquired as part of the Marshall Field Archaeologi-
FLORES HOMINID
1133
Fig. 7. Maximum intensity projection derived from CT scans of the left upper and lower jaws of the
Stuttgart microcephalic, revealing the aberrant structure of the teeth and the complete absence of developing replacement teeth. (Image prepared by Jonathan Brown.)
Fig. 8. Comparison between a hemiskull of an adult male human microcephalic from the collection
the Hunterian Museum in London (RCSHM/Osteo 95.1) and the LB1 skull (after Brown et al., 2004), both
drawn to scale. Drawing by Jill Seagard.
cal Expedition to Western Europe in 1927–1928 and
entered the collections in 1931. A label attached to the
endocast indicates that it was produced in England by
R.F. Damon, but no further information is available in
the museum records. In fact, plaster casts of the skull
and mandible of this same individual are present in the
collections of the American Museum of Natural History
in New York (accession number 99.1 2601 A,B), and
another endocast is held in the Hunterian Museum of
the Royal College of Surgeons, London (RCSHM D684.4).
A literature search revealed that this case had been reported by Dru-Drury (1919–1921), who stated that the
individual concerned was a 32-year-old woman with
severe mental retardation. She reportedly had the body
size of a 12-year-old child and a body mass of only 60 lb
(27.2 kg). The cause of death was recorded as tuberculosis. An endocast from this individual was later included
and illustrated in a discussion of four microcephalics by
1134
MARTIN ET AL.
Fig. 9. Plaster casts of a dentally adult human microcephalic skull from Lesotho and an accompanying
endocast in the collections of the Field Museum, Chicago (accession numbers A219679 and A219680,
respectively). (Photographs by John Weinstein).
Fig. 10. Drawings of (right) an endocast from the hemiskull of the human microcephalic from India in
the collections of the Hunterian Museum (RCSHM/Osteo 95.1) and (left) of the left side of a human microcephalic endocast from Lesotho in the collections of the Field Museum, Chicago (accession number
A219680). Illustrations by Jill Seagard.
Weidenreich (1941), who noted the presence of the skull
cast in the AMNH collection. Weidenreich (1941: p. 396)
stated that ‘‘the form and proportions of the brain . . . as
much as can be defined from the endocast, fail to show
any appreciable differences when compared with the normal human brain.’’ Yet the volume of the Lesotho microcephalic endocast is even smaller than that of the Hunterian specimen, amounting to only 335 cc. Both of these
endocasts, illustrated in Figure 10, have a relatively normal external appearance, lacking the evident pathologies
shown by the brains of some human microcephalics such
as that of Jakob Moegele. The only really obvious macroscopic anomaly in both cases is the extremely small size.
A recent comparative study of virtual endocasts from
19 human microcephalics by Weber et al. (2005), with an
average volume of 404 cc, has emphasized the considerable range of variability in brain shape that exists. The
authors of that study singled out one particular endocast
that appeared to be quite similar to that of the Flores
hominid LB1, although this interpretation was questioned by Falk et al. (2005b) on the grounds that the
degree of similarity was decreased if the two endocasts
were oriented in the same way. Unfortunately, Weber
et al. (2005) did not provide identifying information for
the specimens examined and did not state which individuals were adults.
1135
FLORES HOMINID
TABLE 2. Endocast measurements and derived indices (following Falk et al., 2005a) for the 3 new specimens
included here (Hunterian, Lesotho and Stuttgart microcephalics)
(a) External endocast data
Measurements (mm)
New specimen
Hunterian m/c
(RCSHM/Osteo 95.1)
Stuttgart m/c
(SMN 5297 or 25523)
Lesotho m/c
(RCSHM D684.4)
Indices
[1] Length
[2] Breadth
[3] Height
[4] Frontal breadth
2/1
3/1
4/1
(4-2)/1
3/2
107.10
85.80
77.70
59.20
.80
.73
.55
.25
.91
88.00
84.40
64.80
63.40
.96
.74
.72
.24
.77
108.00
84.00
71.00
65.00
.78
.66
.60
.18
.85
(b) Basal endocast data
Measurements (mm)
New
specimen
Hunterian m/c
Stuttgart m/c
Lesotho m/c
Indices
[3]
[4]
[5]
[6]
[1]
[2]
mbatcobrobrof(tan)bat-bat mat-mat rof(tan) rof(tan) rof(tan) bpc(tan) 1/6 2/6 3/6 4/6 5/6 (3-4)/6 (4-5)/6 (6-3)/6
41.00
59.80
57.40
70.20
68.40
70.60
35.90
25.30
34.60
21.20
22.90
26.30
11.40
8.30
10.50
In order to avoid disagreement about endocast orientation and description (Falk et al., 2005b, 2006) and to
achieve direct comparability with the results reported by
Falk et al. (2005a), we repeated some of their multivariate analyses, expanding their sample by adding an endocast produced from the Hunterian microcephalic skull
from India, and an endocast from the same museum of
the Lesotho specimen. We also included a new endocast
produced from the original Stuttgart microcephalic skull
[corresponding to the virtual endocast from the AMNH
skull cast used by Falk et al. (2005a)]. Two principal
component analyses were carried out on the same sets of
indices as those used by Falk et al. (2005a). The first set
comprised six indexes (five being used in the analysis)
derived from four external endocast dimensions: length,
breadth, height, and frontal breadth. The eight indexes
in the second set were derived from six measurements of
the base of the endocasts (Table 2). In a minor departure
from Falk et al. (2005a), to enhance clarity of data presentation we opted for two-dimensional plots of the first
and second principal components (PC1 and PC2) rather
than three-dimensional plots including PC3. Most of the
information is contained in PC1 and PC2 (Table 3), and
three-dimensional plots (which are difficult to interpret
on the printed page) do not reveal any major differences.
