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Biological and cultural contradictions A reply to MacEachern.

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Biological and Cultural Contradictions?
A Reply to MacEachern
Gabriella Spedini,1* Stefano Mondovı̀,1
Giorgio Paoli,2 and Giovanni Destro-Bisol1
Department of Animal and Human Biology, University
“La Sapienza,” 00185 Rome, Italy
Department of Ethology, Ecology, and Evolution, University of Pisa, 56126 Pisa, Italy
In his comment appearing in this issue of the American Journal of Physical Anthropology, MacEachern
(2001) questions some conclusions drawn in our longterm survey of genetic variation in Cameroon (Spedini et al., 1999). In our reply, we would like to
clarify certain points so as to put AJPA readers in a
position whereby they understand both viewpoints.
The main point in MacEachern’s critique concerns
our claim that the genetic structure of some Montagnard populations has been shaped by the combined effect of genetic drift and isolation. Before
discussing MacEachern’s considerations about ethnographic sources, estimates of endogamy rates, and
cultural evidence, we would like to clarify the exact
meaning of the term “isolation.” The method we
used, kinship analysis, does not give an absolute
estimate of isolation. It simply compares a number
of populations and identifies which are the most (or
least) isolated. Therefore, our results do not imply
that the Podokwo and Uldeme Montagnard are completely isolated, but simply that these two groups
are more isolated than the others. Standard scientific and statistical procedures require any comparison to be carried out on a sufficiently ample portion
of the original data set. However, MacEachern was
concerned only with 4 (Mada, Mafa, Podokwo, and
Uldeme) out of 18 populations studied in Spedini et
al. (1999). Scientifically speaking this subset is too
small, which limits the validity of MacEachern’s
MacEachern claims that the ethnographic sources
of our paper are somewhat outdated. However, he
does not give any details or, at least, citations of
studies. Readers ought to understand the criteria by
which we have chosen our ethnographic sources.
First of all, the term “outdated” is inappropriate.
Some of our ethnographic sources (Boutrais, 1973,
Boutrais, et al., 1984; Marguerat, 1976; Boulet and
Seignobos, 1978; Hallaire, 1991) are more recent
than some of the works cited by MacEachern (Juillerat, 1971; Richard, 1977; de Colombel, 1986). In
addition to this, and more importantly, our ethnographic sources are the results of long-term surveys
in which a large number of populations settled over
a broad geographical area was studied simultaneously using the same methodology. This makes
them a reliable source of information. On the other
hand, the studies considered by MacEachern are
mostly based on small, geographically limited populations, and the studies conducted were methodologically heterogeneous. Therefore, it cannot be denied
that ethnographic sources produce at least two alternative views on the degree of isolation of Montagnards. Our genetic study provides a test of these two
different views, and favors the one sustaining the
existence of marked isolation among Montagnards.
MacEachern raises serious doubts concerning our
estimate of a 100% endogamy rate among Montagnards (see Table 4 on p. 152 of Spedini et al., 1999).
However, we would like to point out that a similar
95% endogamy rate was also observed among
Podokwo by Podleskwi (1966). No substantial evidence against our and Podleskwi’s estimates is given
by MacEachern. He quotes a number of studies
which indicate a marked variability in the endogamy rates of Montagnards, with very high endogamy rates in the Muktele (92–95%; see Juillerat,
1971), “neighbors of the Podokwo.” The field notes
collected by the author himself among the Uldeme/
Plata would seem to contradict our estimates of endogamy in the Uldeme. Unfortunately, a comparison
of the two studies is not possible, since MacEachern
does not give a point estimate but rather a range of
values (60 –70%). Furthermore, the sample size is
not reported, and the endogamy estimate of
MacEachern is questionable. In fact, he carried out
his investigation on a sample of Montagnard women
producers of local pottery. The author himself points
out that these women “circulate among patrilocal
communities in the course of frequent marriages
and remarriages.” Possibly, a more varied sample
from all areas of the community would have been
more appropriate. MacEachern does not indicate
whether exogamic marriages occur more frequently
among female potters than among female nonpotters, as would seem possible. Thus, it is unclear
Grant sponsor: CNR; Grant number: 000516.98.CT04; Grant sponsor: University of Rome “La Sapienza” 60% Funds. Grant sponsor:
M.U.R.S.T.; Grant Number: MM05038334, Cofin. 2000-2001.
