Hen's Teeth and Horse's Toes: Further Reflections in Natural History
Stephen Jay Gould
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"Lively and fascinating. . . . [Gould] writes beautifully about science and the wonders of nature."―Tracy Kidder
Over a century after Darwin published the Origin of Species, Darwinian theory is in a "vibrantly healthy state," writes Stephen Jay Gould, its most engaging and illuminating exponent. Exploring the "peculiar and mysterious particulars of nature," Gould introduces the reader to some of the many and wonderful manifestations of evolutionary biology.
rocks. Since evolution demands progressive change through time, the persistence of these simple and early forms will demonstrate the bankruptcy of Darwinian theory. (I don舗t think Agassiz ever understood that the principle of natural selection does not predict global and inexorable progress but only adaptation to local environments. The persistence of simple forms in a constant deep sea would have satisfied Darwin舗s evolutionary theory as well as Agassiz舗s God. But the depths are not constant,
light can penetrate sea water. Their world is one of total ambient darkness, and they must therefore provide the light of attraction themselves. Their lures glow with a luminescence supplied by light glands舒a death trap for prey and, perhaps, a beacon for dwarf males. A male anglerfish (lower right), about one-and-a-half inches long, embeds itself into a ten-inch female of the same species. REPRINTED FROM NATURAL HISTORY. A simplified cross section shows a male anglerfish attached to a female.
evolved in different directions. Just as the entire deletion of BX-C produces the striking homeotic effect of converting all posterior segments to second thoracics, several mutations in the eight genes produce homeotic results as well. The most famous mutation, called bithorax and commandeered as a name for the entire complex, converts the third thoracic segment into a second thoracic. Thus, the adult fly develops with two second thoracics and two pairs of wings, instead of one pair and a pair of
the entire complex is deleted, then all three thoracic segments begin to differentiate as first thoracics (while the abdominals, regulated by BX-C, develop normally). Apparently, the genes of ANT-C normally turn on in the second thoracic segment and trigger the proper development of the second and third thoracics. Kaufman and his colleagues have found that ANT-C consists of at least seven genes, not all with known homeotic effects, lying right next to each other on the right arm of the third
amateur exchange. Š 3. Teilhard舗s good luck at Piltdown. Although records are frustratingly vague, I believe that all the Piltdown pieces were found by the original trio舒Dawson, Smith Woodward, and Teilhard. (In the official version, a workman may have given Dawson the first piece in 1908.) Dawson, of course, unearthed most of the material himself. Smith Woodward, so far as I can tell, found only one cranial fragment. Teilhard, who spent less time at Piltdown than his two colleagues, was