If you think it's smart to be brainy there are two things you should know: a limited intellect is usually beneficial; and creativity is often the last resort for losers. Behavioural biologist Simon M. Reader reveals the pros and cons of intelligence

Simon M. Reader

AT FIRST glance, Homo sapiens seems an unlikely candidate for world domination. Our bodies are puny and defenceless, with none of the obvious trappings of a top predator. But no matter, the secret of our success is measured not in brawn but in brains. That makes it tempting to rate the creativity and complex learning abilities that characterise human intelligence as the pinnacle of evolution. Tempting, but wrong.
Think about it. If our kind of intelligence is such a good thing, why is it unique in nature? Given around ~.8 billion years of evolution since life began, you might expect other organisms to have come up with the same winning formula. Yet our big brains are the exception, not the rule. Most animals get by perfectly well with tiny brains and apparently limited learning abilities. Perhaps the combination of a large brain and advanced intelligence isn't a universal winning ticket in the evolution lottery, but is instead just another evolutionary adaptation.

This perspective raises some key questions. What is intelligence good for and, more importantly, what is it bad for? Are humans unique in having taken an evolutionary path that emphasises intelligent behaviour, or have other animals taken a similar route? How do we know which animals are smarter than others, anyway? One surprising conclusion is that, often, it pays to have limited intelligence. Another is that where intelligence has evolved it may have been driven by struggling losers rather than successful individuals.

Advanced learning skills form a fundamental part of what we term intelligent behaviour. Superior learning abilities may initially appear unquestionably useful, but this is far from a universal truth. Animals that instinctively know which predators to avoid, which foods to eat, or what their mother looks like, are less vulnerable than those that have to learn such skills. Learning takes time, and you risk making mistakes: if you happen to be looking at a flower while everybody else is freaking out over a snake, you could end up with a mistaken fear of tulips. Still, many animals, from fish to monkeys, do learn about potential sources of danger from others. But they usually have in-built predispositions that influence the kinds of things they can learn. Rhesus macaques, for example, learn from other macaques to fear snakes more readily than flowers.

But other costs of learning are unavoidable. Brain tissue is among the most energy-hungry of all body tissues. Around 20 per cent of your resting metabolism goes to supplying the energy demands of your brain, compared with ~ per cent in a typical smaller-brained mammal. Then there's the cost of protecting this sensitive structure from mechanical and physiological shocks, which means a thick skull, specialised temperature regulation, and adaptations for precisely controlling the brain's chemical environment. Larger brains also take longer to develop, so parents must invest additional time and energy in gestating and raising each offspring. All this meanslarger-brained animals could be at a substantial reproductive disadvantage compared with their smaller-brained counterparts.

Proving this experimentally is difficult, but one recent study provides a fascinating insight into why many species remain less intelligent. Frederic Mery and Tadeusz Kawecki at the University of Fribourg in Switzerland were able to breed a strain of fruit flies that was smarter than average. To do this, the insects were allowed to feed on orange and pineapple-flavoured jellies, one of which contained bitter-tasting quinine. Later, the flies could choose to lay their eggs on either flavour jelly -both now without the bitter taste - but only eggs laid on the flavour that was not previously tainted were allowed to develop into adults. With each subsequent generation, the researchers switched the flavour containing the bitter taste, to ensure that they were selecting flies with better memories rather than a preference for a particular jelly flavour.
They found that within 20 generations their flies had better learning abilities than control flies on a variety of tasks. But the clever individuals weren't some kind of super-fly:
in domains other than learning their more stupid cousins had the upper hand. For example, larvae of flies bred for cleverness did worse than those of regular flies when competing for limited food (Proceedings of the Royal Society of London, vol 270, p2465).
Clearly the lab is an artificial environment for fruit flies, and the costs and benefits of intelligence will be different in the wild, but this experiment reveals that while improved learning capacities may increase an individual's survival chances in one arena, it can reduce them in others. Natural selection will ensure that increased intelligence evolves only in those species where the total benefits outweigh the costs.

Ever since Darwin, biologists have been interested in what kinds of species demonstrate intelligent behaviour, and why. The consensus is that environmental variability is the key. Mathematical models such as those developed by Peter Richerson ftom the University of California, Davis, and Robert Boyd from the University of California, Los Angeles, reveal that when the environment is changing slowly, an organism's best option is genetically encoded stock responses. However, as the environment changes more rapidly, learning becomes a better strategy for survival. At intermediate rates of change, the ideal tactic is learning from others - social learning. At more rapid rates, individual learning works best.

