Because it has extraordinary explanatory power in a very wide diversity of settings. It is certainly consistent with the sciences, and anthropological science in particular.
BTW -- You (on average) ate through your belly button for months 2 through 9 of your existence. Just because you aren't using it _now_ doesn't mean it never served any purpose.
BTW -- You (on average) ate through your belly button for months 2 through 9 of your existence. Just because you aren't using it _now_ doesn't mean it never served any purpose.