*Correspondence to: Gabriella Spedini, Department of Animal and
Human Biology, University “La Sapienza,” P. le A. Moro 5, 00185
Rome, Italy. E-mail:
Received 19 October 2000; accepted 19 November 2000.
whether a marked difference in the potters’ matrimonial behavior from the average could have led to
some confusing results.
We would like to point out that new data collected
in the original locations of Montagnards (villages of
Godigou and Mayo Uldeme in northern Cameroon;
Spedini, 1998, unpublished data) provide further
evidence of a high endogamy rate both for the Uldeme (100% endogamy rate, a total of 50 marriages
considered) and Podokwo (95.1% endogamy rate, a
total of 41 marriages considered).
MacEachern claims that a cultural exchange between populations should automatically homogenize
their gene pool. He fails to take into account two
basic principles concerning cultural and biological
evolution. Firstly, cultural exchange does not necessarily imply gene flow and vice versa. Secondly,
there is a significant difference in time scale between cultural and genetic evolution, so that genetic
effects may appear many generations after any cultural and/or social changes.
MacEachern expresses some doubts concerning
the precision of the geographic distances we used to
assess the correlations between geographic and genetic diversity. Using our map (Fig. 1 on p. 149 in
Spedini et al., 1999), he infers that we have considered a total distance across the territories of the
Podokwo, Uldeme, and Mada of approximately 80
km, which is much larger than his value of 15 km.
His map (Fig. 1 in MacEachern, 2001) better depicts
the area of settlement of Montagnards. At the end of
his comment he states, “One hopes that data from
the map were not used in the calculation of geographic distances matrices produced in the paper.”
The issues raised by MacEachern need to be reconsidered for four reasons.
Firstly, it may be useful to describe briefly how the
geographic distance between populations was calculated in our studies. Since the Montagnard populations are settled in different villages, one should use
the distance between the center of the areas covered
by each population, or alternatively, the distance
between the point central to the most populated
villages. A fine-scaled map is obviously necessary.
Using this method, we obtained a distance of 10 km
between Podokwo and Uldeme, 5 km between Uldeme and Mada, and 15 km between Podokwo and
Secondly, the numbers on our map (as on all maps
of this kind)are used only to show the relative position of populations and not their exact locations.
This is simply due to the fact that the numbers need
to be well separated so that they are easily distinguishable.
Thirdly, even if we accept MacEachern’s speculation that numbers on the map indicate the location
of populations precisely and use the distance between topologically well-defined points as a reference, it remains quite unclear how MacEachern
could have obtained the precise value of 80 km. In
fact, the recalculated distance (in kilometers) between numbers changes depending upon which exact point one considers within the microarea on the
page covered by the number. Notice that the distance recalculated in kilometers between the Mada
(number 3 in Fig. 1 on p. 149 of Spedini et al., 1999)
and Podokwo (number 6) varies from 65 km (using
the closest points) to 92 km (using the most distant
points; see Fig. 1 in this paper). Therefore, the recalculation of the distance between some Montagnard populations made by MacEachern is not only
inappropriate but also approximate.
Finally, the map published by MacEachern does
not contain any known geographical reference,
which makes it impractical for use.
Every critique of any conclusion based on a scientific approach should be accompanied by testable
alternative hypotheses. Unfortunately, this is not
the case with MacEachern’s paper. He invokes “the
existence of larger, less precisely demarcated regional groupings that are also visible in both ancient
and modern distributions of material culture.” In a
subsequent part of the paper he affirms that “genetic
differentiation of a Mada, Podokwo, or Uldemé population sample . . . could indicate relative genetic
differentiation between broader regional populations, within which each of those ethnicities is only a
part.” Some of the terminology used here seems a
little vague and ambiguous. For example, “regional
groupings” seems to imply a certain degree of isolation. However, MacEachern repeatedly claims that
there is a high gene flow among Montagnards. Furthermore, in his first sentence he once more stresses
the idea of a precise link between cultural and genetic change.
