Chat to any god-botherer about evolution and they'll tell you that it doesn't exist, that there's no such thing. They'll pay lip-service to the scientific elbow-grease that has gone into evolutionary research, but they'll argue that the end product is only ever a "theory." Overlooking the obvious confusion over the term "theory," what these folks are really saying is that there is no physical evidence for natural selection. "Where are the transitional fossils," they point out; "where are the intermediate creatures?"
It's no wonder that so many (mostly American) people still doubt evolution; they just don't know what it means. Their eyes start to glaze over when biologists use terms like alleles, macro/microevolution, genetic drift, and speciation. What the evolutionary naysayers want is some definitive bit of evidence that would prove evolution once and for all – a smoking gun.
Unfortunately, evolutionary timescales don't easily work in science's favor; we can't see a limb turn into a wing overnight. But thanks to new analysis techniques, we can actually document natural selection in its slow-and-steady progress.
Biologists at Cornell University, who have been studying genetic changes occurring in the human genome over the last 15,000 to 100,000 years, have found that over this relatively short period of time the human genome has changed by a staggering 10 percent. "We undertook a very careful study of genetic differences within and among major human groups, and aimed to explain why certain parts of the genome differed," says lead author Scott Williamson, an assistant professor of computational biology. "We aimed to eliminate as many possible confounding variables as possible, and when all is said and done, we find that as much as 10 percent of the genome may have been affected by one of these bouts of recent selection." These changes amount to natural selection at work; the adaptations needed for survival.
The Cornell study goes a long way in identifying the small, gradual changes (microevolution) that demonstrate species divergence from a common ancestor millions of years ago (macroevolution). It makes many human-to-human comparisons throughout the complete human genome; rather than comparing a human to mice or chimpanzees. In this way, it can show how we humans have been changing over time, due to our ancestors being exposed to – among other selective pressures – different climates as they spread across the globe.
One example of the type of change humans have undergone is our tolerance to lactose; or lack thereof, in the case of our dairy challenged ancestors. Lactose is an enzyme found in milk, and prior to the domestication of animals humans did not have the capacity to digest milk after infancy. Some time after humans began migrating and domesticating animals, we developed a gene that allowed us to tolerate consuming milk into adulthood. "As humans have populated the world, there has been strong selective pressure at the genetic level for fortuitous mutations that allow digestion of a new food source or tolerate infection by a pathogen that the population may not have faced in a previous environment," explains Williamson.
Now that scientists are readily identifying genomic changes due to selective pressures, what's next? Would it be too far fetched to suggest that social pressures could affect brain function at a genetic level? At least one study has identified collective behavioral differences between Western cultures like the United States and China, possibly suggesting the beginning of brain divergence among humans.
The study, from the University of Chicago, makes the claim that people living in the United States have difficulties with accepting another person's point of view, which they put down to US culture prizing individualism. They say that in China, where a collectivist attitude is encouraged, quite the opposite is true, with Chinese citizens being much more in tune with how others are thinking. As a result, the researchers argue that there may be more scope for communication confusion among Western citizens relative to citizens of China. "Members of these two cultures seem to have a fundamentally different focus in social situations. Members of collectivist cultures tend to be interdependent and to have self-concepts defined in terms of relationships and social obligations," says Boaz Keysar, a Professor in Psychology at the University of Chicago. "In contrast, members of individualist cultures tend to strive for independence and have self-concepts defined in terms of their own aspirations and achievements."
The team's conclusions may seem a little wayward – perhaps verging on cultural propaganda – but they are based on a very straightforward group cooperation experiment. Teams of Americans and Chinese were pitted against each other whilst manipulating objects on a grid, with one person from each team being the "director," and another acting as the worker, or "subject." Time and again it was shown that the Chinese had a clear advantage; the subject understanding the director's perspective, or vision, as though it were second nature. "Despite the obvious simplicity of the task, the majority of American subjects (65 percent) failed to consider the director's perspective at least once during the experiment, by asking the director which object he or she meant or by moving an object the director could not see," explained Keysar. Comparatively, only one of the Chinese appeared to flounder during the course of the experiment.
"Apparently, the interdependence that pervades Chinese culture has its effect on members of the culture over time, taking advantage of the human ability to distinguish between the mind of the self and that of the other, and developing this ability to allow Chinese to unreflectively interpret the actions of another person from his or her perspective," the study's authors concluded.
While studies with children have shown that the ability to appreciate another's point of view is universal, could cultural pressures evidenced by the University of Chicago study actually manifest as selective pressures? It was the brain that was to eventually separate us from our chimp cousins, so could yet more divergence emerge from the mysterious grey goop between our ears?
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