In a plot of PC1 against PC2 for the external endocast
indices (Fig. 11a), the distribution of specimens included
in the original analysis by Falk et al. (2005a) is very
similar to that shown in their Figure 2A and corresponds to descriptions in their text. In Figure 11a, the
endocast prepared directly from the original skull of the
Stuttgart microcephalic, newly included here, falls close
to the virtual endocast derived by Falk et al. (2005a)
from the AMNH skull cast. The approximate matching
confirms general agreement between our measurements;
the minor separation between the points may reflect
measurement deviations and/or distortion in the virtual
endocast derived from the poor-quality AMNH skull
cast. The other new specimens included in Figure 11a,
the Hunterian and Lesotho microcephalic endocasts, fall
108.80
96.70
101.50
.38 .65 .33 .19 .10
.62 .71 .26 .24 .09
.57 .70 .34 .26 .10
.14
.02
.08
.09
.15
.16
.67
.74
.66
close together and are not far removed from LB1. All
three of these specimens are clearly separate both from
the Stuttgart/AMNH microcephalic endocasts and from
normal modern humans. Insofar as the complexity of
brain shape can be captured by such simple indices, this
demonstrates that LB1 is not clearly distinct from all
modern human microcephalics and more closely resembles the two new specimens included here than the more
severely pathological single specimen studied by Falk
et al. (2005a).
In a plot of PC2 against PC1 for the basal endocast
indices (Fig. 11b), the specimens included in the analyses of Falk et al. (2005a) are again distributed very similarly, corresponding to their Figure 2C and to the
descriptions in their text. Falk et al. did not include the
AMNH microcephalic endocast in this analysis. Figure
11b includes all three microcephalic endocasts in our
sample: the Hunterian, Lesotho, and Stuttgart specimens. They are scattered very widely across the plot,
with the Hunterian microcephalic falling closest to
WT17000, Gorilla and Pan, the Lesotho microcephalic
located very close to Sts 5, and the Stuttgart microcephalic closest to modern humans. (It was necessary to
estimate basal measurements involving the olfactory
bulbs for the Hunterian specimen because the impression on the skull from these structures is not clear.
Analysis without this specimen yields a very similar distribution for the remaining specimens.) Intriguingly, as
in the original plot published by Falk et al. (2005a), LB1
lies very close to Homo sapiens in Figure 11b. The overall conclusion that can be drawn from analyses of these
indices is that modern human microcephalics are clearly
very variable, and that specimen choice would greatly
influence any analysis based on a limited sample. Figure
11b suggests that such principal component analyses of
basal endocast indices are not useful for determining
whether or not LB1 could be a modern human microcephalic. Analyses of external endocast indices are potentially more useful, and the results presented here support the conclusion of Weber et al. (2005) and Martin
1136
MARTIN ET AL.
TABLE 3. Results of principal component analyses carried out on the samples
illustrated in Figure 11, showing the first two principal components (PC1, PC2)
(a) External endocast indices
i.
Principal component
1
2
Eigenvalue
Percentage of variance
Cumulative percentage of variance
2.255
2.002
45.107
40.039
45.107
85.146
ii.
Loadings
Indices
Principal component 1
Principal component 2
2/1
3/1
4/1
(4-2)/1
3/2
.964
.216
.401
.716
.779
.264
.864
.811
.520
.507
(b) Basal endocast indices
i.
Principal component
1
2
Eigenvalue
Percentage of variance
Cumulative percentage of variance
4.203
2.747
52.54
34.34
52.54
86.88
ii.
Loadings
Indices
Principal component 1
Principal component 2
1/6
2/6
3/6
4/6
5/6
(3-4)/6
(4-5)/6
(6-3)/6
.861
.794
.031
.916
.620
.897
.895
.031
.243
.254
.985
.383
.627
.373
.061
.985
et al. (2006) that LB1 is quite similar to some modern
human microcephalics.
