Eusocial Climbers No One Knows More About Ants Than EO Wilson
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THE BIG READ Eusocial climbers No one knows more about ants than EO Wilson. Which is why his U-turn on long-held beliefs about their biological altruism has met with outrage from academia. The unrepentant Pulitzer prizewinner and naturalist talks to STEVE CONNOR There is a terrifying beauty in the bustling activity of an ants’ nest. The selfless sacrifice of the sterile workers to the fertility of queen and colony appears to be an act of supreme altruism. It is both commendable and disturbing. If only ants could grow to the size of rats then theirs would probably be the superior social order, based not on individual free will but on blind obedience to their genetic code. In some respects, the social organisation of ants is reminiscent of human society. Their organised workforce is a caste-basedcommunity Continued on P.36 > Building bridges: ants are model organisms for the study of co-operation and communication in complex societies ANDREW MOUNTER/GETTY IMAGES Ask me what ants have to say about how we should behave and what they tell us about our own morality. The answer is nothing < Continued from P.35 Darwin. Why would some individuals give up their ability to procreate for the sake of others? of specialists serving the needs of the queen. In simple Darwinian terms, it doesn’t appear Soldier ants behave as if they have been trained to make sense because a non-breeder would, on a military parade ground, and some species by definition, not leave any offspring behind regularly wage war, fight to the death and even to pass on the non-breeding trait. take ant-child slaves from conquered colonies. There was a time when this selfless act of Other ants cut and gather leaves to act as biological altruism was explained away by fodder for fungus farms, or “milk” domesti- the “benefit of the species” argument. Sterile cated aphids for their sugary juices. Colonies female workers laid down their lives andovaries are a mix of specialist female workers, fighting for the benefit of the wider group because their soldiers, fearsome guards and fertile breeders. colonies would out-compete rival colonies But each ant is programmed to know its place populated by more selfish individuals. in society, with a selfless dedication to the task But then along came a concept known as of protecting and rearing the queen’s offspring “inclusive fitness”, first formalised in math- in well-tended nurseries. ematical terms by the late evolutionary theorist The allegiance to a queen is central to ant soci- Bill Hamilton in the 1960s. Hamilton’s insight ety, even to the extent of sacrificing the repro- was to show that relationships are important ductive potential of each sterile female worker. when it comes to evolution. There was no need Indeed, this enforced infertility of worker ants to invoke so-called “group selection” to explain has fascinated scientists trying to understand the the evolution of eusocial behaviour because by evolution of true eusocial behaviour – a hyper helping your near kin, you also helped your own -socialist version of community living. genes to be passed on. The phrase covers the highest form of social His argument was encapsulated in a math- organisation in the animal kingdom. It defines ematical formula known as “Hamilton’s rule”, species where there is co-operative care of the which stated that a gene for altruism towards brood, a mixture of overlapping generations your kin could spread if the benefit to the recip- living in the same nest or colony, and a division of labour into reproductive and non-reproduc- ient of the altruistic act outweighed the cost to tive groups who jointly defend the home nest the altruist. And, the greater the relatedness of where the young are reared. individuals, the easier it would be for altruism Eusocial behaviour is a relatively new evolu- to spread by Darwinian evolution. tionary invention and appears to be quite rare. It explained why female worker ants are ready Of the millions of species of animals that have to lay down their sterile lives for their queen lived during the 3.7 billion-year history of life and sister. This was especially true given that on Earth, we only know of 20 ancestral lines each female shares 75 per cent of the genes of that are true “eusocalists”. Fourteen of them their sisters (and queen) – rather than the typi- are insects (ants, bees, wasps and termites), cal 50:50 share of siblings – because of their three are species of marine shrimp, and three genetic makeup. are mammals – two species of naked mole rats In these insects, females are more related and, arguably, humans. to one another than they are to their mother. The reproductive division of eusocial animals Genes carried in the bodies of