Cultural diversification promotes rapid phenotypic evolution in Xavánte Indians

Abstract

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. cultural evolution | morphology | mtDNA | multiple factor analysis | Amerindians C lassic hypotheses about modern human evolution frequently assume that the evolutionary forces acting on the populations are triggered mainly by changes in the external (climatic, geographic, topological) environment. However, recent anthropological studies suggest that shifts in cultural practices can potentially modify environmental and behavioral conditions, thus promoting faster evolutionary rates shaped by gene-culture interactions (1-5). Because humans have lived in small aggregates in most of their evolutionary history, studying the influence of cultural practices on the demographic and genetic parameters of small groups can shed more light on modeling the effect of culture on biological evolution. These cultural practices act in combination with geographical and linguistic barriers and can promote faster evolutionary changes shaped by gene-culture interactions.

Shifts in subsistence type and its impact on the human skull's morphological integration

“…Also, studies on phenotypic covariance structures of Neotropical primate skulls demonstrated that it have remained relatively constant, even across phyletic diversification that enabled the phenotypic means to evolve during the last 30 million years (Marriog and Cheverud, ). A similar result was obtained in human populations, where covariance has also been shown to be stable (González‐José et al, , Hünemeier et al, ), even under extreme mechanical stressors experienced during early postnatal phases, as is the case of intentionally deformed skulls (Martínez‐Abadías et al, ).…”

Demographic expansions in South America: Enlightening a complex scenario with genetic and linguistic data

“…If powerful men could marry more than one woman, and preferably sisters, all their children would share the same mitochondrial lineage, whose frequency could significantly increase. Additionally, cultural practices like those mentioned above have prevented fusion between the Xavante and the other Je populations located in the Brazilian Central Plateau, such as the Kayapó (Hünemeier et al, 2012).…”

The Extended Evolutionary Synthesis Facilitates Evolutionary Models of Culture Change

“…Contemporary scholarship in this domain includes investigations of geneculture interaction on the rate of evolution (Hünemeier et al 2012), the role of gene-culture interactions in geographically-restricted adaptation over the last 50,000 years (Laland et al 2010), gene-behavior coevolution in the case of the origins of language (Aoki 2001), the evolution of social norms (Gintis 2003) and the global, early-Holocene experiments with plant and animal domestication. In a recent work on the European Neolithic (Zeder 2008), it has been noted that multiple taxa were significantly coevolving.…”