The core formula of our new inference method is shown. The image depicts a cliff painting, illustrating the population of human ancestor pull together to survive the unknown danger in the darkness during the ancient severe bottleneck. Credit: Shanghai Institute of Nutrition and Health, CAS
Key points:
- A new method called FitCoal determined that early human ancestors went through a prolonged and severe bottleneck during the early to middle Pleistocene era.
- Approximately 65.85% of current genetic diversity may have been lost during the bottleneck.
- The FitCoal method could also be used to answer other questions about early human ancestry and evolution.
Researchers developed a new method to infer ancient population size and found that early human ancestors went through a prolonged, severe bottleneck during which approximately 1,280 breeding individuals sustained the population for about 117,000 years.
The research team used a novel method called FitCoal (fast infinitesimal time coalescent process) to accurately determine demographic inferences by using modern-day human genomic sequences from 3,154 individuals. The study, published in Science, found that early human ancestors experienced extreme loss of life leading to loss of genetic diversity. Possible reasons for the dramatic population downturn include glaciation events leading to changes in temperatures, severe droughts, and loss of food source species.
“The gap in the African and Eurasian fossil records can be explained by this bottleneck in the Early Stone Age,” explained the study’s author Giorgio Manzi of Sapienza University of Rome. “It coincides with this proposed time period of significant loss of fossil evidence.”
An estimated 65.85% of current genetic diversity may have been lost during the bottleneck in the early to middle Pleistocene era. Although the prolonged period of small breeding numbers threatened humanity, the bottleneck contributed to a speciation event where two ancestral chromosomes converged to form what is known as chromosome 2 in modern humans.
“The novel finding opens a new field in human evolution,” said Yi-Hsuan Pan, professor at East China Normal University. “It evokes many questions, such as the places where these individuals lived, how they overcame the catastrophic climate changes, and whether natural selection during the bottleneck has accelerated the evolution of human brain.”
The findings along with FitCoal methodology provide the opportunity to answer more questions about early human ancestry and evolution. Researchers can now focus on data from 813,000 years ago to examine a possible ancestral struggle and the underpinnings of a rapid population increase.