Do Chimps Recognize Others’ Disabilities?

The anthropologist Margaret Mead has been widely credited with an argument that the earliest clue to civilization in the fossil records of our ancestors is in one particular skeleton, 15,000 years old.

The skeleton shows evidence of a badly broken leg that healed—a process that would have taken many weeks, during which the individual would have needed considerable caretaking. Someone brought him food and water, made sure he was protected from cold and predators, and given the nomadic nature of hominids at that time, likely helped him move around.

There’s been some difficulty in recent years definitively attributing the "earliest sign of civilization" comment to Mead, but it’s a thought-provoking one, regardless of who said it. When, and under what conditions, did our ancestors come to value damaged adults in their communities enough to endanger their own survival by assisting them?

Serious Injury as a Test Case

If we look to our closest living relatives, the chimpanzee, there is startlingly little evidence for active, long-term helping of an injured or disabled peer: bringing them food or water, supporting them as they walk, building them a sleeping nest, etc (though see here for immediate helping of those needing a tool). And they do sustain severe injuries in the course of wild living that offer their peers visible evidence and opportunity.

At Ngogo, Uganda, unfortunately—and despite the strong efforts of teams designed to destroy these—illegal poaching snares have damaged the bodies of chimps caught unawares. Lita, now in her mid-50s, is entirely missing her left foot and walks quite slowly on the stump. Richmond lost his right hand above the wrist to a snare when he was very young; Mweya lost his entire left hand to a snare later in life. Carson is missing two of the fingers on her right hand. Though the hands themselves remain intact, Garrett and Renee both lost the function in one hand (right and left, respectively) to tissue and nerve damage from snares.

It does not seem too far-fetched that missing a hand or key fingers would force the injured to adopt a mode of locomotion or food gathering that was noticeably sub-optimal. Both Sills and Beryl are missing an eye from causes unknown and their depth perception is surely impaired—no minor disability for animals who spend much of the day 100 feet above the ground.

We could not expect chimps to reason about the depth perception of others, but it is a clear abnormality, the consequences of which (failure to react to visual stimuli on that side for example, or stumbling) should be noticeable to others. I have wondered if these chimps might more often receive grooming in areas they can’t see or reach (given their injuries) than in areas they can.

It might be, of course, that because they can’t reach these areas the site develops an appearance that elicits more interest from others. Long-term focal observations of chimps with visible and persistent locomotor limitations—specifically for the help they receive—could be illuminating.

Subtle Helping as a Kindness

Alternatively, might it be possible to develop a system for observing indirect help, of the sort offered by humans all the time? How might we record those gentle behavior changes that are variations intended to go unnoticed?

A slowing of our own pace when a child is tired, a “rest break” when you yourself need none, an alternative homeward route that avoids the staircase your friend has trouble managing. We do these things from kindness, a preservation of the dignity we know the other person values. It shows that we know that they’d not want us to know, so we pretend we don’t by creating situations so that they needn’t become aware that we’re aware.

It’s a complex situation, tapping into perspective-taking and theories of others’ minds. If chimps had a version of these awarenesses, how could we observe it?

Source: Kevin Lee, used with permission

The Challenge of Designing a Coding System

On my first trip to Ngogo, I saw a chimp take a technically difficult path across a river, atop a wobbling fallen tree. On my next visit, when she was trailed by her 5-year-old, I watched her travel further upstream to a shallow bank crossing.

Similarly, it seems to me that Hutcherson moves more slowly when in the company of his elderly and arthritic mother Garbo. If he moved at his usual pace and then sat impatiently every 20 yards while she caught up, this would not be evidence of perspective-taking, simply the (frustrating) realities of his day. If he strolled along in slow-motion while casually inspecting leaves he typically ignores, maybe so.

As someone who loves methodology, the question of coding really intrigues me. In this last example, we’d be trying to code some new behavior with no apparent function other than facilitating the other without making it seem so. In another scenario, we could be trying to code the absence of some behavior. It’s a challenge.

Chimpanzees, like us, do various things on various days for various reasons. Careful, longitudinal, and replicable data are needed. If we design a method able to detect the subtle adjustment of their own behavior to account for someone else’s physical difference, in a way that shows they are sensitive to the implications of that someone’s knowledge of the difference, how far might that go in suggesting the beginnings—the very beginnings—of civilization?