Hominoid Cranial Evolution

Abstract

Extant hominoid cranial variability, although marked, represents only a remnant of a temporally and geographically expansive evolutionary history. Attempts to reconstruct the evolutionary processes that have played a role in the morphological divergence of this superfamily have been complicated by a sparse hominoid fossil record, and ambiguity related to phylogenetic relationships. Moreover, morphological variation in the cranium is influenced by a complex combination of functional, developmental and architectural constraints, complicating our ability to tease apart specific evolutionary pressures. However, due to advances in the field of evolutionary quantitative genetics, recent studies of extant hominoid taxa have reconstructed the potential evolutionary processes that have generated cranial diversity. Collectively, these studies have shown that directional selection, although identified in the evolutionary path to hominins, was not the major driving force behind this divergence. Rather, it is a combination of genetic drift and stabilising selection that characterises the evolution of the hominoid cranium. Key Concepts Morphological diversity in the hominoid cranium is extensive. Cranial diversity is influenced by evolutionary, developmental, functional, structural forces and constraints. Extant hominoids are a small fraction of all hominoids that have ever lived. The hominoid fossil record is fragmentary and phylogenetic relationships are ambiguous. Quantitative genetic analyses indicate a combination of evolutionary processes have shaped the hominoid cranium.

Peopling the Americas: Not “Out of Japan”

“…Additionally, the small population size of hunter-gatherer populations like Jomon, coupled with isolation and population differentiation across the archipelago, is consistent with stochastic effects on the genome. Such stochastic effects (genetic drift) are equally powerful modifiers of morphometric phenotypes (Fukase et al 2012;Morita et al 2012;Schroeder and von Cramon-Taubadel 2020;von Cramon-Taubadel 2019). Such patterns of diversity and differentiation among geographically dispersed Jomon might well result in the expanded variation observed in Jomon dental morphology and the apparent affinity of these morphological phenotypes with a variety of early ancestral and subsequent descendant groups.…”