Month: February 2009

Review of WEIT in Science

February 6, 2009 • 7:12 am

Massimo Pigliucci has reviewed WEIT in the latest issue of Science, a review you can find here.  It’s a thoughtful, fair and–I’m glad to say–a positive review.  But that issue of Science is also devoted to speciation, my own area of interest, and contains half a dozen good articles on the origin of species, both overviews and research articles.  If you’re an evolutionary biologist, you’ll want to peruse this issue.

Massimo’s review also singles out for special praise one of the illustrations  (the human, chimp, and A. afarensis given below) produced by the intrepid artist responsible for the book’s illustrations:  Kalliopi Monoyios, whom I’d recommend to anyone needing a good scientific illustrator. Her webpage is here.

716-1-med

Human, Australopithecus, and chimpanzee.

CREDIT: © KALLIOPI MONOYIOS

WEIT makes New York Times Best Seller list

February 5, 2009 • 2:32 pm

A bit of a brag–my editor has informed me that WEIT has made the New York Times’s extended best seller list in non-fiction: number 31. Not something I ever imagined would happen, but it’s really nice. Now begins the futile race to catch up with “Dewey: The Small-Town Library Cat Who Changed the World.” See Dewey’s story here, and if you MUST buy this nefariously competing tome, do so here. Dewey stands at #3, and received a multimillion dollar advance. There is no competing with cat books. I begged my editor to put a kitten on the cover, but for some obscure reason she refused.

Dewey Readmore Books 1988-2006. R.I.P.
Dewey Readmore Books 1988-2006. R.I.P.

A brand-new whale fossil

February 5, 2009 • 2:22 pm

Phil Gingerich and his colleagues at the University of Michigan, the Geological Survey of Pakistan, and the University of Bonn have just described a brand new and intriguing pair of whale fossils in the journal PLoS ONE, which you can find here. Tis whale Maiacetus inuus, lived about 47.5 million years ago, which puts it roughly at the time of the fossil whale ancestor Rodhocetus (see pp. 50-51 of WEIT). Rodhocetus was probably an amphibious creature, living on both sea and land, and this is almost certainly true of the new find as well.
The really intriguing thing about Maiacetus is that the female fossil contained an embryonic individual, apparently near term. This is the first known example of a fossil embryonic whale. What’s more, the embryo was positioned with its head facing the rear, so that it would be born head first. That birth position is characteristic of land-dwelling animals (probably an evolutionary feature to allow the embryo to start breathing as soon as possible), but is not found in marine mammals. In the latter group, babies are born tail first, probably so that a.) they won’t drown during birth and b.) so that they are born in the right position to immediately bond with and start following their mother.

There are other interesting features of this whale, too, like the permanent first molar teeth in the fetus, indicating precocial development
From the structure of its limbs and body, Maiacetus obviously lived on both sea and land, since the hind limbs are still substantial but reduced. The position of the fetal whale shows that it did, however, give birth on the land. Just another link in the ever-growing chain of fossils documenting the evolution of whales.

Cat treats and dead genes

February 4, 2009 • 11:09 am

Lots of research with domestic cats has shown that they are indifferent to sweet foods, and do not show a general attraction to them (the reason your cat likes ice cream is because of its dairy attributes, not its sweetness).  I was watching a video on YouTube of a cat eating a graham cracker (with difficulty), and wondering why it was so fond of the thing given that it couldn’t perceive its sweetness.  A friend who works on olfaction and taste then speculated that maybe cats have the genes for producing the proteins involved in tasting sweetness, but that those genes have become disabled: since the normal diet of cats is meat, there is no reason for them to seek out sweet foods.  This result would be is similar to the many “dead genes” I describe in WEIT (e.g., humans’ broken gene for making vitamin C)–broken remnants that testify to our common ancestry from species in which those genes were active.

A friend of mine who works on genomics sent me a paper from 2005 that verifies the notion that cats do have “sweetness-detecting” genes, but that those genes are inactivated (i.e., they have become “pseudogenes”).  It turns out that mammals detect sweet food by forming a taste receptor from the joined protein products from two distinct genes, Tas1r2 and Tas1r3. A group of biologists from Philadelphia sequenced these genes in domestic cats.  Sure enough, they found that while Tas1r3 is active, Tas1r2 is nonfunctional because of mutations that prevent the gene from making a full protein.  Thus the two proteins necessary for sweet detection cannot combine, with the result that Fluffy can’t taste sugar.  Sequences of the same genes in tigers and cheetahs show the same thing: no ability to detect sweetness.