CASE FOR MICROCEPHALY
All of the factors discussed above led us to give more
detailed consideration to the possibility of pathological
microcephaly raised by Henneberg and Thorne (2004),
particularly as the authors of the original report on the
LB1 skeleton did not discuss the relevant medical disorders known among modern humans. In the original paper, Brown et al. (2004) state without explanation ‘‘neither pituitary dwarfism, nor primordial microcephalic
dwarfism in modern humans replicates the skeletal features present in LB1.’’ The references cited in support of
this statement do not present a modern understanding
of pathological conditions in modern humans characterized by severe short stature with microcephaly. We agree
that pituitary dwarfism and at least one type of ‘‘primordial dwarfism,’’ known as Majewski osteodysplastic primordial dwarfism type 2 [MOPD type 2; taken as the
focal condition by Argue et al. (2006)], differ in several
respects from the LB1 skeleton, yet that skeleton clearly
shares many features with syndromes of severe short
stature and microcephaly as a group, a point to which
we will return.
Similarly, Falk et al. (2005a) state that primary microcephaly or microcephalia vera ‘‘is characterized by small
cranial vaults relative to facial skeletons, sloping foreheads and pointed vertices’’ and imply that the lack of
these shape features in the LB1 skull excludes primary
microcephaly. That conclusion is unjustified as low sloping foreheads and pointed vertices are not seen in all
affected individuals with primary microcephaly (Woods
et al., 2005). Falk et al. (2005a) go on to state that
‘‘microcephaly with simplified gyral pattern (MSG) is
another form of congenital microcephaly . . . manifesting
reduced numbers and shallowness of cortical sulci. The
cortical topography of LB1’s endocast precludes it from
this form of microcephaly.’’ In fact, MSG is not another
form of congenital microcephaly at all, only a descriptive
term that one of us (W.B.D.) has used to describe the
appearance of the brain in individuals with primary
microcephaly (Dobyns and Barkovich, 1999; Barkovich
et al., 2001). In any case, the endocasts shown in the paper by Falk et al. (2005a) lack the fine details of the
FLORES HOMINID
Fig. 11. Plots of the first two principal components (PC1, PC2)
from analysis of indices derived from (a) external endocast measurements and (b) basal endocast measurements. The combined samples
comprise endocasts from modern humans of average stature [Homo
sapiens (1)], a modern human pygmy [Homo sapiens (2)], two australo-
1137
pithecines (Sts 5; WT 17000), five Homo erectus (Trinil 2; ZKD III, X,
XI, XII), LB1, chimpanzees, gorillas, and the AMNH microcephalic skull
cast, all from Falk et al. (2005a), with the addition of three microcephalic endocasts: the Hunterian, Lesotho, and Stuttgart (original for
the AMNH cast) specimens (Tables 2 and 3).
1138
MARTIN ET AL.
gyral pattern and depths of sulci that would be needed
to recognize an MSG pattern.
Thus, the analyses in both the initial paper describing
the LB1 skeleton (Brown et al., 2004) and the subsequent report on the virtual endocast (Falk et al., 2005a)
do not adequately reflect current understanding of
human microcephaly and syndromes involving severe
short stature with microcephaly. Both of these publications assume that only a few types exist, whereas a
search of the OMIM database using the single search
term ‘‘microcephaly’’ finds more than 400 genetic syndromes associated with microcephaly (see also Gilbert
et al., 2005). This figure is cited by Argue et al. (2006),
although Richards (2006) gives a lower figure of 300.
Any discussion of specific syndromes must rely on correct interpretation of the taxonomic status of the LB1
fossil, which remains controversial. The primary published papers (Brown et al., 2004; Morwood et al.,
2005a) devote little attention to the potential existence
of pathological features. Yet examination of a living modern human with similar features in a medical genetics
clinic would yield the following conclusions for a young
adult female with height 106 cm, body mass 16–29 kg,
and head circumference (our estimate) 39–41 cm; relative to modern human standards, these values would be
graphed at 9 to 10 standard deviations (SD) for
height, 4 to 6 SD for body mass, and 10 to 12 SD
for head circumference. Physical examination would
reveal a recessed jaw with no chin, accompanied by congenital dental anomalies consisting of absent mandibular right P4 and maxillary right M3 (questioned by Jacob
et al., 2006), small maxillary left M3, and pathological
rotation of both maxillary P4s. [Lukacs et al. (2006) provide additional comments on the dental anomalies of
LB1.] The long bones of the LB1 fossil appear disproportionately broad and less modeled (less narrowing of the
diaphysis) than long bones in modern humans, as would
be seen on radiographs (see also Jacob et al., 2006). All
of these abnormalities taken together would lead to diagnosis of a severe short stature with microcephaly syndrome, although the available data are not sufficient to
match this to a specific known syndrome (Judith G.
Hall, personal communication).
If LB1 originated from a population in which very
short stature was characteristic, the head size, or at
least brain size, would still be too small (5 to 6 SD as
discussed below), and other syndromes including primary microcephaly would be considered in the differential diagnosis. Some of these syndromes are compatible
with survival into adult life, given help from ‘‘normal’’
individuals. This relates back to our concerns regarding
the capabilities of the extant population first raised in
the section on the stone tools found in Liang Bua.
