You see it quoted so often that you’d be mistaken for thinking everyone agrees on the ‘we are all descended from a small group of Africans that left the continent 70,000 years ago’.
It’s something that pleases the liberal media, not something geneticists agree on. Ive seen research items other than these rip into the ‘out of Africa theory’ before.I’d like to point out (ad nauseum) that human remains have been found in China over 100k old, making the date part ridiculous. There are remains of modern humans 162k old in Morocco, and 125k old in Israel.
I recommend a careful read of this link, it’s an extremely thorough hatchet job on the ‘Out of Africa’ theory, showing the evidence against it better than I ever could.
X chromosome evidence for ancient human histories
Eugene E. Harris and Jody Hey*
Diverse African and non-African samples of the X-linked PDHA1 (pyruvate dehydrogenase E1 subunit) locus revealed a fixed DNA sequence difference between the two sample groups. The age of onset of population subdivision appears to be about 200 thousand years ago. This predates the earliest modern human fossils, suggesting the transformation to modern humans occurred in a subdivided population. The base of the PDHA1 gene tree is relatively ancient, with an estimated age of 1.86 million years, a late Pliocene time associated with early species of Homo. PDHA1 revealed very low variation among non-Africans, but in other respects the data are consistent with reports from other X-linked and autosomal haplotype data sets. Like these other genes, but in conflict with microsatellite and mitochondrial data, PDHA1 does not show evidence of human population expansion.
The human RRM2P4 pseudogene has a pattern of nucleotide polymorphism that is unlike any
locus published to date. A gene tree constructed from a 2.4 kb fragment of the RRM2P4 locus
sequenced in a sample of 41 worldwide humans clearly roots in East Asia and has a most recent common ancestor ~2 million years before the present. The presence of this basal lineage exclusively in Asia results in higher nucleotide diversity among non-Africans than Africans. A global survey of a single nucleotide polymorphism that is diagnostic for the basal, Asian lineage in 570 individuals shows that it occurs at frequencies up to 53% in south China, while only one of 177 surveyed Africans carries this archaic lineage. We suggest that this ancient lineage is a remnant of introgressive hybridization between expanding anatomically modern humans emerging from Africa and archaic populations in Eurasia.
Fossil evidence links human ancestry with populations that evolved modern gracile morphology in Africa 130,000 – 160,000 years ago. Yet fossils alone do not provide clear answers to the question of whether the ancestors of all modern Homo sapiens comprised a single African population or an amalgamation of distinct archaic populations. DNA sequence data have consistently supported a single origin model in which anatomically modern Africans expanded and completely replaced all other archaic hominin populations. Aided by a novel experimental design, we present the first genetic evidence that statistically rejects the null hypothesis that our species descends from a single, historically panmictic population. In a global sample of 42 X chromosomes, two African individuals carry a lineage of non-coding 17.5 kilobase sequence that has survived for over one million years without any clear traces of ongoing recombination with other lineages at this locus. These patterns of deep haplotype divergence and long-range linkage disequilibrium are best explained by a prolonged period of ancestral population subdivision followed by relatively recent interbreeding. This inference supports human evolution models that incorporate admixture between divergent African branches of the genus Homo.
*Howard Hughes Medical Institute, Departments of Human Genetics and Ecology and Evolution, and Committee on Genetics, University of Chicago, Chicago, IL 60637
Edited by Henry C. Harpending, University of Utah, Salt Lake City, UT, and approved October 5, 2006 (received for review August 10, 2006)
At the center of the debate on the emergence of modern humans and their spread throughout the globe is the question of whether archaic Homo lineages contributed to the modern human gene pool, and more importantly, whether such contributions impacted the evolutionary adaptation of our species. A major obstacle to answering this question is that low levels of admixture with archaic lineages are not expected to leave extensive traces in the modern human gene pool because of genetic drift. Loci that have undergone strong positive selection, however, offer a unique opportunity to identify low-level admixture with archaic lineages, provided that the introgressed archaic allele has risen to high frequency under positive selection. The gene microcephalin (MCPH1) regulates brain size during development and has experienced positive selection in the lineage leading to Homo sapiens. Within modern humans, a group of closely related haplotypes at this locus, known as haplogroup D, rose from a single copy 37,000 years ago and swept to exceptionally high frequency (70% worldwide today) because of positive selection. Here, we examine the origin of haplogroup D. By using the interhaplogroup divergence test, we show that haplogroup D likely originated from a lineage separated from modern humans 1.1 million years ago and introgressed into humans by 37,000 years ago. This finding supports the possibility of admixture between modern humans and archaic Homo populations (Neanderthals being one possibility). Furthermore, it buttresses the important notion that, through such adminture, our species has benefited evolutionarily by gaining new advantageous alleles. The interhaplogroup divergence test developed here may be broadly applicable to the detection of introgression at other loci in the human genome or in genomes of other species.
A consideration of the morphological aspects of the earliest modern humans in Europe (more than ≈33,000 B.P.) and the subsequent Gravettian human remains indicates that they possess an anatomical pattern congruent with the autapomorphic (derived) morphology of the earliest (Middle Paleolithic) African modern humans. However, they exhibit a variable suite of features that are either distinctive Neandertal traits and/or plesiomorphic (ancestral) aspects that had been lost among the African Middle Paleolithic modern humans. These features include aspects of neurocranial shape, basicranial external morphology, mandibular ramal and symphyseal form, dental morphology and size, and anteroposterior dental proportions, as well as aspects of the clavicles, scapulae, metacarpals, and appendicular proportions. The ubiquitous and variable presence of these morphological features in the European earlier modern human samples can only be parsimoniously explained as a product of modest levels of assimilation of Neandertals into early modern human populations as the latter dispersed across Europe. This interpretation is in agreement with current analyses of recent and past human molecular data.