We can all agree that if a story took place almost a million years ago, it can hardly be called ‘news’.
But a recent scientific study, based on a vast analysis of genetic material from various today’s populations, has uncovered a cataclysmic event in human evolution that nearly wiped out our pre-Homo-Sapiens ancestors for good.
Complex genetic ‘family trees’ tell a tale of destruction and survival, of endurance and evolution – a pre-historic saga that is bound to make us proud of our ancestral populations.
A small group of around a thousand individuals carried the torch of our future humanity. Everyone alive today is a descendant of these titans.
“Human ancestors in Africa were pushed to the brink of extinction around 900,000 years ago, a study shows. The work1, published in Science, 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 just 1,280 and didn’t expand again for another 117,000 years.
‘About 98.7% of human ancestors were lost’, says Haipeng Li, a population geneticist at the University of Chinese Academy of Sciences in Beijing, who co-led the study. He says that the fossil record in Africa and Eurasia between 950,000 and 650,000 years ago is patchy and that ‘the discovery of this bottleneck may explain the chronological gap’.
Nick Ashton, an archaeologist at the British Museum in London, who wrote a related perspective, says he was intrigued by the tiny size of the population. ‘This would imply that it occupied a very localized area with good social cohesion for it to survive’, he says. ‘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’.”
If you think it sounds like an impossible discovery to make, you are right. Researchers needed to invent new tools to pull this off.
Genome sequencing is a tool used to improve scientists’ understanding the evolution of population sizes.
“The researchers’ method allowed them to reconstruct ancient population dynamics based on genetic data from modern-day humans. By constructing a complex family tree of genes, the team was able to examine the finer branches of the tree with greater precision, identifying significant evolutionary events.”
The period with the population reduction is part of the ‘Early-Middle Pleistocene transition’ — when glacial cycles became longer and more intense.
Sudden changes like that might have wiped out certain human ancestors, and at the same time forced new human species to emerge.
It was only around 813,000 years ago that the population of pre-humans began to grow again. At this point we have no idea how our ancestors managed to survive and flourish once more.
Astonishing. The population of human ancestors dropped to an estimated total of a thousand or so individuals on the whole planet during the mid-Pleistocene ~800,000 years ago. We are all their descendants. https://t.co/2YAUg3DOJW
— Derek Tracy (@Derektracy1) August 31, 2023
“Population bottlenecks are events in which a species’ total population is severely reduced, which causes an overall reduction in genetic diversity across the species. The loss of genetic diversity can cause populations to become less healthy.
[…] The recent team of researchers developed a tool called the fast infinitesimal time coalescent process (FitCoal) to analyze 3,154 present-day genomes from 10 African and 40 non-African populations. The researchers found evidence of a ‘severe population bottleneck’ in each of the 10 African populations that ‘brought the ancestral human population close to extinction’, as the scientists wrote in their paper. The team posits that the bottleneck may have been due to climatic changes.”
Nick Ashton, archaeologist, British Museum:
“Whatever caused the proposed bottleneck may have been limited in its effects on human populations outside the H. sapiens lineage, or its effects were short-lived. This also implies that the cause of the bottleneck was unlikely to have been a major environmental event, such as severe global cooling, because this should have had a wide-ranging impact.”
If this discovery speaks about the vulnerability of early human populations leading to our evolutionary lineage being nearly eradicated, on the other hand it also pays testimony to the endurance of our kind when faced with an extreme, life altering set of circumstances.