Stupid question, I know. I imagine it has been asked here a few times before but I couldn’t find it. But why do we (and other animals) use the same organs for sex and waste? How are they related?
Only males have that feature. Females have totally separate plumbing for urination and intercourse, even if they are located close together.
One point - only males do. A woman has a seperate urethra. On preview, I see Q.E.D already made that point.
Also, this is not common to mammals - birds have an all-purpose cloaca. I think it boils down to the fact that it’s simpler. It doesn’t hinder either activity, and thus it stays. They are related in the fact that they both (for males) involve liquid exiting the body.
I see where ** caracal’s ** question comes from, though. I’ve often wondered the same thing, but my curiosity involved bacteria.
It seems that bacteria in the urine traces (or in the case of birds, fecal traces) left in the urethra of the male might in some way damage the sperm, or in some way affect the female’s uterus or ovaries. In an evolutionary sense, any hinderance to sperm usually is weeded out through natural selection, so is the bacteria not harmful at all?
I assume not, otherwise evolution would have provided an alternate solution by now.
I was under the impression that bacteria wasn’t present in (human, at least) urine typically - otherwise I’d think you’d have a urinary tract infection, which would be extremely painful, not to mention harmful.
It’s because, as the old joke goes, God is a civil engineer. (Who else would put a toxic waste dump in the middle of a recreation zone?)
Becasue sexual organs are filthy and disgusting to God. Duuuuuh.
there’s already a hole in the body, why have another?
Only mammalian females have separate ducting for reproductive and excretory functions. All other animals use common ducting. Perhaps the question should be why are only female mammals different from the rest?
This, among other things, is why the male excretes pre-ejaculate before orgasm (to clear the pathway, as it were) and why the female vagina is such an acidic environment (a tougher breeding ground for bacteria). Frankly, though, the sperm don’t spend that much time in the urethra, they’re already buffered by massive amounts of fluid, and the vagina is already likely to have much worse things living in it (hence yeast infections, etc.).
what, you never heard of multi-tasking?
Urine is sterile. There is no bacteria in it.
Because only female mammals are viviparous. The uterus is a separate organ from the bladder, and it requires a separate tube to deliver its contents to the outside world.
I’m not even sure if oviparous critters tend to have bladders, or if their liquid wastes are ducted directly from the kidneys to the cloaca.
My first thought was ‘Are you sure you’re doing it right?’, being that the term ‘excrement’ more commonly refers to feces. A quick trip to dictionary.com dispelled that notion. That said, I think that perhaps reproduction and waste are related more closely than we tend to think.
Both semen and eggs are excreted from the body. In the case of fertilized eggs, the excretion takes place after gestation, but still takes place. I think it’s our own compartmentalization of the two functions, waste and reproduction, that is to blame here. We think of urine and feces as something valueless that we excrete, but don’t think the same way about semen and certainly not about a child.
Yet in the end (no pun intended), the result is the same. Excretion is a specialized process, so it makes sense to have the organs that excrete closely associated.
“the vagina is already likely to have much worse things living in it”
This conjures up all sorts of terrible images, doesn’t it?
In a perfect world—Our suspected UTIs (People with possible urinary tract infections) go to the lab (Their urine samples, actually) and come back positive for bacteria,WBCs and such nasty stuff.
Not sure i can explain this without getting kinda graphic… bear with me…
As we’ve seen already, this applies essentially to males. So, we’re talking about the penis. Ever notice you can’t pee when you have an erection? That’s because urine is blocked from coming out while erect, so that urine won’t mix with the semen when semen is ejaculated. That’s why you wake up with morning boner, so you don’t pee the bed. Also, I don’t know a technical term for it, but pre-cum is sorta like a cleansing fluid to wash away some (if not all) of the impurities that may prevent the survival of the sperm in their travels.
Hope I didn’t offend anyone.
So God is a Republican, eh?
Think about how mammalian reproduction evolved. You have to go back to when we were fish. Typical reproductive strategy then is for the female to dump a bunch of eggs on the sea floor, and the male swims up and sprays sperm all over them. Not a very complicated system, which uses a common duct to excrete solid wastes, urea, and gametes.
Mammals and other land vertebrates are simply inheritors of this system, albeit modified. Early reptiles evolved a system of internal fertiliztion where they put their cloacas together, the male releases sperm which swims up the female’s cloaca. Some reptiles have versions of penises, which are pretty much simply extensions of the cloaca that make the cloacal “docking” easier. Our mammal-like reptile ancestors had this system, and we’ve elaborated on it ever since with our mammal penises.