Importantly, essentially all of the syndromes in the differential diagnosis have autosomal recessive inheritance
and have the potential to recur within a small, inbred
population. Hence, as occurred in the mid-1800s in the
small village of Plattenhardt with the Moegele family, it
is entirely possible that more than one individual with
the same syndrome could occur in the same place, despite the overall relative rarity of the condition. Jacob
et al. (2006) estimate that any human hunter/gatherer
population inhabiting Flores would have been quite
small, thus increasing the likelihood of inbreeding. However, for the same reason, these authors question the
likelihood of survival of an isolated population on Flores
for over 800,000 years without immigration.
As a next step, we can formally assess the reported
dimensions of LB1 in the light of alternative interpretations regarding the fossil’s population of origin. LB1
could represent a microcephalic individual from a modern human population either with normal stature (hypothesis 1a) or with dwarfed stature (hypothesis 1b).
LB1 could also represent a microcephalic individual from
a contemporaneous Homo erectus population (dwarfed or
undwarfed, hypotheses 2a and 2b) or an early offshoot of
a more primitive hominid line (hypothesis 3). Of course,
in all cases the types of microcephaly to be considered
must be restricted to those in which survival to adulthood is possible. This would include microcephaly with
near normal cognitive abilities or mild-moderate mental
retardation. Human microcephalic syndromes can be divided into two categories, a high-functioning group and
a low-functioning group (Dobyns, 2002; Gilbert et al.,
2005). The former category is most relevant for comparison with LB1, an individual that survived to adulthood,
although in some cases survival into adulthood may
occur even with moderate to severe microcephaly, as in
human Seckel syndrome.
Under the hypothesis that LB1 comes from a dwarfed
population derived from either Homo sapiens or Homo
erectus, we assume that the well-established relationships between body size and cranial volume among hominids would be maintained. If LB1 were a dwarfed Homo
sapiens with an estimated body mass of 16–27.8 kg, the
expected cranial capacity, taking brain-body mass data
and the scaling exponent value for a modern European
population (Holloway, 1980), would be 1,109–1,223 cc
(range, 817–1,604 cc; Table 4). Using the same intraspecific scaling exponent, the expected cranial capacity if
LB1 were a dwarfed Homo erectus, taking cranial
capacity data from Stanyon et al. (1993), would be 794–
876 cc (overall range, 583–1,107 cc; Table 5). Based on
the Dmanisi specimens, the expected cranial capacity of
a similarly dwarfed individual from this population
would be 560–662 cc (overall range, 495–706 cc; Table
5). The cranial capacity of 400 cc of LB1 would be
5.4–6.2 standard deviations below the expected value for
Homo sapiens. Using the same coefficient of variation
for brain size, the cranial capacity of LB1 would be 4.2–
5.1 standard deviations below the expected value for
Homo erectus, and 2.3–3.2 standard deviations below the
expected value for the Dmanisi sample (Tables 4 and 5).
Among modern humans, severe congenital microcephaly
or primary microcephaly is defined as head circumference (a surrogate for brain volume) three or more standard deviations below the mean at birth (Dobyns, 2002)
or more than four standard deviations below age and
sex means (Woods et al., 2005). The brain volume ( 400
cc) and estimated head circumference for the LB1 skull
would be more than four standard deviations below the
mean for either a dwarfed Homo sapiens or a dwarfed
Homo erectus population (Tables 4 and 5).
Microcephalic disorders are not particularly rare, as
one of us (W.B.D.) has ascertained more than 200 such
individuals for study (see also Argue et al., 2006). To
date, four human genes have been cloned that result in
primary microcephaly with mild to moderate mental
handicap and survival well into adult life (Woods et al.,
2005). At least two of these (ASPM and MCPH1) have
1139
FLORES HOMINID
TABLE 4. Calculation of brain size of a dwarfed Homo sapiens with the same body weight as LB1
Variable
Value
Notes on additional calculations
Modern human data (Holloway, 1980):
Average body weight (g)
67100
Average brain weight (g)
1388
Maximum body weight (g)
106000
Minimum body weight (g)
40000
Maximum brain weight (g)
1850
Minimum brain weight (g)
1040
s.d. brain weight
132
Calculated from male and female values
Brain scaling exponent
0.168
Brain scaling intercept
218
Brain scaling intercept – using
286
Calculated using brain scaling exponent,
max brain weight
maximum brain weight and average body weight
Brain scaling intercept – using
161
Calculated using brain scaling exponent,
min brain weight
minimum brain weight and average body weight
Estimated brain weight (g) or cranial capacity (cc) (approximately equivalent (Martin, 1990))
for dwarf Homo sapiens with the same body weight as LB1
At body weight estimate 28.7 kg:
Average brain weight (g) or
1223
cranial capacity (cc)
Maximum brain weight (g) or
1604
Calculated using brain scaling
cranial capacity (cc)
intercept for maximum brain weight
Minimum brain weight (g) or cranial capacity (cc)
902
Calculated using brain scaling intercept
for minimum brain weight
At body weight estimate 16 kg:
Average brain weight (g) or cranial capacity (cc)
1109
Maximum brain weight (g) or cranial capacity (cc)
1454
Calculated using brain scaling intercept
for maximum brain weight
Minimum brain weight (g) or cranial capacity (cc)
817
Calculated using brain scaling intercept
for minimum brain weight
Difference between the average cranial capacity estimate for dwarf Homo sapiens and the actual
cranial capacity of LB1 (400 cc) in standard deviations calculated for brain weight variation for the
Homo sapiens sample
At body weight estimate 28.7 kg:
LB1 cranial capacity in standard deviations below
6.2
expected size for dwarf Homo sapiens
At body weight estimate 16 kg:
LB1 cranial capacity in standard deviations below
5.4
expected size for dwarf Homo sapiens
Data and statistics from Holloway (1980) for a large sample of Danish humans (n ¼ 667) carefully selected by removal of
cases of pathologies likely to affect brain weight, and extremes of body mass. Some further statistics were estimated or calculated, as indicated.
