The first human settlement of the New World: A closer look at craniofacial variation and evolution of early and late Holocene Native American groups

The relative contribution of drift and selection to phenotypic divergence: A test case using the horseshoe bats Rhinolophus simulator and Rhinolophus swinnyi

“…However, evidence for significant deviations from neutrality were also found in craniofacial variation of early and late Holocene Native American groups (de Azevedo et al., ). Contrary to our study, these studies also found that selection (and drift) was differentially expressed across different features of the phenotype and/or across different localities (de Azevedo et al., ). There are currently no examples of studies in which this approach was used on bats.…”

“…Only parametric tests for subsequent analyses were used because the majority of our variables satisfied normality and homogeneity of variances among populations as in Ackermann and Cheverud () and in Ackermann and Cheverud (). Furthermore, variance patterns rather than absolute sizes are central to the approach we used, so that minor violation of homogeneity of variances is generally not considered a major concern (de Azevedo et al., ).…”

“…This rationale was also based on similar reasoning as in de Azevedo et al. () when they excluded a PC at a time to assess whether different regions of human skulls differentially experienced drift/selection. Lande's model was therefore repeated excluding (1) a population at a time, (2) a PC at a time, and (3) a combination of populations and PCs.…”

“…The quantitative theory of genetic evolution as described by the Lande's model (Lande, ) has been applied to assess whether random evolutionary processes alone can explain phenotypic divergence (Ackermann & Cheverud, , ; de Azevedo et al., ; Smith, ). The theory postulates a null model of drift, the rejection of which suggests that selection can be inferred (Smith, ).…”

“…For example, using this approach, the roles of both drift and selection were identified in the skulls of primates (Marroig & Cheverud, ). Although strong selective forces were also identified in some regions of the human skull (de Azevedo et al., ), genetic drift was shown to be the primary process in the diversification of facial features and skull structure of the genus Homo (Ackermann & Cheverud, ; Smith, ) and in the skull morphology of monkeys (Marroig & Cheverud, ; Marroig, Vivo, & Cheverud, ). Thus, adaptive explanations may be over‐represented if not weighed against a null model of drift (Marroig & Cheverud, ).…”