Gradual improvements over time would need a sustained purpose and design in order to arrive at a coordinated result.
No, all that evolution needs is a driver and that is what Darwin provided through the theory of natural selection. Call it survival of the fittest, if you like, but what it really is, is an arms race. The arms race is a major driver. There is no foresight in evolution, there doesn't need to be. Whether it's better eyesight, better hearing, greater speed or more manoeuverability it is the arms race that drives species to adapt. Plants devise, by chance and through millions of generations, defence mechanisms against herbivores, prey animals improve their ability to escape predation, and the carnivores either keep up or die off. An improvement in one species calls for alterations in the next.
NL, nothing in evolution requires coordination between species. Species either adapt or go extinct. It is that simple, and it is estimated that 99.9 % of all species that have ever lived are now extinct. So failures are common. Not all species leave descendants.
nl said:
The human body demonstrates consistent symmetry.
All species show symmetry, that doesn't mean anything. Can you imagine all humans with one leg shorter than the other? People are born that way, and now-a-days they survive, but in an earlier age they would likely have perished. Try to imagine a race of human stone age hunters with one leg shorter than the other. Clearly evolution is responsible for symmetry for the simple reason that it leads to greater survivability – survival of the fittest. Those who have more reproductive success are the ones who leave their genes to posterity. Over thousands of generations nature culls those who are less reproductively fit. This is why Africa is filled with people with dark skin pigmentation. Those with light pigmentation were culled.
Do you believe in Noah's flood? Look at the variety of human types that have arisen in only 4000 years. Not even evolutionists think change can happen that quickly. We think that kind of diversity is the result at least 200,000 years. So creationists must believe in a more rampant form of evolution than even scientists accept.
nl said:
Purposeful intent was necessary to develop the coordinated design between male and female.
That's silly. All fetuses start out as female. Those with the Y chromosome begin, after some weeks, the production of hormones that develop male characteristics. So much for the female being made from the male (that story is the product of a male dominated society).
Besides, if evolution produced such a significant difference between the female and the male as to render reproduction impossible that would be the end of that particular lineage. Evolutionary results that by chance go the other direction and enhance reproductive success leave more offspring, and more members of a species then carry the enhanced genes. What's so hard to understand?
We all understand how the genes of domesticated plants and animals can be manipulated over time by farmers, even if those farmers lived in the Bronze Age and didn't really understand the mechanisms involved. Evolution is simply 'domestication' of species by natural events, instead of by the human hand.
NL said:
The development of the eye required coordinated development of its multiple components. The same thing needed to happen twice to create the second, matching eye.
No, no, no. The genetic change takes place in the mechanism that creates both eyes. Now I see what you are going on about. You think that a change that makes the legs of the ancestral giraffe longer has to happen four times – once for each leg. No, it doesn't work that way. I am taller than my brother. I didn't have to have two genetic changes, one for each leg to make me taller. Think about it. Do you know anyone with arms longer or shorter than your own? Do you think there are chance mechanisms that some how keep an individual’s arms and legs the same length. Tell me, did you read this somewhere or did you come up with it on your own.
Forget about this symmetry argument. It's a red-herring.