Bitch: On the Female of the Species

by Lucy Cooke

Croft’s team discovered that if a male orca’s mother died before his thirtieth birthday, he was three times more likely to die the next year. If she passed away after he turned thirty, he was eight times more likely to snuff it during the following year. But if mum had gone through menopause, his odds of dying the next year went up by fourteen times. The data was irrefutable: sons whose mothers live a long time after giving birth to them have a survival advantage over those whose mothers die earlier, and that only becomes more true as both mother and son age. These post-menopausal orcas thus support the grandmother hypothesis posited by Hawkes.

Marino thinks that orcas are emotionally sophisticated, lightning-quick thinkers with ‘many more dimensions to their communication’ than we have. They are one of the handful of animals that have passed the famous mirror test, paying attention to their own reflection in a way that suggests they have a sense of self.

The reason for the evolutionary longevity of the bdelloid (pronounced with a silent b) is an area of continuing investigation and furious deliberation among scientists. However, one of the secrets to their success seems to be that they ‘steal’ genes from other lifeforms, possibly through the stuff that they eat.

The bdelloids are able to survive and produce viable replicas of themselves because their mosaic of stolen genes code for enzymes that give them the remarkable ability to repair their shredded DNA. The temporary water sources they call home routinely dry out, leaving the bdelloids essentially mummified for potentially years while they wait for their next rain. Such dehydration has the same damaging effect on their DNA as radiation (if less extreme); their stolen genetic repair kit helps them patch things back up. As an added bonus it’s likely this is the bdelloids’ secret to surviving millennia without males; the process of stealing genes and reconstructing their genome looks like it provides the bdelloids with the same evolutionary benefits as sex.

If you trust the maths, this might not even harm the gene pool. Recent models have shown that good mutations can actually spread almost as fast in a population that is primarily parthenogenic. The benefits of sex seem to top out if it happens just once every ten or twenty generations; as one recent paper put it, sexually reproducing just 5–10 per cent of the time is enough to get the same genetic advantages as doing it every time.

The barnacle’s sedentary life is a boon for personal safety, but less so for sex: locating a mate isn’t exactly easy when you’re glued to a rock. Darwin discovered the barnacle’s secret weapon is an extravagant penis, the longest relative to body size in the animal kingdom. Darwin’s customary functional prose takes an almost giddy turn as he describes how the barnacle’s ‘probosciform penis’ is ‘wonderfully developed’ and ‘lies coiled up, like a great worm’ but ‘when fully extended, it must equal between eight and nine times the entire length of the animal!’. Such frivolous length is purely functional. It enables the barnacle to cruise the neighbourhood for sex, whilst remaining cemented to the spot head first.Like a sort of X-rated Mr Tickle. It helps that most barnacles are simultaneous hermaphrodites. Every individual has both male and female reproductive organs so they can fertilize and be fertilized by all of their neighbours. And if there’s no one else within reach, as a last resort the barnacle can recall their roving inseminator and fertilize themselves.

The barnacle’s rapid evolution from one reproductive system to another reveals the surprising flexibility of sex and its expression in nature. Darwin clearly recognized this – he was way ahead of his time. Which is why it is a shame he chose to exclude his beloved barnacles from his musings on the manifestation of sex. They might have prevented him from presenting sex in such a dichotomous and deterministic fashion. Today barnacles, and creatures like them, are at the forefront of teaching us how sex is no static binary, but a fluid phenomenon, with fuzzy borders that can bend to evolution’s whim with astonishing speed.

These tiny two-toned fish became internationally famous as the stars of Finding Nemo. The smash-hit animation, released by Disney, featured the heart-warming tale of a young anemonefish (Nemo) that had lost his mum to a barracuda and ended up going on an incredible adventure before reuniting with his dad (Marlin). Needless to say the movie takes more than a pinch of artistic licence with the real lives of anemonefish. These monogamous reef dwellers set up home together in an anemone, whose stinging tentacles offer the couple, and their eggs, protection. The belligerent female is the boss in the relationship – it’s her job to defend the territory while the male cares for the eggs. The fish live surprisingly long lives – up to thirty years – in the same anemone, often with a bunch of juvenile males in attendance. If the female is removed, say nabbed by a barracuda, it will trigger Mr Anemonefish to transform into the new dominant female, and one of the juvenile males to mature into her mate.

The simple experiment shows that these transitional anemonefish both behave like females and are recognized as females by other fish, even though they have testes. It’s a very clear demonstration that brain sex, and thus all sexual behaviour, and gonadal sex can be uncoupled.