I don't usually resort to cheap tactics like the use of the word "boobs" in the title of an article to attract readers, but I'm sure that it works for a significant cross-section of the potential audience. In any case, what this is really about is not so much the female breast as the concept of natural selection in general. It just so happens in this case that the specific example being used is that of the female breast.

I refer to an article in New Scientist which puts forward its own theory as to the shape of the human female breast in contrast to that of our alleged evolutionary ancestors. In short, it says that the traditional explanation is given in terms of attracting a mate, but they propose an alternative explanation based on the fact that humans have flatter faces than other primates. Thus, there may be selective advantage in a protruding breast on the grounds that an infant may stand a higher chance of suffocating whilst feeding on a flat breast; a problem not shared by the other primates with their relatively protruding jawline. This selective advantage explains the evolution of the bra. Roughly.

My beef with this scenario is not that it's evolutionary and I'm a creationist: I'm quite willing to play the evolution game even if I don't believe it. It's in my interests to have a good understanding of evolution simply so that I can be a good critic rather than an ignorant whiner. My problem with this particular scenario is that it's not only a "just so" story, but that the same selective forces can be used to explain exactly why it wouldn't happen like that. Consider: if we start with a flat breast and a protruding jaw, then any flattening of the face is going to come at a selective disadvantage (increased chance of suffocation). The explanation given in New Scientist presupposes that the face has already become flat for some reason (and is staying that way). The breast then fills the selective vacuum, so to speak.

Natural selection might in fact work that way were it so constrained, but why is it reasonable to ignore the selective pressure on the facial features? As often seems to be the case, any scenario which contains an element of advantage is considered valid; rarely if ever (and certainly not in this case) are the equally valid and opposing forces considered. In any case, the nice black and white stock photo of an infant suckling with which they illustrate the article does not demonstrate the respiratory advantages of a bulbous breast very well: the infant's nose is pressed up against the breast, curves notwithstanding.

Proponents of evolution might step in at this point and say I'm not being fair: this is a small opinion piece in New Scientist, not a scientific proposal. True, but the attitude is pretty pervasive. Read Michael Behe's Darwin's Black Box, for example, and you might come away with the impression that he's dealt a fatal blow to modern evolutionary theory. You'd be mistaken, however, in the opinion of many evolutionary thinkers. Behe's argument goes something like this: there are many highly intricate and complex structures in biochemistry that simply do not work at all unless every last component is in place, just as a stone arch will collapse if you remove any of the stones: every component relies on the operation of every other component in some indirect manner. How can such a system evolve by the kind of microimprovement required by natrual selection?

Behe's critics have met his objections with the verbal equivalent of dismissive hand gestures. For example, one response I read said that even an arch may be constructed with the aid of scaffolding, and after the arch is complete the scaffolding no longer serves a useful purpose. Thus, in biochemistry, what we see now is the arch after the scaffolding has evolved out from underneath it. This style of argument is subject to exactly the same complaint as I have raised above: they are suggesting one seemingly possible solution and acting as though all objections have therefore been answered. No critic attempts to actually demonstrate that such a "scaffolding" scenario is possible. Behe takes specific biochemical systems and demonstrates how the removal of any one component breaks the system; his critics should show at least this much rigor in their responses.

What does all this prove? Mostly it proves that I can't even embark on a slightly saucy article about breasts without ending up in a discussion on intellectual rigorousness. Still, I hope it has raised your awareness of the "unproved but plausible scenario" handwaving method, and that you are well-equipped to detect it in future, whether or not any breasts are involved.