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Among the benefits of advances in genetic testing and analysis are capabilities for analyzing genomic data from thousands of years ago. This permits some initial clues to prehistoric and ancient population features and distributions. Given the relatively sparse (fossil) data and the novelty of the technologies, the results should be treated as tentative or suggestive.
You've probably seen articles discussing what genomic research suggests about the rise and dissemination of human ancestors in the distant past.
There's a lesser-known mystery that's surfaced in such retrospective genomic research concerning the possibility of a notable collapse affecting human males alone, occurring somewhere between 5,000 and 10,000 years ago.
This story began in 2015, with the publication of the following article:
A recent bottleneck of Y chromosome diversity coincides with a global change in culture
Genome Research. 2015. 25: 459-466
https://genome.cshlp.org/content/25/4/459.long
(Full article @ the URL cited above)
The research was originally aimed at finding clues relating to the 'Out of Africa' scenario. It turned out that in addition to their originally expected results, the team discovered what appears to be a marked 'bottleneck' in Y-chromosome (i.e., exclusively male) diversity circa 10,000 years ago. This bottleneck could represent a radical narrowing of male genetic diversity or even a collapse in the human male population.
If interpreted in terms of population, the estimated figures could be taken to suggest up to 17 times as many females as males during the bottleneck period.
The cause of this bottleneck wasn't clear, and the 2015 paper suggests it must have been related to non-biological (e.g., cultural) changes:
(NOTE: Estimated regional population is denoted by Ne )
You've probably seen articles discussing what genomic research suggests about the rise and dissemination of human ancestors in the distant past.
There's a lesser-known mystery that's surfaced in such retrospective genomic research concerning the possibility of a notable collapse affecting human males alone, occurring somewhere between 5,000 and 10,000 years ago.
This story began in 2015, with the publication of the following article:
A recent bottleneck of Y chromosome diversity coincides with a global change in culture
Genome Research. 2015. 25: 459-466
https://genome.cshlp.org/content/25/4/459.long
Abstract
It is commonly thought that human genetic diversity in non-African populations was shaped primarily by an out-of-Africa dispersal 50–100 thousand yr ago (kya). Here, we present a study of 456 geographically diverse high-coverage Y chromosome sequences, including 299 newly reported samples. Applying ancient DNA calibration, we date the Y-chromosomal most recent common ancestor (MRCA) in Africa at 254 (95% CI 192–307) kya and detect a cluster of major non-African founder haplogroups in a narrow time interval at 47–52 kya, consistent with a rapid initial colonization model of Eurasia and Oceania after the out-of-Africa bottleneck. In contrast to demographic reconstructions based on mtDNA, we infer a second strong bottleneck in Y-chromosome lineages dating to the last 10 ky. We hypothesize that this bottleneck is caused by cultural changes affecting variance of reproductive success among males.
(Full article @ the URL cited above)
The research was originally aimed at finding clues relating to the 'Out of Africa' scenario. It turned out that in addition to their originally expected results, the team discovered what appears to be a marked 'bottleneck' in Y-chromosome (i.e., exclusively male) diversity circa 10,000 years ago. This bottleneck could represent a radical narrowing of male genetic diversity or even a collapse in the human male population.
If interpreted in terms of population, the estimated figures could be taken to suggest up to 17 times as many females as males during the bottleneck period.
The cause of this bottleneck wasn't clear, and the 2015 paper suggests it must have been related to non-biological (e.g., cultural) changes:
(NOTE: Estimated regional population is denoted by Ne )
... The surprisingly low estimates of the male Ne might be explained either by natural selection affecting the Y chromosome or by culturally driven sex-specific changes in variance in offspring number. As the drop of male to female Ne does not seem to be limited to a single or a few haplotypes (Supplemental Fig. S3), selection is not a likely explanation. However, the drop of the male Ne during the mid-Holocene corresponds to a change in the archaeological record characterized by the spread of Neolithic cultures, demographic changes, as well as shifts in social behavior (Barker 2006). The temporal sequence of the male Ne decline patterns among continental regions (Supplemental Fig. S4B) is consistent with the archaeological evidence for the earlier spread of farming in the Near East, East Asia, and South Asia than in Europe (Fuller 2003; Bellwood 2005). A change in social structures that increased male variance in offspring number may explain the results, especially if male reproductive success was at least partially culturally inherited (Heyer et al. 2005). ...