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J M Cheverud

Publications and source records attributed to J M Cheverud.

At least 55 records · Page 3Linked to original sources
PubMed1991

Brain surface cortical sulcal lengths: quantification with three-dimensional MR imaging.

The repeatability and accuracy of brain surface cortical sulcal length measurements obtained with three-dimensional (3D) reconstructions of volumetric, gradient-echo magnetic resonance (MR) images were tested. The brains of eight healthy adult volunteers and one cadaver were imaged in both the coronal and sagittal planes to yield a set of 128 1.5-2.0-mm-thick contiguous sections. 3D reconstructions of the brain cerebral cortical surfaces were obtained with computer software. Location and distance measurements of surface sulci were repeated on each reconstructed image. The same structures in the cadaver brain were independently measured with a 3D electromagnetic digitizer to validate the results of the 3D MR imaging method. All measurements from reconstructed images had high repeatability, and there were no statistically significant differences between measurement trials. The accuracy of measurements with 3D MR imaging was also good; the mean difference between digitizer and 3D MR measurements for sulcal lengths was 0.81 cm (average, 5.45-12.9 cm).

Adult↗
PubMed1990

Heritability and association of cortical petalias in rhesus macaques (Macaca mulatta).

Frontal and occipital petalias, the anterior or posterior protrusions of a cerebral lobe on one side or the other, are among the most striking anatomical asymmetries in human brains. Our previous studies of rhesus macaques revealed a relatively high frequency of right frontal petalias, whereas occipital petalias were seen less often and were equally common on right and left sides. In the present study, we test the hypothesis that variation in frontal and occipital lobular morphology is, in part, genetically based, and that frontal and occipital petalias are associated with one another. With a sample of 403 rhesus macaque endocasts, we found that right frontal petalias were more commonly associated with left occipital petalias than would be expected by chance. The concurrence of right frontal and left occipital petalias is the most common variant in human brains. We also found significant but moderate heritability for frontal petalias, while the heritability estimate for occipital petalias was relatively low and not statistically significant. This result suggests a genetic basis for variation in the degree of anatomical cerebral lateralization.

Animals↗
PubMed1987

Partial correlation of distance matrices in studies of population structure.

Anthropological studies of human population structure commonly compare various monogenic and polygenic (metric) distance matrices to distance matrices obtained from measures of geographical dispersion, linguistic differences, and migration patterns in an attempt to infer something about the effects of evolutionary factors (drift and differential selection, in particular). It is, though, commonly recognized that geography, language, and migration patterns may be intercorrelated due to the common effects of historical and social processes. Previous attempts to deal with the problems of assessing relative effects among such sets of intercorrelated factors using partial correlations have resulted in coefficients that are either not well defined or have no known sampling distribution or both. Here, we outline a general approach to partialling distance matrices that results in well-defined coefficients and valid significance testing procedures. Application of the matrix partialling methods to a variety of distance matrices obtained for a sample of eight ethnolinguistic groups from the Harvard Solomon Islands Expedition (Friedlaender et al., 1986) reveals a close association between language dissimilarity and dermatoglyphics controlling for geography, thus reinforcing earlier suggestions that dermatoglyphics, properly used, reflect historical relationships of groups in this region better than do anthropometry, odontometrics, or small batteries of blood polymorphisms.

Anthropology↗
PubMed1986

Cementum annulation and age determination in Homo sapiens. I. Tooth variability and observer error.

In order to test the feasibility of cementum annulations to estimate age in humans, observer error and tooth variability in cementum ring counts were evaluated in a sample of 42 mandibular canine and first premolar pairs. Additionally, two sectioning techniques were evaluated. Demineralized thin sections (7 micron) stained with hematoxylin are the preferred technique since their age related variance is greater than 75% for all tooth types examined. In contrast, less than 50% of the total variance was accounted for among individuals when mineralized sections (80 micron) stained with alizarin red were used. Intertooth variability in ring counts of demineralized sections was large between canines and premolars (43%). Premolars provide counts with lower interobserver error and are the preferred tooth. In an expanded sample (N = 51) of demineralized premolars, intraobserver and interobserver error accounted for 2% and 5% of the total variance, respectively. Evaluation of several experimental designs showed that increasing the number of slides per tooth has the greatest effect on reducing variance followed by increasing the number of observers. Increasing the number of observations has little effect. Cementum ring counts are measurable to a highly repeatable extent and provide a level of repeatability greater than that reported for the pubic symphysis and auricular surface aging techniques.

