The ones who survive are not necessarily the strongest. It might be the quickest, smartest, darkest skinned, one with most body fat stored up, or whatever.
That's the problem. We (in the distant past) don't know what conditions are coming to where we are, or what conditions we will encounter when we move.
In most traits there is a range of variation. There are hundreds or thousands of traits. Some are visible (skin color), some are genetic (resistance to particular diseases). Some individuals are better able to survive and pass on their genes. The differences are often tiny, fractions of a percent, but with lots of time they can add up.
In time, the range of variation shifts toward one end or the other. When people migrated out of Africa and toward the northern end of Europe, skin color lightened. In Africa selection pressure favored protection from intense ultraviolet radiation, and dark skin was necessary. In northern Europe selection pressure favored vitamin D production, and the skin had to be lighter to pass the correct amount of ultraviolet radiation for vitamin D production. There is a cline, or range of variation between Africa and northern Europe, with skin color becoming lighter as you go north.
The mechanism for this is natural selection in favor of those who are best suited for a region.
It is very complex, with lots of traits involved. We study the results using current populations as well as fossils. We have a lot to learn, but there is a lot that has already been discovered.
Both of you have made some good points and has really helped me in understanding what 'natural selection' is all about.
thank you.
I still wonder tho if a mathematical formula is discovered in our biological makeup that shows a definate pattern for life, would that be proof of ID or would that only confirm evolution is not a 'random' selection but process with a specific pattern.
I only ask because I did see a program about a scientist who claims that our biological makeup seemed to be structured rather than random.
His point was that there seemed to be a definate 'design' to it.
But I still wonder if the design was really the result of evolution and not the result of a 'blueprint'.
Don't forget co-evolutionary situations.