Why do some humans and animals engage in sodomy if it allows easy transfer of STDs?

[mad_scientist]

What evolutionary advantage does sodomy give to animals which choose to engage in this activity?

[Phi for All]

I dislike the way your titles differ in intent from your OPs. In the title, you seem to imply that animals know what STDs are, or that there is a correlation between them and sodomy. 

[swansont]

Why do you assume it confers an evolutionary advantage?

[Area54]

2 hours ago, swansont said:

Why do you assume it confers an evolutionary advantage?

It is not an assumption. It is a reasonable inference from observation. The significant proportion of populations expressing homosexuality in a wide range of animals is unlikely to have arisen and persisted unless there was a significant evolutionary advantage, given that it does possess a clear evolutionary disadvantage.

[swansont]

21 minutes ago, Area54 said:

It is not an assumption. It is a reasonable inference from observation. The significant proportion of populations expressing homosexuality in a wide range of animals is unlikely to have arisen and persisted unless there was a significant evolutionary advantage, given that it does possess a clear evolutionary disadvantage.

What's the evolutionary advantage of myopia?

[Area54]

1 minute ago, swansont said:

What's the evolutionary advantage of myopia?

What's the incidence of myopia in non-human animals?

[swansont]

11 minutes ago, Area54 said:

What's the incidence of myopia in non-human animals?

I have no idea. But it's present in humans.

But my point being that not being a detriment should be sufficient to persist. 

Or, a genetic component could persist if e.g. it's recessive , confers an advantage and you have only one copy, while having two copies gives the expression of some (apparently) detrimental behavior. e.g. the genes for sickle cell. Not every trait is advantageous, if more than one trait is tied to the genes involved.

[OldChemE]

In order for some trait to prove an evolutionary advantage/disadvantage it must promote/inhibit successful reproduction.  It seems to me that in order to assert that sodomy has some evolutionary effect (in the absence of statistics) you would need to establish that it affects successful reproduction, as opposed to being something humans/animals do aside from other 'normal' reproductive activities.

[EdEarl]

What evolutionary advantage does X  give to animals which choose to engage in this activity?

Where X=
  nursing another species
  having sex with another species
  killing a perspective mate

People do many things, e.g, own a pet rock, that have nothing to do with evolution. Animals are more limited in things they do that aren't related to evolution.

[Moontanman]

1 hour ago, OldChemE said:

In order for some trait to prove an evolutionary advantage/disadvantage it must promote/inhibit successful reproduction.  It seems to me that in order to assert that sodomy has some evolutionary effect (in the absence of statistics) you would need to establish that it affects successful reproduction, as opposed to being something humans/animals do aside from other 'normal' reproductive activities.

IMHO You would have to define sodomy a little more clearly before we can even talk about the subject.

47 minutes ago, EdEarl said:

What evolutionary advantage does X  give to animals which choose to engage in this activity?

Where X=
  nursing another species
  having sex with another species
  killing a perspective mate

People do many things, e.g, own a pet rock, that have nothing to do with evolution. Animals are more limited in things they do that aren't related to evolution.

Again, let's define what is meant by sodomy and how they transfer disease more often than any other contact? Dogs have an infectious cancer that they can get from sniffing another dog's anus. does that count? 

9 hours ago, mad_scientist said:

What evolutionary advantage does sodomy give to animals which choose to engage in this activity?

Please define sodomy... 

[EdEarl]

@Moontanman

Probably.

[Moontanman]

1 minute ago, EdEarl said:

@Moontanman

Probably.

Close enough for government work...

[swansont]

7 hours ago, OldChemE said:

In order for some trait to prove an evolutionary advantage/disadvantage it must promote/inhibit successful reproduction.  It seems to me that in order to assert that sodomy has some evolutionary effect (in the absence of statistics) you would need to establish that it affects successful reproduction, as opposed to being something humans/animals do aside from other 'normal' reproductive activities.

It's not even necessarily about the individual's reproduction. Evolution is about populations. I could have a trait that helps my siblings survive and reproduce, even if it means I have no offspring of my own. Since I share genes with them, my genes are being passed along.

[DrKrettin]

I'm not a biologist, so shoot me down if you like.  There are many species of animals where there is a dominant male who mates with a lot of females and thus has many offspring, Presumably he is dominant because he carries genes which are positive for the species, so there is an evolutionary advantage that he mates and others do not.

