Latest news with #HumanGenomeDiversityProject
Yahoo
20-03-2025
- Science
- Yahoo
A Mysterious 'Population B' Split From Humans 1.5 Million Years Ago—and Its DNA Is Still Inside You
"Hearst Magazines and Yahoo may earn commission or revenue on some items through these links." Using a new method of modeling genetic data, researchers identified a split in human ancestry dating back 1.5 million years. The two populations later reconnected. The mystery population (Population B) could make up as much as 20% of the modern human genome. Genes from Population B may have improved human brain function, researchers suggest. Research on evolution is... well... ever-evolving, to say the least. According to a study published in the journal Nature Genetics, a new method of modeling genomic data recently identified a split in modern human (Homo sapien) ancestry. The split occurred over 1.5 million years ago, when the ancestor of modern humans split off from an unknown population. The two groups eventually re-converged, and the mystery population may have increased our brain function, the study suggests. 'The question of where we come from is one that has fascinated humans for centuries,' Trevor Cousins, first author of the study, said in a statement. 'For a long time, it's been assumed that we evolved from a single continuous ancestral lineage, but the exact details of our origins are uncertain.' The study used new modeling techniques to analyze vast amounts of data from both the 1000 Genome Project and the Human Genome Diversity Project. In the end, two ancestral populations emerged, which researchers inventively called Population A and Population B. Once the groups split (remember, just a short 1.5 million years ago), the study found that Population A experienced a 'bottleneck,' or a drastic drop in population size and genetic diversity. Population A eventually recovered, however, and groups like the Neanderthal and Denisovans branched off from it. Researchers estimate the two populations re-converged around 300,000 years ago. Genetic analysis suggests that Population A contributed roughly 80% of modern humans' genome, and Population B makes up around 20%. This genetic mixing is especially significant in comparison to other instances of interbreeding. For instance, prior research has shown that Neanderthals mixed with Homo sapiens around 50,000 years ago. But Neanderthal DNA makes up less than 2% of the modern human genome. Interestingly, the genes that Population B contributed—especially 'those related to brain function and neural processing'—could have played a crucial role in human evolution, according to Cousins. Notably, Population B's genetic material decreased individuals' ability to have children, but 'the genome is a complicated place, and regions outside of genes can still do important things,' Cousins told Live Science. Unfortunately, researchers were unable to run their models on available Neanderthal and Denisovans data sets, which continues to be an ongoing research challenge. 'The fact that we can reconstruct events from hundreds of thousands or millions of years ago just by looking at DNA today is astonishing,' Aylwyn Scally, co-author on the study, said in the statement. 'And it tells us that our history is far richer and more complex than we imagined.' Outside of just human history, the team suggests that their findings could help contribute to our understanding of evolution more broadly. 'What's becoming clear is that the idea of species evolving in clean, distinct lineages is too simplistic,' said Cousins. 'Interbreeding and genetic exchange have likely played a major role in the emergence of new species repeatedly across the animal kingdom.' You Might Also Like The Do's and Don'ts of Using Painter's Tape The Best Portable BBQ Grills for Cooking Anywhere Can a Smart Watch Prolong Your Life?
Yahoo
20-03-2025
- Science
- Yahoo
Our Genes Reveal Mysterious Split in Human Population 1.5 Million Years Ago
We've long assumed our species evolved from a tidy, single stream of ancestors. But life on Earth is never quite so straightforward, especially not when it comes to the most socially complex species we know: humans. University of Cambridge researchers have now uncovered an estrangement in our family tree, which began with a population separation 1.5 million years ago and a reconciliation just 300,000 years ago. What's more, according to their analysis of modern human DNA, one of these isolated populations left a stronger legacy in our genes than the other. "The question of where we come from is one that has fascinated humans for centuries," says geneticist Trevor Cousins, first author of the published study. In biology, we often describe genetics and evolution with the metaphor of a branching tree. Each species' lineage begins with a 'trunk' at the base that represents a common ancestor, shared by all species at the crown. As we trace the tree from base to tip, which represents evolutionary time, its trunk forks, again and again, each split representing an irreconcilable rift in populations that meant they could no longer breed with each other, and thus became separate species. What an evolutionary tree does not capture is the on-again/off-again nature of intra-species dynamics, the many near-misses where one breeding group diverges into two, and then blends again back to one. In some situations, this makes quite a mess of the neat and tidy tree diagram, and calls into question where the precise 'species' cutoff is. "Interbreeding and genetic exchange have likely played a major role in the emergence of new species repeatedly across the animal kingdom," Cousins says. Cousins and his co-authors, Cambridge geneticists Aylwyn Scally and Richard Durbin, had a hunch this kind of family drama would apply to our own species, Homo sapiens, which is technically more like a subspecies, except that there aren't any other groups left. Aside from humanity's general penchant for love and war, there's some proof we 'spliced branches' with the Denisovans, and with a fair bit of Neanderthal DNA in our gene pool to this day, we know species lines must have blurred there, too. The team used a statistical model based on the likelihood of certain genes originating in a common ancestor without selection events intruding. This was then applied to real human genetic data from the 1000 Genomes Project and the Human Genome Diversity Project. A deep-rooted population structure emerged, suggesting modern humans, Homo sapiens, are the result of a population that split in two about 1.5 million years ago, and then, only 300,000 years ago, merged back into one. And it explains the data better than unstructured models, the norm for these kinds of studies. "Immediately after the two ancestral populations split, we see a severe bottleneck in one of them – suggesting it shrank to a very small size before slowly growing over a period of one million years," says Scally. "This population would later contribute about 80 percent of the genetic material of modern humans, and also seems to have been the ancestral population from which Neanderthals and Denisovans diverged." It suggests the human lineage became irrevocably tangled much earlier than we thought. For instance, Neanderthal genes are only present in non-African modern human DNA, making up about 2 percent. The ancient mixing event 300,000 years ago resulted in only about 20 percent of modern human genes coming from the minority population. "However, some of the genes from the population which contributed a minority of our genetic material, particularly those related to brain function and neural processing, may have played a crucial role in human evolution," Cousins says. "What's becoming clear is that the idea of species evolving in clean, distinct lineages is too simplistic." The research was published in Nature Genetics. DNA From Beethoven's Hair Reveals Surprise Nearly 200 Years Later Crucial Feature of Human Language Emerged More Than 135,000 Years Ago Mysterious Twist Revealed in Saga of Human-Neanderthal Hybrid Child
