Humanity owes its existence to just 1,280 people who nearly died out, study finds. A new method for estimating ancient populations has revealed a potential way in which humanity could have nearly disappeared. Researchers believe our ancestors dwindled to just 1,280 breeding individuals during the Pleistocene.
A controversial study claims it can explain a gap in the African-Eurasian fossil record. A team of researchers has published a paper in the journal Science arguing that there was a “serious bottleneck” in the human population chain – so severe that 930,000 years ago, the number of human ancestors dropped to about 1,280 breeding individuals, virtually wiping out the human population.
An international research team says glaciations were responsible for the dramatic decline in life between 930,000 and 813,000 years ago. It has created a “new method” – a rapid process of merging infinitesimally small time intervals – to pinpoint demographic data.
A new study points to an estimated 117,000-year-long severe population decline that would have nearly wiped out Pleistocene ancestors, eliminating 98.7 percent of the population before humans could actually establish civilization. That means the entire current human population can be traced back to those 1,280 individuals, according to the study.
“The gap in the African and Eurasian fossil records can be explained by this bottleneck in the Early Stone Age from a chronological point of view,” Giorgio Manzi, senior author and an anthropologist at Sapienza University in Rome, said in a press release. “This coincides with this proposed time period of significant loss of fossil evidence.”
But not everyone is convinced. “The global collapse hypothesis is inconsistent with the archaeological and human fossil evidence,” counters Nicholas Ashton, a paleolithic archaeologist at the British Museum who was not involved in the study, according to Science. “Questions remain about what caused the bottleneck and what, 120,000 years later, led to the expansion.”
The study’s authors believe that glaciations changed temperatures, caused droughts and wiped out species that were potentially used as food sources by human ancestors — all factors that would have made life difficult for humans on Earth. They have no explanation for the sudden population growth that followed.
The authors argue that during the early and middle Pleistocene, which coincides with a long period of minimal reproduction in individuals, approximately 65 percent of genetic diversity may have been lost.
The study also suggests that population decline may have contributed to the differentiation of Neanderthals, Denisovans and modern humans.
“The new discovery opens up a new area of human evolution as it raises many questions, such as where these people lived, how they overcame catastrophic climate change, and whether natural selection during the bottleneck accelerated human brain evolution,” Yi-Xuan Pan, senior author and a researcher in evolutionary and functional genomics at East China Normal University, said in a press release.
However, the accuracy of the results may be a stretch, says Stefan Schiffels, head of the population genetics group at Germany’s Max Planck Institute for Evolutionary Anthropology. He is “extremely skeptical” that the study can come up with such precise numbers, and that it will “never be possible” for such an ancient study to be confident of such a precise figure.
The new study is based on a computational model that looks at 3,154 modern human genome sequences and extrapolates genetic mutations to go back in time and show that early human ancestors suffered huge losses in lifespan and genetic diversity.
Schiffels also noted that the data used in the study is not new, and that none of the previous models showed a population decline.
Janet Kelso, a computational biologist at the Max Planck Institute, told Science that this bottleneck concept may not be as widespread as the authors believe, saying that the genetic signals for it are only strong in modern African populations. This means that any potential bottleneck would likely be limited to certain ancestral populations. The findings, she says, “while intriguing, should probably be taken with some caution and investigated in more detail.”
“There was a ‘virtually unanimous reaction’ among population geneticists, people working in this field, that the paper was unconvincing,” Aylwin Scully, a human evolutionary geneticist at the University of Cambridge, told AFP.