Probing the origins of humanity is actually a lot like being a dentist. The bones of our hominid ancestors tend to fall apart, leaving behind a smattering of shards. But teeth, made of enamel, can do a better job of withstanding the ravages of time. And teeth–particularly those of mammals–are not just tough but interesting. Mammals–us included–have several kinds of teeth, each of which is covered with distinctive bumps, cusps, and roots. All those details vary from one species to another. So even if you find a fragment of a tooth, you may be able to figure out what species it belongs to. And if you have enough teeth to compare to each other, you can probe some pretty profound questions about where we came from.
Category: Blog
I was puzzled by an article in today’s New York Times called “Researchers rewrite first chapter for the history of medicine.” William Honan, the reporter, announced that “an art historian and a medical researcher say they have pushed back by hundreds of years the earliest use of a medicinal plant.” Until now, he wrote, the oldest evidence dated back to 1000 BC, but now researchers had discovered a picture 3500 years old showing a Greek goddess overseeing crocus flowers being made into medicines.
Continue reading “The Dawn of Medicine, Plus or Minus a Couple Million Years”
If you want to hear about brain science at its birth and today, check out the public radio show Tech Nation, this week. In the first half of the show, I’ll be talking about Soul Made Flesh. In the second half, Steven Johnson will be talking about his excellent new book, Mind Wide Open. You can find out where and when you can listen to the show at the program’s web site, or listen to it on their site archive.
In my last post, I wrote about how our genes work in networks, much like circuits made of elements wired together in various ways. As genes are accidentally duplicated, mutated, and rewired, old networks can give rise to new ones. It’s pretty clear our ancestors could have never become particularly complex if not for this sort of network evolution. As they acquired nerves, muscles, and other tissues, animals needed to organize more and more genes into new circuits. But in saying this I don’t mean to imply that single-celled microbes, such as bacteria, live without gene networks. Far from it. In fact, in many ways bacteria are more adept at network engineering than we are.
As biologists figure out more about how life is, they can then figure out how it got to be that way. First there were genes. Mendel noticed that somehow the wrinkles on wrinkled peas could be transmitted down through the generations, even if some of those generations had no wrinkles at all. It turned out that the wrinkles were the result of a gene; a different version of the gene produced smooth peas. For much of the twentieth century, evolutionary biologists worked out how changes in genes produced evolutionary change. A mutation that alters one position in a gene (or chops out a whole chunk of it) can alter the protein it encodes. As the proteins on a virus mutate, for example, their shape becomes harder for an immune cell to recognize.