Evolution isn?t just something that went on in the past, it's still happening today. And some scientists think that evoltion plays out pretty much the same everywhere, meaning that alien life, when we find it, won't be so different from us.
A group of geneticists at the University of Chicago have scanned the entire human genome in search of genetic variations that may signal recent evolution, and found more than 700 genetic variants occurred during the past 10,000 years of human evolution. To their way of thinking, that's recent.
Jonathan Pritchard says, "This approach allows us to take a broad prospective to see what kinds of biological systems are undergoing adaptation. There have been a lot of recent changes?the advent of agriculture, shifts in diet, new habitats, climatic conditions?over the past 10,000 years, and we?re using these data to look for those signals of very recent adaptation. A few thousand years from now, if selection pressure remains the same, everyone will have these new genes."
The data analyzed consists of genetic data from 209 unrelated individuals who are grouped into three distinct populations: 89 East Asians, 60 Europeans and 60 Yorubans from Nigeria. The researchers found roughly the same number of signals of positive selection within each population. They also found that each population shares about one fifth of the signals with one or both of the other groups.
Among the more than 700 signs of recent adaptation that were found were the salt-sensitive hypertension gene and the lactase gene. The lactase mutation, which enables the digestion of milk to continue into adulthood, appears in approximately 90% of Europeans.
"Many of the signals, however, seem to be more specific to modern human adaptation,? he says, ?like skin pigmentation, which may respond to changes in habitat, or metabolism genes, like lactase, which may respond to changes in agriculture.?
Among East Asians, the researchers found a strong signal of selection in the enzymes that break down alcohol. It's widely known that many East Asians have a mutation in a related gene that renders this pathway nonfunctional. "That's why a lot of East Asians can?t metabolize alcohol," Pritchard says. This is one reason that Native Americans, who are of Asian origin, are so susceptible to alcoholism.
One important facet of human evolution to modern diets may be in how food is used and stored in the body. The "thrifty gene" theory suggests some genes encourage efficient storage of food, which leads to rapid weight gain in times of abundant supply. Prior to modern agriculture, it was very important for the body to keep extra resources, but in today's environment, those genes have been linked to obesity. The researchers found signals of selection in several of these genes, including the leptin receptor that is responsible for regulating fat deposits (if YOU have the ?fat gene,? learn the RIGHT WAY to eat. click here and scroll down to Anne Strieber's FREE diet book, "What I Learned From the Fat Years.")
Ker Than writes in LiveScience.com that paleontologist Geerat Vermeij thinks that if the history of life on Earth could be rewound and replayed, much of it would play out in the very same way, although at different times and in slightly different forms.
If evolution is predictable, it means that life on other planets might look a lot more like us than we would expect. And if life on earth should be destroyed for some reason, Vermeij thinks it will probably evolve the same way all over again because "some traits are so advantageous under so many circumstances, or arise so relatively easily by virtue of self-organization, that you're likely to see the same things again and again." Among these are photosynthesis, plant seeds, mineralized bones, intelligence and language.
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