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How do chimps top us in a brain test?


“We are 98.77 percent chimpanzee,” Tetsuro Matsuzawa told me last week. “We are their evolutionary neighbors.”

Matsuzawa’s extraordinary work at the Primate Research Institute at Kyoto University recently made headlines all over the world. In case you missed it, Matsuzawa’s chimps beat humans at a memory game played on a computer. It was the first time that chimps had been shown to have superior brain power to humans — at least in this particular test.

Matsuzawa said that chimp intelligence was underestimated. Other researchers I have spoken to have said the same. If scientists haven’t noticed how much potential chimps have, it’s because of the way they are kept, and the tests that we give them. (Not to mention the fact that we see ourselves as uniquely different — but more of this later.)

The Primate Research Institute at Kyoto is different to most. Chimps are “invited” by name into the lab. If they are interested in playing along, they go in. In the memory tests reported last week, the six chimps involved were three mothers and their three offspring. In the past, tests have been carried out without this tacit “consent” of the chimps. In other words, they might not have been in the right mood to play about on a computer.

Also, the chimp juveniles who performed better than the Kyoto University students had been playing the game for a while. They had been trained to use the touch-screen monitor since they were 5 years old (they were 7 at the time of the tests), when they were taught the sequence of numbers from 1 to 9.

No wonder students failed

Some people complained that the students should have been allowed more time to train. Some wags, obviously thinking of their own days at university, said it was no wonder that students failed on the memory test, with the amount of marijuana and alcohol they consume.

In fact, the tests showed that only young chimps were better than humans; older ones were the same or worse. The tests — in which the chimps had to remember the location of numbers on a screen — show that, given a fair chance, young chimps can make use of a kind of photographic memory. In one set of tests, the numbers 1 to 9 were flashed on the screen for only 210 milliseconds. That’s shorter than the time it takes for the eye to move across the screen and read all the numbers.

So the only explanation is that the young chimps could “photograph” the display, and refer to it when they decided where the numbers were hidden and touched those points on the screen. Some human children, very rarely, have a form of this photographic memory, but it seems that, like chimps, we lose it as we grow up.

So the test really highlights that chimps’ brain-processing ability — not so much their intelligence — can sometimes outperform that of humans.

Probably the strongest point that Matsuzawa’s work brought across to the public is that the differences between us and chimps are just a matter of degree, not of type. Most things we have thought of as being uniquely human have been seen to some degree or other in other animals.

This is only to be expected, especially in an animal with which we had a common ancestor only about 5 million years ago. Some people don’t like this. They would rather insist that there are unique things that humans have that other animals don’t. I’m sorry, but all the things we thought of as being uniquely human at one time or other have eventually been seen in chimps.

Using tools? Jane Goodall documented chimps using tools in the 1960s, and all the great apes have since been found to use tools. Well then, how about using weapons? That too was seen, this year, in chimps (they use sharpened sticks to spear bush babies). A written language? OK, chimps aren’t going to be employed by this newspaper any time soon (though some might argue there are already some monkeys writing columns), but given the chance, they can learn to use symbols to communicate.

OK, so it’s just a matter of degree — but given that we are genetically so similar, how come we are so much better than chimps at most things? What chance would chimps need to get even closer to us, intelligence-wise? They would need a period of intense natural selection.

A paper published this week in the Proceedings of the National Academy of Sciences shows that humans have gone through a period of rapid evolution in the last 5,000 years alone. That’s not very long — only since the Stone Age; only 100 to 200 generations ago. A scan of the human genome found evidence of recent selection on approximately 1,800 genes, or 7 percent of all human genes.

“We are more different genetically from people living 5,000 years ago than they were different from Neanderthals,” said study leader John Hawks, of the University of Wisconsin-Madison.

New selection pressure

Many of the new genetic changes have occurred as a result of changes in the human diet brought on by the advent of agriculture. But the biggest new selection pressure, Hawks says, has been as a result of population size.

As people started living in much larger groups and forming permanent or long-term settlements, epidemic diseases such as malaria, smallpox and cholera could exert dramatic effects. The human population has grown from a few million people 10,000 years ago to about 200 million people 2,000 years ago, to 600 million people in the year 1700 and more than 6.5 billion today.

“What’s really amazing about humans, that is not true with most other species, is that for a long time we were just a little ape species in one corner of Africa, and weren’t genetically sampling anything like the potential we have now,” he says.

As we all know, chimps, along with bonobos and gorillas, are just about surviving in a few corners of Africa. There’s no chance for them to go through the intense bout of natural selection that we have done, but work like Matsuzawa’s can help tease out their potential.

The second volume of Natural Selections columns translated into Japanese is published by Shinchosha at ¥1,500. The title is “Hito wa ima mo shinka shiteru (The Evolving Human: How new biology explains your journey through life).”