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Ethnic and secular influences on the size and maturity of seven year old children living in Guatemala City.

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AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 59:393-398(19821
Ethnic and Secular Influences on the Size and Maturity of
Seven Year Old Children Living in Guatemala City
BARRY BOGIN A N D ROBERT B. MACVEAN
Wayne State Uniuersity, Detroit, Michigan 48202 (B.B.),and Universidad del
Valle, Guatemala City, Guatemala (R.B.M.)
Growth, Maturation, Ethnic influences, Secular
KEY WORDS
trends, Guatemala
ABSTRACT
Three groups of children, those of European parentage, those of
Guatemalan parentage, and those of mixed European-Guatemalan parentage
were measured for height, weight, and skeletal maturity. The children were born
between 1945 and 1965,they were all of high socioeconomicstatus, and they all attended the same private school in Guatemala City. At 7 years, the boys of the
European group were significantly taller than boys of the Guatemalan group.
European and mixed European-Guatemalan girls were significantly taller than
Guatemalan girls. These results are maturity independent. The influence of skeletal age was removed statistically by analysis of covariance. Girls of the mixed
group were significantly heavier than girls of European and Guatemalan groups.
Mixed group girls also had more significantly advanced skeletal ages than European girls. When the patterns of size and maturity status are analyzed by sex,
there is evidence for a relatively greater environmental influence on the boys and a
relatively greater genetic influence on the girls. Dividing the data into two birth
year cohorts, 1945 to 1955, and 1956 to 1965, does not provide evidence for secular
trends in growth or maturation. These results are similar to those from studies in
developed nations that report an end to the secular trend for the “well off” population of those countries.
Most of the many separate phenomena that
contribute to the process of human growth and
development are relatively easy to measure
and quantify but difficult to explain. Two such
phenomena are differences in mean size and
rates of maturation between ethnic groups,
and the secular trend for increases in both the
amount and rate of growth and development.
Eveleth and Tanner (1976) review growth
studies of Europeans (London), AfroAmericans (Washington, D.C.), and Asians
(Hong Kong). The Asian children were shorter
than the European and Afro-Americans at
almost every age between 1 and 18 years.
Asian girls were found to reach menarche onehalf year earlier than Europeans and at about
the same age as Afro-Americans. General
socioeconomic conditions were similar and as
close to optimum as possible in all groups. The
authors consider these differences to have a
genetic basis. However, since these populations are geographically and culturally remote
from each other, environmental factors cannot
be excluded.
0002-948318215904-0393$02.00 :r. 1982 ALAN R. LISS, INC.
The secular trend for growth and development has also been responsible for differences
in size and maturity of similar aged children
between and within populations. Tanner (1962;
1968) and Roche (1979)describe and quantify
the trends for earlier maturation and increased
rate of growth. These trends have occurred in
all the developed nations that have been
studied and some of the developing countries
(Roche, 1979). Most researchers find that the
causes of the secular trend are primarily due to
environmental improvements, e.g., socioeconomic conditions, sanitation, nutrition, and
health care (Krogman, 1972; Tanner, 1968;
Van Wieringen, 1978; Malina, 1979; Roche,
1979). But, there are some data indicating a
possible genetic component to the trend as well
(Hulse, 1958; Schreider, 1967).
There are relatively few studies of secular
trends in growth and maturation for children
Received December 3. 1981; accepted July 7. 1982.
Barry Bogin’s present address is University of Michigan, Dearborn,
M I 48128.
394
B. BOGIN AND R.B. MACVEAN
from developing nations. Basic data are
needed to describe these trends, if present, and
to compare them with the data from developed
nations to understand better the causes and
consequences of these trends.
This paper presents data on the size and
maturity of 7 year old children, born between
1945 and 1965, attending one private school in
Guatemala. Children of three different ethnic
backgrounds are represented. All of the
children are of high socioeconomic class. The
effects of ethnic background and the secular
trend on the growth and maturity of these
children are evaluated. An attempt is made to
quantify each effect and to discuss possible
hereditary and environmental influences on
each.
MATERIALS AND METHODS
Data for this study were taken from the
Longitudinal Study of Child Development conducted by the Universidad del Valle de
Guatemala. The sample consists of children
from the American School of Guatemala.
Children attending this private school came
from families of the highest socioeconomic
levels of the country. The program at the
American School assured each child regular
medical attention, adequate nutrition, an intensive program of exercise and physical
education, progressive academic education
and yearly assessments of physical, and
academic and cognitive status. In light of this
background, we feel justified in describing this
sample as representative of the most affluent
children living in Guatemala.
