Tag Archives: Richard Dawkins

Dead baby monkeys

There’s a dark side to being a primate. Last year a review article summarized data on rates of lethal aggression in non-human animals. The figure below shows some of the results. Several clusters of especially violent species stand out in the figure, including primates.

dead monkeys

Much of the lethal aggression in primates involves infanticide. Sarah Hrdy demonstrated back in the 1970s that infanticide occurs regularly in Hanuman langurs, monkeys in India. A male who takes over a group of females will systematically kill offspring sired by the previous male. If you think evolution is about the survival of the species, this is hard to explain. But it makes sense given the logic of the selfish gene. Females who lose an infant return more quickly to breeding again, and the father of the next infant is likely to be the killer of the previous one.

Primates may be particularly vulnerable to this grim logic, because they spend a long time as infants. Commonly L/G>1, that is to say, the time, L, a female spends lactating for an infant (during which she is unlikely to conceive), is usually greater than the time, G, she spends gestating an infant. This puts particular pressure on males to hurry things along by eliminating nursing infants fathered by other males.

As a result, infanticide is relatively common among primates, and females under particularly strong pressure to find ways to avoid it. Hanuman langurs live in one-male units, where a female has little choice about who she mates with. In other species, by contrast (most baboons, chimpanzees), multiple males reside with multiple females. In these species females are often sexually promiscuous, sometimes actively soliciting multiple males for sex. This is probably mostly a matter of confusing paternity sufficiently to suppress the threat of infanticide. There’s a general lesson here: female promiscuity generally has different evolutionary roots than male promiscuity.

Our Good-Enough Universe

Covering the whole history of the universe naturally raises some Big Questions. We’ll consider some of these over the coming year, along with generous portions of memorable milestones, anecdotes, and curious facts.

Before we get to January 1, here’s a Big Question: why is the universe we live in well-suited for intelligent life? The answer may be related to the answer to another question: why are living things so well-adapted? Why do their various parts work together so well? The Ancient Greeks pondered this question. Some of them (Aristotle, for example) thought it was just the nature of living things to be well-adapted. But some of them offered a materialist explanation: animals with all sorts of combinations of different parts had once existed, but only some of them survived for us to see them. Lucretius, who was sort of the Roman version of Carl Sagan and Richard Dawkins (if Sagan and Dawkins had written in dactylic hexameter) wrote:

“ten thousand tribes of mortals poured forth,

fitted together in all kinds of forms, a wonder to behold. ….

as many heads without necks sprouted forth,

and arms wandered naked, bereft of shoulders,

and eyes roamed alone, impoverished of foreheads.”

But only a small fraction of these monsters – the accidentally well-adapted ones –survived. This sounds like Darwin’s theory of “survival of the fittest,” but in Darwin’s theory, the process is cumulative, and organisms get better and better adapted over time. (You can find biologist John Rees reviewing this history, and sticking up for the pre-Darwinian theory – call it “survival of the viable” – here. Also, literary critic Stephen Greenblatt reviews just how explosive the rediscovery of Lucretius was for the European Renaissance.)

Nowadays, a significant number of physicists defend a similar theory. The same process f inflation that generated our universe automatically generated vast numbers of other universes; only a small fraction of these, including ours, are fit to live in. Here’s one physicist, Leonard Susskind, doing the Lucretius thing:

“Every possible environment has its own Laws of physics, its own elementary particles, and its own constants of nature. Some environments are similar to our own but slightly different, For example, they may have electrons, quarks, and all the usual particles, but with gravity a billion times stronger than ours. Others have gravity like ours, but contain electrons that are heavier than atomic nuclei. Still others may resemble our world except for a violent force … that rips apart glaxies, molecules, and even atoms. Not even the three dimensions of space are sacred … [there may be] worlds of four, five, six, or even more dimenions.” [p.20]