The missing hominids

Many NewAPPS bloggers (Helen, John, Mohan, myself) are favorably disposed towards analyses of human cognition which could be described as ‘naturalized’ in that data from empirical sciences (psychology, biology, cognitive science) play an important role.

Now, one crucial aspect in analyses of this sort in general is the issue of continuity and discontinuity between human and non-human animals. We are all familiar with Darwin’s idea that the difference between ‘us and them’ (Pink Floyd, anyone?) is “one of degree and not of kind”, and this seems to be the basic assumption underlying much of the work on non-human animal cognition that has the goal of producing a better understanding of human cognition. (Naturally, there is also the independent project of studying non-human animal cognition and behavior as a goal in and of itself.)

The two main camps are: those who marvel at the complexity of non-human animal cognition and deplore our tendency towards species chauvinism (fondly referred to as ‘monkey-huggers’ sometimes); and those who emphasize the abysmal distance between human and non-human cognition (whom I will refer to as ‘people-huggers’). (I’m using ‘cognition’ in a broad sense here, meant to include also work on e.g. sociability by someone like Frans de Waal.) And among people-huggers, at least some (but not all) end up defending a position that smacks of “We humans are so damn special and unique! There’s really nothing like us.” (also known as 'humaniqueness')

One aspect that is often (though not always) overlooked is the fact that there have been a bunch of closely-related cousins of ours roaming around the Earth at different times, but as it turns out they are all gone now: the missing hominids.

There is wide agreement among paleontologists that there have been several different species of hominids at different times (and not only those whose traces have been found, most notably the Neanderthals). That they are all extinct now may well be an evolutionary fluke, but it may also be yet another accomplishment that we, the remaining hominids, can add to our list of bragging rights. At any rate, our apparently special status as a species looks different if we bear in mind that it is in fact basically a form of loneliness: the other guys and girls are just not around anymore to set us straight.

I’ve been thinking about writing a post on the missing hominids for a while, but never got around to it. Then, today, I came across an article which appeared in Behavioral and Brain Sciences in 2008: ‘Darwin’s mistake: Explaining the discontinuity between human and nonhuman minds’, by Derek C. Penn et al. From the abstract: “In the present target article, we argue that Darwin was mistaken: the profound biological continuity between human and nonhuman animals masks an equally profound discontinuity between human and nonhuman minds.” I haven’t read the article yet, but my first reaction was to do a search on ‘hominids’ to see if anyone was talking about the missing hominids, and in fact someone was: one of the commentaries (by T. Suddendorf) begins with the following remark: “The real reason for the apparent discontinuity between human and nonhuman minds is that all closely related hominids have become extinct.” Indeed!

Another recent mention to the missing hominids I came across was by psychologist Keith Jensen, who made a special appearance at the already highly stimulating course on developmental pragmatics taught by Nausicaa Pouscoulous, which I attended at ESSLLI in Ljubljana. (Btw, ‘monkey-huggers’ is a term I learned from him.) Keith remarked that the project of knowing more about humans through the study of non-human animals is bound to have a low pay-off, simply because the biological gap between humans and even our closest relatives still alive, the chimps, is just too wide. According to him, in all likelihood, we would discover more about human cognition after spending one weekend with a Neanderthal than in decades of chimp studies, and that struck me as very plausible.

Anyway, so it’s not like nobody ever thinks of the poor missing hominids, but it seems to me that both monkey-huggers and human-huggers tend not to pay sufficient attention to them (even people for whom I have the greatest admiration, such as Michael Tomasello, a people-hugger, and Frans de Waal, a monkey-hugger). If we keep the missing hominids in mind, neither the continuity nor the discontinuity between human and non-human animals is particularly surprising, and inter-species, comparative studies could rid themselves of the burden of the ideological aspects of each position.

UPDATE: Coincidentally, just today there was a new article on the interbreeding between Neaderthals and humans, and consequences for our current immune system. See here, here and here.