by Tim Radford December 18, 2002
Mammals have brains. So they can feel pain, experience fear and react in disgust. If a wildebeest did not feel pain, it would carry on grazing as lions chewed it hind leg first. If an antelope did not experience fear, it would not break into a sprint at the first hint of cheetah. If a canine did not experience disgust, it would not vomit; it would not be, as the saying goes, sick as a dog.
Pain, fear and disgust are part of the mammalian survival machinery provided by tens of millions of years of evolution. Homo sapiens has, however, only been around for about 200,000 years. So all three emotional states owe something to mammal origins. If bipedal mammal members of the Garrick club or Millwall feel those emotions, so do deer, foxes and dogs. The argument is about how "aware" or "conscious" non-human mammals might be during these emotional experiences. When a fox hears the hounds baying and starts to run, is it obeying some instinct inherited from ancestors that knew when to get out of the danger zone? Or does it "know" to be afraid?
That might be the wrong question. A human startled by a strange shape in a darkened corridor experiences a pounding heart, and lungs gasping for air, and a body in recoil. This is the famous flight or fight reaction. A human experiences the full force of fear and has already started to counter the danger a fraction of a second before the brain has time to absorb and order the information contained in menacing shape.This is because mental calculations are too slow to cope with surprise attack. Pain precedes logic. Touch something hot and you withdraw your hand even before you have time to think about doing so. Once again, the wisdom is after the event.
If humans can experience the universal emotions of fear, anger, disgust, happiness, sadness, and surprise, then so can mammals. The real puzzle is: does an animal think about its state of fear? Does it have not just a mind but a theory of mind (ie can it put itself in another animal's shoes)? Does it have a sense of its own identity?
All animals communicate, but only humans have language. So the puzzle remains: do animals think? Can they think about abstractions, about the past, about other animals? So researchers have wrestled with a series of experiments to see whether animals are capable of behaving as if they had the capacity to learn, the will to improvise and the ability to guess what other animals are thinking. Dogs show a remarkable capacity to guess human intentions correctly. But then dogs have lived intimately with humans for 15,000 years, so the domestic dog may not be the ideal test animal.
Apes, as humanity's closest relatives, show unexpected abilities. Researchers from St Andrews in 1999 counted 39 different ways in which chimpanzees deal with food: since these differ according to group and geography, they have used the word "culture" to describe these differing methods. One female chimpanzee in Kyoto two years ago convinced researchers that she can place Arabic numerals in ascending order one to nine. Two rhesus moneys called Rosencrantz and Macduff astonished a team at Columbia University in New York in 1998 by distinguishing groups of objects numbering one to four. Chimpanzees in large captive colonies forge alliances, switch sides and doublecross each other. They have also been seen in the wild systematically searching for leaves that have a medicinal effect: from such observations, a new branch of research has been born. It is called zoopharmacognosy.
Chimpanzees and humans share a common ancestor, and 98% of their DNA. Do more distant mammal relatives share the capacity for cogitation? Keith Kendrick at the Babraham Institute in Cambridge years ago astonished the world by revealing that sheep could recognise up to 50 other sheep, and up to 10 human faces for at least two years after first seeing them. If a sheep can tell the difference between other sheep from flash cards and screen pictures, it must have a sense of these other sheep even when they are not there, and perhaps also have an idea of "self": a sense of ewe and "I".
More disconcertingly, pigs have demonstrated their own theory of mind. Mike Mendl of Bristol university revealed at the British Association science festival in 2002 that experiments showed that a stronger pig that did not know where the food was hidden learned to follow the weaker, but better informed animal, to the trough. At which point the weaker pig would start to use distracting behaviour to keep the bully pig guessing, and only dive for the rations when not being watched. That is, a pig could guess what another pig was thinking and outsmart it. In a human, this is called "intelligence".
However, the highest-flying animal problem solver in 2002 was not a mammal at all. Betty the crow lives in an Oxford laboratory. She repeatedly picked up a straight piece of wire, bent it into a hook and used the hook to lift an appetising treat from a tube too deep for her beak. She had, puzzled observers reported in the journal Science in August, never seen a piece of wire before. So an animal far removed from humankind could identify a challenge, contemplate a simple matter of physics, identify a tool shape, select a raw material, make a tool and retrieve the reward. Birds are cousins not of mammals but of the dinosaurs: humans and birds last shared a common ancestor 200 million years ago. Experiments like these confirm, over and over again, that other mammals are more like us than we thought. So it becomes increasingly difficult to work out what it is that makes humans different. Think of these things next time you take aim at a grouse or saddle up for the hunt.
. Tim Radford is the Guardian's science editor