MacEachern criticizes how we integrate biological
and cultural evidence. He accuses us of having created an artifactual link between genetic and historical data. He seems to be reiterating the classical
claim of “post hoc interpretations” by Binford (1981,
p. 31–32) against ingenuous explanations developed
after an analysis is completed.
His criticisms are based on three points: 1) the use
of “outdated ethnographic sources;” 2) the lack of
genetic differentiation of Mada and Mafa from other
northern Cameroonians; and 3) the view that during
the Holocene there was a process of sedentarization
in a limited number of nuclei.
Point 1 has been discussed above. Concerning the
second point, MacEachern has not adequately con-
Fig. 1. Variation in distance between the Mada (number 3) and the Podokwo (number 6), recalculated from Figure 1 on page 149
of Spedini et al. (1999). Dotted line depicts minimum distance (65 km), whereas the solid line depicts maximum distance (92 km). The
distance between western (point A) and eastern (point B) extremities of the southern border of Cameroon was used as a reference
(airline distance, 718 km).
sidered that the local kinship value (a relative measure of isolation) of the Mada (0.0163) is lower only
than those of Uldeme (0.045), Podokwo (0.037), and
Tali (0.022) (see Table 7 on p. 154 in Spedini et al.,
1999). Furthermore, he does not mention that the
Mada and Mafa cluster separately from other populations in the UPGMA tree shown in Figure 4 of our
paper (Spedini et al., 1999), which further suggests
a certain degree of genetic differentiation of these
two populations from other Afro-Asiatic-speaking
The third point of contention is the least understandable. The concept of a limited number of nuclei
of sedentarization is not ours, but is a synthesis of
the evidence presented in various studies, none of
which is cited by MacEachern (e.g., Lebeuf, 1981;
David, 1981; Essomba, 1991; see also citation on p.
144 –145 of Spedini et al., 1999). MacEachern claims
that the archeological reconstruction of processes of
sedentarization is invalid, since it may be biased by
the geographic localization of excavations. In any
scientific debate one can only make inferences based
on evidence available at the time and considering
current views. Obviously, it is possible that these
views could change in the future as new data are
collected and as they inform research. It would have
been useful to find out whether MacEachern has
substantial reasons to oppose the view of a limited
number of nuclei of sedentarization, but unfortunately he does not comment on this.
On the other hand, MacEachern’s view about processes of sedentarization in prehistoric Cameroon is
rather drastic, since a similar perspective would
eliminate the validity of many archeological studies.
This would be a pity, because archeological studies
combined with research from other scientific areas
have shed light on many important aspects of population histories.
Our analysis of MacEachern’s arguments suggests that had he analyzed our data a little more
closely, he might have drawn quite different conclusions.
Our work apart, we would like to comment on the
usefulness but also on the potential danger of the
message given by MacEachern. He highlights once
more that there is a problem of communication between cultural and biological disciplines. It is clear
that both these fields of research would benefit from
working in tandem. Among the issues raised by
MacEachern, problems concerning ethnic self-identification should be more carefully considered by
biological anthropologists. At the same time, our
analysis of MacEachern’s contribution illustrates
how an understandable lack of knowledge about
principles and methods of field of research that are
different from our own may result in the misinterpretation of works carried out by colleagues in other
areas. While in our case MacEachern clearly has
overlooked the biological evidence, one could easily
find peer-reviewed papers published by physical anthropologists and/or population geneticists in which
cultural evidence is not adequately considered.
The problem is that biological and cultural anthropologists have difficulties in understanding differences and similarities between their scientific approaches, and therefore find any subsequent form of
interaction or collaboration difficult.
To increase the cultural flow among researchers,
it could be useful for biological and cultural anthropologists to meet for discussions, perhaps inviting
researchers from both disciplines with a common
interest in specific populations. Given the attention
of the American Association of Physical Anthropologists (AAPA) to multidisciplinary research, we feel
that the symposia organized by the AAPA could be
the ideal place to start building a bridge between
these two distant but, at the same time, close disciplines.
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