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I think it's interesting with humans because with humans, natural selection isn't so natural anymore. Natural selection means to weed out the people who can't adapt to the environment as well as others but in modern society, we have the technology to keep alive many people who would previously have died (which, don't get me wrong or misinterpret me, is not a bad thing). For instance, people with weaker immune systems might have contracted a disease that might have killed them in their childhood and so they would never have been able to pass their weaker immune systems genes on. Instead, doctors now have the drugs and knowledge to know how to deal with such problems.
Also, I think another thing to note is that humans are the dominant species right now on Earth. Nothing can really threaten us so we aren't... "punished" for being unfit for our environment.
I think if you look at things that do change their genes a little more quickly, you can see evolution in action. Case in point, the influenza virus "evolves" a little each year which is why you have to get the flu shot every year. The virus changes enough so that the previous year's vaccine is no longer effective.
Or another example would be bacteria. Since bacteria are one-celled organisms, it is relatively easily for them to change characteristics. Doctors have been talking about this but over time, antibiotics become less and less effective against bacteria. I wish I had the picture in my bio book to show how a bacteria culture moved closer and closer to penicillin over time. I will post it later if I find it.
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