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Tuesday, June 30, 2020

Why Sex? Biologists Find New Explanations.

Christie Wilcox
Quanta Magazine
Originally posted 23 April 20

Here are several excerpts:

The immediate benefit of sex for the algae is that they form resistant diploid spores that can outlast a bad environment. When better conditions return, the algal cells return to their haploid state through meiosis. But as Nedelcu and her colleagues point out, the process of meiosis also offers unique opportunities for genomic improvement that go beyond diversity.

Like all multicellular organisms, these algae have ways of healing small breaks or errors in their DNA. But if the damage is bad enough, those mechanisms struggle to accurately repair it. In those cases, having a second copy of that strand of DNA to use as a template for the repairs can be a lifesaver. “That’s basically what most organisms have by being diploid,” Nedelcu explained.


Such indirect benefits may extend far beyond meiosis. “Sex also refers to copulation and sexual behaviors,” McDonough said. Researchers studying everything from crickets to mice are starting to see that having sex can have all sorts of unexpected upsides.

Unexpected, that is, because it’s generally assumed not only that sex is inefficient compared to asexual reproduction, but that it imposes an energy burden on the individuals involved. Producing eggs or sperm, finding a mate, the act of mating — all of it takes energy and resources. Consequently, there’s a trade-off between reproduction and other things an organism might do to survive longer, such as growing bigger or bolstering its immune system.


Of course, those consequences go both ways: Cultural beliefs and views on sex influence how we go about studying and interpreting the results from research on other organisms. Our biases regarding sexual activity — like which kinds are or aren’t “normal” or proper — “have essentially affected what it is that we’ve deemed important to study in animals,” Worthington said.

McDonough agrees that our preconceptions of what sex should look like and the reasons why an individual should or shouldn’t have it have biased our understanding of animal behavior. They point to the research on same-sex behaviors in animals as a prime example of this. McDonough and their colleagues noticed that the scientific discourse surrounding same-sex behaviors involves a lot of weak or baseless assumptions — for example, that engaging in sexual acts is inherently costly, so same-sex sexual interactions must provide some overwhelming benefit, such as a large increase in lifetime reproductive output, for the behavior to arise and stick around through natural selection. But “in many situations, it isn’t costly, and it may have some kind of benefit that we don’t understand,” McDonough said.

The info is here.