Western medicine has stopped evolution in its tracks. Gone are the days of survival of the fittest and those with weaker traits passing away before they reach reproductive age and passing those traits on to their offspring. Whatever your weakness, Western medicine can keep you alive, be it by ingesting chemicals into your body or by hooking you up to a machine that forces your organs to operate.
It's hard to argue that this is a bad thing. Many people who wouldn't have lived long, fulfilling lives, have been able to thanks to the technological and scientific breakthroughs that Western medicine provides.
But while this is creates a warm, fuzzy feeling for the millions of people who have benefited from Western medicine's contribution, what does this mean for evolution? If you look at Western civilization's record, new technology tends to mark the end of something natural.
People who otherwise would have died by nature's plan are now afforded life. This has several effects on the world. The first, and most obvious, is the population increase. With so many people populating the planet, institutions such as education suffer from overcrowding and lack of funding. Decent jobs become harder to find because fewer people are properly educated. This furthers the creation of the class system, wherein only the privileged are provided proper education, thereby advancing the "rich-stay-rich" trend that only helps increase the chasm between classes.
As the gap between rich and poor expands, the difference in the quality of education grows. As the quality of education in the lower classes diminishes, so does the idea of its importance. As generations of uneducated people reproduce, they raise their children with a lack of importance in education that increases with each year. As the significance of education wanes, so does rationality and critical thinking. What this does, is promote a society more concerned with the actions of Brittany Spears and Paris Hilton and not so much with the state of the world and the selfish actions of the upper class. The upper class needs a working force to make them more money. They need a mindless group of robots who don't know how to make their lives better. The upper class relishes in the fact that millions of people are too lazy and not determined enough to make real change.
Evolution still occurs. But it occurs in the upper echelon of society. And their ability to evolve is directly related to the lower classes' inability to evolve. Is it too late to change this pattern? Probably not. Does that mean it will change? Absolutely not. One-hundred years from now, the working class will most likely be comparable to androids. They will only be proficient in putting screws in widgets and they will consider Entertainment Tonight real news. Or are we already there.