Different theories and different researchers emphasise different aspects of environmental variability to explain the evolution of intelligence. Social-intelligence hypotheses focus on the benefits of braininess in dealing with a rapidly changing social world. They argue that intelligence helps individuals cope with the demands of social living, allowing them to gain information from others to behave unpredictably - which may be key in outwitting rivals. Thus clever individuals may not only cope better with variability but may actively create variability in their own behavioun And research shows that mammals living in larger social groups - who must presumably keep' track of more individuals and relationships - do have larger brains than less social species, relative to their body size.
Other biologists focus more on the demands of tracking changes in the physical environment, such as the distribution of food, or the need to learn how to access hard-to-eat foods. Supporters of "ecological intelligence" theories point out that species eating foods that are patchily distributed in space and time - such as fruit - have bigger brains than those that eat more dependable, widespread foods such as leaves.
Then there are researchers who suggest that intelligence evolves as a result of positive feedback. They propose that more intelligent species tend to expose themselves to more variable environmental situations where learning is advantageous - eating novel foods, for example - which in turn creates selection pressure for even better learning abilities. However, whales and dolphins present a problem for this theory. Until two million years ago cetaceans had the biggest brains of all mammals - even taking their body size into account - yet their brain volumes have grown little in the past 15 million years.
All these theories invoke natural selection, but it may not be the only force at work. Some people argue that cognitive abilities have less to do with increasing survival and more to do with attracting or choosing mates - sexual selection. The thinking goes that because brains are complex, costly structures, potential mates may view high intelligence as an indicator of a high-quality individual. This might explain why some male songbirds have such an extensive vocal repertoire, for instance.

Geoffrey Miller of the University of New Mexico in Albuquerque has used a similar argument to explain human intelligence. If generations of our ancestors preferred to mate with innovative and creative individid this would have shaped the evolution of ota brains in much the same way that the peahu preferences have shaped the peacock's taiL There is evidence that sexual selection has produced larger brains in some bowerbirds but its part in the evolution of human braja remains firmly at the nice-idea stage.
Nevertheless, all this theorising suggests that there are a variety of reasons why some species might find that the benefits of evobs big, intelligent brains outweigh the costs. In our own species this process has led to a particular kind of learning strategy, characterised by creativity and cultural transmission - the spread of ideas and know-how from person to person. We humans are innovators par excellence, rivalling evolution's powers ofinventionby at least one yardstick:
the number of registered patents outnumbers the living species that have been discovered. We also have an outstanding cultural diversity. What's more, we are especially good at learning from one another, and think nothing of feats such as learning by imitation, which even our closest relative the chimpanzee struggles to do.

So how unique is our kind of intelligence? Experiments with chimps and other higher primates reveal exciting, albeit controversial, parallels with human cognition. But comparing the mental abilities of animals as varied as ants, albatrosses and aardvarks is even more tricky. Obviously you can measure brain size, but are animals with large brains actually more intelligent? We routinely use words like "brainy" as synonyms for intelligence, and even animal behaviourists have assumed they equate, but in fact we have only recently been able to confirm that bigger brains do indeed provide superior cognitive abilities. Even now, controversy rages over why big brains should be betten Meanwhile we have struggled to find a fair test to compare the cognitive abilities of a wide range of species, but recent years have seen a breakthrough. A growing number of researchers, including myselt have been focusing on innovation - the invention of novel behaviour patterns - as a measure of species' cognitive differences in one of the most human of all intellectual abilities, creativity.

This line of enquiry took off about seven years ago when Louis Lefebvre at McGill University in MontreaL Canada, realised that he could plunder the many publications devoted to birdwatching to glean comprehensive and reliable information about innovation in birds. Kevin Laland from the University of St Andrews in Scotland and I made a similar study of ii6 primate species, also using published scientific
reports of individuals' novel behaviour as an index of innovativeness. Both studies found that those animals with the largest brains relative to their body size were also the most innovative (see Diagram, p35) (Brain, Behavior and Evolution, vol 63, p233). Thus it seems that for at least one measure of intelligence -innovativeness - there is indeed a link between brain volume and cognitive capacity.

