Tag: evolution

70 ka Human bottleneck

From one of my favorite projects, the Genographic Project.

Human beings may have had a brush with extinction 70 ka BP. The human population at that time was reduced to small isolated groups in Africa, apparently because of drought. The number of early humans may have shrunk as low as 2k before numbers began to expand again in the early Stone Age.

2023-08-31: And an even more severe, earlier bottleneck

Human ancestors in Africa were pushed to the brink of extinction 900 ka BP. It suggests a drastic reduction in the population of our ancestors well before our species, Homo sapiens, emerged. The population of breeding individuals was reduced to 1280 and didn’t expand again for 117 ka. “98.7% of human ancestors were lost”. The fossil record in Africa and Eurasia between 950 ka and 650 ka BP is patchy and that “the discovery of this bottleneck may explain the chronological gap”. “Of greater surprise is the estimated length of time that this small group survived. If this is correct, then one imagines that it would require a stable environment with sufficient resources and few stresses to the system.”

Hiccups

Spasms in our diaphragms, hiccups are triggered by electric signals generated in the brain stem. Amphibian brain stems emit similar signals, which control the regular motion of their gills. Our brain stems, inherited from amphibian ancestors, still spurt out odd signals producing hiccups that are essentially the same phenomenon as gill breathing.

maybe we should (optionally) get gills back?

100x faster human evolution?

On top you can see human population growth over time on a log scale, so the increase really is much sharper than what you see. Below is a chart which displays the number of selected variants which began to rise in frequency particular time in the past for 2 populations. There seems to be a concomitant rise in adaptive mutations which began to be selected along with increased population size.

has evolution sped up 100x for humanity? Up to 10% of the human genome appears to be evolving at the maximum rate, more quickly than ever before in human history.