Interesting counterpoints. Here is something else to ponder: if homosexuality evolved in humans because at a certain frequency it benefits populations, why do so many cultures make it taboo? Most cultures (I suppose) respect other traits that benefit the group: good hunters, skilled artisans, fertile mothers, bold warriors, productive farmers, healers, storytellers. etc. Could it be because the presumptive benefit of homosexuality is less obvious? Is there any data showing that the more resource-limited a group is, the more appreciative they are of homosexuals (or of others who for some reason withdraw from the reproductive process)?
Martin 2013/3/28 Mitch Cruzan <[email protected]> > > Good points. Of course, we do not know the answers for certain, but we > can make some logical inferences. The compelling observation is that this > trait is too common to dismiss as accidental, so there must be an > evolutionary explanation. Here are some ideas: > 1. There is not wide agreement on the (genetic or perhaps epigenetic) > basis of homosexuality in humans other than it is not reversible. A > maternally inherited mutation would work and there is some evidence to > support this idea. It may also be true that there is an environmental > trigger that promotes homosexuality at an early age, so the allele may > persist in the population without always being expressed. This solves a > lot of the problems raised below. > 2. I think there is pretty good agreement among paleontologists that once > they moved onto the savanna our hominid ancestors were limited by food, or > at least a consistent supply. There are also several other lines of > evidence to support this hypothesis (living in groups, extra fat storage in > females for reproduction, etc.). The primary reason that nomadic groups > move is for food, and early humans probably would not have ventured across > the continents and into much colder climates if they had not been searching > for good hunting grounds. > > Of course, it is important to recognize that any argument we might make to > explain the observation of a high frequency (10% or more?) of homosexuality > in human populations is going to be speculative to some degree or another. > The point is that it needs explanation because, as I argued previously, the > consistent high frequency across human populations is not some accident, so > their must be an adaptive explanation. > > Mitch Cruzan > > > > On 3/28/2013 10:42 AM, Martin Meiss wrote: > > Here are what I see as some problems with the idea that homosexuality in > humans is rooted in the genetics of kin selection, as proposed earlier in > this thread. > > 1. Suppose an individual is born with a mutation that makes him/her > inclined to homosexuality and to avoid reproduction. If this individual > then "helps around the nest" he/she may enhance the survival of near > relatives WHO DO NOT BEAR THE GENE, since the mutation is new. How would > this mutation enter the population? > > 2. Insofar as the kin-selection mechanism requires restricted gene flow, > how can we assume that this condition prevailed for our wondering, > hunter-gatherer ancestors? Wondering groups don't have to be in contact > very long to exchange mates or rape each other. > > 3. It's not clear that an individual's personal inclination to engage in > mating behavior would have much to do with whether they actually mated. I > refer, of course, to rape, but also other forms of social persuasion. > Also, just because a few males in the group may prefer each other to > females, that doesn't mean the remaining males couldn't keep all the > females pregnant, thus favoring their genes over the non-players. > > 4. The hypothesis, as presented in this thread, seems to rely on early > populations having been resource-limited, so they would benefit from > decreasing the number of mouths to feed. But isn't it also possible that > they were NOT resource limited. If migratory groups were expanding into > new territory, they might have faced abundance of resources, especially as > their tools and weapons made more things available to them. Also, given > the defenselessness of naked humans or pre-humans when unarmed, and the > dangers of hunting nasty animals when armed, it is quite possible that > those early populations were limited by predation and traumatic injury. In > that case, limiting reproductive output would seem to be very unfavorable. > > I realize that some of these hypothetical conditions, if they obtained, > might tend to contradict each other, or cancel each other out, but I > nevertheless believe they indicate against ready acceptance of the > kin-selection mechanism. > > Martin M. Meiss > > 2013/3/28 Mitch Cruzan <[email protected]> > >> This neglects that fact that homosexuality is not an accident of history >> or just a artifact of modern human societies. This trait is too widespread >> and occurs at too high a frequency in human populations to be explained by >> chance - there must have been a selective advantage in the past. The >> widespread nature of this trait across human populations suggests that it >> must have been present in the human lineage by at least the time of the >> second major migration of hominids out of Africa around 60,000 ybp. The >> inclusive fitness argument mentioned several times by contributors to this >> listserve is probably the best explanation for the maintenance of >> homosexuality in human populations. >> >> Mitch Cruzan >> >> >> On 3/28/2013 7:46 AM, Culliney, Thomas W - APHIS wrote: >> >>> I was referring to strict homosexuality in humans. Granted, there >>> probably are cases in which children of a (perhaps deceased) sibling or >>> other close relative would be raised by a homosexual, thus raising his or >>> her inclusive fitness, but such cases would be rare. The Darwinian fitness >>> of a strict homosexual is, as a rule, zero. Helpers at the nest do forgo >>> their own reproduction to help relatives raise offspring, but, as far as I >>> know, there is no requirement for them to be homosexual. >>> >>> Tom Culliney >>> >>> From: Jonathan Colburn [mailto:[email protected]] >>> Sent: Thursday, March 