These studies of innovation give us an unusual insight into the behaviour of a wide variety of animals in the wild. They can also provide clues to the evolutionary benefits and repercussions of innovative minds. In an intriguing follow-up to Lefebvre's work, Daniel Sol, now at the University of Barcelona in Spain, again took advantage of the fantastic record-keeping of bird enthusiasts to investigate how innovation affects survival. He looked at the ioo-plus species of birds that human immigrants had introduced into New Zealand, often in deliberate attempts to recreate the fauna of their homeland. Combining detailed data on the success of these introduced species with Lefebvre's avian innovation database, Sol found species that were innovative in their original habitat were more likely to survive in New Zealand. For these birds at least, innovativeness seems to have helped in the struggle to cope with a new environment.
Even more noteworthy is the finding by Lefebvre and colleagues that innovation may affect the evolutionary process itselt with innovative lines of birds evolving more rapidly than less inventive lineages (see Diagram, above) (Animal Behaviour, vol 6~, p445).
Studies of innovation reveal a wide range of creative ability in the animal world. While a monkey eating a new kind of root hardly seems to be making a cognitive leap, chimpanzees that create novel and highly effective courtship displays, such as flipping their upper lips over their noses, are more impressive. And top marks must surely go to Betty the New Caledonian crow who, when faced with a food basket at the bottom of a plastic tube, bent a piece of wire to make a hook-shaped tool to access the food: a novel solution to a novel problem (New Scientist, 17 August 2002, p44).

But does even Betty demonstrate the same kind of creativity involved in human innovation? This question remains difficult to answer because we have only a rudimentary understanding of the mental processes involved. Many cases of innovation - including human creativity - can be explained in terms of simple trial-and-error learning, without the need for special cognitive skills, although Betty's achievements would be difficult to explain in these terms. The next challenge is to determine what is going on inside innovative minds, both human and animal, so we can see exactly what makes human creativity so special.

In one way, at least, the creative talents of animals do seem to mirror those of humans. In those animals examined up to now the adage "necessity is the mother of invention" rings true. My own experiments with guppies reveal that hungry, small and uncompetitive fish tend to be the most innovative. And among primates, innovators are usually individuals of low social rank. In humans too, innovation is often used only when things are going badly. Businesses and individuals both tend to stick to tried-and-tested formulas if they can.

If inventiveness were indeed a universal panacea, this reluctance to use it might seem bizarre. But once you understand that intelligence is just another survival strategy, it makes more sense. Innovation may provide benefits, such as novel food sources or more efficient foraging techniques, but it also carries costs - the risk of poisoning or the energy wasted trying something new that doesn't work out. In humans, pursuing innovation at the wrong time has led to numerous bankruptcies and even death. So we should expect those animals using their full creative potential to be either individuals who can afford to bear the potential costs of their experimentation or those in such dire need that they are turning to innovation as a last resort. It's a high-risk strategy, but if the gamble pays off they might just hit the evolutionary jackpot.
In other words, the story of the evolution of human creative intelligence is perhaps not one of successful individuals innovating to do still better, but rather one of losers innovating to do less badly.

"Intelligence may even affect the evolutionary process itself, with innovative animals evolving more rapidly than less inventive ones"
Birds with larger brains are not only more innovative but also belong to groups with greater numbers of species, suggesting that intelligence may speed up the rate of evolution
lTJtIy2OOts NtvvscTtntist 137

Angles show ants the way home PHARAOH ants use an appreciation of geometry to find their way home. Worker pharaoh ants travel to and from their colony along a senes of branching paths scented with pheromones. But until now it was unclear how the ants knew which branch would lead them home. Duncan Jackson and his colleagues at the University of Sheffield, UK, noted that various species of leafcutter and pharaoh ants (Monomorium pharonis) lay trails radiating out from the nest that fork at an angle of 50 to 60 degrees. When a returning ant reaches a fork in the trail,it usually takes the path which deviates least. In other words, it will change direction slightly to the right or left but will not make an acute turn back on itself. This means it always takes the path that leads back to the colony. The rseaerchers confirmed that 60 degrees is the optimum angle by pplacing ants on artifidal scent-laden trails in the lab (Nature, vol 432, p907). As the angles of the forks were increased from 60 to 120 degrees, the ants became less and less successful at returning home. Overall, the researchers say, the geometry of the forking paths optimises the flow of ants through the network of trails, especially when ants are walking along them in two directions, and minimises the amount of energy individuals waste by going In the wrong dlnectlon. This means more efficient foraging.

Further Reading

Behavioural biologist Simon M. Reader is an assistant professor at the University of Utrecht in the Netherlands. He is co-editor with Kevin Laland, of Animal Innovation, published last year by OUP