sterile females into breeding and non-breeding individuals are programmed to work for copies of the same has mystified biologists as far back as Charles gene in the fertile body of the queen. Female worker ants appear unselfish but in fact they scientific mainstream, forming, for instance, carry genes that are effectively working for their a theoretical basis for evolutionary psychology own selfish survival. It meant that something – the idea that human evolution over many tens called “kin selection”, which incorporates the of thousands of years may have shaped the way concept of inclusive fitness, could explain the we think and behave today. evolution of eusocial behaviour. After such a stormy career, you might expect But this neat explanation, which has held Wilson to be taking things a little easier in the sway for more than half a century, no longer late autumn of life. Not so. He has once again cuts any ice with the world’s most distinguished poked a stick into the wasps’ nest of academia myrmecologist, and no one knows more about by publicly denouncing Hamilton’s inclusive ants than the Harvard entomologist Edward fitness and the concept of kin selection. Osborne Wilson, better known as the double “It was a mistake and I went along with it to Pulitzer-prizewinning author and naturalist begin with. But it’s finished. It’s over,” Wilson EO Wilson. tells me, with a flick of his hand. He has thought about ant societies for To add petrol to the fire, he has embraced longer and deeper than anyone alive. In a “group selection”, a concept thought to have career spanning nearly 65 years, he has per- been comprehensively debunked in popular sonally described more than 450 new species style by the Oxford zoologist Richard Dawkins of ant. It is perhaps not surprising that ants in his 1976 bestseller The Selfish Gene. havefigured largely in his thinking and writing, When Wilson co-authored a 2010 scientific and they take a leading role in his latest book paper in Nature magazine with two young The Meaning of Human Existence. Harvard mathematicians rejecting inclusive fit- “Ants are wonderful model organisms for the ness in favour of group selection, he unleashed study of certain phenomena of great interest to a torrent of criticism. About 140 evolution- humans, namely the basics of the evolution and ary biologists wrote to Nature denouncing nature of co-operation, communication and Wilson’s revisionist thinking and re-affirming altruism in the formation of complex societies,” thecentral role played by the selection of genes Wilson explains. and individuals rather than the “multilevel” “But ask me what ants have to say about group selection proposed by Wilson. how we should behave and what they tell us “What happened was confusion and unhap- about our own morality. The answer is nothing. piness because a lot of people had based their Their societies are almost completely female. life’s work on this idea of inclusive fitness,” They eat their injured and they are in almost Wilson says. He now believes that the protest constant, obliterating war with colonies of the was orchestrated by one person, whom he same species. And whereas we send our young declined to name, rather than being the spon- men to war, they send their old ladies. There’s taneous outpouring it first appeared to be. not much there to be learnt,” he says. “We just corrected a mistake made originally Despite a lifetime with his nose stuck in the by Hamilton and then repeated by a number of forest undergrowth, Wilson, 85, has a remark- people, myself included,” he says. able track record in provoking controversy. Wilson argues that multilevel selection – both When his seminal textbook Sociobiology: The at the level of individuals and groups – has led to New Synthesis, was published in 1975, he single- the creation of eusociality in ants and humans. In handedly defined a new scientific discipline, but the simplest terms, individuals who co-operate it led to a fierce reaction from academic leftists, together in groups achieve more and enhance including a few in his own university department the survival of their group, while selfish indi- at Harvard who were furious with him for com- vidualism does not, even in terms of Hamilton’s paring human society to that of insects. inclusive fitness and kin selection. Such was the outrage that Wilson even had “Within groups, selfish individuals beat a jug of water poured over him at one scien- altruistic individuals but in the selection of tific conference by Marxist activists who other traits of individuals that are interactive denounced him as a quasi-fascist genetic with other individuals – social traits – then determinist – which was odd given his lib- groups of altruists defeat groups of selfish eral, Democrat leanings. Four decades later, individuals,” Wilson explains.