Tooling Through the Trees

By Carl ZimmerNov 1, 1995 6:00 AM


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Carel van Schaik had a dilemma. In August 1993 he was sitting in a crude shelter in the Suaq Balimbing swamp in Sumatra, deciding whether he should make the place his scientific home. Van Schaik, a primatologist at Duke University, studies orangutans. Suaq had a lot of them--as many as 20 individuals per square mile. But Suaq is a godforsaken place. Never mind the prevalence of malaria, dengue fever, and typhoid--simply following the orangutans as they moved high overhead in the trees required wading through thigh-high muck. Every day was an exercise in exhaustion.

We were sitting there in our little shelter, thinking, ‘Well, the place certainly has a lot of orangutans,’ says van Schaik. But it was such a terribly deep swamp. We were really tearing our hair out, wondering whether we should stay there or not. And then Ibrahim, one of my Indonesian assistants, just dropped in a little observation: ‘You know, boss, I saw something really weird today. I don’t know what to make of it. Sarah’--one of our orangutans--‘was putting a stick in her mouth and then hammering away at a tree with it.’

I said, ‘What?’

Sketchy as Ibrahim’s news was, van Schaik began to wonder if he had actually seen something never witnessed before: a wild orangutan using a tool. Slogging through Suaq suddenly seemed worth the effort.

Toolmaking was once considered a hallmark of the unique intelligence of human beings. Researchers began to question that notion, however, as they discovered that wild chimpanzees, our closest relatives, use a number of tools, including sticks to get termites out of nests, and stones to crack open nuts. Moreover, they don’t just use whatever happens to be lying around--they tailor their tools to fit a particular job.

The last common ancestor of chimps and humans lived 6 million years ago. Gorillas split off from the ancestor of chimps and humans 8 million years ago, and while they sometimes play with tools in captivity, they never use them in the wild. Orangutans, which branched away from the other apes 14 to 16 million years ago, have a different story. Captive orangutans have been taught to wield hammers, screwdrivers, and keys (among zookeepers they’re notorious as lock-picking escape artists), and even to make stone-flake knives. But since they needed a human to teach them and had never been seen to use tools in the wild, it appeared they weren’t in the same league as chimps. Animals do a lot of things in captivity that they will never do in the wild. It’s the difference between having the capacity to do something and having the actual skill, says van Schaik. Researchers believed that the ability to make and use tools was something that only emerged in our chimplike ancestors.

Van Schaik and his co-workers came back to Suaq in January 1994, built a boardwalk through the swamp to make their lives a little easier, and began following up on Ibrahim’s report. They quickly discovered that the Suaq orangutans used tools for a number of purposes. As Ibrahim had seen, sometimes an ape will break off a branch about a foot long, snap off the twigs, fray one end, and put the other end in its mouth. Holding on to a tree trunk with its arms and legs, the orangutan rams the stick into a hole containing a termite nest. It then flicks out the broken-up chunks-- full of delectable larvae and pupae--and eats them. The Suaq orangutans also use sticks to scare out ants from tree colonies. But the most common use is when they go for honey, says van Schaik. They put a stick in and poke through some nest wall and move it around and catch the honey, pull it out, turn it around and stick the other end in their mouth, and then go back in. If the stick is too long to use comfortably, they snap off one end.

Orangutans also use tools to eat fruit. When the fruit of the Neesia tree ripens, its hard, ridged husk softens until it falls open. Inside are seeds that the orangutans love, but they are surrounded by fiberglass-like hairs that, as van Schaik can personally attest, hurt like hell. A Neesia-eating orangutan will select a five-inch stick, strip off its bark, and then carefully collect the hairs with it. Once the fruit is safe, the ape pops the seeds out with the stick or with its fingers.

Every adult orangutan van Schaik’s team has followed for more than five minutes at Suaq uses tools. It’s clearly a routine thing, a population-wide, year-round phenomenon, says van Schaik. It’s not the idiosyncrasy of one genius.

On the other hand, other orangutan populations don’t seem to do it. One reason may be ecological: the trees in Suaq are especially riddled with insects, and the orangutans there depend heavily on insects for food, so they’re under pressure to figure out how to get bugs out of trees. Yet there are similar swamps in Borneo where researchers have not seen orangutans use tools. Van Schaik thinks cultural factors may play a role, too. In any given population, some genius does have to figure out how to use sticks first. In Borneo, says van Schaik, the inventor may simply not have been born yet; in other environments, an individual orangutan may have invented tools only to have its peers ignore the skill because it was superfluous there.

It’s possible, of course, that the very first invention of tools among orangutans happened relatively recently in Suaq. Van Schaik thinks that’s unlikely. Of the four types of great apes, he points out, three-- chimps, orangs, and humans--have now been observed to use tools in the wild. The simplest explanation, says van Schaik, is that the apes’ common ancestor did, too. Gorillas, the fourth great ape, lost the skill because they developed an easy diet of leaves and nettles that made tools pointless. But by the time humans evolved, toolmaking was a long- established art. We don’t have to see early hominids as these heroes that invented 10,000 different things in five minutes, says van Schaik. There may have been little that was new there--they already had the capacity and most likely the skill.

Van Schaik’s observations complement a growing body of research that suggests the real quantum leap of intelligence did not happen 6 million years ago among the earliest hominids but 16 million years ago among the earliest great apes. It was then, in this view, that animals first evolved insight--an ability to make connections between concepts, recognize cause and effect, and plan actions. The sort of thinking required for using tools, for symbolic communication, for empathy--for all these supposedly quintessentially human gifts--may be far older than we imagined.

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