In 1829, Francis Henry Egerton, the eighth Earl of Bridgewater, bequeathed 8,000 pounds sterling to the Royal Society of London to pay for publication of works on "the Power, Wisdom, and Goodness of God, as Manifested in the Creation."

The resulting "Bridgewater Treatises," published between 1833 and 1840, were classic statements of "natural theology," seeking to demonstrate God's existence by examining the natural world's "perfection."

Current believers in creationism, masquerading in its barely disguised incarnation, "intelligent design," argue similarly, claiming that only a designer could generate such complex, perfect wonders.

But, in fact, the living world is shot through with imperfection. Unless one wants to attribute either incompetence or sheer malevolence to such a designer, this imperfection — the manifold design flaws of life — points incontrovertibly to a natural, rather than a divine, process, one in which living things were not created de novo, but evolved. Consider the human body. Ask yourself, if you were designing the optimum exit for a fetus, would you engineer a route that passes through the narrow confines of the pelvic bones? Add to this the tragic reality that childbirth is not only painful in our species but downright dangerous and sometimes lethal, owing to a baby's head being too large for the mother's birth canal.

This design flaw is all the more dramatic because anyone glancing at a skeleton can see immediately that there is plenty of room for even the most stubbornly large-brained, misoriented fetus to be easily delivered anywhere in that vast, non-bony region below the ribs. (In fact, this is precisely the route obstetricians follow when performing a caesarean section.)

Why would evolution neglect the simple, straightforward solution? Because human beings are four-legged mammals by history. Our ancestors carried their spines parallel to the ground; it was only with our evolved upright posture that the pelvic girdle had to be rotated (and thereby narrowed), making a tight fit out of what for other mammals is nearly always an easy passage.

An engineer who designed such a system from scratch would be summarily fired, but evolution didn't have the luxury of intelligent design.

Admittedly, it could be argued that the dangers and discomforts of childbirth were intelligently, albeit vengefully, planned, given Genesis' account of God's judgment upon Eve: As punishment for Eve's disobedience in Eden, "in pain you shall bring forth children." (Might this imply that if she'd only behaved, women's vaginas would have been where their bellybuttons currently reside?)

On to men. It is simply deplorable that the prostate gland is so close to the urinary system that (the common) enlargement of the former impinges awkwardly on the latter.

In addition, as human testicles descended — both in evolution and in embryology — the vas deferens (which carries sperm) became looped around the ureter (which carries urine from kidneys to bladder), resulting in an altogether illogical arrangement that would never have occurred if, like a minimally competent designer, natural selection could have anticipated the situation.

There's much more that the supposed designer botched: ill-constructed knee joints that wear out, a lower back that's prone to pain, an inverted exit of the optic nerve via the retina, resulting in a blind spot.

And what about the theological implications of all this? If God is the designer, and we are created in his image, does that mean he has back problems too?

The point is that these and other incongruities testify to the contingent, unplanned, entirely natural nature of natural selection. We are profoundly imperfect, cobbled together rather then designed. And in these imperfections reside some of the best arguments for our equally profound natural-ness.