28, 2013 10:05 AM >>> To: Culliney, Thomas W - APHIS >>> Subject: Re: [ECOLOG-L] Exclusive homosexuality >>> >>> >>> Hi Tom, >>> >>> Respectfully, the Darwinian fitness sounds like inclusive fitness, which >>> is often measured by reproductive success. However, reproductive success >>> of a homosexual is not always a good measure of their inclusive fitness >>> (e.g. helpers at the nest). Ultimately, any action that staves off >>> fixation of alleles to zero is about as close as we can come to determining >>> that something is inclusively fit... >>> On Mar 28, 2013 9:20 AM, "Culliney, Thomas W - APHIS" < >>> [email protected]<mailto:[email protected]>> >>> wrote: >>> I note that the albatross article mentioned the words "natural" and >>> "normal." Homosexuality certainly is natural, as it occurs in nature, in >>> animals from groups ranging from arthropods to mammals (who knows what goes >>> on in the plant kingdom?). In all cases, there appears to be an adaptive >>> reason for the behavior. However, in its reproductive consequences, >>> exclusive or strict homosexuality, as exhibited in humans, cannot be >>> considered normal sexual behavior. The Darwinian fitness of homosexuals is >>> zero. To the extent that there is a genetic component to the behavior in >>> humans, with their diverse sexuality, the trait undoubtedly persists in the >>> population largely through the actions of bisexual individuals leading to >>> the production of offspring. >>> >>> The above is an argument strictly from a biological perspective, and is >>> not a moral judgment. What two consenting adults do in private is their own >>> business and no one else's. >>> >>> Tom Culliney >>> >>> -----Original Message----- >>> From: Ecological Society of America: grants, jobs, news [mailto: >>> [email protected]<mailto:[email protected]>] On Behalf >>> Of Kristen Dybala >>> Sent: Wednesday, March 27, 2013 10:55 PM >>> To: [email protected]<mailto:[email protected]> >>> Subject: Re: [ECOLOG-L] Expedition notice and question >>> >>> Laysan albatrosses are a fairly well-known example. Here's a (lengthy) >>> article describing it: >>> >>> http://www.nytimes.com/2010/04/04/magazine/04animals-t.html?pagewanted=all >>> >>> -Kristen >>> >>> >>> On Wed, Mar 27, 2013 at 6:53 PM, Merav Vonshak <[email protected] >>> <mailto:[email protected]>> wrote: >>> >>> This story reminds me of a similar story - a male pair of Griffon >>>> vultures (Gyps fulvus). They incubated eggs and reared other pairs' >>>> youngs as part of a breeding in captivity effort in Israel some years >>>> ago. >>>> Merav >>>> >>>> Merav Vonshak >>>> Postdoctoral Fellow >>>> Gordon Laboratory >>>> Department of Biology >>>> Stanford University >>>> Stanford, CA 94305-5020 >>>> >>>> Phone: 650-725-6791<tel:650-725-6791> >>>> email: [email protected]<mailto:[email protected]> >>>> http://www.stanford.edu/~mvonshak >>>> >>>> On 27, Mar2013, at 12:08 PM, Montblanc, Genie wrote: >>>> >>>> WT, >>>>> >>>>> Since I don't study this, I'm giving a, "What I've heard in the news," >>>>> >>>> response. There were two stories awhile back, both relating to >>>> animals in captivity, about homosexual pair bonding. One was with >>>> penguins, I think they also raised a chick together, and the other was >>>> with dolphins. Given that long-term pair bonding only occurs in 8-11 >>>> species in the entire animal kingdom, the question might be moot anyway. >>>> >>>>> That is my inexpert response. Have a great expedition! >>>>> Génie >>>>> >>>>> Eugénie MontBlanc >>>>> Great Basin Fire Science Delivery Coordinator University of >>>>> Nevada/Mail Stop 0186, Reno, NV 89557 >>>>> Phone: 775-784-1107<tel:775-784-1107> (Fax: -1109) >>>>> Email: [email protected]<mailto:[email protected]> >>>>> Web: www.gbfiresci.org<http://www.gbfiresci.org> >>>>> Twitter: @GBfirescience >>>>> >>>>> -----Original Message----- >>>>> From: Ecological Society of America: grants, jobs, news [mailto: >>>>> >>>> [email protected]<mailto:[email protected]>] On Behalf >>>> Of Wayne Tyson >>>> >>>>> Sent: Wednesday, March 27, 2013 10:32 AM >>>>> To: [email protected]<mailto:[email protected]> >>>>> Subject: [ECOLOG-L] Expedition notice and question >>>>> >>>>> [NOTE:] I will be on expedition (with a stop at the National Native >>>>> Seed >>>>> >>>> Conference in Santa Fe NM on April 10) until the two weeks at the end >>>> of April and the first week of May, then gone again beginning the 2nd >>>> week of May until around May 24. I will not be checking email during >>>> those periods, but will respond to as many email messages as possible >>>> during those hiatuses. A third expedition following those is likely, >>>> but the period of hiatus is iffy.] >>>> >>>>> Here is my parting question. Please feel free to post it on other >>>>> lists. >>>>> >>>>> Re: Homosexuality in animals other than Homo sapiens. We know that >>>>> >>>> homosexual behavior occurs in other species in some forms (Bonobo >>>> chimpanzees [Pan paniscus], for example), and we know that >>>> hermaphrodites of some species fertilize each other simultaneously. >>>> But my question is in which species other than humans, does EXCLUSIVE >>>> homosexuality, especially in the form of pair bonds, occur? >>>> >>>>> WT >>>>> >>>>> I'll pick up my answers in late April. If I have time, I may be able >>>>> to >>>>> >>>> respond to some today. Please respond on-list, and not to me personally. >>>> >>>> >>> >>> -- >>> ---------------------------------------------------------- >>> Kristen Dybala, Post-doctoral Researcher Museum of Wildlife and Fish >>> Biology University of California, Davis [email protected]<mailto: >>> [email protected]> >>> (415) 218-9295<tel:%28415%29%20218-9295> - cell >>> >>> >>> >>> >>> >>> This electronic message contains information generated by the USDA >>> solely for the intended recipients. Any unauthorized interception of this >>> message or the use or disclosure of the information it contains may violate >>> the law and subject the violator to civil or criminal penalties. If you >>> believe you have received this message in error, please notify the sender >>> and delete the email immediately. >>> >> > >
