PLANT AND ANIMAL SCIENCES BY FRANCISCO J. AYALA Department of Ecology and Evolutionary Biology University of California, Irvine Irvine, Calif. " Male threespine sticklebacks exhibit a red nuptial coloration on the throat that functions to attract females and intimidate rival males. The red nuptial trait does not occur in some populations, a phenomenon that has been attributed to selection by salmonid predators. However, there is no corre,lation between nuptial-color loss and presence or abse

PLANT AND ANIMAL SCIENCES BY FRANCISCO J. AYALA Department of Ecology and Evolutionary Biology University of California Irvine, Calif. " The great lakes of Africa each contain a unique radiation of cichlids. Lake Tanganyika has more than 140 endemic species, Lake Victoria more than 200, and Lake Malawi about 500. Around 1960, the Nile perch, a piscivorous fish, was introduced in Lake Victoria in order to improve the fisheries, but it has eaten its way through much of the lake and caused a

PLANT AND ANIMAL SCIENCES BY FRANCISCO J. AYALA Department of Ecology and Evolutionary Biology University of California, Irvine Irvine, Calif. " Infanticide has evolved in some animals as a behavior that increases the fitness of the killer. Killing of siblings occurs in birds, amphibians, fishes, and a number of invertebrates. Killing or abandonment of offspring occurs in many vertebrates (as well as humans). A special case of this is filial cannibalism. In the cortez damselflsh, Stegastes

PLANT AND ANIMAL SCIENCES BY FRANCISCO J. AYALA Department of Ecology and Evolutionary Biology University of California, Irvine Irvine, Calif. " The cuckoo Cuculus canorus parasitizes a variety of hosts, but particular strains favor just one species and lay eggs colored to match those of their particular host. Host discrimination against badly matching eggs is the selective force. Cuckoos lay a better mimetic egg whenever the host species is more discriminating. M. de L Brooke, N.B. Davies,

The Scientist has asked a group of experts to periodically comment upon recent articles that they have found noteworthy. Their selections, presented here in every issue, are neither endorsements of content nor the result of systematic searching. Rather, they are personal choices of articles they believe the scientific community as a whole may also find Interesting. Reprints of any articles cited here may be ordered through The Genuine Article, 3501 Market St., Philadelphia, Pa. 19104, or by t

PLANT AND ANIMAL SCIENCES BY FRANCISCO J. AYALA Department of Ecology and Evolutionary Biology University of California, Irvine Irvine, Calif. " The gene that switches embryonic development into the male rather than the female pathway is located on the short arm of the Y chromosome in humans as well as in mice. How this gene exerts its effects is still a mystery. A. McLaren, “Sex determination in mammals,” Trends in Genetics, 4 (6), 153-7, June 1988. " Many insect species carry v

The theory of evolution asserts  ' that evolution has occurred  and explains how it occurred.  Biological evolution is a fact established beyond reasonable doubt. Living beings descend from other organisms more and more different as we go farther back into the past. Our ancestors of many millions of years ago were not human. We are related to the apes and other animals by common ancestry. Biological evolution is a fact established with the same degree of certainty as the rotation