Age Determination by Teeth↗
PubMed1986

Cementum annulation and age determination in Homo sapiens. II. Estimates and accuracy.

The cementum annulation aging technique was evaluated in a sample of 80 clinically extracted premolars (age range 11-70 years). Demineralized thin sections (7 micron) stained with hematoxylin were used. The correlation (r) between age and adjusted count (number of annulations added to age of tooth eruption) was 0.78 for the entire sample (N = 73) and 0.86 for a subsample in which teeth with periodontal disease were excluded (N = 55). Standard error of the estimates ranged from 4.7 to 9.7 years depending on sex and health status of the tooth. The technique provided significantly better estimates for females than for males. The overall inaccuracy (mean absolute error) of the technique was 6.0 years, with a bias (mean error) of 0.26 years. Reduced major axis regression of adjusted count on age produced a slope of 0.797 for the entire sample and 0.889 for the nonperiodontal disease subsample. These slopes are consistent with a hypothesis of annual deposition of cementum rings given a decrease in cementogenesis with increasing age.

Adult↗
PubMed1986

Finite element scaling analysis of human craniofacial growth.

The study of form change is central to traditional cephalometric research. Unfortunately, traditional cephalometric studies operate within systems of measurement that are based on registration and orientation. Measurements produced in registered systems are insufficient for the craniofacial biologist who is interested in locating morphological differences between forms. In this article we apply a registration-free method called finite element scaling analysis in a study of the form change occurring during growth of the normal human craniofacial complex. The method provides form change data that can be summarized at various morphological levels. Twenty normal male individuals are used to analyze the form change that occurs from age 4 to ages 5, 7, 8, 9, 10, 12, 13, and 15 years. The magnitude and direction of growth expressed as shape and size change specific to craniofacial landmarks are presented. Although exceptions occur, our analysis shows that localized size change is, on the average, greater than localized shape change. The relation between size and shape change during growth shows allometry (shape change increasing during growth along with size change) but at a lesser magnitude and slower rate. We conclude that although shape change occurs throughout ontogeny, the magnitude and rate of shape change in relation to size change diminishes as age increases. This analysis represents new insights into the understanding of human craniofacial growth at various levels of morphological integration.

Adolescent↗
PubMed1985

Comparison of distance matrices in studies of population structure and genetic microdifferentiation: quadratic assignment.

Questions concerning the relative effects of various evolutionary forces in molding the genetic variability exhibited by groups of human populations have typically been investigated by comparing a variety of genetic and cultural/historical "distance" matrices. A major methodological difficulty has been the lack of formal testing procedures with which to assess the degree of confirmation or disconfirmation of an estimated measure of relationship between such matrices. In this paper, we examine a very flexible matrix combinatorial procedure which generates statistical significance levels for correlational measures of pattern similarity between distance matrices. A recent generalization of the basic procedure to the three-matrix case allows questions concerning which of two matrices best fits a third matrix to be formally tested. Applications of these hypothesis testing and inference procedures to two separate sets of genetic, geographic, and cultural distance matrices illustrates their potential for finally solving a long-standing problem in anthropological genetics.

Anthropometry↗
PubMed1984

Quantitative genetics and developmental constraints on evolution by selection.

It has often been argued that the principles of random mutation and selection are insufficient to account for macroevolutionary phenomena, such as the origin of morphological novelty and directionality in evolution. A third, epigenetic, principle is said to be required and this principle is thought not to be included in microevolutionary theory. The third principle has most recently been identified as internal selection and/or non-random phenotypic effects of mutation. It is shown that the genetic variance/covariance matrix of quantitative genetic theory measures developmental constraints due to internal selection and non-random mutation. The genetic variance/covariance matrix causes the response to selection to deviate from the optimal rate and direction as specified by the selection gradient, which measures direct selection on the phenotypes. Therefore, microevolutionary theory takes account of developmental constraints on evolution by natural selection through the genetic variance/covariance matrix. Theories for predicting the pattern of genetic variance and covariance from stabilizing selection and the phenotypic effects of mutation are discussed.

