I strongly reject any conceptual scheme that places our options on a line, and holds that the only alternative to a pair of extreme positions lies so… - Stephen Jay Gould

We are, whatever our glories and accomplishments, a momentary cosmic accident that would never arise again if the tree of life could be replanted from seed and regrown under similar conditions.

In his anti-Darwinian book... (and eponymously named The Neck of the Giraffe), Francis Hitching tells the story... "The need to survive by reaching ever higher for food is, like so many Darwinian explanations of its kind, little more than a post hoc speculation." Hitching is quite correct, but he rebuts a fairy story that Darwin was far too smart to tell - even though the tale later entered our high school texts as a "classic case" nonetheless.

We inhabit a complex world. Some boundaries are sharp and permit clean and definite distinctions. But nature also includes continua that cannot be neatly parceled into two piles of unambiguous yeses and noes. Biologists have rejected, as fatally flawed in principle, all attempts by anti-abortionists to define an unambiguous “beginning of life,” because we know so well that the sequence from ovulation or spermatogenesis to birth is an unbreakable continuum—and surely no one will define masturbation as murder.