How do genes know when they need to evolve?

Question

In evolution, species change and mutate in to different species to adapt to the new environment. But how does your body know what to keep and what to change. Like how does the body know what to evolve into? Do genes have minds of their own and they know when they are needed or not? Or is it that the body knows which part of itself is not being used well and gets rid of that part and the parts of the body that is being used constantly tells the body that they need an upgrade?

Some one enlighten me!

Answer 1

It doesn't work like that; there is no "conscious" input into evolution.

The thing to remember is that, within a population, there is diversity: not all individuals are the same. Additionally, because of mutation, this variation will constantly be arising.
So, some individuals are better-adapted for a particular set of conditions than others, and they become more common in that environment (with other, detrimental traits becoming less common, and perhaps disappearing entirely). Therefore that population has changed, with more of the beneficial traits.
With mutation, other, different traits will arise, and some of these will also be beneficial, so they will become more common with time.
Rinse and repeat...

The *environment* is what performs the selection, not the genes themselves.

Answer 2

Nature 'decides' what genes are beneficial stick around (or are detrimental and get the boot).

Let's take Sickle Cell Anemia (SSA), for example. It is a very simple mutation (one amino acid), so it would be very easy for it to pop up in a population due to random mutation. It has undoubtedly showed up in Europe before, but since causes serious health problems, those people that acquired it probably didn't survive (or weren't seen as desirable mates) and thus weren't able to pass the genes on to their children. As a result, though SSA would probably show up occasionally in an individual, it wouldn't become a trait common to the population.

In Africa, however, Malaria is a serious and life-threatening problem. The malaria parasite can't survive in affected blood cells, so people with SSA have an innate resistance to the disease. Though SSA would cause health problems, those problems aren't as life-threatening as malaria. Thus, the people with the SSA mutation would survive and would pass the mutation on to their children. After many generations of selecting FOR the SSA mutation, its prevalence in the population would increase. If malaria were to be wiped out, it could be possible that the trait would be selected against, and would return to situation similar to that seen in Europe.

Evolution is driven by random mutation, but controlled by selective forces in the environment. I like the analogy of monkeys at a typewriter. It is said that a thousand monkeys at a thousand typewriters would eventually, inadvertently, reproduce a work of Shakespeare. This isn't an accurate analogy, though, since it assumes true randomness with no selection, and that evolutionary steps happen in an 'all or nothing' fashion.

I prefer to change it a little:
Imagine a thousand monkeys but also a bunch of people wandering around (representing the selective force of nature). Every time a monkey types a real word, they cut it out and tack it up on a board. A monkey types "To." It's two letters, not a big step, and certainly plausible that a monkey would stumble upon it. It gets cut out and tacked on the the board. Eventually one comes up with "be" and it gets tacked up. Eventually, you end up with "To be or not to be" etc. etc. You have Hamlet up on the board (the final evolutionary result) and reams upon endless reams of monkey gibberish cut up and discarded (mutations that never quite made it).

So in the end, the evidence suggests that evolution is random steps that have worked and survived, or haven't worked, and died out. While it is truly amazing, there is no conscious or intellgent motivator behind it.

Answer 3

Your body doesn't know what to keep and what to change. The body doesn't know what to evolve into. That's not how it works. Whatever your body is, it is. It cannot evolve. What it can do is live successfully and successfully pass on the successful genes to a new generation. OR, it can die because it can't survive the environment or it can be too sickly to successfully produce offspring to pass on it's genes.