Biological Evolution↗
PubMed1984

The relationship between cranial metric and nonmetric traits in the rhesus macaques from Cayo Santiago.

This study addresses the relationship between cranial metric variables and nonmetric traits using the skeletal sample of rhesus macaques from Cayo Santiago. Discriminant function analysis is used to study the metric differences between macaque crania grouped according to the presence or absence of nine nonmetric traits. The computation of total structure coefficients from the discriminant function analyses provides information regarding how closely each metric variable is related to the discriminant functions derived. Total structure coefficients have not been used previously in the study of the relationship between metric and nonmetric traits. The results of the analysis are interpreted using an explicit approach to cranial morphogenesis-functional cranial analysis. It is concluded that the relationship between cranial metric and nonmetric traits is explicable in terms of a common developmental pathway shared by the two types of traits. Identification of the specific etiology of nonmetric traits depends on future anatomical studies or organisms throughout the period of nonmetric trait development.

Animals↗
PubMed1984

Genetic correlations between sides and heritability of asymmetry for nonmetric traits in rhesus macaques on Cayo Santiago.

The use of nonmetric traits for estimation of biological distance is a long-standing practice in biological anthropology. Nonmetric traits can be scored using either the individual or the side of the individual as the unit of measure. If sides of the individual are genetically correlated the use of sides would produce redundant genetic information. For this reason, Korey (Am. J. Phys. Anthropol. 53:19-23, 1980) argues for the use of individuals as the unit of measure for nonmetric traits. Ossenberg (Am. J. Phys, Anthropol. 54:471-479, 1981), however, argues that bilateral occurrence of nonmetric traits indicates greater genetic liability for the trait and that therefore the sides are the more biologically correct unit of measure. Genetic correlations for 13 cranial nonmetric traits are estimated for a sample of rhesus macaque skeletons from Cayo Santiago. In addition, heritability of asymmetry is estimated for these 13 traits as a test of Ossenberg's contention that asymmetry is genetically influenced. Significant genetic correlations between sides support Korey's contention that nonmetric traits should be scored by individual. Only two asymmetry heritabilities were significantly different from zero, providing no significant support for Ossenberg's contention that asymmetry is genetically determined. Our results support the theory that asymmetry represents a measure of the ability of an organism to buffer stresses. Therefore, a measure of the heritability of asymmetry is a measure of the heritability of the ability to buffer stresses. This ability does not appear to be heritable in this sample.

Animals↗
PubMed1984

Quantitative genetics and the evolution of ontogeny. II. Genetic and environmental correlations among age-specific characters in randombred house mice.

In this study, phenotypic, genetic, maternal and residual environmental correlations among all pairs of six ages (17, 24, 31, 38, 45 and 52 days) were calculated for each of five morphometric characters (body weight, head length, trunk length, trunk circumference, and tail length) in ICR randombred house mice. The maternal correlations between ages averaged nearly unity for all characters, and the overall level (and integration, I) of the genetic correlations (mean level = 0.82, mean I = 0.85) was greater than that for the residual environmental correlations (mean level = 0.26, mean I = 0.32). The patterns of the phenotypic and genetic correlations were similar, with the highest correlations being between contiguous ages and a relatively smooth decrease in correlations for increasingly distant ages. Nearly all of the genetic covariation among ages was explained by the first (average = 86%) and second (average = 14%) components derived from principal components analysis of the genetic correlations. Genes with basically equal pleiotropic effects presumably generated the first component, genes with different effects among ages the second component. From the patterns of genetic correlations, it is predicted that direct selection on any given age would result in a moderate, positive response at most other ages, with more change in the height relative to the shape of the growth curve for each characteristic.

Aging↗
PubMed1982

Relationships among ontogenetic, static, and evolutionary allometry.

