# The evolutionary placement of genitalia **URL:** \ **Category:** Factual Questions\ **Created:** [October 14, 2014, 11:36am UTC](https://boards.straightdope.com/t/the-evolutionary-placement-of-genitalia/701289 "2014-10-14T11:36:15Z")\ **Posts on this page:** 10\ **Page:** 2
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [October 15, 2014, 2:54pm UTC](https://boards.straightdope.com/t/the-evolutionary-placement-of-genitalia/701289/21 "2014-10-15T14:54:23Z")
> [@](#): > > Quoth **Mangetout** : > > Not really. A penis is pretty specifically a copulatory device. A duct that releases semen is by no means necessarily a penis and a duct that releases ova probably isn’t actually a vagina. That’s why I said “like”, not “is”. ---
**Author:** ![Budget\_Player\_Cadet](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/budget_player_cadet/32/205_2.png) [@Budget\_Player\_Cadet](https://boards.straightdope.com/u/Budget_Player_Cadet)\ **Post date:** [October 15, 2014, 3:32pm UTC](https://boards.straightdope.com/t/the-evolutionary-placement-of-genitalia/701289/22 "2014-10-15T15:32:10Z")
> [@Lemur866](#): > > Because they retract their genitalia into their bodies. If you look at a male walrus he’s just got a slit–until it’s business time. Then out comes the wedding tackle, reinforced with a two foot long bone. Like, a literal bone. Native Alaskans used to use them as war clubs. This may just be my very favorite piece of trivia ever. > [@standingwave](#): > > Could be worse. We could have [these](http://en.wikipedia.org/wiki/Cloaca)… > In zoological anatomy, a cloaca /kloʊˈeɪkə/ is the posterior opening that serves as the only opening for the intestinal, reproductive, and urinary tracts of certain animal species. All amphibians, birds, reptiles, and monotremes possess this orifice, from which they excrete both urine and feces, unlike most placental mammals, which possess two or three separate orifices for evacuation. “Personally, not what I’d choose - I like to have a little more room between the breathing and the pooping - but I won’t judge.” ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [October 15, 2014, 4:26pm UTC](https://boards.straightdope.com/t/the-evolutionary-placement-of-genitalia/701289/23 "2014-10-15T16:26:40Z")
Most (male) mammals have penis bones, and most marine mammals keep their genitalia inside. ---
**Author:** ![PlumBob](https://avatars.discourse-cdn.com/v4/letter/p/ee59a6/32.png) [@PlumBob](https://boards.straightdope.com/u/PlumBob)\ **Post date:** [October 15, 2014, 7:09pm UTC](https://boards.straightdope.com/t/the-evolutionary-placement-of-genitalia/701289/24 "2014-10-15T19:09:41Z")
> [@standingwave](#): > > Could be worse. We could have [these](http://en.wikipedia.org/wiki/Cloaca)… > In zoological anatomy, a cloaca /kloʊˈeɪkə/ is the posterior opening that serves as the only opening for the intestinal, reproductive, and urinary tracts of certain animal species. All amphibians, birds, reptiles, and monotremes possess this orifice, from which they excrete both urine and feces, unlike most placental mammals, which possess two or three separate orifices for evacuation. Three separate orifices? Hmmm I want to Google this but I’m not sure where that would take me. :eek: ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [October 15, 2014, 7:10pm UTC](https://boards.straightdope.com/t/the-evolutionary-placement-of-genitalia/701289/25 "2014-10-15T19:10:13Z")
> [@Chronos](#): > > That’s why I said “like”, not “is”. It’s not even ‘like’, in any meaningful sense. ---
**Author:** ![dracoi](https://avatars.discourse-cdn.com/v4/letter/d/90db22/32.png) [@dracoi](https://boards.straightdope.com/u/dracoi)\ **Post date:** [October 15, 2014, 7:33pm UTC](https://boards.straightdope.com/t/the-evolutionary-placement-of-genitalia/701289/26 "2014-10-15T19:33:46Z")
> [@PlumBob](#): > > Three separate orifices? Hmmm I want to Google this but I’m not sure where that would take me. :eek: Anus, vagina, urethra. Males are missing one of those, obviously. 🙂 ---
**Author:** ![dracoi](https://avatars.discourse-cdn.com/v4/letter/d/90db22/32.png) [@dracoi](https://boards.straightdope.com/u/dracoi)\ **Post date:** [October 15, 2014, 7:37pm UTC](https://boards.straightdope.com/t/the-evolutionary-placement-of-genitalia/701289/27 "2014-10-15T19:37:31Z")
> [@Budget\_Player\_Cadet](#): > > This may just be my very favorite piece of trivia ever. It’s certainly mine. When I was in elementary school, we went on a museum tour. The tour guide gave us a very long talk about how that “extra” bone in the seal skeleton was a vestigial structure that proved evolution, blah, blah, blah. When she came up for air, one of the other adults pulled her aside and explained what it really was. ---
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [October 15, 2014, 7:37pm UTC](https://boards.straightdope.com/t/the-evolutionary-placement-of-genitalia/701289/28 "2014-10-15T19:37:35Z")
As has been stated, orifices that shed waste products are usually located at the rear of an animal, so as the animal moves it leaves the waste products behind. Having your butthole on your head means you’re constantly traveling through your own waste. Note that snails with their twisted body plan, are one of the exceptions and have their [anal opening over their shoulder](http://oldspouse.files.wordpress.com/2014/03/el-gastropodo.jpg), not at their rear. And since the organism already has an orifice for releasing various bodily excretions into the environment, it is evolutionarily conservative to use that same orifice to release gametes. As has been stated, most vertebrates have a single cloaca for releasing urine, feces, and gametes. A penis or analogous copulatory organ is just a way to directly deposit sperm into the cloaca of another organism, rather than just pressing cloacas together, or releasing gametes into the water. ---
**Author:** ![PlumBob](https://avatars.discourse-cdn.com/v4/letter/p/ee59a6/32.png) [@PlumBob](https://boards.straightdope.com/u/PlumBob)\ **Post date:** [October 15, 2014, 7:43pm UTC](https://boards.straightdope.com/t/the-evolutionary-placement-of-genitalia/701289/29 "2014-10-15T19:43:49Z")
> [@dracoi](#): > > Anus, vagina, urethra. Males are missing one of those, obviously. 🙂 Oops, All I had to do was ask the wife. :o :smack: ---
**Author:** ![Kobal2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kobal2/32/20_2.png) [@Kobal2](https://boards.straightdope.com/u/Kobal2)\ **Post date:** [October 15, 2014, 7:48pm UTC](https://boards.straightdope.com/t/the-evolutionary-placement-of-genitalia/701289/30 "2014-10-15T19:48:21Z")
> [@Budget\_Player\_Cadet](#): > > This may just be my very favorite piece of trivia ever. Oh, that’s nothing. Elephants not only have retractable bits, they have \*prehensile \*retractable bits mounted on reciprocating springs. They’re too big to do the old in-out-in-out via pelvic motions, see, so their penis has to do all of the work on its own. No, I do not know whether that means they can also discreetly masturbate without having to move at all. But… wouldn’t you ? [Previous page](https://boards.straightdope.com/t/the-evolutionary-placement-of-genitalia/701289.md?page=1)