Scientists have determined that population decline caused by climatic change occurred about 930,000 years ago. The analysis doesn’t persuade other specialists.
Homo sapiens have affected every area of the globe, from the rainforests that were destroyed to make way for agriculture to the deep oceans that are now contaminated with microplastic to the jet streams that have changed the climate. The number of people on earth surpassed 8 billion in November.
But despite the fact that we may currently be everywhere, a group of experts now asserts that humans nearly did not exist at all.
The ancestors of contemporary humans may have experienced a severe population decline 930,000 years ago, according to data discovered by Chinese researchers. They attribute the cause to a significant change in the climate that took place around that period.
During a time known as a bottleneck, our ancestors stayed in small numbers—fewer than 1,280 breeding individuals. Before the population started to grow again, it persisted for more than 100,000 years.
In the onset of the bottleneck, “about 98.7 percent of human ancestors were lost, thus threatening our ancestors with extinction,” the researchers wrote. The journal Science published their research on Thursday.
The research will have interesting ramifications if it holds up. It suggests that early humans may have divided into two evolutionary lineages, one of which gave rise to Neanderthals and the other to modern humans, as a result of a climate-driven bottleneck.
But outside specialists claimed they had doubts about the cutting-edge statistical techniques the study’s authors had employed. According to Stephan Schiffels, a population geneticist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, “it is a bit like estimating the size of a stone that falls into the middle of a large lake from only the ripples that come at the shore some minutes later.”
By examining the genomes of live humans, researchers have been reconstructing the evolution of our species for many years. All of the research make use of the same fundamental biological truths: every child is born with a variety of new genetic mutations, some of which can be passed down over hundreds or even millions of years.
With the advancement of DNA sequencing technology, these research have become more complex. These days, researchers can compare the whole genomes of individuals from other groups.
Each of the nearly 3 billion genetic letters in the human genome, each of which has been passed down for tens of thousands or millions of years, serves as a massive archive of human history. Researchers now utilize ever-more-powerful computers that can process the enormous numbers of computations necessary for more accurate models of human evolution to read that history.
Over the course of more than a decade, Haipeng Li and his colleagues at the Chinese Academy of Sciences in Shanghai developed their own approach to reconstructing evolution.
Fast Infinitesimal Time Coalescent is how the researchers refer to their technique, which they call FitCoal. Scientists may develop a model of a million years of development divided into periods of months using FitCoal, which enables them to slice history into precise time slices.
It’s a technique we developed to understand the evolution of various groupings of living things, from people to plants, according to Dr. Li.
“All humans with 24 pairs of chromosomes turned extinct, while only a tiny isolated population with 23 pairs of chromosomes fortunately lived and passed down from generation to generation,” said Ziqian Hao, a bioinformatics researcher at Shandong First Medical University and one of the study’s authors.
Dr. Schiffels, however, is not yet convinced by the theory of the bottleneck: “The finding is very unexpected indeed, and I think the more shocking the claim, the better the evidence should be.”