Links that won't waste your time, Jan. 27 edition27 Jan 2008
Stories about genetics, paleoanthropology, and other stuff have been falling this week faster than I can keep up, but happily I'm not alone. Here are some of the more interesting blog-takes on recent stuff:
Pigment use by Neandertals
Julien Riel-Salvatore writes about recent work by Maria Soressi and Francesco d'Errico establishing that Mousterian pigment nodules were used as crayons:
The reason why this ongoing study is so convincing is that the authors used replicative referents that objectively establish the microscopic and rugosimetric features of blocks of coloring materials worked in different manners and with different tools. This provides an objective baseline against which to compare the characteristics of objects found in assemblages attributed to Neanderthals and to determine whether they bear evidence of having been purposefully manufactured by human action.
I'll write more about this when I get a chance, but Julien's post is valuable and provides translated (from French) excerpts of the relevant papers.
Genetic diversity in African cattle
Razib writes about a New York Times Magazine article that details the cultural and economic pressures around cattle breeding in Uganda. People are bringing in Holsteins, because even though they are finicky in the African climate, they can give as much as 20 times the milk of the native Ankole cattle. The Ankole breed resembles those that American cattlemen would call "Watusi."
Here's a passage from the article:
Not everyone in Uganda, however, agrees that the foreign breeds are an upgrade. President Yoweri Museveni once imposed a ban on imported semen. Museveni belongs to the Bahima ethnic group. When he was a baby, in a sort of Bahima baptism ritual, his parents placed him on the back of an Ankole cow with a mock bow and arrow, as if to commit him symbolically to the defense of the family's herd. Museveni, now in his 60s, still owns the descendants of that very cow, and he retains a strong bond to the Ankole breed. Two years ago, I accompanied a group of Ugandan journalists on a daylong trip to one of the president's private ranches, where he proudly showed us his 4,000-strong herd of Ankole cattle. At one point, a reporter asked if the ranch had any Holsteins. "No, those are pollution," Museveni replied. "These," he said, referring to his Ankoles, "the genetic material is superior."
Razib's comment on another passage:
I guess it's nice that [the author] put quotes around [genetic] dilution, but the rest of the article suggests to me that the author hasn't internalized that genetics is discrete, and that information isn't destroyed through cross-breeding. Rather, it seems that a good program of cross-breeding could result in a superior breeds of Holstein optimally suited to the local climate. That's what happened with indigenous African lineages as they hybridized with introduced South Asian ones 2,000 years ago to produce the Ankole according to the article! This sort of piece in a widely circulated publication such as The New York Times Magazine could have been a serious examination of agricultural and quantitative genetics, and just how much we depend on these unsexy sciences to feed the world. As it is, there's a lot of hand-waving scare-mongering....
The usual argument in favor of preserving diversity of domesticated species is as a hedge against future uncertainties like climate change or novel diseases. Another reason is to preserve local flavor -- that's why people grow "heirloom" vegetables, for instance. But it is quite certain that the pasturage devoted to traditional breeds of cattle well decline if imported breeds provide a net economic advantage. In that case, the best way to preserve diversity is cross-breeding -- which also has the direct advantage of introducing locally adapted genes into the descendants of the foreign breed.
This is what African herders have been doing for thousands of years, as evidenced by the spread of zebu genes across the continent. These European imports are merely the newest version.
What are genetic tests good for?
Hsien-Hsien Lei has an invited post by Ann Turner, noted for her book, Trace Your Roots With DNA. Turner comments on the new genetic tests from deCODEme and 23andMe:
Since I'm interested in genetic genealogy, I am more attuned to the ancestry components of the deCODEme results. The admixture results are interesting to anyone who suspects they may have ancestors from different geographical areas. The detailed chromosome graphs also show the potential for tracing segments of DNA shared with even more distant relatives. For instace, it was recently found that a block carrying a colon cancer gene could be traced back to a couple who arrived in the US in the early 1600's. This sort of thing might very well show up in the "Compare Me" feature.
Evo-devo and its detractors
On the subject of guest posts, Carl Zimmer is running an essay from Jerry Coyne. The essay is a response to a blog post by Olivia Judson, in which she reviewed the ideas of Richard Goldschmidt and suggested that the macromutation theory may be primed for a comeback, using recent results from evolutionary developmental biology (evo-devo) as a jumping-off point. Coyne has been one of the foremost critics of the idea that evo-devo is somehow "changing" basic conceptions in evolutionary biology.
Unfortunately, her piece is inaccurate and irresponsible, especially for a journalist with a strong science background (Judson has a doctorate from Oxford). I've admired Judson's columns and her whimsical and informative book Dr. Tatiana's Sex Advice to All Creation. But this latest posting is simply silly. As an evolutionary biologist, I'm used to seeing our field twisted out of shape to satisfy the demands of journalists who love sensational new findings--especially if they go against long-held Darwinian beliefs like the primacy of gradual, stepwise evolution. But I'm not used to seeing one of my own colleagues whip up excitement about evolutionary biology by distorting its findings.
I have to say I find the entire concept of a "New York Times blog" to be interesting. They have quite a lot of them now, and they are not clearly demarcated from other editorial content at the Times website. That's not a criticism, but it does mean that readers tend to think they come with the full authority of the Times' editors. To me, they read just like any other blog post anywhere, but for a picture of how people perceive their importance, just look at their comment sections.
That was enough in this case to bring Jerry Coyne out of the woodwork. I think his slapdown is a little extreme (Remind me not to get on his bad side!). But Judson was clearly mistaken to equate today's evo-devo results with Goldschmidt's ideas -- a link that evolutionary developmental biologists themselves deny. At any rate, Coyne's forceful advocacy for his point of view makes for good reading, and I would recommend it to anybody interested in where evolutionary developmental biology is going and how it will influence our ideas about evolution over the next few years. Here at Wisconsin I am at one of evo-devo's epicenters, and I can see a number of ways that it may transform our ideas of human evolution. So in that sense, I am more sanguine than Coyne about the prospects for understanding morphological changes with developmental insights. At the same time, I agree substantially that the genetic questions must ultimately be answered in genetic terms.
The discussion in Zimmer's comments section digresses into what Stephen Jay Gould may or may not have thought about saltational changes in evolution. I think that is essentially unenlightening, in the sense that quote-pulling out of Gould can reinforce almost any point of view.