However studies of protein polymorphisms as well as mt DNA haplotypes, X-chromosome and Y-chromosome haplotypes, autosomal microsatellites and minisatellites, Alu elements, and autosomal haplotypes indicate that the roots of the population trees constructed from these data are composed of African populations and/or that Africans have the most divergent lineages, as expected under a recent African origin rather than a multi-regional emergence model.Additionally, studies of autosomal, X-chromosomal haplotype and mt DNA variation indicate that Africans have the largest number of population-specific alleles and that non-African populations harbor a subset of the genetic diversity that is present in Africa, as expected if there was a genetic bottleneck when modern humans migrated out of Africa.
Our divergence from other primates may thus be due in part to alternative splicing.
If we consider the likely effects of the out of Africa hypothesis, we would expect that founding African populations not subject to active expansion and migration would have greater genetic diversity and that the genetic makeup of other world populations would come from a subset of the African diversity, consisting of those subgroups who migrated.
A recent bottleneck event and/or colonization and extinction events among non-African populations, or a more recent onset of population growth in non-Africans, could also cause a decrease in genetic diversity (Tishkoff and Verrelli R692).
In fact the complete inter-fertility of all human populations and the relative lack of genetic divergence by comparison with the few remaining chimp colonies in the wild (Hrdy R330 183) does indicate a significant bottleneck.
The insertions and deletions of the million or so Alu elements in the human genome (p 332) are particularly useful, as the most active sub-population of about 1000 Alu is actively transcribing and undergoing rapid change.
A subpopulation of Alu are capable of generating new coding regions (exons), when inserted into non-coding introns between spliced sections of a translated m RNA, because one base-pair change within Alu leads to formation of a new exon reading into the surrounding DNA.
Analysis of genetic variation among ethnically diverse human populations indicates that populations cluster by geographic region (i.e., Africa, Europe/Middle East, Asia, Oceania, New World) and that African populations are highly divergent.
The mt DNA studies hypothesize a primal female ancestor - the African Eve - around 150,000 years ago (Chen et. R116) while the Y-chromosome Adam is more recent, at around 90,000 years ago (Underhill et. R711) consistent with the greater reproductive variance of males than females.
Alus may have given rise, through alternative splicing, to new proteins that drove primates' divergence from other mammals.
Recent studies have shown that the nearly identical genes of humans and chimps produce essentially the same proteins in most tissues, except in parts of the brain, where certain human genes are more active and others generate significantly different proteins through alternative splicing of gene transcripts.
The Volcanic Winter/Weak Garden of Eden model proposed in Ambrose 1998.