Inferring archaic introgression from hominin genetic data.

Shyamalika Gopalan,Laura T Buck,Brenna M Henn,Elizabeth G Atkinson,Timothy D Weaver

doi:10.1002/evan.21895

Abstract

Questions surrounding the timing, extent, and evolutionary consequences of archaic admixture into human populations have a long history in evolutionary anthropology. More recently, advances in human genetics, particularly in the field of ancient DNA, have shed new light on the question of whether or not Homo sapiens interbred with other hominin groups. By the late 1990s, published genetic work had largely concluded that archaic groups made no lasting genetic contribution to modern humans; less than a decade later, this conclusion was reversed following the successful DNA sequencing of an ancient Neanderthal. This reversal of consensus is noteworthy, but the reasoning behind it is not widely understood across all academic communities. There remains a communication gap between population geneticists and paleoanthropologists. In this review, we endeavor to bridge this gap by outlining how technological advancements, new statistical methods, and notable controversies ultimately led to the current consensus.

Highlights

During the 1980s and 1990s, several models of modern human origins were vigorously debated by paleoanthropologists
H. sapiens originated over 1 million years ago and speciation between regional subpopulations was prevented by substantial gene flow.[1,2]
In light of the Neanderthal nuclear data, Currat and Excoffier revisited their spatially explicit models, and found that a hybridization rate of less than 2% was compatible with the estimated levels of Neanderthal ancestry in modern humans, and concluded that the new observations were still compatible with strong reproductive isolation between Neanderthal and anatomically modern humans (AMH) populations and a complete lack of mitochondrial DNA (mtDNA) sharing.[57]

Summary

Introduction

During the 1980s and 1990s, several models of modern human origins were vigorously debated by paleoanthropologists. The multiregional model proposed significant continuity between anatomically modern humans (AMH) and “archaic” progenitors in different regions of Eurasia and Africa. According to this view, H. sapiens originated over 1 million years ago and speciation between regional subpopulations was prevented by substantial gene flow.[1,2] The RAO model describes an exclusively, and relatively recent, African origin for H. sapiens, with subsequent global dispersal and rapid replacement of other hominin taxa at around 50,000–60,000 years ago (ka).[3,4,5] Intermediate between these extremes were models such as Bräuer's “hybridization and replacement” model, which posits an African origin, but allows for gene flow between African-derived H. sapiens and other hominin taxa during dispersals.[6,7] Likewise, Smith's and Trinkaus' assimilation models[8,9] are variations on the multiregional model in that they emphasize substantial and widespread gene flow between H. sapiens and other groups while acknowledging the central role of Africa as the primary birthplace of the species (Box 1)

Objectives

Methods

Findings

Conclusion