Wednesday, December 14, 2005

Recent News on Human Evolution

Subject: new material on human evolution at The Loom, Evolgen, and Panda's Thumb!

Before getting to the really interesting stuff, I should let you know that I plan on doing essays, and typically they will be somewhat long, maybe 1400 words or so. I started off with three different essays, and I will try to keep it to perhaps one a week, will try to insure that each essay will have some real gems for links. Oh, and if you are looking for some ideas for some of your own essays, you might check out the links on the right side of the main page of Evolving Perspectives.

In any case, there has been a fair amount of news regarding human evolution recently. (I am not going to cover the brain at this point, but simply the evolution of the human species.)

One of my favorite authors is Carl Zimmer. Just today he put up a new essay entitled Tree or Trellis. He just attended a panel by the American Anthropology Association on the topic of "Updating Human Evolution," and "Tree or Trellis" focuses on some of the recent results. Did humanity spread out in several waves emanating from Africa as far back as nearly 200,000 years ago, as Allan Wilson suggested back in the 1980s, or did humanity only begin to spread out much more recently? Well, if what you are looking at are the mitochondria which we inherit only from our mothers (as part of the cytoplasm), then it appears that all of humanity can be traced back to a woman living approximately 200,000 years ago. However, if one looks at the male Y-chromosome which men inherit only from their fathers, then it appears that all men can be traced back to a man who lived only 59,000 years ago. (Why is there such a difference? You may want to check out one of Carl Zimmer's earlier articles: Adam and His Eves. The clue, of course, is in the title.) But different genes will tell you different stories, and while none of them lie, none of them are telling you the whole truth, either.

More recently, we have come to know that humanity branched off from a common ancestor with the chimps and the bonobos approximately 6,000,000 years ago. Through further genetic analysis, Alan Templeton has been able to bring forth evidence there was a wave of humanity which left Africa much further back than what Wilson's team had suggested: 2,000,000 years ago -- but there have been other major waves -- and our genomes have a very rich story to tell us once we learn how to listen to them. To give another example, by analyzing the retroelements in the human genome, scientists have more recently uncovered evidence that human evolution has undergone several periods of rapid expansion. You may wish to check
'Punctuated' evolution in the human genome, or if you are interested in the technical details, perhaps "Periodic Explosive Expansion of Human retroelements Associated withthe Evolution of the Hominoid Primate" (pdf).

Yet there is more: in "Hooray for Humanzee" RPM tells us that only recently scientists have begun to discover not simply what kind of story the human genome has to tell about human evolution, but what it has to say about evolution in general, and the nature of mutation in particular, both in terms of the fusion of two chromosomes, and in terms of rearrangements of the genome itself which exist in humans today. Mutations -- it seems -- aren't nearly as harmful as creationists might wish you to think.

And this just in: there is a great deal more to find regarding the role of retrotransposons in mammalian, primate and particularly human evolution at the Panda's Thumb today. See: Human Evolution: It’s all in the testes. And yes, there is a very good reason for the title of the Panda's Thumb piece! (Hint: where do retrotransposons come from?)

In any case, you may wish to check out "The Loom" by Carl Zimmer, "evolgen" by RPM and The Panda's Thumb. In fact, you might want to link to their main webpage -- like I have from my main page!

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