Month: January 2009

More on the evolution of flight

January 30, 2009 • 4:51 pm

As I discuss in WEIT, the evidence shows that birds evolved from theropod dinosaurs–gracile, carnivorous beasts that walked on two legs. Some of the important evidence comes from Chinese fossils showing theropods with various types of feathers. The incipient stages of feather evolution appears to be filamentous feathers (T. rex might well have been covered with fluff!), implying that flight feathers originated as devices to help insulate the theropods. In a recent paper in Nature, however, F. Zhang et al. found a theropod fossil (Epidexipteryx hui), about 160 million years old, which had not only the downy feathers (feathers completely unsuitable for flight) but also four very long tail feathers that could not have been used for either flight or insulation. E. hui also showed a number of morphological features that seem to make it closely related to modern birds. The most likely explanation for these tail feathers is that they were ornaments–ornaments that evolved for either species recognition or via sexual selection. The evolution of flight, then, may have begun with feathers that were used for display. A somewhat fanciful reconstruction of the beast is shown below.

Epidexipteryx hui (reconstruction)
Epidexipteryx hui (reconstruction)

Review of WEIT in Wall Street Journal

January 29, 2009 • 9:38 am

A very nice review of WEIT appeared today in the Wall Street Journal.  It was written by the distinguished philosopher Philip Kitcher, who has written extensively on evolution, creationism, and evolutionary psychology.  I highly recommend his recent book, Living with Darwin: Evolution, Design, and the Future of Faith, which not only dismantles intelligent design, but deals with the thorny problem of how nonreligious people can find the same kind of solace and social networking that is provided by religion. Philip also wrote what I consider the definitive critique of evolutionary psychology (then called “sociobiology”): Vaulting Ambition: Sociobiology and the Quest for Human Nature.  Finally, his avocation is James Joyce, and he’s just penned an introduction for the general reader to Finnegans Wake: Joyce’s Kaleidoscope: An Invitation to Finnegans Wake, an accomplishment which I can regard only with astonishment.

Does science promote values?

January 28, 2009 • 3:51 pm

In a remarkably frank and hard-hitting article (here) celebrating the return of real science to American politics, New York Times science writer Dennis Overbye contends that, contrary to received opinion, the practice of science does indeed promote values–precisely those values that help one do good science.

As he says:

“The knock on science from its cultural and religious critics is that it is arrogant and materialistic. It tells us wondrous things about nature and how to manipulate it, but not what we should do with this knowledge and power. The Big Bang doesn’t tell us how to live, or whether God loves us, or whether there is any God at all. It provides scant counsel on same-sex marriage or eating meat. It is silent on the desirability of mutual assured destruction as a strategy for deterring nuclear war. . . . .

“Worse, not only does it not provide any values of its own, say its detractors, it also undermines the ones we already have, devaluing anything it can’t measure, reducing sunsets to wavelengths and romance to jiggly hormones. It destroys myths and robs the universe of its magic and mystery.

“So the story goes.

“But this is balderdash. Science is not a monument of received Truth but something that people do to look for truth.

“That endeavor, which has transformed the world in the last few centuries, does indeed teach values. Those values, among others, are honesty, doubt, respect for evidence, openness, accountability and tolerance and indeed hunger for opposing points of view. These are the unabashedly pragmatic working principles that guide the buzzing, testing, poking, probing, argumentative, gossiping, gadgety, joking, dreaming and tendentious cloud of activity — the writer and biologist Lewis Thomas once likened it to an anthill — that is slowly and thoroughly penetrating every nook and cranny of the world.

“Nobody appeared in a cloud of smoke and taught scientists these virtues. This behavior simply evolved because it worked.

“It requires no metaphysical commitment to a God or any conception of human origin or nature to join in this game, just the hypothesis that nature can be interrogated and that nature is the final arbiter. Jews, Catholics, Muslims, atheists, Buddhists and Hindus have all been working side by side building the Large Hadron Collider and its detectors these last few years.”

Bravo! This is a level of frankness and contentiousness (and truthfulness!) that the Times rarely achieves when writing about science and its right-wing and religious critics.

A really cool evolutionary timeline

January 28, 2009 • 11:14 am

One of the best ways to appreciate not only how long life has had to evolve, but also how short the period has been since “modern life” (aka birds, mammals, and humans) arose is to look at an evolutionary “timeline” that is drawn to scale. In the footnotes of WEIT I direct readers to one of these, but I have since found a much better one on the Web. It was constructed by John Kyrk, and is seen here. It’s a great teaching tool, with nice graphics, including eight telescoping timelines, each one a small piece of the previous one.

More evidence of selection in action

January 26, 2009 • 4:59 pm

I’m going to try to post fairly frequent updates about new observations and experiments in evolutionary biology that are relevant to my book.  Here’s the first.

Two weeks ago, in an article in The New York Times, Cornelia Dean summarized a recent article in The Proceedings of the National Academy of Sciences about how inadvertant selection by humans has led to evolutionary change.  (The original article, by C. T. Darimont et al., can be found here.)  Darimont et al. showed that in 29 species for which long-term data exist—species ranging from fish to caribou—human harvesting has led to extraordinarily large genetic changes in size at reproductive maturity and age at which reproduction begins.  Actually, these changes were predictable from evolutionary theory, which tells us that if we selectively remove from nature the biggest fish or the largest sheep, we  leave  behind those individuals who reproduce at a smaller size, and those will be the the ones who contribute their genes to the next generation.  This will eventually cause the observed evolutionary changes in age of maturity and body size at maturity.

What is remarkable is the speed of this evolutionary change: it is far faster than normal rates of evolution produced by “natural” (i.e., non-human-based) natural selecction (for example, the changes in beak size in Galapagos finches during periods of drought), and faster even than observed rates of evolution produced by other cases of human-caused selection.  These cases supplement and extend the examples of human-caused evolution described in my book, but also add a new dimension because in these new cases selection was inadvertent–people were not trying to change the population, they were just catching the biggest fish and shooting the most desirable rams.  It thus differs from deliberate artificial selection such as that involved in dog breeding. It proves yet again that if there is genetic variation for a trait and selection operates on that trait, evolution will follow.