Today is Saturday, September 09, 2023.
We start quoting Science Magazine Editor Mrs. Sacha Vignieri, from her summary about this study: "Today, there are more than 8 billion human beings on the planet."
(Carbon Credit Markets adds that around 1950 we were about 2 billion).
She goes on "We dominate Earth’s landscapes, and our activities are driving large numbers of other species to extinction ... a newly developed ... model detected a reduction in the population size of our ancestors from about 100,000 to about 1,000 individuals, which persisted for about 100,000 years. The decline appears to have coincided with both major climate change and subsequent speciation events."
She refers to a recent study led by Wangjie Hu of the Chinese Academy of Sciences in Shanghai, whose team developed a method that allowed them to reconstruct ancient population dynamics on the basis of genetic data from present-day humans. By constructing a complex family tree of genes, the team was able to precisely identify significant evolutionary events. And eventually explain the chronological gap of the lack of fossil records in Africa and Eurasia between 950,000 and 650,000 years ago.
According to a Nature article, "This period was part of the Early-Middle Pleistocene transition, a time of drastic climate change, when glacial cycles became longer and more intense and long periods of drought spread in Africa.
There are several scientific and geologic studies indicating that indeed the mid-Pleistocene - 1.2 to 0.5 millions years ago - records fundamental changes in Earth’s climate state, where low-amplitude 41 thousand-years regular cycles gave way progressively to the high-amplitude, quasi-periodic 100 thousand-years fluctuations. Here is one (to download).
One co-author suggests “that the bottleneck was a global crash in population” and that the changing climate might have wiped out human ancestors and forced new human species to emerge. Eventually, "these might have evolved into the last common ancestor of modern humans and our extinct relatives, the Denisovans and Neanderthals."
On the other hand, refering to existing archaeological sites outside Africa, other scientists suggest that instead of an event of global scale it could have been of regional impact, with only parts of the Earth turning uninhabitable.
Interesting.
Click here for the original article at Science (only Abstract and Editor's summary are free access).
But if you click at the image below (Shutterstock) you have the article at Nature.
