My scientist leads the creation of a new theory for the "population census" of ancient humans. About 900000 years ago, human ancestors were almost extinct
On September 1, 2023 (Beijing time), the international academic journal Science published the latest research results of Li Haipeng Research Group of the Chinese Academy of Sciences Shanghai Institute of Nutrition and Health and Pan Yixuan Research Group of the Institute of Brain Functional Genomics of East China Normal University online. This study created new theories in population genetics and computational biology, and found that humans experienced severe population bottlenecks during the transition period between the early and middle Pleistocene, around 900000 years ago, due to rapid climate and environmental changes, and their ancestors were almost extinct.
Conduct a "census" of ancient human populations
The changes in prehistoric population comprehensively reflect the changes in climate and environment during that period. Therefore, by using population genetics research methods to trace back, we can gain a deeper understanding of the formation of modern humans. Fossil records indicate that the last one million years were a critical period of human evolution, but research on human population history is mostly limited to the last 300000 to 100000 years. In recent years, ancient DNA sequencing technology has developed rapidly, but due to hot conditions that are not conducive to DNA preservation, it is impossible to extract ancient DNA from African human ancestor fossils dating back 300000 years.
Although there is no written record of the number of populations in prehistoric times, the effective population size can affect the ancestral tracing rate of each generation, which is the probability that two lineages come from the same ancestor in the previous generation. Therefore, human ancestors left imprints in the population genome, reflecting the size of the population at that time. The older the group's history, the weaker the imprint signal that remains to this day. To accurately interpret these signals and estimate the history of human populations millions of years ago, researchers have created new theories in population genetics and computational biology to estimate population history and conduct a census of ancient human populations.
Based on this new theory, researchers further analyzed genomic data from 50 modern human populations, including the "Thousand Genome Project" and the "Human Genome Diversity Project". For the first time, it was found that 930000 years ago, human ancestors lost about 98.7% of their member individuals in a short period of time due to drastic climate changes during the transition period between the early and middle Pleistocene, and were almost extinct. Over a period of 117000 years, the average number of adult individuals was only 1280, and estimates of this population size were almost identical from two independent data sets, the Thousand Genome Project and the Human Genome Diversity Project, at 1270 and 1300, respectively.
This milestone event has a significant impact on human evolution
Researchers further validated using two southern African populations from the Human Genome Diversity Project dataset, and although the sample sizes were only 6 and 8, they still detected bottlenecks in ancient populations. The decline in the number of ancient populations has reduced the genetic diversity of modern populations by 65.85%, and has had a profound impact on human life and health.
"The research team has discovered for the first time that human ancestors experienced severe population bottlenecks during the transition period from early to middle Pleistocene, almost on the brink of extinction. This milestone event has a significant impact on human evolution and may have determined the formation of many key phenotypes in humans," said Professor Yang Jian, head of the Statistical Genetics Laboratory at West Lake University.
Professor Wu Zhongyi from the School of Life Sciences at Sun Yat sen University said that the significant contribution of the research team is the proposal of a theoretical framework, which is based on tracing the frequency spectrum of gene variation back millions of years to see this phenomenon.
"This is a very good example of methodology driving scientific development," said Professor Liu Xiaoming from the University of South Florida in the United States. "This is currently the most accurate method for estimating the history of effective population size, and the data format is highly adaptable and computationally fast, with very broad application prospects.".
This significant discovery in the history of human evolution is an international collaborative research achievement led by Chinese scientists, jointly completed by researchers from the University of Rome in Italy, the University of Florence, and the University of Texas in the United States.
