Most writers wouldn’t be pleased to see their name in a national newspaper next to the headline “I haven’t had sex for 40 million years. Should I worry?” But what are science writers, if not a little strange…
The headline adorns my latest feature, which appears in today’s issue of of Eureka, the monthly science magazine from the Times. It’s about a group of animals called bdelloid rotifers that have lived a completely asexual existence for at least 40 million years, and potentially up to 100 million. The piece is part of Eureka’s sex issue, including some great features on spontaneous sex changes by Hannah Devlin and what it’s like to be a sex researcher by Petra Boynton.
I pitched the article because sex, for all its fascinating and relatable human aspects, is one of the most interesting topics in evolutionary biology. Rotifers provide a perfect hook for exploring it; their unusual lifestyles raise questions about the pros and cons of sex versus a lack of it (in evolutionary terms, no sniggering in the back), why the vast majority of animals practice sex, and how this group have managed to get away without it.
Also, I loved the idea of pitching a story about the world’s longest dry spell in an issue that’s devoted to sex (and ducks are so last year).
As a teaser, here are the opening paragraphs:
Many of us would balk at the idea of going a year without sex, but that is nothing compared with the longest dry spell in the animal kingdom. In freshwater ponds around the world live tiny animals called bdelloid rotifers. As a group, they have not had sex for somewhere between 40 and 100 million years.
The bdelloids (pronounced with a silent b) are apparently the only group of animals to have abandoned sex for such a long time. They live in an all-female world in which mothers give birth to daughters who are genetically identical clones. No males have ever been found. In this respect they are unique. Many animals, including aphids, sharks and Komodo dragons, can reproduce asexually from time to time but sex is still their default setting. Only a smattering of animal species has gone completely down the asexual path and almost all of them have arisen relatively recently. Bdelloids are the tiniest twigs on a tree of life that is otherwise dominated by sex.
There is a good reason for this. Sex has many important benefits that are not abandoned lightly. Giving up these benefits is a poor long-term strategy and one typically rewarded with extinction. The bdelloids are the exceptions that prove the rule. Despite their unusual lifestyles, they have not only avoided extinction but they positively flourish. Today, there are more than 300 species all over the world. In the past few years, scientists have finally discovered some of the secrets that underlie their success. They have evolved ways of achieving all the evolutionary benefits of sex without actually doing the deed.
To see the rest, you’ll have to buy the Times. Paywall subscribers can also read the online version.
Image by Diego Fontaneto