Ancient intelligent species predating man Tenns web cam desnudas gratis
Complex life might have come and gone on Earth long before the multicellular organisms we're familiar with today arose, a new study suggests.
It's generally thought that the evolution of complex life was a rare, once-in-4.5-billion-years event.
"But what it looks like now is, there was a period of a quarter of a billion years or so where oxygen came quite high, and then sunk back down again." It wouldn't have been enough time for complex life to diversify and take hold on the planet, but it's possible that some complex organisms could have arisen before dying off again when the oxygen crashed.
So why wouldn't this hypothetical life have survived until today if it did evolve?In the absence of much fossil evidence, the best way to study Denisovans is through the genes they left behind in modern humans.So population geneticists Sriram Sankararaman at the University of California (UC), Los Angeles, and David Reich at Harvard University sifted through 257 genomes of present-day people from 120 non-African populations around the world.(Africans, whose ancestors didn’t leave original home, do not have any Denisovan heritage.) They confirmed an earlier finding that among humans living today, people from Papua New Guinea, Australia, and other parts of Oceania have the most Denisovan ancestry, between 3% and 6% of their genomes.This compares with about 2% from Neandertals for all non-African genomes.
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But new research suggests that conditions were right for complex cells to evolve and die off at least once - or perhaps several times - before our lineage even got started. Billions of years ago, there could have been other complex life forms on the planet, totally unrelated to anything we see on Earth today. Earth has been around for an estimated 4.5 billion years.