As far as I know (and I’m going by my layman’s (or woman’s) understanding of things) three things cause / contribute to the process of evolution. Natural selection, climate change and TIME.
Interracial marriage is not an example of evolution, it is an example of natural selection which, over time, contributes to changes to a species, and that process of change over time is called evolution.
A hundred years ago the percentage of people who had to wear corrective lenses was less. The further back in time you go, very likely the less people you find with impaired vision. Why? Because visually impaired humans living more closely with nature are a lot more likely to become bear fodder and never reproduce. Because before we invented our way to the top of the food-chain, we needed our senses a lot more to survive; our ability to hear, and see, and RUN. So, just like it is still in nature, survival of the fittest.
Of course this doesn’t apply today. People like myself who get laughed out of the building when we try to enlist in the Navy (for being too blind) still manage to cope quite well thanks to corrective lenses. We hold down jobs, we raise children–who likely will also inherit our weak vision. Over time we have more and more people needing corrective lenses because it no longer happens that the weak sighted humans are killed off by bears, or by accidentally falling off cliffs or, whatever perils our ancestors had to face who didn’t have the benefit of corrective lenses, seeing eye dogs or white canes.
This is an example of natural selection working against a species. Because those of us with weak vision are able to live and procreate we are creating more visually impaired people. Usually the opposite effect comes from natural selection. Weaker traits do not get passed on because the individual with that weaker trait doesn’t get to survive. Not in the natural world. Anyone who knows anything about wolves or lions or any of the big predators knows–it is the sick or the aged or the weak that predators target and go after. Why? Because predators naturally do not want to have their rib cages kicked in or their skulls crushed, and the bigger stronger younger prey are more likely to cause serious harm–assuming they can catch them at all.
So natural selection, over time, does change a species. If you go to Europe and check out the doorways of those cool old castles, I hear the doorways are very short. Like….people over 5 feet tall have to stoop over to walk through them. Why? Because people were shorter back then.
Even in my lifetime…I was the tallest girl in my school growing up. That was back in the day when there weren’t any professional women sports teams and girls were just beginning to have the same kind of physical education/fitness programs in schools as boys. in the 30 years since I graduated I have seen more and more taller young women. Girls that make me look short. My guess is because women are finally “allowed” and even encouraged to use their bodies more–push themselves like boys to discover what they can do–they are getting stronger. Or maybe it’s just that the human race is still just getting a little bigger with each passing generation. This is evolution. Environmental changes or natural selection over time causes species to adapt physically. That changing process is evolution. If human beings survived another million years (highly doubtful) or more, those humans of the future might look a lot different than we do now. Especially as we replace what we used to do physically to survive, with machines to do it for us.
Another thing that creates change–diet. In the horse example I gave in my previous blog, what I copied for that from Wikipedia describes how horses teeth changed as the horse’s diet changed.
If only brown haired, brown eyed people were allowed to have children, eventually blue or green eyed people would disappear–with maybe the occasional throw back now and then. If interracial marriage became more and more accepted and popular, over time it is very possible the races now existing on this planet might be effected. There might not be white people one day. Because the more interracial couplings that happen, the more mixing of the races occurs, over a short amount of time, like 50 years or 100 years or 200 years, the face of humanity will change. If all tall people were forbidden to procreate and only short people had children, the human race would likely start to get shorter again.
If the climate changes and the sun becomes more intense, again, white people might find it harder to survive than people with more pigment in their skin. This would be a case where environment change is reshaping a species. If the gravity on this planet were to change and become stronger…very likely many species would die out altogether, while other species might have a few individuals with stronger thicker bones, survive. Those individuals with the stockier bone structure would mate with other individuals with stockier bone structure and that species would slowly adapt more and more to the new gravity, producing stockier offspring–and any offspring born without the thicker bone structure would die and not pro-create, until one day a stockier thicker boned version would exist, completely replacing the lighter framed earlier version of that same species that could not survive.
This is evolution or what causes evolution, as I understand it. When you have the conditions of survival change and the life in that environment must adapt to the changes or die.
Another example–river dolphins. Copied from Wikipedia:
Differences between marine and river dolphins
Both river dolphins and marine dolphins belong to a group of mammals called cetaceans, but they differ somewhat in appearance. For example, the snout of a river dolphin measures about 58 centimeters (2 ft) long, approximately four times as long as that of most marine dolphins. River dolphins have smaller eyes than marine dolphins, and their vision is poorly developed because they live in dark, muddy water. This environment also makes river dolphins less active than marine dolphins. River dolphins feed primarily on fish.[1
So….dolphins who do not use their vision very much because their environment doesn’t let them see, develop smaller eyes and weaker eye sight than dolphins in clear water who need and use their vision to survive. Two examples of marine mammals very different from each other because of their environment. And yet, both are dolphins.
Another example of animals who have adapted to suit their environment–Siberian tigers. Gorgeous cats. The largest of the big cats. He has feet the size of platters–great big huge feet, why? Because he travels on snow–needs to be able to run on snow. So his feet have adapted. Where humans have to wear snow shoes to walk on snow, the Siberian Tiger has his larger paws to achieve the same result.
An interesting animal to watch is the polar bear. Either he will become extinct in the next 50 years, or he will adapt to his radically changing environment. If he adapts he will physically change. His diet will have to change. How he gets fresh water to survive will have to change. How well he can endure warmer temperatures will have to change. If he can’t adapt fast enough, he will die and there will no longer be polar bears.
But there will be other bears.
Just like once upon a time there were Neanderthals and now there are not, while other species of humans who lived alongside Neanderthals did not die but endured. Neanderthals didn’t become us…but they did leave their genetic signature behind and contributed to what has made humans what we are today.
I don’t know how to end this. I hope this makes some kind of point. I guess what I’m trying to describe is, the ingredient Creationists don’t want to take into account is time. Creationists are used to thinking a deity said “let there be–” and there it suddenly was. They apply that same kind of thinking to evolution. They think one species just suddenly becomes something else. That’s not how it happens. It takes time–millions of years. Over time creatures that looked rather like wolves started hunting more and more in the water, started feeding more on fish than prey animals on land. Over time these animals adapted to hunting in water, and came out onto dry land less and less. Over time these animals developed limbs more like paddles instead of legs, and longer leaner bodies to make them cut through the water more swiftly. And over a really long period of time these animals became cetaceans–dolphins, Orcas, whales. Warm blooded mammals that live like fish in the sea.
Given enough time, a species will adapt itself to its changing environment. Because if it doesn’t, or if the change happens too soon, it goes the other route. It becomes extinct. Or changes to the point that it hits a roadblock and cannot change or adapt anymore, which is what they guess happened to the Neanderthal.