evolved rapidly in hominids and other primates and are
hypothesized to have contributed to the rapid increase
in brain size shown in Figure 1 (Zhang, 2003; Evans
et al., 2004; Kouprina et al., 2004; Wang and Su, 2004;
Gilbert et al., 2005). It has been proposed that genes
involved in regulating brain size, particularly a subset
of microcephaly genes in which mutations produce highfunctioning forms of microcephaly, may have undergone
advantageous mutations in evolution leading to brain
enlargement with few deleterious side effects (Gilbert
et al., 2005). Thus, it is certainly conceivable that LB1
could represent a microcephalic individual from a small
hominid population.
Alternatively, LB1 could be derived from an extant population of normal hominid stature, more likely Homo
sapiens than Homo erectus. Under this hypothesis, LB1
would have a short stature with microcephaly syndrome
in which both body size and brain volume are far below
the norms for the extant population. Various syndromes
with severe intrauterine growth retardation and proportionate (at least at birth) microcephaly have been de-
scribed in modern humans, including Bangstad, Bloom,
Buebel, de Lange, Dubowitz, Kennerknecht, Meier-Gorlin,
Okajima, and Seckel syndromes, as well as Majewski
(microcephalic) osteodysplastic primordial dwarfism (MOPD)
type 1, MOPD type 2, MOPD-Cervenka type, and MOPD-Toriello type (Toriello et al., 1986; Bangstad et al., 1989; Opitz
and Holt, 1990; Meinecke et al., 1991; Lin et al., 1995; Buebel
et al., 1996; Bongers et al., 2001; Silengo et al., 2001; Faivre
et al., 2002; Okajima et al., 2002; Hall et al., 2004). Several of
these syndromes are associated with survival to adulthood.
In their original report on LB1, Brown et al. (2004)
state without discussion that primordial microcephalic
dwarfism in modern humans does not replicate the skeletal features present in LB1. To the contrary, we find
such a comparison interesting. The best studied of these
syndromes is MOPD type 2. While the reported skeletal
features of LB1 differ from this syndrome in several
regards, the similarities in overall size are remarkable
and instructive. Affected children have severe intrauterine and postnatal growth retardation and microcephaly
with normal or mildly impaired intelligence and may
1140
MARTIN ET AL.
TABLE 5. Calculation of brain size of a dwarfed Homo erectus or dwarfed individual
from the Dmanisi population with the same body mass as LB1
Dmanisi
Variable
n
Average body weight (kg)
Average cranial capacity (cc)
Maximum cranial capacity (cc)
Minimum cranial capacity (cc)
Homo erectus
Stanyon
et al.
Gabunia et al.;
Rightmire et al.;
Vekua et al.
28
60
3
50
991
1251
727
664
775
600
Notes
Kappelman (1996);
Gabunia et al. (2001)
Calculated using coefficient
of variation for brain weight of
Homo sapiens sample (see Table 4)
and average cranial capacity
for Homo erectus sample
Estimated population s.d. cranial capacity
94
63
Using value for Homo sapiens sample
Cranial capacity scaling exponent
0.168
0.168
Cranial capacity scaling intercept
156.2
107.8
Cranial capacity scaling intercept 197.3
125.9
using maximum cranial capacity
Cranial capacity scaling intercept 114.6
97.4
using minimum cranial capacity
Estimated cranial capacity (cc) for dwarf Homo erectus and Dmanisi population with the same body weight
as LB1
At body weight estimate 28.7 kg:
Average cranial capacity (cc)
876
605
Maximum cranial capacity (cc)
1107
706
Calculated using cranial
capacity scaling
intercept for maximum
cranial capacity
Minimum cranial capacity (cc)
643
547
Calculated using cranial
capacity scaling intercept
for minimum cranial capacity
At body weight estimate 16 kg:
Average cranial capacity (cc)
794
548
Maximum cranial capacity (cc)
1103
640
Calculated using cranial
capacity scaling intercept for
maximum cranial capacity
Minimum cranial capacity (cc)
583
495
Calculated using cranial capacity
scaling intercept for minimum
cranial capacity
Difference between the average cranial capacity estimates for dwarf Homo erectus and dwarf Dmanisi
individual and the actual cranial capacity of LB1 (400cc) in standard deviations
At body weight estimate 28.7 kg:
LB1 cranial capacity in standard deviations
5.1
3.2
below expected size or dwarf Homo erectus
At body weight estimate 16 kg:
LB1 cranial capacity in standard deviations
4.2
2.3
below expected size or dwarf Homo erectus
Data from Gabunia et al. (2000, 2001), Kappelman (1996), Rightmire et al. (2006), Stanyon et al. (1993), and Vekua et al.
