Cultural diversification promotes rapid phenotypic evolution in Xavánte Indians.

Shifts in social structure and cultural practices can potentially promote unusual combinations of allele frequencies that drive the evolution of genetic and phenotypic novelties during human evolution. These cultural practices act in combination with geographical and linguistic barriers and can promote faster evolutionary changes shaped by gene-culture interactions. However, specific cases indicative of this interaction are scarce. Here we show that quantitative genetic parameters obtained from cephalometric data taken on 1,203 individuals analyzed in combination with genetic, climatic, social, and life-history data belonging to six South Amerindian populations are compatible with a scenario of rapid genetic and phenotypic evolution, probably mediated by cultural shifts. We found that the Xavánte experienced a remarkable pace of evolution: the rate of morphological change is far greater than expected for its time of split from their sister group, the Kayapó, which occurred around 1,500 y ago. We also suggest that this rapid differentiation was possible because of strong social-organization differences. Our results demonstrate how human groups deriving from a recent common ancestor can experience variable paces of phenotypic divergence, probably as a response to different cultural or social determinants. We suggest that assembling composite databases involving cultural and biological data will be of key importance to unravel cases of evolution modulated by the cultural environment.

Fibroblast growth factor receptor 1 (FGFR1) variants and craniofacial variation in Amerindians and related populations.

OBJECTIVES: The polymorphic site rs4647905 of the FGFR1 gene was previously associated with a decrease in cephalic index (CI). Here, we evaluate the relationships between genotypes and cephalometric measurements and indices in one Mexican Native and two mestizo Mexican populations using two haplotype-tag SNPs (rs4647905 and rs3213849) that represent >85% of the FGFR1 variability, plus three other SNPs (rs2293971, rs2304000, and rs930828) situated nearby. In addition, we genotyped five South American natives, two European, one African, and one Siberian populations to evaluate their intra and intercontinental population diversity. METHODS: The five SNPs were tested and the craniofacial measurements and indices were collected using standardized procedures. Principal Component Analysis was used to verify individual/population comparisons. Associations were performed through the generalized linear model (GLM), coefficient of determination R(2) and linear regression tests. RESULTS: We found a tendency for a decrease in CI in individuals homozygous for allele rs4647905C, regardless of the population to which they belong, though the effect is more pronounced in mestizo. When the GLM analyses were performed using the absolute/linear cephalometric measurements, a statistically significant association was found between four SNPs and head length in the mestizo population. CONCLUSIONS: FGFR1 polymorphisms, especially rs4647905, can have an important role in the normal human skull variation, primarily due to their influence in head length, which would affect other cephalometric absolute/linear measures as well as indices like CI as a result of the pervasive nature of the morphological integration that characterizes the human skull.

Genetic diversity of HLA system in three populations from Guanajuato, Mexico: Guanajuato City, León and rural Guanajuato.

We studied HLA class I (HLA-A, -B) and class II (HLA-DRB1, -DQB1) alleles by PCR-SSP based typing in 262 Mexicans from the state of Guanajuato living in the cities of Guanajuato (N = 78), León (N = 22) and rural communities (N = 162), to obtain information regarding allelic and haplotypic frequencies. We find that the most frequent haplotypes found in the state of Guanajuato include 12 Native American and three European haplotypes. Admixture estimates revealed that the main genetic components in the state of Guanajuato are Native American (50.64 ±â€¯2.11% by ML, 43.35% of Native American haplotypes) and European (44.14 ±â€¯1.14% by ML; 39.35% of European haplotypes), while African genetic component is less apparent (5.22 ±â€¯2.08% by ML; 8.36% of African haplotypes).

Genetic diversity of HLA system in two populations from Michoacán, Mexico: Morelia and rural Michoacán.

We studied HLA class I (HLA-A, -B) and class II (HLA-DRB1, -DQB1) alleles by PCR-SSP based typing in 498 Mexicans from the state of Michoacán living in the city of Morelia (N = 150) and rural communities (N = 348), to obtain information regarding allelic and haplotypic frequencies. We find that the ten most frequent haplotypes found in the state of Michoacán include 12 Native American and two European haplotypes. Admixture estimates revealed that the main genetic components in the state of Michoacán are Native American (48.79 ±â€¯1.44%) and European (43.10 ±â€¯0.86%), while African genetic component is less apparent (8.11 ±â€¯0.85%). Our findings add to the growing knowledge on the population genetics of Western Mexico and provide new HLA data on populations from Michoacán.