Deciphering African late middle Pleistocene hominin diversity and the origin of our species

Marta Mirazón Lahr,Aurélien Mounier

doi:10.1038/s41467-019-11213-w

Abstract

The origin of Homo sapiens remains a matter of debate. The extent and geographic patterning of morphological diversity among Late Middle Pleistocene (LMP) African hominins is largely unknown, thus precluding the definition of boundaries of variability in early H. sapiens and the interpretation of individual fossils. Here we use a phylogenetic modelling method to predict possible morphologies of a last common ancestor of all modern humans, which we compare to LMP African fossils (KNM-ES 11693, Florisbad, Irhoud 1, Omo II, and LH18). Our results support a complex process for the evolution of H. sapiens, with the recognition of different, geographically localised, populations and lineages in Africa – not all of which contributed to our species’ origin. Based on the available fossils, H. sapiens appears to have originated from the coalescence of South and, possibly, East-African source populations, while North-African fossils may represent a population which introgressed into Neandertals during the LMP.

Highlights

The origin of Homo sapiens remains a matter of debate
The early H. sapiens group is morphologically close to the H. sapiens virtual Last Common Ancestors (vLCAs) and fits within the 95% confidence envelope computed around them
The data were collected by a single operator; we reduced the number of variables by using PCs53 instead of aligned 3D coordinates throughout the study, and test models were run on nonslid semilandmarks, as well as subsamples of landmarks and semilandmarks (Supplementary Figs. 7–10)

Summary

Introduction

The origin of Homo sapiens remains a matter of debate. The extent and geographic patterning of morphological diversity among Late Middle Pleistocene (LMP) African hominins is largely unknown, precluding the definition of boundaries of variability in early H. sapiens and the interpretation of individual fossils. Our results support a complex process for the evolution of H. sapiens, with the recognition of different, geographically localised, populations and lineages in Africa – not all of which contributed to our species’ origin. Models for the origin of our species, H. sapiens, have moved away from the confrontation of two extreme antagonistic points of view: (1) the Multiregional Model of modern human origins implying the gradual evolution of global archaic hominin populations towards a modern human morphology over the course of the last 2 million years;[9,10] and (2) the hypothesis of a unique Out of Africa event[1], known as the Recent African. Origin (RAO) model, implying a single African origin (200,000–100,000 years ago (ka)) of modern humans and subsequent replacement of all archaic populations. Along with the understanding of the evolutionary mechanisms that gave rise to the Neandertals in Europe[12], and a growing number of genetic studies[13,14], those models paved the way for a shift of emphasis from replacement to the potentially varied demographic and genetic outcomes of recent hominin interactions[7,9,15,16,17]

Methods

Results

Conclusion