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Discovery may prompt scientists to redraw human family tree -- again

By Marshall Connolly, Catholic Online (NEWS CONSORTIUM)
December 5th, 2013
Catholic Online (www.catholic.org)

It's time to go back to the drawing board over human evolution, following a discovery based on the analysis of prehistoric hominid DNA. Of course, scientists are always redrawing the human evolutionary tree as new discoveries reveal new complexities.

LOS ANGELES, CA (Catholic Online) - The analysis of prehistoric hominid DNA, dating back 400,000 years, reveals that the DNA is strikingly human. Until now, the oldest human DNA ever found dated back only 100,000 years and the now-smashed version of the human evolutionary tree says that humans as a species are only 100,000 years old.

We now suspect that may be wrong.

In the journal Nature, scientists reported that DNA recovered from a bone taken from a prehistoric hominid site in Spain, is human and dates back four times farther than any other sample of modern human DNA. This suggests that genetically modern humans have walked the Earth for nearly half-a-million years.

It's a shattering find because it will require the reworking of the human family tree and raises a lot of new and perplexing questions.

The DNA was extracted from a thigh bone fossil previously thought to have come from a forerunner species to the Neanderthals. The Neanderthals are a distinct species of human that died out in the past 50,000 years.

Instead of matching Neanderthal DNA however, the sample more closely matches Denisovan DNA, whis was another species of human that lived around 80,000 years ago in Siberia.

So what is Denisovian DNA doing far away from Siberia in a place where Neanderthal DNA should be?

The answer is purely speculation, at least until further DNA and peer review are performed. However, a preferred scenario is that our pre-human ancestors traveled more and interbred more than we might have previously thought.

Although there are some key differences between species of pre-human ancestors, the most recent ancestors of modern humans were quite similar to one another and they interbred. In fact, modern Homo Sapiens Sapiens (that's us) are believed to have interbred with Denisovans and Neanderthals both. A minority of living humans today carry DNA traces from both Denisovans and Neanderthals.

Neanderthals and Denisovan humans both became extinct yielding to modern humans who themselves evolved out of Africa and probably out-competed and out-bred their earlier cousins.

If the story of human evolution makes your head spin, you're not alone. Ultimately, anthropologists have a modicum of evidence from which to draw upon and make conclusions. New discoveries, which happen all the time, lead to new knowledge and periodically compel anthropologists to redraw the human family tree.

Although these discoveries can cause shifts between the branches, the basic story of human evolution remains enshrined in scientific theory. There is virtually zero doubt among professional, peer-reviewed scientists that humans evolved from primitive ancestors, as did apes and all other organisms on Earth. Although it should be mentioned-to clarify, that humans are in no way descended from apes and the story of human evolution does not assert this oft-mistaken claim.

In fact, evolution seems to be a basic natural fact with real-world implications. For example, evolution is the reason why antibiotics are becoming useless as people overuse them. If evolution did not occur, then new versions of antibiotics would not be necessary.

Understanding human origins is key to understanding humanity itself, as well as deciphering history and prehistory. Hominid migration patterns followed animals, diseases followed humans, and behind humans came the domestication of crops and animals, the evolution of new diseases, and civilization itself. The story of human evolution is important because it helps us understand ourselves and our place in the world, and how the creative forces which shaped us work.

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