About Rationally Speaking
Rationally Speaking is a blog maintained by Prof. Massimo Pigliucci, a philosopher at the City University of New York. The blog reflects the Enlightenment figure Marquis de Condorcet's idea of what a public intellectual (yes, we know, that's such a bad word) ought to be: someone who devotes himself to "the tracking down of prejudices in the hiding places where priests, the schools, the government, and all long-established institutions had gathered and protected them." You're welcome. Please notice that the contents of this blog can be reprinted under the standard Creative Commons license.
Monday, December 24, 2007
The difference between science and bullshit
Now, for a taste of how real science works, we can turn to two very recent discoveries in evolutionary biology: the answer to the question of how pregnant women maintain their balance despite their obviously shifted center of gravity, and the quest for the earliest ancestor of whales.
Research co-authored by Liza Shapiro of the University of Texas has provided an elegant evolutionary explanation for how women cope with the gravitational challenges imposed by pregnancy: it turns out that two slight modifications of their skeletal structure, compared to men, do the trick. In particular, women have one of their hip joints that is about 14% larger than the corresponding structure in men; also, in women one of the lower lumbar vertebrae has the shape of a wedge, instead of the more square form it takes in men. That’s it, and yet these minor changes make it possible for women to carry their pregnant bellies without causing too much stress on their back muscles.
But wait, I can already hear our ID friends shout in excitement, isn’t that a wonderful example of intelligent design? No, because these two changes simply makes it possible to improve on what still is a pretty bad situation: other primates who walk on all four have a much easier time dealing with their pregnant bellies than any human female. But once human ancestors evolved bipedalism, natural selection favored whatever adjustment would make enough difference to their survival and reproduction. In other words, as biologist Francois Jacob observed many years ago, evolution works by tinkering with already existing structures, not by designing them from scratch. The result is a series of suboptimal adjustments, not an intelligent design.
Let us turn now to whales. Until a few years ago we knew pretty much nothing about the evolution of Cetaceans. Then several key intermediates were discovered in the fossil record, allowing paleontologists to reconstruct important steps of the transition between land animals belonging to the even-toed ungulates (like hippos) to modern whales. However, until recently scientists were missing any clue to the very early steps in that evolutionary trajectory. Not any more: work co-authored by J.G.M. Thewissen at Northeastern Ohio University has identified the raoellid genus Indohyus from the Indian Kashmir region as very close to the root of the evolutionary tree to which whales belong.
Indohyus was a terrestrial animal that found refuge in shallow water, similar to the modern African mousedeer, probably as a means of defense against predators. Indohyus has several characteristics that identify it as belonging to the phylogenetic tree of whales and separate it from the even-toed ungulates, including the density of its limb bones and the anatomy of its premolar teeth. Most interestingly, Thewissen and colleagues have concluded that the aquatic habit evolved first in the lineage that led to whales, followed by a later switch to an aquatic diet: Indohyus is the perfect “missing link” in that it lived a partially aquatic life, but still maintained a terrestrial diet.
Now, that is how real science works. But if you prefer bullshit, by all means, go ahead and read the intelligent design literature. It’s entertaining.