(2002).
survive to adulthood (Hall et al., 2004). They are remarkably small, with weight, length, and head circumference at birth proportionately reduced to the size of a
28-week gestation fetus. Postnatal growth is poor, with
head growth much slower even than stature, resulting
in an adult height of 100–110 cm and head circumference of 38–41 cm. These values are well in line with the
LB1 skeleton. A small jaw with deviant development of
the chin and dental anomalies is common, including dysplastic and missing teeth in both primary and secondary
dentition. The LB1 fossil also has a small jaw with dys-
plastic and missing teeth, although, as we have noted,
other skeletal changes differ. Development of the chin is
highly variable in microcephalics. The chin is particularly prominent in some cases, as in the Stuttgart microcephalic (Figs. 3 and 6), whereas in others the mental
eminence is weak or lacking. Dokládal (1958), for example, reported on a 57-year-old microcephalic with a cranial capacity of 405 cc having a small mandible with
weak development of the chin.
Seckel syndrome consists of similar intrauterine and
postnatal growth retardation and microcephaly, typically
FLORES HOMINID
more than seven standard deviations below the mean,
with moderate to severe mental retardation but frequent
survival to adulthood (McKusick et al., 1967; Majewski
and Goecke, 1982; Faivre et al., 2002). Skeletal changes
are present, but less severe than in MOPD type 2 (Tsuchiya et al., 1981).
While it is not possible to match any of these syndromes exactly with the LB1 fossil based on the limited
data available, the features of several are informative.
We find that this group of syndromes shares several features with the LB1 fossil, including very similar small
stature and head size, a small and receding jaw, and
dental anomalies. Lacking the soft tissues and some
skeletal components of LB1, we cannot conclude that
LB1 had any particular one of these syndromes, but we
do think that the substantial overlap in features supports this possibility. One major limitation for comparative studies is the absence of information on the postcranial skeleton in museum specimens of human microcephalics. In closing, it should be noted that the third
hypothesis, that LB1 may derive from a more primitive
(pre-erectus) population, cannot be addressed by consideration of modern human developmental abnormalities.
CONCLUSIONS
We conclude that the features of LB1 best support the
interpretation that it is a pathological, microcephalic
dwarf specimen of Homo sapiens (see also Jacob et al.,
2006). Richards (2006), in a study emphasizing growth
processes, reached a similar conclusion that LB1 probably belonged to a modern human population with
reduced stature (attributable to a modification in the
growth hormone/insulin-like growth factor I axis), but
also suffered from a mutation in the MCPH gene family.
However, he differs in regarding this combined condition
as nonpathological. If further specimens directly resembling the Flores skull with respect to the tiny cranial
capacity were to be discovered, the probability that such
an explanation is correct might diminish. However, the
likely autosomal recessive inheritance of such a syndrome means that such evidence would not necessarily
be critical. On the basis of present evidence, it seems
most likely that the LB1 specimen is a pathological
anomaly, not a new species.
While this account has focused on the LB1 skeleton,
because brain size is known only for that individual,
some comment is required on the other specimens that
have been reported from Flores. These have been interpreted as providing evidence that a small-bodied hominid inhabited Flores at least between 95,000 and 15,000
years ago. As has been explained, the presence of other
small-bodied individuals in itself poses no problem. It is
the tiny brain size of LB1 that poses a problem. However, the discovery of a second mandible lacking a chin
(LB6/1) does raise questions, particularly because it is
claimed that it is only 15,000 years old and hence 3,000
years younger than the LB1 skeleton (Morwood et al.,
2005a). If the lack of a chin is interpreted as a side
effect of microcephaly in LB1, it would be difficult to ascribe this condition in the second mandible to persistence of a rare autosomal recessive condition for 3,000
years on Flores. However, the dating of the second mandible depends on the interpretation that the cave sediments have remained undisturbed and that no intrusive
1141
burials occurred. The apparent mingling of at least two
different assemblages of stone tools in the deposits suggests that the sediments have not remained completely
undisturbed. An alternative possibility is that the LB6/1
mandible is from a small-bodied individual that did not
suffer from microcephaly and that the absence of a chin
in both known mandibles is in fact a local variant attributable to some other cause. It should be noted that a significantly reduced chin is found in some modern African
and Indonesian pygmy populations and Australo-Melanesians (Jacob et al., 2006; Richards, 2006). Furthermore, it should be emphasized that, although the two
Flores mandibles are broadly similar in overall size,
there are several differences of detail. Unlike that of
LB1, the LB6/1 mandible shows no obvious dental
anomalies, its dental arcade differs in shape, and the
ascending ramus is markedly smaller in height.
