chimps, humans and big numbers

The entire chimpanzee genome has been mapped!
Like me, you've probably heard that we share 99 percent of our genes with chimps. Well, it now turns out it's only 96 percent overlap.
The number has changed, but so what? That old "99 percent the same as chimps" has been bandied about in all sorts of contexts, from evolution-versus-creation arguments to animal rights. But without scientific context (like, how much do chimpanzees vary from one to another? or, how much of a real difference can a 4 percent change make?), such numbers are just useless pieces of information.
This is not unlike the Great Eskimo Snow Hoax. Maybe you've heard that Eskimos have 50 words for snow? This factoid is supposed to deliver psychological shock and awe. Well, sorry to shatter your illusions, but they don't. They've got about half a dozen, same as English. (yes, English has more than one word for snow: for example blizzard and sleet). As anthropologist Laura Martin points out, they don't have 50 words for snow, but would it even be that amazing if they did? After all, typesetters have hundreds of names for different kinds of fonts.
The Great Eskimo Snow Hoax appeals to us because it is suggestive of so many things: how differently other cultures see the world, how languages reflect the worldview of the language community, and of course, how strange those crazy Eskimos are.
Another big number out of context: the man who conceived of the X-Files got the idea when he read an article claiming that 3 million americans believe they've been abducted by UFO's. That's an astounding figure, until you realise that it's about 1 percent of the American population. You can find just about anything in 1 percent of the population. For example, one percent of people are schizophrenic. One percent are geniuses. One percent have epilepsy.
He may have thought he'd hit the marketing jackpot, but really, the article was just a trigger that encouraged him to let his creative impulse run free. The truth is, there's a niche market for pretty much anything. But that three million number apppeals to our suspicions about suburban mid-western Americans, about the idea that there are lots of people out there who have some wacky ideas, and for some, leaves uncertainty about whether so many people could be wrong.
But back to chimps. What's so appealing about the ninety-nine percent (now ninety-six)?
Lots. It suggests we should not be too arrogant as a species, that we should treat other animals well, and that we ourselves are really just beasts underneath. Compelling ideas. But like the Eskimo Snow Hoax, if you think about it, the high number is actually rather banal. Chimps and humans both have two arms, two legs, red blood cells, a liver, heart, lungs, spleen, and brain. They have taste buds and eyes and digestive tracts and skin and ears. They feel hot, cold, and pain, they smile and fight and play and congregrate in small societies. They eat many of the same foods as us. Ninety-six percent doesn't seem like a stretch.
Geneticists now believe that it is a single, crucial gene that makes all the difference between us and chimps. Now that's interesting, because it gives us a handle on the underlying structural differences. One gene, not a cluster.
We love to blow our minds with amazing facts, and huge numbers are a great way to do it. However, interpreting those numbers correctly usually requires context, and that context frequently cuts our amazing fact down to size.
To me, the most fascinating thing about the ninety-six percent is not the number itself, but that we know what the number is. This is a testament to years of hard work by many dedicated, smart people. It's also part of the gold vein of information we are discovering about how humans are built.
Humans are the first species to peek behind the curtain. And armed with our knowledge of the process, for better or worse, we are the first to take control of that process, whether by embryo selection, artificial insemination, gene therapy and other procedures just over the horizon. We are on the cusp of actually controlling and altering our own evolutionary path. But most of all, it is a testament to humans' insatiable drive to understand everything... especially ourselves.

footnote:
here's the reference for the Eskimo snow hoax:
Martin, Laura (1986). "Eskimo Words for Snow: A case study in the genesis and decay of an anthropological example". American Anthropologist, 88 (2), 418-23.