Wednesday, March 24, 2010

X-Woman: New Human Species?

Discover magazine's web site has a story today about a fossil dubbed "X-woman."

The fossil is nothing but a finger bone—and a pinkie at that—but scientists managed to sequence the mitochondrial DNA. It's hominid DNA, but it differs from human by twice as much as Neanderthals do.

There's not really much more information on the creature from whom this pinky came. You can't tell what a hominid looks like from its pinky.

But here's what we can know ...

Mitochondria DNA

All of us have little cells inside our cells. These cells are called mitochondria, and they produce power for our cells.

Mitochondria (no, not medichlorians, this is not Star Wars) have their own DNA, separate from the DNA in the nuclei of your cells.

The DNA in your cell nuclei is inherited from your father and mother and combined. The DNA in your cell mitochondria is inherited only from your mother. It is not recombined, and it is not changed. It changes only through errors in duplication, called mutation.

Fascinating Mitochondrial History

The history of mitochondria may be very cool. Mitochondria may be the best surviving species in history.

It's been suggested that mitochondria were once single-celled creatures living on their own like bacteria or amoeba. Somehow, one managed to get itself embedded in another cell and provide a service for it. Over time, they came to inhabit every living cell.

That is why there's a completely separate packet of DNA in the mitochondria of cells.

If this is true, then mitochondria have been the most successful species ever, and they did so by serving all other living things.

Now that's an interesting allegory for a Christian: "If you want to be great in God's kingdom, learn to be the servant of all."

Mitochondria and Human Evolutionary History

Because mitochondrial DNA only changes by mutation, and because we know—roughly—the rate at which it mutates, when we run across divergent DNA, it's possible to determine—roughly—how recently we share a common ancestor.

In the case of Neanderthals, it's about 460 thousand years. In this case, it's just over a million.

There are some other ways that rogue mitochondria DNA could have descended to 50,000 years ago, which is the age of the fossil, but it is very possible that we have discovered a new species. It's only been since 2004 that we found a third modern hominin species (besides us and Neanderthal man), Homo floriesiensis, the "hobbit."

Anyway, we'll wait to hear more. They are going to continue to search the area—Siberia, in this case—for fossils, and they're busily working on this creature's nuclear DNA, which they were also able to extract.

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