how "much" a species changes depends to the changes of the environment, which can come a) through the change of the environment itself or b) by changing location to "another" environment.
there are not so many "global" species on this planet, but we are "global" and fitted ourselfs into most of the niches life offers.
also, the more "complex" a species is (or becomes?) or its genetic code the more possibilities are there for changes and variations.
and how we can be sure if some million years before us there wasnt another species changing in such a "dramatical" speed. or do you know how long it took until the first "animal" became wings and flew up? or how long it took from the "first scorpion" to those with a tail and stinger?
and in a million years there will be perhabs none of us anymore. maybe chimps have made their way then, or their is no longer any form of "higher intelligence".
or we are far beyond the point of now, and "left" earth as species and started to "spread (life) into space" and this would be a must if we want to live "longer" than earth.
err.. and what skinwalker said.