The latest issue of Nature and Science simultaneously published scientists' in-depth analysis of ancient genomes: scientists from the Max Planck Institute for Evolutionary Anthropology in Germany and the University of California, Berkeley in the United States tested the genomes of 300 modern and ancient modern humans, including 59 individuals living between 2000 and 45000 years ago. This study helps people understand the impact of gene function and gene flow on human ancestors, providing more precise details for the "hybrid timeline" of Neanderthals and modern humans. Modern humans arrived in Europe over 45000 years ago, overlapping with Neanderthals for at least 5000 years. The analysis of the ancestral origins of ancient humans shows that they had two 'mixed race events'. The research team analyzed a high coverage genome and five low coverage genomes isolated from bone fragments estimated to be approximately 45000 years old. In another high coverage genome they analyzed, important genetic relationships were discovered, indicating that these individuals belong to the same ethnic group and are the earliest known group to have separated from Africa. By observing the length of Neanderthal DNA fragments, the team inferred that gene flow began about 50000 years ago and lasted for approximately 7000 years. This timeline is highly consistent with archaeological evidence of overlap between European Neanderthals and modern humans. Some early modern humans still possess a large number of unique Neanderthal genes, but 40000 years later modern humans no longer have these genes. The study also found that the diversity of humans outside of Africa may have originated during or shortly after the gene flow of Neanderthals, which can partially explain the different levels of Neanderthal ancestry in populations outside of Africa. The team also analyzed the changes that occurred over time in the entire genome of Neanderthal ancestors. Many Neanderthal sequences may have been harmful to humans, so they were actively and rapidly eliminated during the evolutionary process. This study reveals the complex history of gene flow from Neanderthals to modern humans, emphasizing the power of genomic data in elucidating the legacy of human migration and gene flow. Neanderthals are representatives of the intermediate stage in human evolutionary history. Neanderthals and modern humans coexisted in the same time and space for a long time. Although extinct, they still leave evidence of their existence forever in the genes of modern humans. In 2010, the draft genome of Neanderthals was released. Research has shown that modern humans on the Eurasian continent, excluding Africans, contribute an average of 1% to 4% of Neanderthal genetic makeup. Nowadays, the only surviving species under the genus Homo is Homo sapiens, but using genetic methods, we can look back at the magnificent era of human origin and gain a deeper understanding of the question of 'where did humans come from'. (New Society)