More on the association between low sperm motility or reduced sperm count with some y-haplogroups :
Y chromosome haplogroups may confer susceptibility to partial AZFc deletions and deletion effect on spermatogenesis impairment
AZF deletions and Y chromosomal haplogroups: history and update based on sequenceOriginally Posted by Yang et al.
Evidence for the association of Y-chromosome haplogroups with susceptibility to spermatogenic failure in a Chinese Han population
The haplogroup implicated in impaired spermatogenesis in the Chinese population is O3*.Originally Posted by Yang et al.
The association of Y chromosome haplogroups with spermatogenic failure in the Han Chinese
K is the ancestor of 90% of Y-DNA lineages in the world. But K* has virtually disappeared, except if some isolated parts of Asia, including western China. New mutations arose that obviously conferred an advantage over K*, so that only the men with the new mutations passed on their Y-DNA.Originally Posted by Lu et al.
Spermatogenic ability is different among males in different Y chromosome lineage
The haplogroup in question is D. This is not surprising as it was the first with C to reach Asia, but now survives only in isolated regions like Japan, Tibet, Yunnan, some Indonesian islands or the Andamans.Originally Posted by Kuroki et al.
Identification of a Y chromosome haplogroup associated with reduced sperm counts
The haplogroup numbers were taken from the Europe-wide study of Rosser et al. (2000). Based on the geographic distribution and the STR markers given, hg26 correspond to haplogroup Q.Originally Posted by Krausz et al.
The haplogroup with the highest sperm count in the study was hg1, which unsurprisingly is R1b, followed by hg3 (R1a) . This supports my hypothesis that R1a and R1b became dominant in Europe, in spite of their late Bronze-age arrival, thanks to a genetic predisposition to father more boys compared to other haplogroups. Indeed, a higher sperm count is one of the principal factors in raising the chances of having a boy rather than a girl.
The fourth haplogroup in the study, hg2+, represents haplogroup I. The difference in sperm count between I and Q is not huge (41.4 against 30.8 mill/ml) in comparison to R1b (75.8 mill/ml).
Krausz et al. explain that :
With such a fast replacement rate, it could even be imagined that R1b arrived later than 2500 BCE in Western Europe, in fairly small number, and still would have become dominant without any massacre of indigenous men nor polygamy required.Most of the hg26+ men have very low sperm counts. Sperm counts within this range are associated with very poor reproductive success and, in the absence of assisted reproduction, these chromosomes will be rapidly eliminated from the population. Taking into account the hg26+ frequency in the Danish population (∼5%) and assuming a mean selective disadvantage for these chromosomes of 0.5, this Y chromosome lineage would disappear from the Danish population within 12 generations.
Considering that other studies have found that haplogroup E also had a low sperm count by European standard (but probably higher than most subclades of hg A and B), it is easy to imagine how R1b (V88) could have boomed in some parts of Africa. Once the haplogroup penetrated a tribe, the proportion of R1b to haplogroup A, B or E would rise very quickly, explaining how it could reach over 95% in some tribes of North Cameroon.