Sex on Six Legs_ Lessons on Life, Love, and Language From the Insect World - Marlene Zuk [69]
Why Should You Care?
SO IF most insects, and indeed most animals, get by with recklessly flinging eggs to the four winds, metaphorically speaking, why has more elaborate parental care evolved where it has? People often assume that human children require as much care as they do because of two characteristics of our species: high intelligence, sometimes seen as a reliance on learning rather than instinct, and being born at a comparatively early and helpless stage of development. Our intelligence, and the accompanying complexity of our lives, supposedly means that parents need to spend a great deal of time teaching their offspring the ins and outs of life in society. If we were simple little automatons, the conventional wisdom goes, we too could dump our babies into the world and let them fend for themselves. But faced with an unopened cereal box and a carton of milk, much less a gazelle or a yam, a child needs someone else to open, kill, or cook the meal, and hopefully that someone will make sure that eventually the child will be able to do the same thing unassisted.
The problem with that argument is obvious once you think about insects. Although they do learn more than had previously been believed, as I discussed earlier, not even I am going to champion their qualifications for Mensa. And yet many groups still show elaborate parental care. Furthermore, the species that have doting parents don't seem any more or less intelligent than those lacking them.
What about the idea that we are stuck with helping our children because they are born at such a nascent state? Our big brains mean that the female pelvis can't accommodate a baby born any later, according to this notion, so it is related to that "we are so smart we have to toddle around for years before we can manage to leave our mothers" idea. But here too the insects make that suggestion look dubious, since egg size doesn't have much to do with the size of the brain of the bug that is hatched from it. Earwig mothers, doting though they are, never labor to bring forth their six-legged progeny.
What is essential is the guiding principle behind the evolution of every trait, whether that trait is a behavior, such as offspring care, or the shape of a body part, such as the length of a tail. Doing it has to increase the bearer's fitness, the likelihood of passing on its genes, more than not doing it. When it comes to parental care, that means that even if tending the young takes away valuable time and energy that could theoretically be used to have more offspring, it's worth it if you leave more copies of your genes that way than you would if you deserted your young and went off to have more children. Having offspring is valuable, certainly. But it will win you the evolutionary jackpot only if those offspring survive. Rampant fecundity for its own sake goes unrewarded.
For insects, and maybe for the rest of us, the threat that made it worth giving up future offspring to focus on the current batch seems to be predation. It's a beetle-eat-beetle world out there, so to speak, and eggs are about as vulnerable a stage to be exposed to it as can be imagined. In a small, unassuming black bug called a burrower bug, females guard the mass of eggs they produce in the leaf litter on the forest floor. Once the young hatch, the mother