Ancient human ancestors faced a critical brush with extinction during a significant ‘evolutionary bottleneck’ around 800,000 to 900,000 years ago, as per findings by scientists. An examination of the genetic makeup of over 3,000 contemporary individuals has indicated that the overall population of our ancestors dwindled to approximately 1,280 breeding individuals over a span of about 117,000 years. Researchers posit that this bottleneck, which came alarmingly close to eradicating our ancestral lineage, might have been triggered by an extreme climatic event.
The numbers that emerge from our study correspond to those of species that are currently at risk of extinction.
Prof. Giorgio Manzi, an anthropologist at Sapienza University of Rome and a senior author of the research
Nonetheless, Manzi and his colleagues propose that the survival challenges presented by this bottleneck could have catalyzed the emergence of a new species, Homo heidelbergensis, which some speculate to be the common precursor of contemporary humans, as well as our relatives, the Neanderthals and Denisovans. Homo sapiens are generally believed to have appeared around 300,000 years ago.
We know that between about 900,000 and 600,000 years ago, the fossil record in Africa is very scarce, if not almost absent, while both before and after we have a greater number of fossil evidence. The same can be said for Eurasia: for example, in Europe we have a species known as Homo antecessor around 800,000 years ago and then nothing for about 200,000 years.
Prof. Giorgio Manzi n anthropologist at Sapienza University of Rome and a senior author of the research
Published in the journal Science, the study scrutinised genomic sequences extracted from a diverse cohort of 3,154 contemporary individuals hailing from 10 African and 40 non-African populations. By examining the various genetic variations within a population, it becomes possible to make approximate estimates of when specific genes first appeared. The greater the time elapsed, the higher the likelihood of encountering different gene variants. By tracking the frequency of gene emergence over time, scientists can glean valuable insights into the historical growth and contraction of ancestral populations.
The timing of this bottleneck roughly aligns with the period when it is believed that our last common ancestor with Neanderthals and another ancient human lineage, the Denisovans, inhabited the Earth. Researchers are now eager to explore whether genetic samples from these distant relatives also exhibit signs of this same bottleneck event, as it could provide fresh insights into when, where, and why these species diverged.
