The story of human origins is partly a story of Big Things like the Taming of Fire and the Dawn of Speech. (We’ll have more to say about language origins soon.) But it’s also the story of some odd byways and quiddities. A nice introduction to some of these is Chip Walter’s book Thumbs, Toes, and Tears: And Other Traits That Make Us Human. (His more recent Last Ape Standing is good too.) Walters considers funny bits of anatomy like our unique big toes and thumbs, and funny bits of behavior like our habits of laughing, weeping, and kissing. Toes and thumbs fossilize, but it can be hard to put dates on when behaviors evolved. Presumably it was sometime before modern humans evolved and spread, so let’s make it today’s date, 570-547 thousand years ago. It’s also hard to figure out the exact evolutionary rationale for these behaviors. Humor, for example, is not a simple phenomenon: intellectually appreciating a joke, actually finding it funny and enjoying it, and finally laughing, each involve separate areas of the brain.
Another and overlapping set of human particularities involve facial expressions of the emotions. Darwin got a whole book out of this. He concluded (admittedly based on somewhat anecdotal methods) that different emotional expressions are largely innate. It’s an interesting illustration of his ability to reason from small facts to large conclusions that he also drew a big conclusion about human evolution from this. In Darwin’s day, there were scientists who believed that different human races had evolved from very different prehuman progenitors: one prehuman species giving rise to Europeans, another to Africans, and so on. But Darwin reasoned that the very close similarity in facial expressions (and he had traveled a lot, and witnessed a lot of expressions in a lot of places) and the very similar emotional makeup of humans around the world was evidence that human populations shared a fairly recent common ancestry. Here as in several other cases, a mixture of close reasoning and sheer luck led Darwin to the correct conclusion about evolution long before there was much solid evidence.
Darwin’s work on emotions was neglected for most of the twentieth century by anthropologists favoring a blank slate view of human behavior, but was eventually largely vindicated by a number of researchers, notably Paul Ekman. There is now good evidence for six basic facially expressed emotions: Fear, Disgust, Joy, Anger, Sadness, and Surprise.
If you made it to the movies last summer, this list may seem familiar. These emotions (all except for Surprise) are all depicted as little homunculi living inside the head of an 11 year old girl in the animated feature “Inside Out.” (The movie gets a strong thumbs up from Logarithmic History). Somebody at Pixar Studios knows their Ekman.
So the sappy song is right: There is just one moon and one golden sun, and a smile means friendship to everyone.