A lot of people over a lot of years have disliked Darwin’s contention that humans are just “big-brained apes.” They’ve fought to maintain a suitable distance between us and our closest primate cousins.
While the least sophisticated of these people are motivated by Bible literalism, and others by an often unrecognized or unadmitted need for human dignity, the most thoughtful objectors argue that we can’t rely on perceived similarities as real evidence that there is an uninterrupted continuum from the ai ai to the academic.
After all, these critics point out, we don’t fully understand what goes on in the human mind, and it’s going to be much harder to prove a significant connection between humans and, say, neural blood flows in gibbons or sexual behaviour in bonobos.
Still, the research into the behaviour of non-human primates continues. Three articles available online illustrate the kinds of research that lends credence to the “big-brained ape” description.
Whether the interpretations in these studies are reasonable, or just further instances of an inappropriate extension of “theory of mind” to other species, you’ll have to decide for yourself.
A few weeks ago, the buzz was all about Dan, the baboon who could “read.” Not really read, you understand, but he did learn to distinguish word-forming letter groups from nonsense letters. When he was tested with letter groups he hadn’t encountered before, he correctly identified the words at a rate significantly above chance. Of course, Dan had no idea what the words the letters spelled meant, but he did appear to learn some general rules for letter grouping in English words, favouring sequences like GROW and RAKE over sequences like WGOR and EKRA. Dan’s not ready for Shakespeare, but he might do well in certain free-form poetry slams.
More recently, science digest sites have reported the behaviour of Santino, an alpha male chimpanzee at a zoo in Sweden. Many zoo chimpanzees “interact” with their human visitors by throwing things. Sometimes it’s sticks, sometimes it a rock, often it’s a few pieces of feces. Some animals are so prone to this behaviour that zoo keepers have to post warning signs around their enclosures. “Watch out for chimps throwing poop!”
Santino is clever. In an earlier study, he was observed calmly stockpiling rocks for later use. This planning behaviour advanced to the point that Santino would break off small chunks of the concrete walls of his enclosure — in effect, not just using but making weapons. The chimp was calm and methodical as he prepared his rock piles, which he would line up conveniently at the front of his space, near where the visitors would stand.
Planning ahead with a clear goal in mind is pretty impressive in itself, but now Santino’s behaviour has, dare I say, evolved into something even more complex. As the study “Spontaneous Innovation for Future Deception in a Male Chimpanzee” reports, Santino’s fun was curbed when zoo workers warned visitors just before Santino threw his rocks and concrete pieces. So the chimp altered his preparation.
Santino began to hide his projectiles, first in opportunistic places around his enclosure but later, rather remarkably, in piles of hay that he had constructed for the purpose of concealment. He would gather hay, make a pile near the front of the enclosure, then place rocks and concrete bits under the hay. In this way, he could wait near his weapons cache until an unwary human came within range, then whip out a rock and zing!
Not just planning now for a future event, but altering those plans as a counter to the frustration of the initial plan’s goal. That’s pretty complex for a “lower” animal!
The last article adds a twist to the primate intelligence mix: culture. Not just habitual behaviour passed on from animal to animal, but significant differences among different “societies” of the same species under similar conditions.
It’s one thing to allow our primate cousins to share in our mental skills, but it’s quite another to concede that they have distinctive cultures. That seems just too human to be comfortable for the exceptionalist defenders of a separate human identity.
Science Daily reported in “Chimpanzee cultures differ between neighbors” that evidence continues to build that “in several animals, differences in behaviors between populations actually reflect the presence of culture in these species.”
Some of the studies have been criticized because the contrasting populations have typically been widely separated geographically, raising the possibility that observed differences in behaviour may have been due to environmental differences or genetic drift.
The new study, conducted by a team at the Max Planck Institute for Evolutionary Anthropology, compared three neighbouring chimpanzee groups in the Ivory Coast. Animals in all three groups use stone and wooden “hammers” to crack nuts. But, the study showed, each group has developed its own tool “style.”
At the beginning of the season, when the nuts are hardest, chimps in all three groups favour stones with which to break nuts that have been placed on root “anvils.” As the season progresses and the nuts soften, differences in nut-cracking tactics begin to appear.
Since the chimp groups share the same ecosystem, there is no reason to suspect an environmental cause for the differences in behaviour. And since they are not isolated subgroups, there’s also no reason to posit a genetic difference. Take away the ecological and genetic causes, and you seem to be left with cultural deviation as the most likely cause of the observed differences.
When the nuts have softened, two of the three groups switch from stone to wooden tools. But they choose wooden hammers of characteristically different sizes. At this point, three genetically similar groups of a single species, sharing a single environment, approach the same problem in three different but persistent ways. One group keeps on using rocks, one uses bigger sticks, and one uses smaller sticks.
So it seems that our nearest relatives are not only pretty smart, they’re also showing preferential differences in behaviour, another word for which is “culture.”