evolution... have people got something very wrong ?

[jetsetjason]

I keep reading where people talk about things effecting us, because it was 'like that for a long time' in our evolutionary past, but, surely, we are just the product of the last round of natural selection, of our parents, and their environment ?

[Joseph]

Natural selection can only cause fairly small genetic shifts over the course of a single generation.

[jetsetjason]

says who ?

Surely it depends on the changing environment ?

[mickthinks]

Genetic traits come into being overnight. eg. as the result of a chance mutation. However a new trait needs hundreds, if not hundreds of thousands, of generations of breeding success to spread throughout a large gene pool. If the environmental pressure which favours individuals with a new trait is short-lived, the trait might persist as a variation, but it won't become a species characteristic.

[John]

You can't just be the product of your parents and their environment because they are also the product of their parents (your grandparents) and their environments and so on and so on.

Evolutionary change is cumulative in very small steps. Just because a trait was important in the past and is no longer as relevant in our current environment doesn't mean it will automatically dissapear. It will only dissapear if those who possess the trait don't produce offspring to pass the trait on to.

So you'll inherit characteristics from your parents but they'll have done the same and so on and so on.

[jetsetjason]

the black death

the industrial revolution

short, sharp, changes in the environment ?

[Joseph]

In addition, I would note these other reasons:

--Species are usually spread out enough in space such that selection pressures differ from population to population. It is thus rather difficult for some variant to spread over the whole species. Over long periods of time, not much directional change occurs.

--Selection can only work with existing genetic variation. An allele may be favored in some environment, but if it isn't there, it cannot be selected for.

--Even favorable variants can be lost due to chance before they can become fixed.

[John]

the black death

the industrial revolution

short, sharp, changes in the environment ?

What about it? What effect on evolution are you proposing such events might have had?