The data analyzed were the heights, weights,
and skeletal ages of those study participants
born between 1945 and 1965 (inclusive) assessed when each child was 7 years old (7.00 to
7.99 years). Height and weight measurement
techniques and reliabilities were described by
Bogin and MacVean (1978).Skeletal ages were
assessed from hand-wrist radiographs. Exposures and assessments were made following
the protocol of Gruelich and Pyle (1959). One
technician read all the radiographs. Blind testretest readings of the same radiographs indicate a reliability coefficient of 0.89 for this
technician.
Seven years of age was chosen because it afforded the greatest number of children for each
ethnic group and for the secular trend analysis.
I t is an age a t which environmental influences
on growth can be clearly demonstrated (Gold-
stein, 1971), as well as population and ethnic
differences (Eveleth and Tanner, 1976).
The sample numbers 1208 children and was
divided by sex and into three ethnic groups:
American School Guatemalan (ASG), American School European (ASE), and American
School Mixed (ASM). Children are classified
ASE if both parents and all four grandparents
were born in Europe or North America and
have European (not Spanish) surnames.
Children are classified as ASG if both parents
and all four grandparents were born in
Guatemala and have Spanish (not Mayan) surnames. Children classified as ASM are the offspring of marriages between an ASG and an
ASE parent. The few individuals who did not
meet any of these criteria were excluded from
the sample. This genealogical classification is
supported by data from the analysis of ABO
blood group frequencies; ASG children have
phenotypic frequencies significantly different
from those of ASE children (Johnston et al.,
1973). Ethnic identifications were made after
all heights, weights, and skeletal ages were
recorded. The identifications were based on information parents provided when completing
school registration forms.
RESULTS
The data were first analyzed by a three-way
analysis of variance to test for the main effects
of year of birth, ethnicity, sex, and their interactions. In order to separately compare the
effects of these variables on size and maturity,
the heights of all children were adjusted to
remove the influence of skeletal maturity by
analysis of covariance. Table 1 is a summary of
the results of the three-way ANOVA with
height adjusted for skeletal age. Given in the
table are the F ratios and beta values (betas
may be interpreted as standardized partial
regression coefficients). As can be seen there
are some significant main effects but no interactive effects on each of the size and maturity variables.
The data were further analyzed to describe
the nature of the main effects. Table 2 shows
the descriptive statistics for chronological age,
height, weight, and skeletal age for boys of
each ethnic group for all birth years combined.
Corresponding statistics for the girls are given
in Table 3. Heights were adjusted for skeletal
age by covariance. Analysis of variance and
post-hoc Scheffe tests were used to compare
these means.
There were no significant chronological age
differences. For boys, there was one significant
395
ETHNIC AND SECULAR INFLUENCES ON SIZE AND MATURITY
TABLE 1. Three way analysis of variance on height, weight, and skeletal
age for the effects of year of birth, ethnicity and sex'
Height'
Weight
F
Beta
F
Beta
Main effects df
Year of birth 19
1.68*
0.14
1.74* 0.16
E thnicity
2
13.55** 0.13
2.50
0.06
Sex
1
66.00**
0.20
2.31
0.04
Interactions
No simificant two-wav or three-wav interactions.
Skeletal age
F
1.23
4.27*
39.41**
Beta
0.14
0.08
0.18
'n = 1208
'Heights were adjusted by covariance to statistically remove the effect of skeletal age.
*p < 0.05: **p < 0.001.
TABLE 2. Descriptive statistics for chronological age, height, ueight,
and skeletal age for boys of the Guatemalan (ASG), European (ASE), and
mixed Guatemalan-European (ASM)ethnic groups
Chronological
age (years)
Height (cm)
Weight (kg)
Skeletal age
(years)
ASM
ASE
ASG
n=412
n=171
ii
sd
X
sd
7.51
124.16
25.36
0.28
4.80
3.95
7.47
125.59
25.75
0.29
4.80
4.74
6.93
1.09
6.84
1.19
n=102
ii
sd
7.48 0.32
124.70 4.78
25.59 3.88
7.09
0.93
'Heights were adjusted by covariance to statistically remove the effect of skeletal age.
'ASE X > ASG X;p = 0.001.
