The importance of gene flow in human evolution
-
Published:2023-07-02
Issue:
Volume:
Page:1-22
-
ISSN:
-
Container-title:Human Population Genetics and Genomics
-
language:en
-
Short-container-title:Hum Popul Genet Genom
Affiliation:
1. Department of Biology & Division of Statistical Genomics, Washington University, St. Louis, MO 63130, USA
Abstract
By the latter half of the 20th century, there were three dominant models of human evolution. All three accepted an African origin of humans at the Homo erectus stage, with H. erectus expanding out of Africa and colonizing Eurasia near the beginning of the Pleistocene. The candelabra model had H. erectus splitting into mostly isolated geographical lineages that independently evolved into the modern African, European and Asian “races”. The out-of-Africa replacement model starts out like the candelabra model, but then posits that Homo sapiens first evolved in Africa and then expanded out of Africa in the late Pleistocene and replaced all of the archaic Eurasian populations without interbreeding with them. Neither of these models assign an important role to gene flow (genetic interchange). In contrast, the multiregional model regarded the human populations in Africa and Eurasia as experiencing gene flow throughout the Pleistocene and evolving as a single human lineage with some local differentiation. Studies on mitochondrial DNA in the 1980’s claimed to support the out-of-Africa replacement model and to falsify both the candelabra and multiregional models by mistakenly equating the two. In fact, the mitochondrial DNA studies were fully compatible with both the replacement and multiregional models. The first statistically significant discrimination between these two models appeared in 2002 and revealed a hybrid model in which there was a mid-Pleistocene and a late Pleistocene expansion of humans out of Africa that resulted in limited genetic interchange with Eurasians rather than complete replacement. Moreover, significant gene flow and population movements led to genetic interchange throughout the mid-Pleistocene to the present. Studies on genomic data and ancient DNA have strongly confirmed these inferences. Moreover, our modern species of humans was forged in an African multiregional metapopulation rather than arising from one local area of Africa. Thus, gene flow has played a dominant role in human evolution since the mid-Pleistocene whereas splits and isolation have not. This undercuts the idea that human races are biologically real categories or separate branches on an evolutionary tree.
Publisher
Pivot Science Publications Corporation
Subject
General Medicine,General Medicine,General Medicine,General Medicine,Energy Engineering and Power Technology,Fuel Technology,General Medicine,General Medicine,General Medicine,General Medicine,General Medicine
Reference70 articles.
1. Rightmire GP. Homo sapiens in Sub-Saharan Africa. In: Smith FH, Spencer F, editors. The Origins Of Modern Humans: A World Survey Of The Fossil Evidence. New York: Liss; 1984. p. 295–326.
2. Coon CS. The Origin of Races. New York: Knopf; 1962.
3. Weidenreich F. Some problems dealing with ancient man. Am Anthropol. 1940;42:375–383.
4. Weidenreich F. Apes, Giants, and Man. Chicago: University of Chicago Press; 1946. vii, 122 p.
5. Dobzhansky T. On species and races of living and fossil man. Am J Phys Anthropol. 1944;2(3):251–265.