Male fruit flies dampen the libido of sexual rivals with smelly pheromone.
The struggle to reproduce and leave behind a genetic legacy has seen the evolution of a variety of weird and wonderful mating features. While male birds such as the peacock don fancy feathers and conduct elaborate courtship dances to outcompete rivals, male fruit flies employ a far less savoury tactic.
For the fruit fly Drosophila melanogaster, the tiny workhorse of the genetics lab, mating isn’t a guarantee of reproductive success. A male who has successfully mated with a female could still be outdone if a rival comes along and mates with his partner after he has wandered off in post-coital bliss. Sperm from both males will compete for the ultimate prize of fertilising the female’s egg.
One way that male fruit flies try to keep their sexual conquests to themselves is by offering their lover a smelly pheromone perfume as a parting gift to repel further would-be suitors.
You’ve committed a crime. You and your co-conspirator have been nabbed, but fortunately, there’s not enough evidence to put you both away for the time you deserve. You’ll be sentenced to just one year in prison. Unless, that is, you turn on your criminal associate, who will take the fall for a three-year sentence, while you walk free. The one catch: the prosecution have offered your partner the same Faustian bargain. If you both keep your mouths closed, you’ll each serve a year. But if you both spill the beans trying to profit at the expense of your partner, you both get two-year sentences. No conferring — you’re both in separate cells. What do you decide?
This is the Prisoner’s Dilemma, first framed in 1950 by mathematicians Merrill Flood and Melvin Dresher, and later given its evocative name by Albert Tucker. In its original form, the best option for both parties would be to each adopt a ‘no-squeal’ policy — in other words, cooperate with each other for mutual benefit. But if you think your partner is a bit of a soft touch who’s likely to cooperate, then as an individual, the option of betraying them (or defecting) becomes almost too tempting to pass up. Except, of course, that your partner could be thinking along exactly the same lines, which would lead to both of you getting a longer sentence than if you just cooperated. But do you cooperate, knowing that your compatriot might end up taking you for the sucker? Continue reading “The prisoner’s dilemma — how cooperation leads to “survival of the fastest””→
Graduating from a crawler to a toddler is a significant developmental milestone for every child. Tentative steps turn into more confident toddles, and soon they are scampering off in whatever direction their insatiable curiosity takes them. At the same time as kids are learning to place one foot reliably after the next, significant changes are also occurring in how they use their hands. Whereas crawlers are happy to grab with either hand, by the age of three, a preference for the left of right hand has usually been established. The transition from crawling on hand and knees as a quadruped, to walking bipedally on two feet, creates a strong bias that can be seen both at the individual level – the vast majority of us has a preference for one side over the other – and at the population level – only around one in 10 people are left-handed. So, too, if we look at handedness from an evolutionary perspective. In mammals, the more upright the posture, the more likely that the species has a left- or right-hand bias. Ambidexterity, it seems, remains the preserve of quadrupeds. Continue reading “Right hand or left? If you have a preference, it may be because you walk upright”→