TABLE 3. Descriptive statistics for chronological age, height, weight,
and skeletal age for girls of the Guatemalan (ASG), European (ASE),and
mixed Guatemalan-EuroDean(ASMI ethnic grouus
Chronological
age (years)
Height' Icm)
Weight' (kg)
Skeletal ageJ
(wars)
ASG
ASE
ASM
n=276
n=158
n=92
X
sd
X
sd
X
sd
7.47
121.71
24.83
0.29
4.80
4.25
7.47
123.32
25.20
0.29
4.79
5.07
7.51
123.37
26.45
0.31
4.81
5.69
7.30
0.84
7.22
0.91
7.50
0.98
'Heights were adjusted Iiy covariance to statistically remove the effectof skeletal age
'ASE X > ASCi X. p = 0.001: A S M X
ASG X,p = 0 004.
'ASM X > ASG X: p = 0.005: ASM > ASE X: p = 0 05.
'ASM > ASK P = 0.02.
x
x.
x
difference for height: ASE boys were taller
than ASG boys. No significant differences existed for weight or skeletal age. ASE and ASM
girls were taller than ASG girls. ASM girls
were significantly heavier than both ASE and
ASG girls. ASM girls were more mature than
ASE girls. The ASG girls were intermediate in
value, but not significantly different from the
other two groups.
The data were then analyzed for secular
trends within each ethnic group. Children were
placed into two birth year cohorts, those born
1945-55 and those born 1956-65. Table 4 summarizes the analysis for trends in growth and
396
B. BOGIN AND R.B. MACVEAN
TABLE 4. Descriptiue statistics for height, weight, and skeletal age for earlier born (1945-1955) and later born
(1956-1965) cohorts o f children o f the Guatemalan (ASG), European (ASE), and mixed Guatemalan-European(ASM)
ethnic groups
ASG
-~
Earlier born Later born
n =.__
142
n = 270
X
sd
X
sd
~~~
~
-
~
~~
Boys
Height (cm)
Weight (kg)
Skeletal age (years)
Chronological age (years)
Girls
Height (em)
Weight (kg)
Skeletal age (years)
Chronological age (years)
ASE
Earlier born Later born
n = 71
n = 98
-~
Z __
sd
X
sd
~
~
~
~
ASM
Earlier born Later born
n = 46
n = 56
X
sd
%
sd
~~
~
123.08 5.18 124.02 5 0 8 125.76 5.66 124.22 5.84 123.76 4 68 125.43 4.66
25 38 3.99 25.35 3 94 26.22 4.73 25.44 4.77 25.20 3 52 25.90 4.15
7.06 1.18
6.67 1.19* 6.90 0.92
7 24 0 9 2
694 106
6 9 1 1.15
7.53 0.31
7.41 0 32
7.44 0.29
7.51 0.28
7.52 0.29
7 49 0 26
n = 87
n = 39
n = 53
n = 176
n = 71
n = 99
122.29 5.51 122.32 5.35 123.31 6.55 123.94 5.60 124.54 6.25 124.47 6.54
24.90 4.09 24.82 4.34 25.34 5.57 25.09 4.66 26.53 5.18 26.40 6.09
7.56 1.07
7.46 0.91
7.19 0.94
7.24 0.88
7.32 0.85
7.28 0.83
7.52 0.30
7.50 0.32
7.51 0.30
7.43 0.28
7.47 0.29
7.47 0.28
*Earlier born mean significantly greater t h a n later born mean. p < 0.05.
maturation between the earlier born and later
born cohorts. Means and standard deviations
are given for all comparisons and significant
differences between birth year cohorts were
assessed by t-tests. For the girls, none of the
ethnic groups showed significant differences.
ASE boys showed a significant decrease in
skeletal age. No other significant change was
found for other variables in any of the ethnic
groups.
DISCUSSION
The physical size and skeletal maturity of
children of the same chronological age varies
between and within populations. Differences
in size and maturity a t a given age reflect
hereditary factors, environmental conditions,
and their interactive effects (Ashcroft and
Lovell, 1964; Ashcroft et al., 1966; Garn and
Rohmann, 1966; Hunt, 1966; Eveleth and Tanner, 1976; Johnston et al., 1976). The influence
of heredity and environment are usually confounded in studies of child growth and development due to the nonexperimental nature of this
research. However, some studies have attempted to statistically control for “nature vs.
nurture.” Most of these studies found that during childhood growth and development were
influenced relatively more by environmental
factors, but during adolescence hereditary influences predominated (Gard and Rohman,
1966; Hunt, 1966; Habicht et al., 1974;
Greulich, 1976; Johnston et al., 1976; Bogin,
1978; Tanner, 1978; Frisancho et al., 1980).
Two exceptions to this general finding are
studies by Ashcroft and Lovell (1964) and
Ashcroft et al. (1966). They measured the
heights and weights o f 4 to 17 year old children
and youth of European, African, Afro-European, and Chinese background living in
Kingston, Jamaica. All children were of uppermiddle to high socioeconomic status and attended private fee-paying schools. There were
no significant differences between the European, African, and Afro-European groups.