Dogs, however, can detect sweetness, and sequencing of other groups show that the common ancestor of cats and dogs must have been able to taste it as well.  Obviously, the gene has been inactivated by mutations in the ancestor of many cats (more DNA sequencing needs to be done in other cat species).  Sweets are not part of cats’ diet in the wild–they are carnivores–so there is no need to have a gene that, by causing pleasurable sensations when encountering sugar, leads the animal to seek out sugar-rich foods.  So don’t bother offering Fluffy a piece of chocolate–give her an anchovy!

n.b.  Don’t feed your dog chocolate to see if he likes sweets.  The theobromine present in chocolate can be lethal to dogs, as described here.

Genes for surviving after reproduction

February 3, 2009 • 1:03 pm

An alert reader has written me about a statement I made in WEIT:

You write that “a gene that knocks you off after reproductive age incurs no evolutionary disadvantage.” And you go on to say that selection would not favour genes that helped survival after reproduction has finished. “One example would be a gene that helps human females survive after the menopause.” I understand and accept this point. But could there be an exception (in theory) as follows? If women were giving birth right up to menopause, they would need to survive after menopause to bring up their last children. Also, if a woman who survived post-menopause helped her daughter to bring up her grandchildren and had the effect of improving the survival rate of those grandchildren, wouldn’t her “live longer genes” then get passed on?

The reader is absolutely right–I glossed over the nuances of this idea in the interest of space, and probably shouldn’t have.  Indeed, a woman will be selected to live until all the benefits she can confer upon her children (the most important being maternal care) have already been bestowed, and that means staying alive until she has brought up all her offspring.  To the extent that children are grown and independent before menopause, selection will be very small against a gene that bumps mom off.  That is, of course, unless she can help her grandchildren grow up, for in that case she is still contributing to the survival of her own genes in her offspring’s offspring.  So there are exceptions to what I said.  Let me then rephrase my statement to say that “a gene that knocks you off after you’ve made all possible contributions to rearing related individuals incurs no evolutionary disadvantage.”

Review of WEIT and Darwin books in The Scotsman

February 2, 2009 • 10:09 am

An anniversary review of several of the new Darwin-year books, including mine, appears today in The Scotsman. Of special note are my friend Steve Jones’s new book, Darwin’s Island: The Galapagos in the Garden of England, and Adrian Desmond and James Moore’s Darwin’s Sacred Cause: How a Hatred of Slavery Shaped Darwin’s Views on Human Evolution. Jones, in particular, is a witty and incisive writer of popular science who is not as well known in the US as he deserves to be. Both of these books should make absorbing reading.


Is “The Hobbit” a fraud?

February 1, 2009 • 10:50 am

As recounted in WEIT, one of the most remarkable hominin fossils is that of Homo floresiensis, discovered on the island of Flores in Indonesia in 2003. This creature was remarkable in that although it lived only 18,000 years ago, when modern H. sapiens had already evolved, it was only a meter tall, weighed 50 pounds, and had a brain of less than 500 cc.–similar in size to of our distant cousin Australopithecus afarensis (“Lucy”). It seemed that some relict populations of Homo had survived on this Indonesian island, bypassed by modern humans.

Ever since H. floresiensis (dubbed “The Hobbit”) was found, it has been the center of heated controversy. Some have said that rather than being a long-surviving ancient hominin, for example, the one good specimen found is simply that of a modern human afflicted with a growth disease (such as goiterious cretinism) that produced a small skull. Others counter-claim that the wrist bones of the hobbit are clearly not that of a modern human, but of an earlier relative.

Now another criticism has surfaced–the claim that the hobbit’s teeth show dental work! In particular, an anthropologist at the University of Adelaide in Australia, Maciej Henneberg, claims that a lower molar of H. floresiensis shows a filling (and possibly a root canal) of the type performed in Indonesia in the 1930s. (See the articles about this claim here and here.) Could the hobbit be another Piltdown Man, a fraud foisted on a credulous scientific community?

Well, probably not. In a careful analysis of the dentition of H. floresiensis and a comparison with other ancient skulls, Peter Brown, one of the hobbit’s discoverers, debunks Henneberg’s claims. X rays and careful analysis (see the pictures on Brown’s page) show absolutely no evidence of dental work. Thus this claim, at least, has been debunked.

It is starting to look as if H. floresiensis really was a genuine species, but an anomalous one: a small population of tiny humans who hunted dwarf elephants with miniature spears. There will undoubtedly be more argument before this is settled.

flores_sapiens

H. floresiensis (l.), H. sapiens (r.). Photograph courtesy of National Geographic news.