There is undoubtedly variation in living things; the environment is undoubtedly selective and organisms compete for resource; and organisms undoubtedly reproduce. So all of Darwin's three prerequisites for evolution were present: variation, selection and reproduction.
It was so manifestly obvious to a mind of sufficient grasp that, as Huxley said on reading Origin, "How stupid not to have thought of it oneself!".
The physical evidence of kinship between closely related organisms, which becomes less as they become less closely related, is self-evident, so Carl Linne's classification system fitted with and is explained by the theory Darwin and Wallace were proposing. Cats, dogs and bears are more like one another than they are like humans and elephants; humans, chimps and gorillas are more like one another than they are like bats or whales; humans, bats, elephants, whales and dogs are more like one another than they are like birds or frogs or cabbages, so if you arrange organisms according to decreasing similarity you get a hierarchy, which can be explained by natural selection from small variation, accumulated over time, like the branching of an ever-growing tree all growing from a single origin.
So biological classification, diversification and development had an explanation.
However, there remained a few major problems for the theory; not with the theory itself, but with how it fitted with the rest of 'known' science.
|Alfred Russell Wallace|
So earth had to be much older.
For earth to have been old enough, the sun would have to be at least that old, and yet the received wisdom was that it must be only a few thousand years old otherwise it would have used up all its fuel by now.
So the sun had to be much older.
But the received wisdom was that the universe and the sun were created at the same time so the universe was not old enough for the sun to be old enough for the earth to be old enough for evolution to have had enough time.
And yet a mind of sufficient grasp could see that Darwinian evolution was so obviously true and explained just about everything about biology and how life came to be the way it is.
Then guess what!
Geologists found that earth was very much older than received wisdom thought. It was certainly many millions of years old, maybe even a few billion, so earth was certainly old enough.
But what about the sun? What about the problem of it having enough fuel to burn for many millions, even billions of years? Surely, if the sun wasn't old enough then the geology must be wrong.
Then guess what!
Physicist found that the received wisdom was wrong and the sun's energy came not from oxidation of combustible fuel like a conventional fire, but from fusion of hydrogen to form helium, and the mass was just enough for the sun to be old enough for earth to be old enough for evolution to have happened the way Darwin and Wallace said.
But what about the age of the universe? And what about the heavier elements that earth was made from? Where did they came from?
Then guess what!
Cosmologists found that the universe was expanding at a rate which, projected backwards, meant it started out very small fourteen billion years ago, and other physicists found there was an echo of a vast burst of energy and that echo was exactly as 'loud' as it should be if the universe was as old as its rate of expansion suggested.
And so physicists and cosmologists and geologists proved that the universe was old enough for earth to be old enough for evolution to have occurred just like Darwin and Wallace said.
But there was one more major problem for evolution.
No one had any idea how the information about difference was stored and passed on to the next generation or where the accumulated differences were stored and built up from one generation to the next, and how this information translated into different organisms.
Then Gregor Mendel found that there were rules of inheritance and that these rules must be the expression of some entity which was passed from parent to offspring, so we knew that there was something carrying the information but we didn't know what or how.
Then guess what!
Biochemists found the structure of DNA and how it acts as an information store and governs the growth and development of new organisms and so we now know how evolution works and where natural selection operates and where the information about variation is stored and how it is used to make different organisms.
But there was just one little nagging doubt left. Clearly related land-bound species had a habit of living on land-masses that weren't joined, so no one could satisfactorily explain how they got there and land bridges between Africa and South America seemed so unlikely. Didn't this mean that they couldn't have evolved from a common ancestor?
And then geologists discovered plate tectonics, which not only explained very much of why earth is the way it is, complete with mountains, oceanic trenches and volcanoes, but occurred in a way which exactly matched what it would need to be to explain why animals on disconnected land-masses evolved from a common ancestor, just the way Darwin And Wallace said they had.
And so now we know that Darwin and Wallace were absolutely right all those years ago and the science which was thought to have falsified it, or at least cast severe doubt on it, was wrong.
The geologists and physicists and cosmologists should have listened to the biologists and recognised that biology had discovered a fundamental law so powerful it can be used to validate other science. In fact, many of the more enlightened ones do, of course. Just like the laws of thermodynamics where we can be as sure as it is possible to be with science that if the science seems to contradict the laws of thermodynamics, the science is wrong, so we can say that if science seems to contradict evolution, the science is wrong.
Ah! But what about theology? Isn't that a major objection to the Theory of Evolution?
Not at all. Just as we can say that the science is wrong if it contradicts evolution, so we can say that theology is wrong if it contradicts evolution. Science is the tool we use for telling what's right from what's wrong. If theology fails the test of science, theology is wrong.
Unlike science, which can revise and correct itself when the evidence changes or more is added, just as it did when it seemed to conflict with evolution, theology is capable of revising and correcting itself only with immense difficulty and usually after much kicking and screaming, and so becomes progressively at odds with reality as time goes by, until it is forced to do an about turn and look silly as it does so. Like it did with the flat earth, geocentrism and the age of the earth and the universe it formed in, it has now been forced to pay official lip-service to basic science but still behaves as though the old ideas are right - which is why an increasing number of educated people are laughing at it as it tries to ride two horses going in opposite directions and simply makes an ass of itself.
That is a problem for theology, not for science.