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A team of American microbiologists may have discovered the genetic origins of sexuality by examining differences between the algae volvox carteri and its ancestor chlamydomonas reinhardtii, both of which can reproduce both sexually and asexually. Volvox carteri, primarily known for its distinctive round colonies, doesn’t have sexes in the sense that we understand them; it has colonies with a “male” mating type, and colonies with a “female” mating type.

By successfully manipulating triggers associated with mating type, microbiologists can change a colony’s role in the reproductive process. By examining how flexible this process is in the microbial world, we further complicate the loaded concept of biological sexes (which we tend to look at through the less-than-scientific lens of socially constructed gender roles) and may one day redefine sexuality from the ground up, using the more fluid and culturally neutral terminology of reproductive mating types.

But there’s still a lot of work to do. To begin with, we still don’t really know the answer to the question this article asks: who invented sex? While volvox carteri and chlamydomonas reinhardtii have shown scientists a mechanism by which sexual reproduction may have developed, and it is reasonable to suspect that our oldest ancestor to reproduce sexually was (like volvox carteri) also able to reproduce asexually, we don’t know which of our ancestors first learned how to do the deed.

Microbiologists believe our first sexually active ancestor was a single-celled organism that emerged at least 1.2 billion years ago, but—as you might expect—our knowledge of microscopic organisms that existed 1.2 billion years ago is a little incomplete. The sex life of volvox carteri gives us some means by which we can approximate what might have happened, and it is through this kind of microbial pornography that scientists can begin to understand where sex came from, why it’s a beneficial adaptation, and what it all means.

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Tom Head is an author or coauthor of 29 nonfiction books, columnist, scriptwriter, research paralegal, occasional hellraiser, and proud Jackson native. His book Possessions and Exorcisms (Fact or Fiction?) covers the recent demand for exorcists over the past 30 years and demonic possession.
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