IOWA Alumni Magazine | February 2012
Question: What's the Point of Sex?

I n what researchers jokingly call the "red-light district" of the Biology Building, Maurine Neiman and John Logsdon study sex.

The UI biology professors investigate some 160,000 New Zealand freshwater snails, whose genomes could help answer one of the most important mysteries in evolutionary biology: Why sex?

Bacteria multiply by dividing; they don’t seem to need sex. A wide variety of animals, plants, and fungi can persist for many generations without sex—although none are known to have given it up for good. But, as simple, asexual ways of reproducing exist in nature, why do most organisms still rely on a mate?

With a four-year, $876,752 National Science Foundation grant, Neiman and Logsdon are decoding the genomes of asexual and sexual snails to look for answers. Some possibilities include:

  • To increase genetic diversity. Changing environments generate pressure to diversify. One major source of environmental change is disease, which can devastate genetically homogenous populations.
  • To prevent the buildup of harmful mutations. An earlier study found that sexual snails accrued negative DNA mutations at only about half the rate of asexual snails. "When organisms reproduce asexually, it’s like they’re making a Xerox copy of themselves," says Logsdon. "The copies get worse over time."
  • To bring good mutations together. Some mutations are much more beneficial when combined with other good mutations. Since only sex can combine mutations—good or bad—within a single individual, it offers an advantage over asexual reproduction.
  • To add spice to life. Although there are solid scientific reasons why sex exists, it also has some unexpected side benefits. From the colorful feathers of a peacock to the glow of fireflies at night, many of the most beautiful features in organisms exist to attract mates. Says Logsdon, "Without sex, there would be little beauty in this world."

A: In her “Sexual Ethics” course, UI religious studies professor Diana Cates gives students an overview of the range of secular, Jewish, and Christian perspectives on sexuality. Though beliefs can vary dramatically even within a single faith tradition, here are some views that Cates’ class covers on the purpose of sex:

  • Procreation. Traditionally, Jews and Christians have viewed marital sex as a means to bring new life into the world. Children can perpetuate one’s culture or religion.
  • Mutual self-giving. In both Judaism and Christianity, sex is seen as a way of bonding and encouraging each other to become whole.
  • Pleasure. Many people celebrate sex for the enjoyment, recreation, and health benefits it can provide.
  • An insight into the divine. In some religious traditions, sex allows the couple to commune not only with each other, but also with God.
  • Whatever you want it to be. Secular ethicists don’t emphasize the meaning of sex; only that participants give their mutual, informed consent and avoid certain negative consequences.
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