Random Thoughts About Human Impact On Evolution

Charles Darwin celebrated his 200th birthday February 12 of this year. So of course many of the science podcasts I listen to, as well as many of the science and skeptic sites I visit, have been talking about evolution and Darwin and all that good stuff. Evolution is often paraphrased as the term, survival of the fittest, which is inaccurate. Here is how Dictionary.com defines it, as well as some other terms, just so we're all on the same page:

• Survival of the Fittest
  a 19th-century concept of human society, inspired by the principle of natural selection, postulating that those who are eliminated in the struggle for existence are the unfit.


• Natural Selection
  n. The process in nature by which, according to Darwin's theory of evolution, only the organisms best adapted to their environment tend to survive and transmit their genetic characteristics in increasing numbers to succeeding generations while those less adapted tend to be eliminated.


• Evolution
  Biology. change in the gene pool of a population from generation to generation by such processes as mutation, natural selection, and genetic drift.

I've been slowly forming some random thoughts regarding the human population and evolution and I thought I'd write them down. Your input would be most welcome, as usual.

I heard on The Naked Scientists ( podcast number or which exact one, I'm not sure) recently that humans aren't really evolving and haven't for the last couple of thousand years or so. Chris, the Naked Scientist, was talking about something else so it was one of those explanations for something else, not the topic of conversation. So he didn't go into detail.

My ears perked up though because I've been vaguely wondering about human evolution in the past several thousand years. Mainly because humans seem to do things backwards from the rest of nature. Or we seem to do that lately in our history.

For instance, we take care of the old and sick, to the point that otherwise frail and less than hearty people are able to reproduce, and to reproduce much longer into older age than ever before. This is when a woman's eggs may have more genetic defects in them. Which is why women who are pregnant over a certain age are encouraged to get tested for genetic defects more than younger women are.

I have an aunt who was born with a serious birth defect - spina bifida. She needed countless surgeries over her childhood, and several in her adulthood as well. She ended up getting married and having a child, which even a hundred years ago would not have been possible.

There are huge differences in child mortality and survival throughout the world even today, based on availability of medical care, basic nutrition and other factors. But even 100 years ago the infant mortality rate was higher, right? What was it 2,000 years ago when medical care was rudimentary at best?

So what does this do to the gene pool and to human evolution?

I was talking to my friend Jeff about this yesterday and he made a comment that we are evolving, just with machines now. But I would suggest that's not the same thing. It certainly doesn't fall into the biological definition of evolution. I'm not saying that we aren't evolving at all. But we seem to have stalled at least. Instead of natural selection within the human race, we have technology of all different sorts to compensate for whatever lack of genetic strength we may have.

This could be as simple as red headed people living in the Mediterranean. They don't need to get sunburned and get skin cancer because they can wear sunblock and protective clothing and stay indoors more. Or a child can be born with asthma, something that would have shortened her life long ago, perhaps. Instead while she may take medication and change her lifestyle a bit, she can grow up to have children, who may also be prone to asthma.

Did you see that movie, Idiocracy? I didn't watch it because, well, it looked really dumb. But the concept is interesting and is something I see in my life nowadays, to a small degree. The premise of the movie, from what I gathered, is that smart people stop having children so only stupid people have kids, giving birth to dumber and dumber people, until everyone is idiotic. I don't know about that idea. Because both my husband and I are way smarter than our parents. But I do see people who can barely function in society having kids while smart people make the decision to refrain from reproducing.

Here's another point. Let's talk about fishing. I've been hearing about how we fish and hunt. Humans take the biggest and strongest animals and fish from the population in huge numbers. Now, when it comes to cattle and poultry, we raise what we want to eat. But for fish we still get them from the wild in a lot of cases. The impact on those populations has actually caused the fish to evolve, but in a reverse sort of way.

There was this study published recently which I heard about. Basically they took this population of fish and treated them as if they were being fished as is common practice today - taking the biggest, leaving the smallest. After 12 years they found that the fish had to adapt and start reproducing earlier than they used to. This has a negative impact on the population, which then affects what is available for us to harvest.

In the wild a lion will target the weak and the young, which makes sense. But we don't do that. We go for the biggest and strongest, leaving the young and weak. We seem to do it backwards. Which seems like it's bad for the rest of the environment.

The good news is that this reverse evolution can be reversed. I found the fishing study. Here's a link: 'Undesirable' Evolution Can Be Reversed In Fish, By Letting The Big Ones Go

Those are just some ideas I've been knocking around in my head. Your thoughts are welcome, as usual.