The Evolutionary Radiation of Hominids: a Phylogenetic Comparative Study

S. Ivan Perez,Guido Rocatti

doi:10.1038/s41598-019-51685-w

Abstract

Over the last 150 years the diversity and phylogenetic relationships of the hominoids have been one of the main focuses in biological and anthropological research. Despite this, the study of factors involved in their evolutionary radiation and the origin of the hominin clade, a key subject for the further understanding of human evolution, remained mostly unexplored. Here we quantitatively approach these events using phylogenetic comparative methods and craniofacial morphometric data from extant and fossil hominoid species. Specifically, we explore alternative evolutionary models that allow us to gain new insights into this clade diversification process. Our results show a complex and variable scenario involving different evolutionary regimes through the hominid evolutionary radiation –modeled by Ornstein-Uhlenbeck multi-selective regime and Brownian motion multi-rate scenarios–. These different evolutionary regimes might relate to distinct ecological and cultural factors previously suggested to explain hominid evolution at different evolutionary scales along the last 10 million years.

Highlights

The origin and evolution of humans have been the main focus of biological and anthropological research during the last 150 years[1,2,3]
Changes in cranial size and shape were important for the evolutionary radiation of a clade as Hominoidea because they are believed to be related to numerous aspects of primate biology
Changes in craniofacial shape in extant and fossil Hominoidea species were studied by means of geometric morphometric techniques[28,30], using landmarks and semilandmarks on cranial surfaces obtained from computed tomographies (Fig. 1)

Summary

Introduction

The origin and evolution of humans have been the main focus of biological and anthropological research during the last 150 years[1,2,3]. In Primates there seems to be a close relationship between the locomotion and the relative position of the foramen magnum, the diet and the size and shape of the arcade, the social group size and the size and shape of the brain endocast, among others[22,23,24,25,26] In this context, studies interested in the evolutionary radiation of hominids have hypothesized some of these behavioural or ecological factors as the responsible for, or related with, the morphological changes observed in their crania[12,16]. Of this work is to gain new insights into the pattern of cranial diversification in hominid’s —with special emphasis on hominins— evolutionary radiations by using a full quantitative approach, and to compare the magnitude and pattern of variation with the closest relative clade, Hylobatidae family

Methods

Results

Conclusion