Evolution, in its simplest terms, refers to a change in the gene pool of a species. That's it. As a scientific theory, it does not directly address origin of life questions. It does what a scientific theory is supposed to do: Explain a range of physical phenomenon. However, in order for natural selection to work (for a change in the gene pool to spread throughout a species), life at some early point had to have the capacity to (1) adapt and (2) pass on changes to subsequent generations. It seems reasonable that these commonalities would have arisen very very early.
"Spontaneous" in this WT "definition" of evolution will lead to JWs imagining a modern cell popping into existence all on its own. I virtually guarantee that's what will be in most Witness minds when this is studied. Yet the fact of the matter is that any "spontaneous" generation of life would have happened over hundreds of millions of years and the very first stages would likely have been nothing that we would identify as life in the modern sense. Interestingly (as a side point), it seems that life appeared relatively early in earth's timeline)
This (horribly inaccurate and misleading) WT also descrives evolution as "human reasoning." This is a trigger phrase, shutting down critical examination or reflection, since it immediately "brands" the notion as human "philosophy" which is tantamount to "teachings of demons." The fact is that Newton's Laws of Motion are "human reasoning," just as Einstein's Theory of Relativity, theories of electromagnetism, economic theories of supply and demand, etc. These are all "human reasonings" supported by (in the case of evolution) literally reams of diverse yet convergent evidence from genetics, geology, paleontology, zoology, and a host of other fields that I cannot summon at the moment, and proven over and over and over by new discoveries.
It's terribly ironic that the WT is pointing fingers at young earth creationists when they themselves are just another flavor--old earth creationists and the evidence for an old earth (which JWs believe) overlaps with the same evidence for evolution (which they reject). The belief in six literal days of creation is just as farcical as the belief in figurative creative days lasting "thousands" of years, as JWs believe, since both camps are rejecting evidence that, in this year 2013, is as close to irrefutable as we can get.