"Morning wood" and the other primates

Two questions about this pheomenon with which all males are acquainted:

  1. Do other, non-human members of the primate family experience the same thing?

  2. Is there any known or speculated reason that we tend to greet the morning this way?

Oh, this thread is gonna get plenty o’ hits.

IANAZoologist, biologist, or anything else relevant, however IIRC most (possibly all) other primates have a bone in the penis. Whether or not they tend to wake up with an engorged penis and a retracted penile sheath, I don’t know.

I’m curious as to why you confined the question to other primates. If dogs, bulls, or whales wake up with morning wood, wouldn’t that teach us something about the phenomenon? If cygnets and cockroaches wake up with morning wood, wouldn’t that be deeply educational?

As for your second question, the best hypothesis I’ve heard is that the erection is in response to the sensation of a full bladder and inhibits urination.

This has been pretty well debunked. See post #5 in this thread, for instance.

Posts 15 and 23 both offer support of the bladder stimulation hypothesis. I’m not disputing that erections occur during REM. However, morning wood may be unrelated to REM.

Um… read the whole thread, and read it carefully. In that thread I debunked the debunk and provided neurological reference on how a full bladder can cause erections. Not saying there can’t be other factors.

Forget the thread – it’s correct overall, but you have plenty of people chiming in who don’t know what they’re talking about. Try a link from a medical authority, like this.

As for the “urination” explanation – do you usually get an erection when you have to piss? I think not.

Actually, I had thought it was most other non-primate males that had the bone in the penis; the lack of that, plus the fact that we’re all dangly (lacking the attached prepuce most other mammals have) is one of the quintessential primate features, along with leathery palms and soles and a fondness for bananas. But I’m none of those things either, so I certainly might be wrong.

Confining the question to primates was due to an unspoken hypothesis that it -is- confined to primates–in my personal experience, I’ve never seen (for example) a dog wake up sportin’. They’ve also all been neutered, but if the reaction is a response to a full bladder, that wouldn’t seem to matter since we’re dealing with another system entirely.

Looking at the other thread linked, I see that question two seems to have been dealt with; shame on me for not looking first. Still leaves me curious about the first, though, and I don’t think I could go to the zoo and ask the primatologist without feeling very awkward… :o

I’m sorry, Chuck, but significant medical evidence from various medical sites actually supports Brain Wreck’s position (even though he was guilty of a logical fallacy in that other thread). I wouldn’t have believed it, but there is persuasive evidence that a full bladder – at least under certain circumstances that apparently coincide with the REM explanation – can indeed induce erections (but perhaps not by itself).

You apparently didn’t read far enough into the referenced thread. See here (post 23) for two compelling links from a responsible, professional medical source that Wreck provided.

Oddly, “Alice” at Columbia.edu flatly contradicts herself. In this link you provided, “Alice” says: “Many men think their penises are erect upon waking because of urine buildup in the bladder, but this is false”, which seems to settle it. However, on the exact same site at this page from seemingly the same person, “Alice” states: “In addition, when a person has a full bladder, the pressure exerted by the bladder upon the prostate gland can cause erections.”

Given this contradition and all things considered, especially given Wreck’s two spinal chord links, it seems to me that the preponderance of the quality evidence is generally in Brain Wreck’s favor.

And does everyone always wake with an erection after REM sleep? Are you prepared to make that statement?

Full bladders can influence erections. Medical information has been provided. You would have seen it in that thread except you quietly disappeared after it had been posted.