If births are 50% male and 50% female, that leaves a lot of males with nothing to do (the stag party), but who have the same sexual urges as the dominant male. It follows that homosexual behaviour of the inferior males would have the advantage that the alpha male can carry on producing, with less hassle from competing males. If so, then homosexual behaviour would have an evolutionary advantage, albeit indirectly.

How's that for a theory?

[Area54]

1 hour ago, DrKrettin said:

How's that for a theory?

It is a crap theory, but it is a neat hypothesis. As Huxley said to Darwin, "That's so obvious, why didn't I think of that?" The odds are several others have and the literature is probably full of relevant research.

[EdEarl]

On 9/9/2017 at 8:56 PM, Moontanman said:

IMHO You would have to define sodomy a little more clearly before we can even talk about the subject.

Again, let's define what is meant by sodomy and how they transfer disease more often than any other contact? Dogs have an infectious cancer that they can get from sniffing another dog's anus. does that count? 

Please define sodomy... 

Dogs sniff each others rear all the time; sodomy has little or nothing to do with it. In fact, two animals near each other, regardless of species or intent, may transfer disease to one another. Disease may cause genetic or epigenetic changes that may be inherited.

[Thorham]

On 9/9/2017 at 6:12 PM, mad_scientist said:

What evolutionary advantage does sodomy give to animals which choose to engage in this activity?

Not every activity that animals (including humans as a species) engage in must necessarily have an evolutionary advantage.

[Moontanman]

2 hours ago, Thorham said:

Not every activity that animals (including humans as a species) engage in must necessarily have an evolutionary advantage.

 

2 hours ago, EdEarl said:

Dogs sniff each others rear all the time; sodomy has little or nothing to do with it. In fact, two animals near each other, regardless of species or intent, may transfer disease to one another. Disease may cause genetic or epigenetic changes that may be inherited.

Again we have failed to define sodomy, are we going by the old "I can't define it" but I know it when I see it" adage? Here is the dictionary definition:

Dictionary

sod·om·y

ˈsädəmē/

noun

sexual intercourse involving anal or oral copulation.

Fruit bat females perform felletio on males to insure a successful mating. Male bull elephants often have anal intercourse among themselves, only the largest and strongest getting to mate with females. These are not isolated cases, this behavior in some form occurs all across the animal. When two female whip tailed lizards mimic mimic sex so they can lay eggs sodomy? There are no males in that species, so sexual contact between females is necessary.

IMHO sodomy is archaic word that was made up by people who thought they had the right to say how people should sex. So far I have seen no data  that would indicate sodomy is any more or less likely to transfer STDs...

Edited September 12, 2017 by Moontanman

[Uncommon Ancestor]

On 10/9/2017 at 11:54 AM, DrKrettin said:

I'm not a biologist, so shoot me down if you like.  There are many species of animals where there is a dominant male who mates with a lot of females and thus has many offspring, Presumably he is dominant because he carries genes which are positive for the species, so there is an evolutionary advantage that he mates and others do not.

If births are 50% male and 50% female, that leaves a lot of males with nothing to do (the stag party), but who have the same sexual urges as the dominant male. It follows that homosexual behaviour of the inferior males would have the advantage that the alpha male can carry on producing, with less hassle from competing males. If so, then homosexual behaviour would have an evolutionary advantage, albeit indirectly.

How's that for a theory?

That's interesting because it seems to reflect the actual behaviour observed in number of species. At least, I know that Spanish Fighting Bulls, as they are being kept in all-male enclosures, design an "effeminate" (shy or weak) mate that will be sodomised* by several partners. Also, @Moontanman above says it also happens with elephants. Those both are very aggressive animals, so they would probably fight each other until the death of all the rivals, with great damage for the winner, if they couldn't canalise their sexual impulses but accessing the harems. Given that in some cases harems and their offspring will depend upon the protection of the dominant male(s), a damaged male could mean a great lack of females in future years. Also, young mature males probably have to wait a gape of time between the moment they have "sexual urges" and the time when they can actually outcompete older males in a fight (just as it happens in humans), so "sodomy" could fill the gap and prevent them from dying before ever mating.

