Yesterday I came across the best description of evolution I’ve ever read--in an unlikely place. It was in Alan Weisman’s The World Without Us. Weisman devoted a chapter to pondering the question of whether another sentient creature would evolve if humans suddenly disappeared from Earth. I haven’t finished the chapter, so I can’t tell you his final conclusions, but along the way he mentions some interesting things about monkeys in Africa. Apparently, there are some places where the resources are so thin that, to survive, different types of monkeys have begun mating with each other (“…out of desperation or creativity.”). The monkeys have different numbers of chromosomes, so it is likely that some of the offspring of these matches are sterile, however, researchers were surprised to discover that a few of them are not. This is one way we are seeing evolution at work before our very eyes. Resources are scarce and the monkeys have to get creative about their survival, even to the point of trying to join up with other animals. It should be noted that the two types of monkey in question are thought to be distant relatives. At some previous point in evolutionary history they were the same monkey, but time, distance and different circumstances forced them to take on different characteristics until they were no longer the same animal at all.
Wiesman's other knock-out example takes place in a deep, fertile, jungle-filled rift valley in Africa that is home to many monkeys. Though the valley is rich with resources, there is not enough for all the monkeys that live there. Scientists (and, I assume, locals) have observed the occasional adventurous monkey climbing to the tops of the trees and climbing out of the rift valley, standing on wobbly two feet to look around across the Savannah. The monkey picks out a tree or group of trees nearby and takes a run for it, hopefully without being spotted by any scary Savannah predators on the way. Those few seconds, when the monkey stands on two feet and scans the horizon for the first time, are like a glimpse into our own evolutionary history, and it is happening today--right in front of us.
I'd also like to post a quote from Richard Dawkins' book The Blind Watchmaker, which is also about evolution. Dawkins eloquently describes our difficulties in understanding the amount of time that evolution requires. He explains that skeptics (including the highly-religious) will admit that evolution seems to work on a small scale. For example, they are willing to concede that dark coloration has evolved in various species of moth since the industrial revolution, a well-established and documented fact. "But having accepted this, they point out how small a change this is. ...[It's] no match for the evolution of the eye, or of echolocation [in bats]. But equally, the moths only took a hundred years to make their change. One hundred years seems like a long time to us because it is longer than our lifetime. But to a geologist it is about a thousand times shorter than he can normally measure."
Puts it into perspective, huh? Dawkins goes on later to point out that if we make the time when humans began breeding dogs (such as Pekinese, Bulldogs, Chihuahua, etc.) from wolves to the present time equivalent to a footstep, then we need to make the amount of time from the first human fossils equivalent to two miles and geologic history the equivalent of walking from London to Baghdad!