Right. Of course, reality would lie somewhere between the two extremes: there exists positive feedback mechanisms, so that beneficial mutations are more likely to be propagated than bad ones, but some beneficial mutations won't be propagated while some bad ones are.
The $1,000,000 question, though, is whether there exists a sequence of mutations which could occur to go between major species with at most a few mutations not being beneficial in and of themselves. If there are sequences of mutations which would have to occur without the individual mutations themselves being useful, then those situations would represent the sort of improbability to which the author is alluding.
Personally, I suspect that the 'truth' of the matter is that evolution and natural selection account for some, but not all, of the diversity of life on this planet. The Theory of Evolution, while it does not explain everything, is nonetheless scientifically useful within those areas of taxonomy where it is effective. I find it puzzling that some would argue that even such a narrow-scope view of evolution contradicts the bible when there is far more biodiversity on this planet than could ever have fit within the Ark. If one is to accept as true anything even remotely resembling the story of the Great Flood, it would follow that some level of evolution must have occurred between then and the present day.
I'm off to sleepytime soon, so I'll try to put together a fuller response in the morning, but for now, consider this: Remember that evolution is all about what's advantageous right now - there's no planning for the future involved at all. If you have some trait that's advantageous right now, it'll be passed along. If it's dysfunctional right now, it's less likely to be passed on - if you are born with a genetic predisposition towards having two heads, you are very likely going to die without passing on that trait.
So, you're right, in a sense. Some trait that might be advantageous in a hundred years, but isn't advantageous in the here and now, is not necessarily going to be passed on. But, like I said, there's no element of planning involved. If there were, it would certainly be advantageous for all of us to already possess potential desirable traits that we don't immediately need - we might wonder why our designer didn't see fit to properly future-proof us ;)
And to give a fuller answer - traits that are neither advantageous nor dysfunctional might be passed along. They won't be selected for, but neither will they be selected against. And someday those seemingly useless changes just might prove useful to you. And when the ones with the changes survive and the ones without don't, we start wondering if we've witnessed speciation.
I find it puzzling that some would argue that even such a narrow-scope view of evolution contradicts the bible when there is far more biodiversity on this planet than could ever have fit within the Ark.
I always wondered if Noah had a kangaroo and a polar bear on board ;)
If one is to accept as true anything even remotely resembling the story of the Great Flood, it would follow that some level of evolution must have occurred between then and the present day.
It is one possibility. Unfortunately, I think that, depending on when we date the Flood, we'll very likely find that the length of time since then is not really adequate for large-scale evolutionary change, such as the rise of thousands or millions of new species.
Anyway, that's not so impossible to deal with. Belief in evolution and belief in God are not mutually exclusive - you can believe in both quite comfortably. What evolution is incompatible with are some very literal readings of the Bible, which is what turns these threads into marathon flamewars ;)