Brown et al. (2004) stated that LB1 is megadont relative to both Homo ergaster and Homo sapiens. In fact,
examination of the scaling of lower molar teeth area in
various hominids compared to a large sample of monkeys and apes reveals that LB1 is similar to typical
anthropoids and early Homo, with relatively smaller
teeth than the truly megadont australopithecines (Fig.
12). While normal modern humans have relatively small
teeth in relation to body size, the mandibular molar area
in the Lesotho microcephalic is very close to the value
for LB1, at a very similar body mass. Hence, if LB1 is
megadont to any degree, so is the Lesotho microcephalic.
However, because scaling of teeth follows a similar pattern to the scaling of brain size during dwarfing, individuals with reduced body size would be expected to show
somewhat overscaled dental dimensions (Shea and
Gomez, 1993). Interestingly, the molars in the LB6/1
mandible are appreciably smaller in area than those of
the LB1 mandible, providing a further difference between
the two specimens.
Argue et al. (2006) recently applied canonical variate
analysis (CVA) to compare the skull of LB1 with a comprehensive sample of modern Homo sapiens, two microcephalic H. sapiens, representatives of fossil Homo
(specimens attributed to H. erectus and H. ergaster),
australopithecines (Australopithecus and Paranthropus),
and chimpanzees (Pan paniscus and P. troglodytes). In
separate plots of CV1 against CV2 using different data
sets, the two microcephalics were found to occupy a peripheral position relative to the general cluster of points
for Homo sapiens, while the point for LB1 was distant
from that cluster and close to Homo ergaster (notably
KNM-ER 3733). In fact, the microcephalics are in both
cases located in the general vicinity of LB1, but LB1 is
undoubtedly further removed from the general cluster
for H. sapiens. As Argue et al. (2006) themselves acknowledge, ‘‘microcephaly is an extremely heterogeneous condition and, while our results are suggestive, it may be
that they would differ should a larger sample of microcephalics be studied.’’ In fact, the two microcephalics
included in their study are problematic in various
respects. Both are archaeological specimens dating back
2,000 y or more, one from Crete (Poulianos, 1975) and
one from Japan (Suzuki, 1975), and therefore lack any
documentation of their condition. In the Minoan microcephalic skull from Crete, the third molars were not
fully erupted, so the individual concerned presumably
died before reaching adulthood. For reasons explained
1142
MARTIN ET AL.
Fig. 12. Plot of unilateral summed mandibular molar area for 76
monkeys and apes (nonhominid anthropoids) compared with a sample
of hominids. A least-squares regression line has been fitted to the
nonhominid anthropoids as a visual guide. As expected, the megadont
australopithecines (Australopithecus and Paranthropus) all lie above
the line, whereas representatives of Homo lie on the line or below it.
Key to points for Homo: 1 ¼ Homo habilis; 2 ¼ Homo erectus; 3 ¼
Tasmanian aboriginal Homo sapiens; 4 ¼ 17th-century European
Homo sapiens (London); 5 ¼ Lesotho microcephalic Homo sapiens; 6
¼ Flores LB1 mandible; 7 ¼ Flores LB6/1 mandible. Molar dimensions
for nonhuman anthropoids from Kanazawa and Rosenberger (1989),
Lucas et al. (1986), and Swindler (1976); for fossil hominids from Blumenberg and Lloyd (1983); for modern Homo sapiens from Brace
(1979); for LB1 from Morwood et al. (2005a). Gary Sawyer kindly provided measurements of the lower molars from the AMNH cast of the
Lesotho microcephalic mandible. Body mass values for nonhuman
anthropoids from Smith and Jungers (1997) and for fossil hominids
from McHenry (1994). Note that the same body mass of 23 kg has
been taken for both LB1 and LB6/1.
above, that skull is therefore not really suitable for comparison with LB1. This objection does not apply to the
Japanese skull (Sano 3), which is dentally adult. However, both the Minoan and the Sano skulls have larger
cranial capacities than LB1. Unfortunately, Argue et al.
(2006) give two different values for the cranial capacity
of the Minoan microcephalic: 350 and 530 cc. It is the
higher value that is correct. In the case of the Sano
skull, the recorded cranial capacity of 730 cc is almost
twice the average of about 400 cc for modern human
microcephalics and the value of about 400 cc for LB1.
Argue et al. (2006) also considered certain postcranial
elements (radius and femur) in comparing LB1 with
apes and hominids (though not with microcephalics, as
no postcranial elements were discovered with the Minoan or Japanese microcephalic skulls). As had been
noted previously, in the LB1 skeleton the arms are unusually long relative to the legs (Morwood et al., 2005a).
