Sex Will Make You Clean, Genetically Speaking
This week’s issue of Science includes a report from two evolutionary biologists who studied one theory for why sexual reproduction (as opposed to asexual reproduction) continues to occur. The news release explains:
Sexual reproduction is biologically costly and at times complicated. In mammals, sex is usually preceded by intricate mating behaviors. It requires the compatibility of sexual structures, an insertion event, fertile eggs and sperm, and the successful unification of egg and sperm into a viable zygote. All of this adds up to a big energy investment -- energy an organism might have used for other purposes. Scientists have long been left to ponder, what is it about sex that justifies its big energy investment?
The researchers used as their model a water flea and found evidence to support the idea that sexual reproduction is an “evolutionary housekeeper” providing an opportunity to reorder genes and remove harmful mutations. The study also suggests sexual reproduction maintains its own existence by punishing, in a sense, individuals of a species that meander into asexuality.
Biologists have come up with a wide variety of competing (and, in some cases, complementary) hypotheses to explain why sex continues to exist in the midst of recurrently evolving asexual competitors. The most widely accepted explanation has been that sexual reproduction confers the benefit of "unlinking" genes, meaning bad versions of genes won't always get to ride the coattails of good versions, and vice versa. In essence, the theory holds that natural selection operates best when parts of the genome are free to shuffle.
Eureka Release – Sex, Cleaner of Genomes
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