Dna Works in Mysterious Ways

THE THEORY OF EVOLUTION SUGGESTS THAT THE deepest drive of all living things is the urge to perpetuate their genes. How that's done varies widely from species to species. Take pilot whales, for example. While most guys living with relatives will leave home to find a mate, thus avoiding the genetic pitfalls of inbreeding, male pilot whales have found a reproductive strategy that better suits their oceangoing life-style. An analysis of the DNA of whale families, called pods, published in the journal Science, suggests that these young males wait until their pod collides with another, then mate with females they bump into. Afterward, though, they return to their original pod to protect the offspring of female relatives. While their return does little to assure the survival of the fathers' genes, it improves the odds for the closely related genetic material carried by other members of their own pod.

According to a report in Nature, Arizona tiger salamanders have evolved a very different strategy for doing pretty much the same thing: they turn into cannibals. In their larval stage, these amphibians usually find something besides salamanders to feed on. But when raised in mixed broods, a few larvae will assume a larger, more fearsome shape. These "cannibal morphs" seem to exist for one purpose only: to consume cousins (and nonrelatives) and thus make it easier for their brothers and sisters to thrive and multiply. The study does not explain how the cannibals distinguish kin from non-kin. It may be a matter of taste.