However, the Chinese sample was significantly shorter and lighter than the other three
groups at almost every age.
Our results are similar to those of Ashcroft
and colleagues. Both our study and their’s
show significant differences in growth between some ethnic groups of children reared in
similar environments. These ethnic differences
cannot be automatically ascribed to genetic
factors. Neither the Jamaican study nor our
Guatemalan study controlled for child rearing
practices in the home, the length of residence
of each family in the country, family size, or
other cultural and behavioral variables that
may have influenced growth.
However, there is support for a genetic component to these ethnic differences when the
results for boys and girls are compared. The
mean heights and weights of the ASG, ASE,
and ASM boys were more similar than the
mean heights and weights of the girls. The
variances for the boys were also relatively
smaller than the variances for the girls. The
data of Johnston e t al. (1976) also followed this
pattern. They studied longitudinal growth patterns for children from the same population as
that studied here. At 7 years ASG and ASE
boys in their sample had identical mean
heights, 123.5 cm (sd = 5.0 and 5.8, respective-
ETHNIC AND SECULAR INFLUENCES ON SIZE AND MATURITY
ly), and mean weights of 24.9 (3.7)and 25.6 (5.2)
kg, respectively. The girls’ heights and weights
were, ASG; 122.8 (5.6)cm and 25.2 (4.2)kg, versus ASE: 125.0 (6.2) cm and 26.1 (5.6) kg.
Several other studies show similar findings.
That is, when children of different ethnic
groups live under similar environmental circumstances, the boys show similar amounts of
growth and less variability, but the girls show
less similarity and more variability between
ethnic groups (Greulich, 1976; Bielicki and
Charzewski, 1977). The interpretation of these
observations given by Greulich is that the
growth of boys is more “sensitive”to environmental influences. The growth of girls is less
environmentally sensitive, rather it is influenced more by genetic factors. Our study
supports this interpretation. There was only
one significant difference for height between
the three groups of boys. But, there were
significant differences between the three
groups of girls for all the growth variables. It is
noteworthy that the ASM girls were consistently taller, heavier, and skeletally more
mature than ASE and ASG girls. An additive
genetic model cannot account for these results.
I t would predict ASM children to be intermediate in size and maturity. Influences
such as assortative mating, home environment, and others must be considered to explain
the results. Unfortunately, we do not have
data available for these influences.
Finding significant ethnic differences between the ASG and ASE groups was, at first,
surprising, since Johnston et al. (1976)did not
find differences in growth between children
from these same two groups. The discrepancy
between our results and those of Johnston et
al. may be due to sample size, 1208 vs. 58
respectively, or, more likely, to the crosssectional design of our study versus the longitudinal design of theirs. They were comparing
patterns of accumulated growth, while we
dealt with size at one age.
Our results for the secular trend analysis are
more easily interpreted. There has been no
secular trend for the growth or maturation of
upper socioeconomic children living in
Guatemala, born between the years of 1945 to
1965. Our results parallel those from some
developed countries, e.g., England, Japan,
Norway, and the United States (Tanner, 1968;
Dammon, 1968; Maresh, 1972) where children
of the upper socioeconomic classes no longer
experience secular growth changes.
Presumably, these populations have realized
397
their maximum genetic potential for growth
and maturation.
On the other hand, in a study of low to middle socioeconomic status Guatemalans, Castefiada (1972) found a decrease in the age of
menarche for three generations of women.
Retrospective, self-reported data were used in
this study. The mean age of menarche for
school girls was 12.78 years, for their mothers
13.66 years and for their mothers’ mothers
14.18 years. There are also reports of positive
secular trends for children living on the
developing island nations of Jamaica (Ashcroft and Lovell, 1965), St. Vincent (Ashcroft
and Antrobus, 1970),and Aruba (van Wering,
1981) during the past 30 years. These studies
include children of all socioeconomic levels. All
the authors explain their results in terms of the
general socioeconomic, health, and nutritional
improvement of the poor and middle class
children during these years. This is the explanation for the secular trend favored by most
researchers (Tanner, 1978; Malina, 1979;
Roche, 1979).
By negative evidence, our results also support the socioeconomic, health care, and nutrition explanation for the secular trend. All of
our subjects were affluent, healthy, and well
nourished. When these environmental factors
do not inhibit growth, the child‘s hereditary
potential for growth and development may be
fully realized. Ethnic differences in growth and
development may be observed between some
groups, but secular trends are absent.
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