The relationship between ontogenetic, static, and evolutionary levels of allometry is investigated. Extrapolation from relative size relationships in adults to relative growth in ontogeny depends on the variability of slopes and intercepts of ontogenetic vectors relative to variability in length of the vector. If variability in slopes and intercepts is low relative to variability in length, ontogenetic and static allometries will be similar. The similarity of ontogenetic and static allometries was tested by comparing the first principal component, or size vector, for correlations among 48 cranial traits in a cross-sectional ontogenetic sample of rhesus macaques from Cayo Santiago with a static sample from which all age- and sex-related variation had been removed. The vector correlation between the components is high but significantly less than one while two of three allometric patterns apparent in the ontogenetic component are not discernable in the static component. This indicates that there are important differences in size and shape relationships among adults and within ontogenies. Extrapolation from intra-or interspecific phenotypic allometry to evolutionary allometry is shown to depend on the similarity of genetic and phenotypic allometry patterns. Similarity of patterns was tested by comparing the first principal components of the phenotypic, genetic, and environmental correlation matrices calculated using standard quantitative genetic methods. The patterns of phenotypic, genetic, and environmental allometry are dissimilar; only the environmental allometries show ontogenetic allometric patterns. This indicates that phenotypic allometry may not be an accurate guide to patterns of evolutionary change in size and shape.

Aging↗
PubMed1982

Quantitative genetics of skeletal nonmetric traits in the rhesus macaques of Cayo Santiago. III. Relative heritability of skeletal nonmetric and metric traits.

This study addresses the long-standing controversy in skeletal biology concerning the relative utility of skeletal metric and nonmetric traits for studies of biological relationship. This controversy centers on the relative heritability of these two trait sets. This paper presents heritabilities for a series of skeletal metric and nonmetric traits measured with the same sample of mother-offspring pairs from the Cayo Santiago skeletal collection of rhesus macaques. Skeletal nonmetric traits display significantly greater heritability estimates than metric traits. This difference is due primarily to the high heritability estimates of hyperostotic nonmetric traits. Foraminal traits are not significantly more heritable than skeletal metric traits. The generality of this pattern of heritability values, in which hyperostotic nonmetric traits are more highly heritable than foraminal nonmetric and metric traits, depends on future empirical study of the correlation of heritability values in populations and theoretical work.

Animals↗
PubMed1981

Quantitative genetics of skeletal nonmetric traits in the rhesus macaques on Cayo Santiago. I. Single trait heritabilities.

The use of skeletal nonmetric traits in studies of biological relationships often involves the assumption that variation in these traits is genetic. Studies of nonmetric traits in human groups and in inbred strains of mice and rabbits have indicated a genetic component to nonmetric trait variation. Skeletons of animals with known matrilineage membership were obtained from the Cayo Santiago skeletal collection in order to obtain a direct estimate of the heritabilities of several nonmetric traits in the free-ranging population of rhesus macaques on Cayo Santiago. Falconer's (1965) method was used to calculate heritability. Heritability estimates range from zero to one, and half of them are greater than 0.5. This indicates that there is a considerable amount of genetic variation for these traits among the Cayo macaques. There is a significant tendency for traits scoring the number of foramina to have lower heritabilities than those scoring hyperstotic or hypostotic traits.

Animals↗
PubMed1981

Quantitative genetics of skeletal nonmetric traits in the rhesus macaques on Cayo Santiago. II. Phenotypic, genetic, and environmental correlations between traits.

The general lack of phenotypic correlation among skeletal nonmetric traits has been interpreted as indicating a lack of genetic correlation among these traits. Nonmetric traits scored on animals in the skeletal collection of rhesus macaques from Cayo Santiago are used to calculate phenotypic, genetic, and environmental correlations between traits. The results show that even when phenotypic correlations are low, there may be large, significant genetic correlations among these traits. The genetic correlation pattern suggests that genes which affect nonmetric trait variation act primarily at a local level in the cranium, even though there are genes with pleiotropic effects on skeletal nonmetric traits throughout the cranium. Environmental and phenotypic correlations do not show this neighborhood pattern of correlation.

Animals↗
PubMed1981

Deciduous tooth dimensions in fetal rhesus monkeys from mothers with induced diabetes.

Thirty-four measurements of the deciduous dentition in 21 fetal rhesus monkeys from diabetic mothers (FDM) and 36 nondiabetic fetuses were compared in order to assess the effects of induced maternal diabetes on the teeth of third-trimester fetuses. After exclusion of 14 variates due to significant age-related variation, univariate statistical analysis suggested a trend toward smaller teeth in the FDMs. Multivariate discriminant function analysis indicated not only a clear separation between the two groups, with molar breadths and some incisor length and breadths serving as the best discriminators, but also that the deciduous dental dimensions in FDMs are smaller than in nondiabetic fetuses.

Animals↗