Natural History Museum, London
Until 2 October
Sex has been around for about a billion years - plenty of time for it to get complicated. Male bedbugs stab their mates to inject them with sperm. Birds present the most fabulous displays, many of them invisible to humans until they are shown under ultraviolet light. Hermaphrodite sea hares form chains of love, with those in the middle both penetrated and penetrating. And "an 82-year-old recycled teenager" can advertise that she's "looking to be swept off my feet".
Sexual Nature starts with the most basic question: since a few creatures, if push comes to shove, manage to fertilise themselves, why do we need sex at all?
It considers the different challenges of sex underwater and on dry land. It explores seduction techniques, ferocious fights between males and "sperm wars" to ensure it is they, rather than their rivals, that pass on their genes to the next generation. Dragonflies clean out the reproductive tract of their mates, while hedgehog semen sets solid within the female. Other animals remain locked together for hours or even days.
It is part of the fun of an exhibition like this that it goes in for plenty of jokey anthropomorphic comparisons while also undermining them. There's no shortage of homosexuality in the animal kingdom - gay orang-utan sex is apparently much more tender than the straight variety - but is there really any sadomasochism? "All conceivable domestic arrangements have evolved in the animal world", we are told at one point, although it later emerges that hands-off fathering is the norm "for most mammals and many birds".
Isabella Rossellini has been submitted to many strange indignities in films such as Blue Velvet. But they are nothing compared with what she puts herself through in a series of eight short films, titled Green Porno and Seduce Me, that accompany the exhibition. In one, she dresses up as a duck and addresses the camera: "Are they trying to seduce me? What am I, a duck? They all want to mate with me with their corkscrew penises. I evolved vaginal complexity to keep control...I can discombobulate the phallus."
The final section turns to those "undeniably sexy beasts", human beings. Just in case footage of sea slugs mating has put visitors in the mood, a panel asks: "What do you find attractive? Does anyone here catch your eye?" But there is also a section where people can contribute their own experiences, memories and chat-up lines.
"Got drunk," recalls one, "vomited all over date. End of."
"I would probably be bisexual if I had the courage," proclaims another.
"Crying after intercourse is so satisfying," notes a third.
Even life as a sex-changing limpet sounds simple by comparison.