garrysylvester has a glimmer of the correct answer, but then took it to an absurd conclusion.
Direct evidence is the observation of evolution as it occurs. Indirect evidence is looking for signs of its results.
But then garry eliminated indirect evidence as being evidence at all! This shows a complete lack of understanding of science.
Allow me to explain. (And in the process, answer your question about the difference between direct and indirect evidence.)
Evolution is defined as "change in allele frequencies of a population" ... or "change in the inherited traits of a population over time". To see this *directly* takes experiments such as those performed routinely by geneticists using organisms like fruit flies that have two properties (1) they have some visible trait that is easy to count; and (2) reproduce fast enough that we can see changes within a few generations. Centuries of breeding of livestock, crops, cocker spaniels, racehorses, and championship orchids also is direct evidence of evolution (as the breeder is *deliberately* manipulating breeding partners in order to *cause* a change in the frequencies of certain traits).
garry is absolutely wrong when he says the following:
> "We do have direct evidence for genetic change through selection. Eg farm animals. This is often quoted as direct evidence for evolution, but it is not."
Of course it is! Evolution *IS* "genetic change." That is how it is defined. So if we see "genetic change" in a population ... this is *direct* evidence of evolution.
But garry's bigger error is in his dismissal, with a wave of his hand, of *indirect evidence*.
Indirect evidence includes all the evidence that this same process of evolution has been occurring for a very long time (billions of years), and that modern species are related by common ancestry (e.g. that wolves, foxes, and coyotes, while now separate, non-interbreeding *species* have a common genetic ancestor). Indirect evidence includes fossil evidence, evidence from radiometry, stratigraphy, DNA, shared genetics, shared junk DNA, the very existence of junk DNA, proteins, physical structures, vestigial structures, homologous structures, atavisms, the ways that embryos develop, biogeography (the distribution of organisms on the planet), the immunity of insects to pesticides, etc. etc. Even the way that viruses adapt in a single year to our flu vaccines (which is why we need new flu vaccines) would seem to be direct evidence, but if we are not directly measuring the *frequency* of a certain trait (like immunity to a vaccine), it would more correctly be called another piece of *indirect* evidence.
To dismiss all this (as garry has) as simply not evidence at all, is to dismiss the role that indirect evidence plays in science.
For example, do we have *direct* or *indirect* evidence that the sun is made of hydrogen? Answer ... indirect. We cannot take a direct sample from the sun ... we never will. We *deduce* from the lines in the spectrum of sunlight the unmistakeable signs of hydrogen. That is *indirect* evidence ... but it is absolutely compelling evidence.
The same with evolution. We *deduce* that evolution has occurred, and that any two modern species share a common ancestor, from the unmistakeable *signs* of that evolution ... indirect evidence. But that is absolutely compelling evidence.
The same is true with most findings in astronomy. And astrophysics, and geology, archaeology, paleontology, atomic and subatomic physics, quantum theory, much of chemistry, etc. etc. ... all founded primarily on *indirect evidence* ... and all perfectly valid fields of science.
---- P.S. -----
I like firedawg's theory. I rarely give creationist answers in the Biology section a thumbs up, but I did in his case.
At least his theory is honest, and self-consistent. (It is also theologically profound ... but that's a topic for the R&S section.)
His theory, of course, is not a scientific theory ... because by definition it is untestable (as it postulates that the Creator would go through the trouble to create false evidence of a long history ... and therefore any evidence of long history is explained away).
But at least firedawg does not attempt to deny that the evidence (like fossil evidence of dinosaurs) exists at all. He also recognizes that his theory is a personal one that would have to be accepted on the basis of personal faith. That is at least honest.