Y chromosome diversity, human expansion, drift, and cultural evolution

Abstract

The relative importance of the roles of adaptation and chance in determining genetic diversity and evolution has received attention in the last 50 years, but our understanding is still incomplete. All statements about the relative effects of evolutionary factors, especially drift, need confirmation by strong demographic observations, some of which are easier to obtain in a species like ours. Earlier quantitative studies on a variety of data have shown that the amount of genetic differentiation in living human populations indicates that the role of positive (or directional) selection is modest. We observe geographic peculiarities with some Y chromosome mutants, most probably due to a drift-related phenomenon called the surfing effect. We also compare the overall genetic diversity in Y chromosome DNA data with that of other chromosomes and their expectations under drift and natural selection, as well as the rate of fall of diversity within populations known as the serial founder effect during the recent “Out of Africa” expansion of modern humans to the whole world. All these observations are difficult to explain without accepting a major relative role for drift in the course of human expansions. The increasing role of human creativity and the fast diffusion of inventions seem to have favored cultural solutions for many of the problems encountered in the expansion. We suggest that cultural evolution has been subrogating biologic evolution in providing natural selection advantages and reducing our dependence on genetic mutations, especially in the last phase of transition from food collection to food production.

The ‘extremely ancient’ chromosome that isn’t: a forensic bioinformatic investigation of Albert Perry’s X-degenerate portion of the Y chromosome

“…Therefore, the opportunity for a stochastic change differs correspondingly and has profound effects on the Y chromosome, particularly when occurring in small populations with low effective deme sizes, such as those that The 'extremely ancient' chromosome that isn't E Elhaik et al have characterized humankind for most of its evolution. 31 In the Mbo samples described by Mendez et al, 2 as having A00 haplotypes, the main contribution to the variation was by genetic drift. Consequently, these haplotypes are derived from a common ancestor who lived only a few centuries ago (Mendez et al 2 ), not 338 000 ya, when a common ancestor of A00 population was reported to live.…”

The phylogenetic and geographic structure of Y-chromosome haplogroup R1a

“…Within R1-M173, most variation extant in Eurasia is confined to R1a-M420 and R1b-M343. 16 In Europe, R1a is most frequent in the east, and R1b predominates in the west. 17 It has been suggested that this division reflects episodic population expansions during the post-glacial period, including those associated with the establishment of agricultural/ pastoral economies.…”

A major Y-chromosome haplogroup R1b Holocene era founder effect in Central and Western Europe

“…2,3 Although haploid genealogies capture only a narrow ancestry spectrum of the history of a population's gene pool, they afford a relatively uncomplicated and unique approach to disentangle and investigate complexities created by the superimposition of later gene flow patterns onto preexisting substrates, revealing population formation and affinities as well as insights into gender-related levels of reproductive success. 2,4 Using the conventional Y-chromosome haplogroup nomenclature, the majority of lineages observed in contemporary European populations fall into the following main haplogroups: E, G, I, J, N and R. Typically, 450% of men in Europe are affiliated with haplogroup R. 5,6 Members of haplogroup R are also widespread in Western, 7,8 Central 9 and Southern Asia 10,11 as well as in some parts of the Sahel region of Africa. 12,13 In Europe, essentially all R associates belong to its sub-clade R1 defined by M173.…”