I received an unexpected e-mail from the Dutch zoologist/cognitivist/linguist Johan Bolhuis that, among other things, asked rhetorically, “How do you evolve a blank slate?” He was referring to John Locke’s famous metaphor for the human mind of the newborn baby. We are born, said Locke, with a blank paper on which experience writes what we learn. The image gained a powerful place in western philosophy and afforded one more separation between humans and animals. Humans learn what their world teaches them and what they figure out; animals, meanwhile, live by instincts.
Although I have thought about the issues behind Bolhuis’s question for many years, I don’t think I have ever heard the matter put so bluntly and neatly. If animals have instincts and humans have blank slates, and if humans evolved from animals with instincts, how did we come to replace those instincts with a blank slate?
We evolve traits, but blank slates do not seem to be traits in the way leopard spots and elephant tusks are traits. They seem more like the eyeless fish living in perpetual darkness. Eyelessness is not a trait; or at least it is not a trait supported by genes. Rather, the ancestors of these fish had eyes but no use for them. Thus, as mutations damaged the eyes, there was no selective pressure to remove these myopic fish from the gene pool. The eyes became increasingly bad and eventually disappeared altogether. Is that what happened in the human lineage? Did we quit selecting for one instinct after another and finally end up with a blank slate?
If yes, there must have been a series of handoffs as instinct was released. Suppose, for example, that our ancestors had an instinct to run away whenever they saw lions. Then that instinct weakened so they were sometimes able to dash in as part of a group, yelling and throwing stones and chase a lion or two away from a zebra carcass.
Something like that may have sometimes happened, but the truth is that much human behavior is not just the result of liberated animal instincts. Even dashing at a group of lions takes more than a modified flight-or-fight response. You have to be a member of a team, have to be skilled at chucking stones, and have to be able to yell at will. In other words, even if some inborn behavior has faded, other instincts are needed to pick up the slack.
Another possibility is that instinct has been overemphasized and that experience does play a role in animal behavior. A dog may learn its territory. In this case, no internal map of canine-land ever evolved and each dog must learn its territory by exploration. A dog might develop an instinct to explore and learn, but what it learns gets written on some internal blackboard and remains outside the gene pole.
I’m not sure whether Bolhuis thought I was a blank slater or not. For the record, I believe we have certain built in ways of understanding our perceptions, so that we we all share the basic case relations—actor/acted upon; whole/part—, some spatial relations, and whether or not an action is still underway. These are the basis of what I am willing to call a universal grammar (UG), misleading though the term is, but I do not believe in the “generative procedures” that Chomsky and Bolhuis claim are part of any UG.
My basic evolutionary story holds that we have tens, or more likely hundreds, of millions of years behind us of evolving a perceptual understanding of the world. That knowledge was extremely concrete and practical. I see no reason to suppose that our pre-Homo ancestors ever thought abstractly or had any need for the symbol manipulations needed to support a hierarchy of symbolic structures. (I'm with those who call things like bird songs "triggers" rather than symbols.)
As Homo appeared, we began developing the new instincts needed to support a community-dependent species. As part of that community we used a very rudimentary language, sharing joint attention, at first, in the same way toddlers do today, with words and phrases. We probably developed some language-specific skills such as the ability to bind points of attention into a single sentence, and the ability to talk at length without becoming giddy from our irregular breathing.
How about all those weird differences in language that we have to pick up as part of growing up? That’s where the blank slate comes in. We never evolved any genetic basis for the peculiarities of French, Swahili, or Japanese. We just pick them up, in much the spirit of an ape picking up features of its troop's territory. And if we can’t pick them up? Then they do not become regular features of the language. It’s not that we evolved a blank slate, it’s just that we never evolved a genetic tendency to organize words in a particular way. Our brains got much bigger very quickly, so we obviously got a much bigger blackboard to write on. But cultural change outpaces genetic evolution, so we did not evolve a substitute for the blank slate. And thank heavens for that. I have seen many changes in my lifetime—e.g., fax replaced mail, e-mail replaced fax, and texting replaced e-mail—and I have needed a busy eraser just to keep up.