Chimpanzees are smarter than humans. Orangutans are smarter than chimpanzees. Humans are smarter than chimpanzees. Which of these statements is true?
The question was answered this month in an investigation by an exceptionally productive group of scientists, many of whom are based at the Max Planck Institute in Leipzig. Published in Science, their project is remarkable for its comprehensiveness. For the first time, a large-scale, systematic three-way comparison of great apes using the same individuals has been carried out. One hundred and six chimpanzees, 32 orangutans, and 105 human children participated.
The findings provide a clear but complicated picture about the mental life of apes, all of us. Since they were released two weeks ago, they have been hailed as evidence of what makes humans unique, but their real value lies in how they demonstrate that you can't discover what makes us different without fully engaging in what makes us the same.
So, it turns out that the first statement is true. Chimpanzees are smarter than humans. In a task that required an understanding of causality, chimpanzees were better than humans and orangutans at using a stick to retrieve a reward. Also, the third statement is true. In other causality tasks where the subject has to work out whether a hidden reward produced noise and which properties of a tool were functional (or not), human children outperformed the other apes. Overall, when presented with an array of tests that tapped the ability to understand space and causality, chimpanzees and humans were typically either the best or equally good.
With respect to the same tasks, the second statement is not true. Orangutans came last. It's worth noting that humans and chimpanzees shared a common ancestor with orangutans about 14 million years ago, and it's possible that because the tests were devised by a chimp-like species, they were biased towards our capabilities. (Indeed, there is a saying among primate keepers that if you give a screwdriver to a chimp, it will throw it at someone. If you give a screwdriver to a gorilla, it will scratch itself. But if you give a screwdriver to an orangutan, it will let itself out of its cage.) All three species scored the same when tested for their understanding of quantity.
When the researchers measured social intelligence, the field changed completely. Although all three apes were skilled in understanding the nature of objects and manipulating them, humans were significantly better at understanding other minds (chimpanzees and orangutans were equal second). Communicating with and learning from other people, as well as understanding their intentions, is --- if not uniquely human -- then much more human than ape. Keep in mind, the human subjects in the experiment were only two-and-a-half years old so differences in social intelligence show up long before the influence of writing, math and a school education.
Once and for all, this investigation shows that when it comes to a comparison of the species, the idea of general intelligence -- a single dimension along which mental ability can be contrasted -- is not only a fraught concept, but a rigged one. It's like saying one animal is better-looking than another. The animal voted more attractive is guaranteed to be the one making the comparison in the first place.
Once you leave behind the idea that humans are always smarter than everything else, life gets a lot more interesting. That the two year olds were more or less the same in their understanding of the physical world as the chimpanzees will be a validation for all parents of young children. When your two-year-old magically appears on top of the kitchen bench in the one second that you looked away, the sense that he is more chimp than human is not far off the mark.
What's really gripping about this sameness is that what the child and the chimp share are characteristic of the abilities of our common ancestor. If you ever wondered what proto-humans were like six million years ago, your own little strange little monster is in this respect a fairly good stand-in.
Obviously, if you're an animal lover, you will embrace the comparison laid out here, and most likely these findings will be used by groups who argue for extending ethical and legal rights to other great apes. Oddly, if you are an unrepentant speciesist, you are going to feel the same way.
In addition to the clever partitioning of physical and social knowledge along species lines, the real revelation of this work is the way it demonstrates how lining up different genomes side-by-side with different behavior is the only way to truly understand where we came from and what kind of animal we are. Such comparative work produces knowledge that is profoundly more deep than anything learned by examining humans alone.
If non-human apes go extinct (and by extension any other animal), there is much about our minds, our brains, and our evolutionary past that we will never know. Worse, there will be countless questions about who we are and where we came from that we won't even begin to formulate in their absence. You don't need to be some kind of Gaia-loving, pan-animal equalist to realize that the human world is enriched by investigations like this one.
Indeed, you can consider the biosphere as clinically as you like -- think of it as a free market, where the greater good is served when everyone follows their own self-interest. Even if your interest includes only your world, it is still in your self-interest that all thrive. No doubt, your concern for humans arises from the conviction that you are unique. It's true -- you are. But if you really want to know how special you are, the other apes have to stick around.