However, those examples seem to be more of a b-option bisexuality than of a true homosexuality as we understand it in humans. A possible better explanation for true homosexuality would probably be to keep the group united (with a bigger proportion of bisexuals and a lower rate of homosexuals, as it seems that could happen in humans), in cases where not all males are capable of mating females each year but they necessary for group deffense (as would happen in humans or yaks). It's a kind of keen selection, to which @swansont referred. There are other kinds of keen selection, like eusociality for instance, but there are few examples of eusocial vertebrates.

 

*Sorry for those that dislike the word, so I do, but failed to find a synonym. Interpret here "sodomy" as "anal intercourse",with no derogatoryality intended.

[EdEarl]

Hmm, I might be confused Moontanman. I'm not sure why you quoted me as if I didn't understand the meaning of sodomy, and cited the dictionary.

Every dog I have known smells the ground, telephone poles, fence posts, trees, and other things to find out which dogs have been where. Then, when they meet another dog, they smell their rear end, and I believe, remember where they have smelled the other animal. During that ceremony, they probably learn about bitches in heat and other things; it isn't specifically associated with sodomy or sex. It is how dogs identify other dogs. They also have good eyesight, but, for example, it is sometimes difficult to identify two black labs by sight. Dogs that look alike are fairly common. I'm convinced recognition by smell is helpful to them. 

[Area54]

13 hours ago, EdEarl said:

I'm convinced recognition by smell is helpful to them. 

I disagree. It is essential.

I was equally confused by Mootanman's excursion into the definition of sodomy. Your observations delinking dogs smelling other dogs rear ends implictly recognised the standard definition.

[mistermack]

I also think that the definition of what the original poster meant by sodomy is important.

I've always understood sodomy to mean anal penetration with a penis. But the OP seems to be talking about homosexuality. Not the same thing at all, but linked. You can be homosexual without ever engaging in sodomy, and you can sodomise without being homosexual.

Sodomy itself would appear to be easy enough to understand. Males don't need to be too fussy when they mate, in many species. If they get it wrong, it doesn't have much of a cost. But if they miss a chance of mating by hesitating, another male might get in before them. So it pays to mate first, and check later.

Many males will mate with something that bears only the slightest resemblance to a female of their species. The urge overrules almost everything. 

Homosexuality is harder to explain. But the answer is probably mainly that nothing is perfect in nature. And we have vestiges of our earlier ancestors remaining that are hardly noticeable. Like the human remnants of a tail, or the appendix. Our distant ancestors were originally hermaphrodites, and homosexuality could be a throwback to that type. From an evolutionary point of view, the disadvantage is only there in the most extreme cases. Lots of male homosexuals have plenty of children, and of course lesbians in a wild situation might well get mated, whether they wanted to or not. So the disadvantage to the species would be very marginal.

There is also the fact that in humans, non-fertile members play an important role in child protection and care. Females live on well past their menopause. They help raise the young, and contribute to the survival of the species, even though they can't have any more offspring themselves. That might well apply to the homosexual humans who don't produce young of their own. Humans evolved living communally in extended groups, like chimps. And child care is more extended in humans than any other animal. So non-breeding individuals can still help their own genes to survive in nephews and nieces etc.

 

[delboy]

On 10 September 2017 at 10:54 AM, DrKrettin said:

I'm not a biologist, so shoot me down if you like.  There are many species of animals where there is a dominant male who mates with a lot of females and thus has many offspring, Presumably he is dominant because he carries genes which are positive for the species, so there is an evolutionary advantage that he mates and others do not.

If births are 50% male and 50% female, that leaves a lot of males with nothing to do (the stag party), but who have the same sexual urges as the dominant male. It follows that homosexual behaviour of the inferior males would have the advantage that the alpha male can carry on producing, with less hassle from competing males. If so, then homosexual behaviour would have an evolutionary advantage, albeit indirectly.

How's that for a theory?

But it would have an evolutionary advantage to a different individual, so the homosexual genes, if that's what they are, would be selected against and reduce in the population.

[Area54]

6 minutes ago, delboy said:

But it would have an evolutionary advantage to a different individual, so the homosexual genes, if that's what they are, would be selected against and reduce in the population.

Evolution is about populations, not individuals.

[swansont]

1 hour ago, delboy said:

But it would have an evolutionary advantage to a different individual, so the homosexual genes, if that's what they are, would be selected against and reduce in the population.

I've already given a scenario showing that this is not necessarily the case. As Area54 notes, this is about populations.