January 30, 2016 | David F. Coppedge

Sexual Selection Tossed Again

150 years of speculation about “female mate choice” doesn’t hold up under observation of fruit fly behavior.

It sounds like a neat hypothesis. Females have more invested in care of the young, so they are more choosy about who they mate with. But can that kind of planning be expected in the tiny brains of fruit flies?

To test the idea, researchers at McMaster University got females aroused, then showed them the fruit fly equivalents of a macho dude and a punk. The females seemed to show no preference. What’s most interesting about this is the headline of the press release on Science Daily: “What if Darwin was wrong?

A provocative study by evolutionary biologists at McMaster University takes on one of Charles Darwin’s central ideas: that males adapt and compete for the attention of females because it is the females who ultimately choose their mates and the time of mating.

Instead, new research using fruit flies as a representative species indicates that females do not have specific preferences, suggesting that 150 years of evolutionary theory around mating choice may need to be tossed out.

There’s a lot of baggage to get tossed out with it:

Darwin’s female-choice theory has become the foundation for explaining the presence of exaggerated secondary sexual traits in many males, such as the peacock’s tail feathers,” says evolutionary biologist Rama Singh, an author of a paper in the journal PLOS ONE that explains the findings.

“It has also led to a cottage industry based on the idea that female choice is based on the genetic quality of the males, known as the ‘good gene hypothesis’,” Singh says. “Sexually exaggerated traits are said to be male advertisements to females of their good genes, when in fact they may simply be a means of making the male more visible to females or intimidating other males.

Singh and colleagues put the effectiveness of mating on the male sex drive—the opposite of Darwin’s notion. They suggest that Darwin was influenced by of his culture.

Did Darwin get it right? Could it be that the Victorian values of his time, when men tipped their hats and made other exaggerated displays of sensitivity to women, subtly affected Darwin’s scientific thinking, leading him to attribute a veto power to females in matters of sexual negotiations? Is female choice more apparent than real?

But then they appear to slip into the same personification fallacy, this time for the males:

When a female seems to “choose” a large male over a small male, how do we know if she really prefers the large male or she is making the “choice” under coercion or threat, or if the large male has eliminated others from the competition?

This contradicts their own findings that the female shows no preference for large males. The males do tend to be stronger, they say, because of competition, and that translates into their mating behaviors.

In matters of mate choice and mating, there is no such thing as pure male charm, Singh says. All male moves can be seen as tinged with direct or indirect coercion or threat of physical force.

But there are always going to be counter-examples. The hopeful dances of the male peacock spider, for instance, don’t seem to intimidate the larger females, who can attack and eat them if not satisfied with the performance. And what about humans? Here, they make an exception:

In the case of humans, Singh says, things are different. Sexual behaviors are not hard wired; we assume that they can be modulated and moderated through rules of social interactions imposed by the brain’s veto power over the body.

Why should things be different for humans? Surreptitiously, they introduced into nature a brain that is not hard-wired, but can contradict its own tendencies through “rules” of some kind and veto what its body wants. But wouldn’t an “evolutionary biologist” think that the brain is also a material product of impersonal selective forces?

The paper in PLoS One reveals that the authors still believe in sexual selection. They just demote the “female choice” bit, although they allow it in some situations. What appears to be female choice may instead be the longer time it takes for a female to become aroused, and that’s the reason for the male courtship displays, they say. It gives the male (who gets aroused faster) something to do while the female gets ready.

Our results show that larger males are indeed better at eliciting faster acceptance behaviors in females. Increasing male competition has little effect on mating negotiations. A novel and interesting result shows that once females have crossed the courtship arousal threshold, the relationship between male body size and mating speed and success no longer holds, i.e., females indiscriminately mate more quickly with large or small males. These results have important bearing on our understanding and the relative importance of male mating behaviors and female choice in sexual selection. The results also support Darwin’s idea of the selective advantage of male mating behaviors in driving sexual selection.

But if, as they contend, there is a continuum between female choice and male dominance, do they have an explanation at all? What governs those differences? Why is the male spider puny and the male gorilla large? If larger males get the female, why aren’t all males larger than females? Why can’t evolution produce females that get aroused faster than males? Sexual selection theory reduces to “stuff happens.”

The authors seem to raise more questions than they answer. One question of logic is whether results from tiny fruit flies can be extrapolated to the entire animal kingdom. They readily admit, “The extensions of our results to taxa other than D. melanogaster remain speculations until tested, but our study does bring out the need for revising our understanding of how sexual selection works, and the relative importance of interacting behaviors of the sexes during mating.” A follow-up question, though, is why humans could be exempted from the inexorable laws of mindless selection.

Maybe these authors just wanted to attract readers with their provocative headline, “What if Darwin was wrong?”

What if Darwin was wrong? Here’s what. The world could have been spared a lot of needless suffering, and once scientists admit Charlie led them down the wrong path, the world could be a brighter and better place going forward. All this sexual-selection talk cheapens human behavior. The poetry of Cyrano becomes “nothing but” male coercion or female choice acted on by mindless material urges. Toss out literature, opera, theater, and much of the world’s music; it’s all just mindless selection. Worse yet, it’s selfish genes getting their way through human props.

If the selectionists are right, then science gets tossed out, too. Writing papers is “nothing but” selfish genes getting their way through objects that vocalize the word “scientist” as their genes dictate their propensities. Then realize that the “selfish gene” metaphor is a personification fallacy, and the whole house of cards implodes, leaving Charlie with a mess labeled, “Stuff Happens.”

If the conceptual world is real; if thoughts have real significance; if the brain can veto real illogical nonsense like self-refuting selectionism; then yes, Darwin was wrong. Have a nice, mindful day. A little “Cowboy Logic” is wiser than this 150-year mishmash of conflicting speculations. Join in the tossing-out party and sing along; “If she’s a lady, treat her like a queen; that’s cowboy logic.”




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