Sex on Six Legs_ Lessons on Life, Love, and Language From the Insect World - Marlene Zuk [71]
Under what circumstances do we expect these and other less dramatic efforts by parents to show up? In his classic book Sociobiology: The New Synthesis, Harvard biologist (and ant lover) E. O. Wilson lists the "prime movers" that make the evolution of parental care more likely. First is the threat of predators that I mentioned earlier. Other contributors include the kind of environment in which a species finds itself. If food is unpredictable or the climate harsh, offspring will benefit from a parent's buffering them from the vagaries of the world.
Doug Tallamy and Thomas Wood from the University of Delaware took this one step further and pointed out that in addition, the species that evolve parental care have to have several preconditions. They have to reproduce only during a narrow window of time and during a brief period of the year, simply to make parenting cost-effective. They have to survive long enough to provide enough care to be meaningful, a tall order for animals as short-lived as most insects. And because insect eggs don't last well unprotected, particularly during long cold periods, the adults can't spend much of the summer or other favorable time of year growing up themselves. Instead, they have to be mature, or nearly so, at the start of clement weather so that the young ones get the full benefit of their care over the nicer times of the year. And last of all, some behavior patterns that could be adapted to parental care have to be present already in the species; Tallamy has seen the same kind of aggressive display used by mother lace bugs in defense of their brood when the females are discouraging overly ardent males during the mating season.
These kinds of traits are sometimes called preadaptations, characteristics that happen to be present for some other reason and that can then be co-opted for a different use under different selective pressures. Natural selection can't use an empty palette; the raw material for parenting, or flight, or digesting a new food, or any other evolutionary innovation, has to be there already. Preadaptations aren't to be confused with evolutionary premonitions—you don't live in a climate with fleeting resources or bursts of cold because nature decided you should be a parent someday and thought those things would nudge you in that direction. They are more like the bits and pieces that happen to be lying around in your garage; if you want to build a bookshelf, and Home Depot doesn't exist, you are stuck using what you have available. So parenting used the lifestyles already out there and built upon them to make the patterns of care that we see today.
Your Turn, or I Got Up Last Time
Mothers are fonder than fathers of their children because they are more certain they are their own.
—ARISTOTLE
A MALE friend of mine says that when he used to take his son to day care, the other parents—all mothers—would stare at him like he was a child molester. Social progress of the last few decades notwithstanding, women in virtually all parts of the world do much more of the child care than men. It's also much more common for mothers than fathers to take care of the young in animals, insects included. Why is that?
As with many basic truths, Aristotle was onto something when it came to parenting. The concept he alludes to above is what behavioral biologists call confidence of paternity. It implies nothing about a conscious awareness of one's likelihood of having been cuckolded. A male bird, say, that fetches mouthful after mouthful of painstakingly collected caterpillars to the chicks whose beaks gape insistently in his nest will not pass on his genes if it turns out that the female mated with another male during her fertile period several days or weeks earlier. Even worse, he has wasted time he could have spent trying to mate with other females himself. The female, on the other hand, either laid those eggs