No, I didn’t think you meant that it was tunneled out. However, the way you stated it implied that the crack itself was a path for the passage of waste, not that it allowed spreading of the butt-cheeks for easier defecation. That was what I was calling nonsense.
However, you are falling in to the adaptionist mode of explaining it by recourse to a single adaptive explanation. The crack actually allows greater mobility for all kinds of movements of the leg, including movements to the side, not just for squatting. So explaining it just as an adaptation for ease of defecation is unnecessary. The crack may be necessary for the buttocks to work in locomotion in general.
The main point about the butt-crack being a spandrel is not that it has no utility or purpose at all, but that it is a consequence of the hypertrophy of the buttock muscles themselves, not something that evolved for independent adaptive reasons.
OK, I agree that would have been nonsense. I sometimes assume that what’s obvious to me - that it was to facilitate the muscle groups parting - is obvious to everyone else - sorry.
It may well be there for locomotion in general. It, or something similar must exist as the anus cannot be covered over. If the anus wasn’t there I think it could be pretty well guaranteed that that area of our bodies would not be configured the way it is.
Your original explanation referred solely to an almost accidental evolution into that configuration (as opposed to, for example, two hillocks with a gentle valley or more closely joined lumps of muscle, perhaps forming a smooth hemisphere) and it was that with which I was disagreeing.
Plenty of animals have butt cracks. They are just covered up or filled in by a tail. The combination of no tail and bipedalism make the butt crack more apparent in humans. It is simply evidence that body form is established by constraints, not a genetically encoded picture.
Also, as usual, sexual selection plays a role. I doubt men’s eyes auto-focus on a young woman’s butt crack by accident.
Perhaps I shouldn’t have used the word “non-adaptive.” The butt-crack may have an adaptive reason in that it allows for greater mobility of the buttocks, whether for locomotion or for defecation; however, the actual adaptation is the buttocks. The butt-crack is not adaptive in and of itself, but only with respect to the buttocks.
Humour may be a side effect, but it’s debatable whether it confers an evolutionary advantage.
Humour in modern society is supremely important. People want to have friends who are funny. Women want to date guys with GSOH. Any social gathering devoid of humour is seen as a disaster.
My own theory is that humour is a way of demonstrating intelligence. But not intelligence in a book smarts way, which wouldn’t have been so useful to our remote ancestors. Instead it demonstrates skills of pattern recognition / association and other mental skills, which may be useful in more serious contexts.
For most of our recent evolutionary history, the main selection force on our genes has been the opinions and actions of other human beings. I think humour has evolved as part of this process, along with other abstract mental skills and sex-selected physical characteristics.
I just wanted to say I’ve never encountered such a serious and pedantic conversation that involved butt cracks and pictures of horse’s asses. Congratulations, all of you. Thirty posts in, and barely any jokes. sniff I’m so proud!
So, You are “the horse of a different color” from the Wizard of Oz? I saw lots of different colored horse’s asses on the first page, and I didn’t even look at the second. Your page rank is slipping, call your search engine optimization people. They aren’t doing their jobs.