Human
Inbreeding With Neanderthals Left Humans A Genetic Burden
Johnson D
First Posted: Jun 09, 2016 05:20 AM EDT
Recent studies have shown that Neanderthal genome involved harmful mutations that made the hominids around 40% less reproductively fit than modern humans. New analysis claims that Neanderthal DNA may have hidden clues as to why they shuffled of the evolutionary stage, and may have left modern humans genetically weaker.
According to the latest issue of the journal Genetics, non-African humans got some of the genetic burden when they interbred with Neanderthals. Although most of the burden has been lost overtime, the results suggest that these harmful genes continue to lower the fitness of some people in the human population today.
Researchers believe that as inbreeding number decrease, it would have led to a build-up of genetic mutation that made Neanderthals unable to reproduce effectively. Phys.org reported that study leader Kelly Harris from Stanford University explained how fascinating Neanderthals to geneticists are. "Neanderthals are fascinating to geneticists because they provide an opportunity to study what happens when two groups of humans evolve independently for a long time-and then come back together." She also said that the result of their study suggest that the Neanderthal DNA being passed on to humans came at a price.
Past studies of DNA taken from Neanderthal remains showed that Eurasian hominids were more interbred and less genetically different than modern humans. . For thousands of years, the Neanderthal population size remained small, and mating among close relatives seems to have been common, Science Daily reported.
Then, 50,000-100,000 years ago, groups of modern humans left Africa and moved to the homelands of their distant Neanderthal cousins. The two groups interbred, combining their previously distinct genomes. But though a small fraction of the genome of non-African populations today is Neanderthal, their genetic contribution was still uneven. Neanderthal sequences are concentrated in certain parts of the human genome, but missing from other regions. According to Mail Online, Harris said that whenever they find a non-random arrangement like that, they look for the evolutionary forces that may have caused it.
Harris and her colleague Rasmus Nielsen from the University of California, Berkeley and University of Copenhagen, guessed that the force in question was natural selection. In small populations, like the Neanderthals', natural selection is not very effective and the chance has a huge influence. This allows weak harmful mutations to persist, rather than being removed over the generations. But once these mutations are introduced back into a larger population, such as modern humans, they would be exposed to the surveillance of natural selection and eventually lost.
Harris and Nielsen used computer programs in order to quantify the results and to simulate mutation that accumulated during Neanderthal evolution. This was also used to estimate how humans were affected by the influx of Neanderthal genetic variants. The simulations incorporated data on the mutation rates, genome properties, and population dynamics of hominids.
The findings suggest that Neanderthals have mutations with mild, but harmful effects. The combined effect of these weak mutations would have made Neanderthals at least 40% less fit than humans in evolutionary terms--that is, they were 40% less likely to reproduce and pass on their genes to the next generation.
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First Posted: Jun 09, 2016 05:20 AM EDT
Recent studies have shown that Neanderthal genome involved harmful mutations that made the hominids around 40% less reproductively fit than modern humans. New analysis claims that Neanderthal DNA may have hidden clues as to why they shuffled of the evolutionary stage, and may have left modern humans genetically weaker.
According to the latest issue of the journal Genetics, non-African humans got some of the genetic burden when they interbred with Neanderthals. Although most of the burden has been lost overtime, the results suggest that these harmful genes continue to lower the fitness of some people in the human population today.
Researchers believe that as inbreeding number decrease, it would have led to a build-up of genetic mutation that made Neanderthals unable to reproduce effectively. Phys.org reported that study leader Kelly Harris from Stanford University explained how fascinating Neanderthals to geneticists are. "Neanderthals are fascinating to geneticists because they provide an opportunity to study what happens when two groups of humans evolve independently for a long time-and then come back together." She also said that the result of their study suggest that the Neanderthal DNA being passed on to humans came at a price.
Past studies of DNA taken from Neanderthal remains showed that Eurasian hominids were more interbred and less genetically different than modern humans. . For thousands of years, the Neanderthal population size remained small, and mating among close relatives seems to have been common, Science Daily reported.
Then, 50,000-100,000 years ago, groups of modern humans left Africa and moved to the homelands of their distant Neanderthal cousins. The two groups interbred, combining their previously distinct genomes. But though a small fraction of the genome of non-African populations today is Neanderthal, their genetic contribution was still uneven. Neanderthal sequences are concentrated in certain parts of the human genome, but missing from other regions. According to Mail Online, Harris said that whenever they find a non-random arrangement like that, they look for the evolutionary forces that may have caused it.
Harris and her colleague Rasmus Nielsen from the University of California, Berkeley and University of Copenhagen, guessed that the force in question was natural selection. In small populations, like the Neanderthals', natural selection is not very effective and the chance has a huge influence. This allows weak harmful mutations to persist, rather than being removed over the generations. But once these mutations are introduced back into a larger population, such as modern humans, they would be exposed to the surveillance of natural selection and eventually lost.
Harris and Nielsen used computer programs in order to quantify the results and to simulate mutation that accumulated during Neanderthal evolution. This was also used to estimate how humans were affected by the influx of Neanderthal genetic variants. The simulations incorporated data on the mutation rates, genome properties, and population dynamics of hominids.
The findings suggest that Neanderthals have mutations with mild, but harmful effects. The combined effect of these weak mutations would have made Neanderthals at least 40% less fit than humans in evolutionary terms--that is, they were 40% less likely to reproduce and pass on their genes to the next generation.
See Now: NASA's Juno Spacecraft's Rendezvous With Jupiter's Mammoth Cyclone