A new transitional fossil between the australopithecene and human lineages has been discovered. Naturally, there will be argument over this. But there are two points to this: (1) these discoveries are continually being made, leading to an ever more complex picture of human evolution and (2) science involves testable hypotheses and our picture of what's true is constantly being updated to reflect the most recent evidence.
So what the hell does this have to do with fantasy literature? Not much, but I'm going to make a link anyway, in honor of Terry Brooks, since The Measure of the Magic is now out (I haven't read it, but the first sentence is not as sucky as that in Bearers of the Black Staff).
I'm thinking of these transitional books between the world of The Word and the Void and the Shannara books. You've got civilization as we know it declining at a rapid rate. The problems are sort of generic -- crime and violence, pollution, etc. It's pollution that seems to be causing people to mutate. At one point, in one of these books, and no, I'm not going back to look it up because it's like a needle in a haystack, someone says that over 3000 years of evolution were necessary for humans to diverge into gnomes and trolls and lizards and whatever the hell else. (And when I say lizards, I don't mean actual lizards, but instead people with scaly skin and sh*t like that.)
There are so many problems with this concept of evolution that I don't even know where to start. Let's go with the time frame. It's been about six million years since humans diverged from chimps. If you took humans from 1000 BCE and put them next to us (so you know, separate them by 3000 years), they wouldn't be all that different. Maybe more affected by disease, with a shorter lifespan, and differences in phenotype (height, etc.) based on poorer diet. But the point is, 3000 years isn't all that much in terms of human evolution. Sure, for example, some traits could become fixed in small populations in that period of time. But let's assume a human generation is 20 years. That means 3000 years is 150 generations. Six million years, on the other hand, is 300,000 generations. Speciation might occur over 300,000 generations. But 150? In a multicellular organism? No. So Brooks gets the time frame waaaaaaay wrong.
Then, there's the issue of mutation. Yes, it is entirely plausible that pollutants in the environment could cause mutations. But there are a couple of really bad assumptions in Brooks's stories. First of all, that entire groups of people, sometimes people in diverse geographic areas, would all get mutations that pushed them towards becoming a separate species, at similar points in time (even allowing for a couple of decades, here). It doesn't work that way. There are numerous reasons why. Let's examine a few.
(1) Most mutations are deleterious. That is, they cause proteins to misfold or become nonfunctional. So if they do anything to their carriers, it's likely to cause harm. (Obviously, some mutations are not deleterious, and lead to improvements in function. But many more are either neutral, substituting one codon for an amino acid for another codon for the same amino acid, or downright dangerous.) Since lizards, trolls, and all the rest, are still capable of speech, civilization, action, etc., they're still functional organisms and therefore the mutations required to divide into these groups wouldn't technically be deleterious, even if it did make them aesthetically less pleasing to human eyes.
(2) For a mutation to be passed on to a subsequent generation, it has to occur in a germ cell (which gives rise to sperm or eggs), not a somatic (body) cell. There are a hell of a lot more somatic cells than germ cells, and many somatic cells are in systems that can get exposed to mutagenic agents. For example, skin (UV light), digestive tract (from consumption of foods), liver and kidneys (concentration of wastes and detoxification). But if you get a mutation in a cell in your arm and get, say, lizard skin there, your kids aren't going to get the same mutation. Most likely, the cell will undergo apoptosis (programmed cell death). If not, you might get cancer (remember those deleterious mutations?). And the people in Brooks's books are accumulating mutations that cause the appearance of their skin to change and that can be passed on to their children...
So, there's more I could say, but I think people have limited attention spans, especially when it comes to science in a blog devoted to fantasy literature. This is actually why I avoid reading science fiction most of the time, because the science is just ridiculous and as I have Bachelor of Science degrees in biology and chemistry, and I'm about a year from getting a PhD in biochemistry, I just can't let that stuff pass.
In Brooks's defense, I like the idea that Dick Cheney caused the downfall of civilization.