Taking an unconventional ratio of radius length to femur length, Argue et al. (2006) conclude that LB1 is intermediate between African apes and extant Homo sapiens, being more similar to Australopithecus garhi than
to other hominids. It should, however, be noted that the
radius is unknown for LB1 and that the length of the
radius taken by Argue et al. (2006) was actually inferred
from the length of the (incomplete) ulna of LB1 by
Morwood et al. (2005a). While it is surely true that
the forelimb:hindlimb ratio of LB1 shows some resemblance to a more primitive condition in hominid evolution, the significance of this cannot be properly assessed
without information on the condition of the postcranial
skeleton in modern human microcephalics. In fact, as
noted by Richards (2006), the ratio of forelimb length to
hindlimb length (intermembral index) increases with
decreasing body size as a consequence of allometric scaling
(Shea and Bailey, 1996), although this does not account for
the extreme condition found in LB1 (Argue et al., 2006).
It is marginally possible that the hominid remains
from Flores provide evidence of a new species from a lineage that diverged at a very early australopithecine
stage, about 3 Ma ago, when cranial capacity was still
very small. However, this would require convergent evolution of many similarities to Homo species, and the
complete lack of documentation of such a lineage in the
fossil record represents a major problem. Furthermore,
in this case it certainly cannot be argued with any
degree of plausibility that Homo floresiensis produced
the stone tools found in association with the skeletal
remains. On the basis of all the evidence presented here,
it seems to us most probable that LB1 was a microcephalic modern human.
ACKNOWLEDGMENTS
Thanks are due to Martyn Cooke for preparation of
the endocast of the microcephalic hemiskull at the Hunterian Museum, Royal College of Surgeons, London; Ken
Mowbray at the American Museum of Natural History,
New York, for providing initial information on the micro-
1143
FLORES HOMINID
cephalic skull cast and for measurement of its cranial
capacity; Matt Grove at the Field Museum, Chicago, for
preparation of an endocast from the original Stuttgart
microcephalic skull; Will Pestle for locating the microcephalic skull cast and endocast from Lesotho in the collections of the Field Museum and for measurement of
the endocast volume; Jill Seagard for providing drawings for Figures 8 and 9; John Weinstein for producing
the photographs for Figure 9; and Michel Hofman for
providing access to the data used in his 1984 paper.
Dean Falk readily provided information on the AMNH
microcephalic skull from which a virtual endocast was
generated for her published study (Falk et al., 2005a).
We are grateful to Ian Tattersall and Gary Sawyer in
the Department of Anthropology, AMNH, for their help
in providing access to the microcephalic skull cast and
accompanying documentation from the collections in
their care. Ian Tattersall kindly provided permission for
the removal of minute samples by Gary Sawyer from the
cast for chemical analysis. Gary Sawyer also generously
prepared an endocast from the AMNH microcephalic
skull cast and drew our attention to the key paper by
Vogt (1867) that proved to contain a description of the
original skull in Stuttgart. Thanks are also due to Jeffrey Schwartz for generating electronic images of the
AMNH microcephalic skull cast. Chemical analysis of
samples from the calotte and lower part of the cranium
of the AMNH microcephalic skull cast was conducted by
Laure Dussubieux using an ICP-MS acquired with a
grant from the National Science Foundation (PI: P. Ryan
Williams). Thanks are due to Laure Dussubieux and P.
Ryan Williams of the Field Museum for valuable discussion both in planning of the chemical analysis and in
interpretation of the results. Elmar Heizmann kindly
provided valuable information, including electronic
images, concerning the original microcephalic skull in
the collection of the Staatliches Museum für Naturkunde, Stuttgart. Doris Morike in the Zoology Department of the Staatliches Museum für Naturkunde helpfully provided an estimate of the age of that individual
and also graciously provided permission for a 6-month
loan of the specimen. Edna Davion and Elizabeth
Shaeffer provided valuable logistic support at the Field
Museum, notably with literature searches, data collection and analysis, and preparation of several figures.
Able assistance with final preparation of figures was
also provided by Julie Delamare-Deboutteville. Jonathan
Brown deserves special thanks for conducting computed
tomography of the Stuttgart microcephalic skull and
producing virtual reconstructions. Computed tomography of the Stuttgart skull was carried out at Northwestern Memorial Hospital using a Siemens Somaton Sensation 64 CT Scanner, and the support of Northwestern
University Feinberg School of Medicine Department of
Radiology is gratefully acknowledged. Three-dimensional
image reconstruction from CT data was performed with
an iView workstation, kindly loaned to the Field Museum by TeraRecon, Inc. (San Mateo, CA). Thanks are
also due to Judith Hall for helpful discussions regarding
human syndromes characterized by short stature and
microcephaly, and to Louise Roth for providing information on dwarf elephants. We are grateful to Robert Eckhardt for providing valuable information and numerous
comments, and to Ralph Holloway for sharing his expert
knowledge of hominid endocasts.
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