Humans in their history have gone through “bottle neck effects” that nearly destroyed the chances of human existence as we know it today. It falls on the period between 930 and 813 thousand years ago, when climate change significantly worsened the living conditions of people.
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This was shown by a new method for determining the number of ancient people, reports EurekAlert, citing the Chinese Academy of Sciences.
It is noted that an international team of scientists, which included researchers from China, Italy and the United States, was able to accurately determine data on ancient demographics using modern human genomic sequences obtained from 3,154 people.
These findings indicate that early human ancestors went through a long, strict bottleneck in which approximately 1,280 breeding individuals could support a population for approximately 117,000 years.
This period also accounts for a gap in the identification of African and European fossils.
The reasons for this decline in the number of human ancestors are mainly climatic: glaciation around this time leads to temperature changes, severe droughts and the disappearance of other species that could potentially serve as a source of food for human ancestors, the article notes.
Scientists estimate that 65.85% of modern genetic diversity could have been lost due to this bottleneck, and a long period of minimum breeding numbers threatened humanity as we know it today.
However, this period also appears to have contributed to speciation—during it, two chromosomes in the human genome likely fused to form what is now known as “chromosome 2” in modern humans. As a result, humans now have 23 pairs of chromosomes, as opposed to 24 pairs of chromosomes in other primates such as chimpanzees.
It was probably during this period that the last common ancestor of modern humans lived, Neanderthals and Denisovans, who are also believed to have 23 chromosomes.
The new find opens up a new area in 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 the evolution of the human brain, the researchers note.
In the future, the “taming” of fire, as well as climate change to a more favorable for life 813 thousand years ago, could contribute to further rapid growth in the human population.
Source: EurekAlert
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I am David Wyatt, a professional writer and journalist for Buna Times. I specialize in the world section of news coverage, where I bring to light stories and issues that affect us globally. As a graduate of Journalism, I have always had the passion to spread knowledge through writing.