The Indiana University News Room informs us: Sex, as we know it, works thanks to ever-evolving host, parasite relationships, IU biologists find. Here are some excerpts, with bold font added by us:
It seems we may have parasites to thank for the existence of sex as we know it. Indiana University biologists have found that, although sexual reproduction between two individuals is costly from an evolutionary perspective, it is favored over self-fertilization in the presence of coevolving parasites. Sex allows parents to produce offspring that are more resistant to the parasites, while self-fertilization dooms populations to extinction at the hands of their biological enemies.
This is good to know. We never cared much for self-fertilization. Let’s read on:
The July 8 report in Science, “Running with the Red Queen: Host-Parasite Coevolution Selects for Biparental Sex,” affirms the Red Queen hypothesis, an evolutionary theory who’s name comes from Lewis Carroll’s Alice in Wonderland text: “It takes all the running you can do, to keep in the same place.” The idea is that sexual reproduction via cross-fertilization keeps host populations one evolutionary step ahead of the parasites, which are coevolving to infect them. It is within this coevolutionary context that both hosts and parasites are running (evolving) as fast as they can just to stay in the same place.
You’ll need a subscription to read more than the abstract, but here’s a link to the paper: Running with the Red Queen: Host-Parasite Coevolution Selects for Biparental Sex. That same issue of Science has another article on the same subject: Sex, Death, and the Red Queen. We continue with the university’s news story:
“The widespread existence of sex has been a major problem for evolutionary biology since the time of Charles Darwin,” said lead author Levi T. Morran. Sex does not make evolutionary sense, because it often involves the production of males. [Hey!] This is very inefficient, because males don’t directly produce any offspring. Self-fertilization is a far more efficient means of reproduction, and as such, evolutionary theory predicts that self-fertilization should be widespread in nature and sex should be rare. However, as we all know, this is not the case.
Yes, we know. Here’s more:
“The Red Queen Hypothesis predicts that sex should allow hosts to evade infection from their parasites, whereas self-fertilization may increase the risk of infection,” said co-author Curtis M. Lively.
By combining the DNA of two parents, sex allows parents to produce offspring that are genetically diverse and different from their parents. Parasites that have adapted to infect one generation may have difficulty infecting the next generation. However, offspring produced through self-fertilization inherit the DNA of their single parent, thus any parasites adapted to infect the parent should also be capable of infecting the offspring.
We know you’re interested, so no further excerpts are necessary. Click over to the News Room at Indiana University and read the entire story. And stop complaining about parasites — they made your life far more interesting than it would have been without them.
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