![]() ![]() We also consider 250,000 base pairs of X-chromosome alignments and find an effective population size much smaller than 75% of the autosomal effective population sizes. Furthermore, around 50% of the human genome coalesces with chimpanzee after speciation with gorilla. We find a very recent speciation time of human–chimp (4.1 ± 0.4 million years), and fairly large ancestral effective population sizes (65,000 ± 30,000 for the human–chimp ancestor and 45,000 ± 10,000 for the human–chimp–gorilla ancestor). We apply the HMM to four autosomal contiguous human–chimp–gorilla–orangutan alignments comprising a total of 1.9 million base pairs. Our HMM is an analytically tractable approximation to the coalescent process with recombination, and in simulations we see no apparent bias in the HMM estimates. We develop a hidden Markov model (HMM) that incorporates this variation and relate the model parameters to population genetics quantities such as speciation times and ancestral population sizes. This article originally appeared on DiscoveryNews.The genealogical relationship of human, chimpanzee, and gorilla varies along the genome. Related: Ape-like ancestors had human-like hands Our hands, however useful, may instead represent a very primitive anatomical structure that's been around for millions of years. The new study challenges the assumption that the evolution of a more "sophisticated" hand in humans first appeared in the common ancestor of chimps and our species. Even then, the tree scaling is just to escape threats or to forage for food. While we tend to think that gorillas spend much of their time hanging around in trees, the truth is that they only spend about 5 to 20 percent of their time in trees. While chimps and orangutans became tree-climbing specialists, humans evolved to become more terrestrial. Each gorilla foot has five toes, but their big toe is opposable and can move much more flexibly than ours can.Īlmécija and his colleagues suspect that all living primates survived a late Miocene (12 to 5 million years ago) extinction event by specialising to exist in certain habitats. Like human hands, gorilla hands have five fingers, including an opposable thumb. Gorillas also appear to have inherited our more primitive hand structure. As a result, chimps and orangutans do not have opposable thumbs as we do. Since the thumb is not as long, it just meets up with the palm, while the chimp's other four fingers extend upward. "Human hands are marked by a relatively long thumb when compared to the length of their four other fingers - a trait that is often cited as one of the reasons for the success of our species because it facilitates a 'pad-to-pad precision grip,'" says Hiatt.Ĭonversely, chimp hands are much longer and narrower. The researchers, led by Sergio Almécija, a scientist in the university's Center for the Advanced Study of Human Paleobiology, analysed the hands of humans, chimps and orangutans, as well as the remains of hands for early apes like Proconsul heseloni and the hands of human ancestors, such as Ardipithecus ramidus and Australopithecus sediba.Īlmécija and colleagues, Jeroen Smaers and William Jungers from Stony Brook University, discovered that human hands today are not that different from those of the early human ancestors. ![]() "The findings suggest that the structure of the modern human hand is largely primitive in nature, rather than, as some believe, the result of more recent changes necessary for stone tool-making," says Kurtis Hiatt, a spokesperson for The George Washington University. The study, published in the the journal Nature Communications, found that human hand proportions have changed little from those of the last common ancestor of chimps and humans, while the hands of chimps and orangutans have evolved quite a bit. Hand evolution The development of an opposable thumb that enables humans to grip and manipulate objects is widely believed to give us an evolutionary edge.īut new research finds that human hands are more primitive than those of our closest primate ancestors chimpanzees. Human hands are marked by a relatively long thumb when compared to the length of their four other fingers (Source: stockdevil/iStockphoto) ![]()
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