Darwin’s Finches: Researchers Tweak the Beak
Every once in awhile, a new angle on Darwin’s finches (an icon of evolution) appears in print. Peter and Rosemary Grant, who have devoted their life to studying everything possible about these related species of birds that inhabit the Galápagos Islands – only to find that evolutionary changes are reversible (see 04/26/2002 headline) – have a new molecular story to tell. In an effort to tie the evolution of beak shape to embryonic development, they and three Harvard geneticists searched for the actual proteins that build beaks in the egg, and found one named Bmp4 (bone morphogenetic protein #4) that appears to singlehandedly influence beak width and stubbiness. Their results are printed in the Sept. 3 issue of Science.1
In the same issue,2 USC scientists Ping Wu et al. studied the same protein in chickens and ducks. They studied Bmp4 expression in the growth zones of developing beaks, and found that “By ‘tinkering’ with BMP4 in beak prominences, the shapes of the chicken beak can be modulated.” It was not clear, however, whether BMP4, a signalling molecule, is solely responsible or affects other upstream factors in the developmental process.
Each article assumes these studies are important to evolutionary theory. The Grants say, “Darwin’s finches are a classic example of species diversification by natural selection.” Ping Wu et al. generalize, “Beak shape is a classic example of evolutionary diversification.” Elizabeth Pennisi, Science writer who usually makes evolutionary stories grist for her mill, writes in the same issue,3 “Darwin’s finches are to evolutionary biology what Newton’s apple is to physics.” (Did she mean the obvious comparison, considering that the story of an apple hitting Newton led to his theory of gravitation is a myth?) “Today,” she continues, “these songbirds are often cited as a perfect example of how new species arise by exploiting ecological niches” (emphasis added). Yet the classification of these birds into separate species is controversial, since apparently most of them (at least) are interfertile.
Though the scientists Pennisi quotes are impressed with the studies, and find the evidence convincing that BMP4 shapes beaks, one cautions that “Other genes and molecules will also be involved.” Indeed, Pennisi admits, “neither group knows what makes the BMP4 gene more active in birds with bigger bills.” And neither study explains “why some birds, such as the finches, rapidly form new species—with the different lifestyles that are possible because of changes in their shapes—while others living in the same place, for example, warblers, do not.” Nevertheless, Pennisi is confident, “Darwin would be pleased.”
1Abzhanov, Protas, Tabin, Peter and Rosemary Grant, “Bmp4 and Morphological Variation of Beaks in Darwin’s Finches,” Science, Vol 305, Issue 5689, 1462-1465, 3 September 2004, [DOI: 10.1126/science.1098095].
2Ping Wu et al., “Molecular Shaping of the Beak,” Science, Vol 305, Issue 5689, 1465-1466, 3 September 2004, [DOI: 10.1126/science.1098109].
3Elizabeth Pennisi, “Bonemaking Protein Shapes Beaks of Darwin’s Finches,” Science, Vol 305, Issue 5689, 1383, 3 September 2004, [DOI: 10.1126/science.305.5689.1383].
The findings are really no help to evolutionary theory. Neither of these studies account for the origin of BMP4 and the many other complex proteins that interact with it; they just show you can get freaks by tweaking the beaks. We already knew that with humans. Failures in the complex developmental pathways of any embryo can produce grotesque or useless deformities. These studies only tinkered with expression of existing genes, not with the origin of new genes or their “improvement.” The studies were not tied to adaptation, which is what Darwinism purports to explain.
Picture the highly specialized beaks of hummingbirds, spoonbills, pelicans, owls, hornbills, woodpeckers, eagles, ducks, and the other thousands of species of birds. To explain these, an evolutionist is going to need a lot more than just differences in the local expression of BMP4. He or she is going to need millions of transitional forms, and proof of heritable adaptive changes in all the developmental pathways that affect beak morphology. Even if the Grants can tie finch beak changes to this molecule, and show that beak changes are adaptive for various ecological niches on the islands, they have not explained the origin of BMP4, the beak, or the finch itself.
Creationists and evolutionists both are comfortable with slight morphological changes in existing species. It is very probable that a tougher beak will aid a finch in a drought, so that it can crack the nuts and get to the seeds better than a cousin with a thinner beak. But when the rains return, and seeds are plentiful, the change is no longer adaptive and the populations can revert back. Over time, no one has shown that these slight changes to Darwin’s finches have led to any long-term morphological change. Certainly they have not shown that they came from, or are leading to, anything other than finches.
If the Grants want to spend their lives measuring beaks to fractions of a millimeter, and weighing the little birds to fractions of a gram, and studying the ways their eggs grow and what genes and proteins are expressed, that’s fine and wonderful and praiseworthy. But if anyone claims their work has defended Chairman Charlie’s wild speculation that humans had bacteria ancestors, beak airful.