It's a Jungle in There: How Competition and Cooperation in the Brain Shape the Mind Read Online Free PDF Page B

or happens to freeze or drown, some other animal may be able to take its place. If there are many plants and one gets plundered by flood or gets blown away by a strong gust of wind, some other plant that’s still rooted in the soil can carry on. Having many plants and animals boosts the chances that life continues. This is
replication
, one of the three functional mechanisms in Darwin’s theory.
    Another functional mechanism in Darwin’s scheme is
variation
, otherwise known as diversity. Diversity allows species to be prepared, in effect, for what may happen. If all the members of a species are the same, with exactly the same capacity for lifting themselves out from under fallen rocks, for withstanding cold temperatures, or for escaping floods, then all the members of the species will be equally susceptible to those mishaps. However, if the members of the species happen to differ in their physical or behavioral features, then some of them will be more likely to survive than others.
    The term used in Darwin’s theory to refer to survival is
selection
. That’s the third functional mechanism in his model. Selection is vital in natural selection because it provides the means of choosing members of a species that have what it takes over those that don’t. The choosing isn’t divine. There’s no Zeus hurling lightning bolts at creatures whose time, he has decided, has come.Rather, the process is random. Organisms that happen to have features that enable them to survive tend to generate more offspring than organisms that don’t. The surviving organisms are selected-for. The others, the ones that don’t make it, are “selected out.”
    Even well-adapted organisms don’t live forever. Darwin appreciated that it would be bad for organisms to live interminably. Elephants surviving endlessly would pile up. Impalas enjoying immortality would run out of running room. This is because resources are scarce. There are only so many goods to go around—only so many leaves for lunching, so many holes for hiding, and so on. Surviving requires competition for food and shelter, not to mention mates.
Sex
    Mentioning mates brings up the matter of sex, which is another key part of Darwin’s theory. Why should sex exist? What’s the point of it? The question, I realize, may sound ridiculous. “It feels good!” you may exclaim, not quite sure what planet I live on. Before you focus too much on my hedonics—no worries there, I assure you—it’s more pertinent to recall the pragmatic, less hedonistic, side of sex: Sex produces offspring. Without sex, there would be no babies, no puppies, no kittens, no cubs.
    The feeling-good part of sex is, strictly speaking, not critical to its practice. Still, the hedonic (pleasure) part of sex promotes its continuation in generations to come. People don’t watch X-rated movies because they want to fantasize about wheeling baby strollers. They don’t ogle sex gods or goddesses because they’re contemplating the tax deductions they’ll enjoy by claiming more dependents. Sex, or at least the kind that comes with pleasurable moans and groans, is all about the here-and-now. When you watch Nature TV and see animals copulating, you know they’re not planning for their children’s educations. Instead, they are reveling in the buildup to
oh-that-feels-good
. That feeling, or the drive toward it, impels animals (including humans) to do all the strutting, prancing, dancing, and displaying that constitute courtship.
    The fact that sex feels good motivates organisms to do what they do to complete sex acts, thereby generating next generations. Sex also spreads genes. If a guy has one set of genes and a gal has another, their offspring get a mélange of ma and pa chromosomes. The genes the kids pick up may be good ones from dad and bad ones from mom, or vice versa. It’s impossible to tell in advance all the genes that will have positive or negative effects.
    “Good” and “bad” are relative terms,