Shrinkwrapped has a long discussion of the differences between conservatives and liberals and their stances on evolution.
It is a misnomer to say Liberals/leftists believe in evolution AS IT IS UNDERSTOOD BY SCIENCE RIGHT NOW, which includes enormous swathes of wholly unacceptable scientific evidence, like IQ differences among the races and gender differences. They do not. Remember, they are political animals at heart, not philosophers or scientists, they are not required by their own belief system to be consistent or to follow any viewpoint to its nth degree. They believe in the very old rudimentary Darwinism of the late 19th-early 20th century ONLY in so far as they can use it as an argument to counter assertions that the diversity of life could only have been brought in to being by the existence of God. They have no real other interest in “science.” Its also important to note that after Hitler, the “Progressive” left had to “purge” itself of anything that smacked of their earlier love affair with “eugenics.” Erasing eugenics from their program left a gaping hole in their belief system that THEY incongruently began to fill with a radical egalitarianism they had heretofore eschewed.
I have yet to meet a liberal/leftist who has any notion of current evolutionary science. They always bring up old heads like Stephen J. Gould, who was a Marxist (so is Jared Diamond BTW) and only a paleontologist, yet as a popularizer of science wrote books way outside his field of expertise that released very damaging concepts into the intellectual air, like his silly assertions in “The Mismeasure of Man” on IQ and the wholly ludicrous “punctuated equilibrium.” Marxists are not “liberals” and Jared Diamond will twist himself into giant Lysenkovean knots to avoid the aspects of evolutionary psychology that go against the fundamental grain of his creed.
Almost all of the other advocates of evolution as it stands (particularly evolutionary psychology) today are of the Right in some manner, though usually more along the libertarian lines. Evolutionary psychology, for the non-leftist, stands as a bulwark against the forces who say the human conventions, traditions and taboos are arbitrary and can’t be tossed out at whim with no consequences for the human condition. It gives a solid grounding in nature for upholding the traditional sexual mores, behavioral norms, marriage structures etc. that conservatives hold so dear. Don’t let the liberals fool you, they don’t believe in evolution, they just hate GOD.