How We Came to Be Human; Becoming Human; Special Editions; by Ian Tattersall; 8 Page(s)
When we contemplate the extraordinary abilities and accomplishments of Homo sapiens, it is certainly hard to avoid a first impression that there must somehow have been an element of inevitability in the process by which we came to be what we are. The product, it's easy to conclude, is so magnificent that it must stand as the ultimate expression of a lengthy and gradual process of amelioration and enhancement. How could we have got this way by accident? If we arrived at our exalted state through evolution, then evolution must have worked long and hard at burnishing and improving the breed, must it not? Yet that seems not to be how evolution works; for natural selection is not--it cannot be--in itself a creative process. Natural selection can only work to promote or eliminate novelties that are presented to it by the random genetic changes (influenced, of course, by what was there before) that lie behind all biological innovations. Evolution is best described as opportunistic, simply exploiting or rejecting possibilities as and when they arise, and in turn, the same possibility may be favorable or unfavorable, depending on environmental circumstances (in the broadest definition) at any given moment. There is nothing inherently directional or inevitable about this process, which can smartly reverse itself any time the fickle environment changes.
Indeed, as we'll see a little later, perhaps the most important lesson we can learn from what we know of our own origins involves the significance of what has in recent years increasingly been termed "exaptation." This is a useful name for characteristics that arise in one context before being exploited in another, or for the process by which such novelties are adopted in populations. The classic example of exaptation becoming adaptation is birds' feathers. These structures are essential nowadays to bird flight, but for millions of years before flight came along they were apparently used simply as insulators (and maybe for nothing much at all before that). For a long time, then, feathers were highly useful adaptations for maintaining body temperatures. As adjuncts to flight, on the other hand, they were simply exaptations until, much later, they began to assume an adaptive role in this new function, too. There are many other similar examples, enough that we can't ignore the possibility that maybe our vaunted cognitive capacities originated rather as feathers did: as a very much humbler feature than they became, perhaps only marginally useful, or even as a by-product of something else.