riddle@ut-sally.UUCP (Prentiss Riddle) (05/13/85)
> Any gene that caused homosexuality would not survive. It doesn't > matter if gay people have children. They have LESS children, and that > is all it takes. Any trait that reduces the likelihood of reproduction > will disappear exponentially. Not necessarily. Remember, the genes found in an individual member of a species are found to varying degrees among the relatives of that individual as well. It is quite possible for there to be traits -- especially recessive ones -- which cause an individual to be less likely to produce offspring, but which are beneficial to the individual's kin and therefore survive into future generations indirectly. There are several very different examples of this which come to mind. One which I can (fuzzily) recall from high school biology is sickle cell anemia, which is deadly when an individual has two of the genes in question but highly beneficial (in tropical climates) to those who only have one, as it reduces susceptibility to malaria. In this case, the gene has very different consequences in heterozygous and in homozygous form. More interesting are species with neuter forms, such as the social insects. Drone ants don't breed, but they certainly contribute to the survival of their genes anyway. And a final example which is known to be highly developed in humans is what sociobiologists call "altruism." When, say, a parent bird or mammal dies protecting its young from a predator, it is destroying its own specific set of genes but increasing the chances of survival for the portion of its genes carried by its children. This can apply to less closely related kin as well, and in the case of humans certainly does. (Humans are so altruistic that they are often willing to die for other humans who are hardly related at all, or even for an idea or a symbol.) Could any of this apply to a hypothetical "gay gene"? Maybe. The gene could be linked by chance to other, desirable traits, or it could even be desirable in and of itself in ways we don't understand. (Some wild-eyed speculators have noted the alleged creativity common among gays, and credited homosexuals as being the "wild cards" among the human race that give the species much of its ability for innovation.) Or perhaps the prevalence of homosexuality among humans (10% is much higher than in many species) is a spin-off of the general "sexiness" of the human race: we as a species are much more sex-oriented than any of our relatives, and use sex for all sorts of things other than just reproduction. If sex evolved as part of the glue that keeps primates and especially humans together in social groups, mightn't homosexuality be just another (perhaps highly beneficial) sort of glue? Maybe bands of early hominids that weren't strictly hetero in their sexual attachments functioned better as groups than those that didn't. Who knows? I certainly don't. But I think that what constitutes a survival characteristic is far too complex a question for us to rule out the possibility of a genetic component to homosexuality. --- Prentiss Riddle ("Aprendiz de todo, maestro de nada.") --- {ihnp4,harvard,seismo,gatech,ctvax}!ut-sally!riddle --- riddle@ut-sally.UUCP, riddle@ut-sally.ARPA, riddle%zotz@ut-sally
hes@ecsvax.UUCP (Henry Schaffer) (05/15/85)
The survival of an individual's genes via collateral relatives is a well known concept in population genetics, and goes back at least 50 years. (R. A. Fisher, in the Genetical Theory of Natural Selection has an extensive treatment.) But I have to make a small quibble - its the worker in the ants and bees which is a sterile female, and so doesn't breed. The drone is a male, and does (or can) breed. --henry
friesen@psivax.UUCP (Stanley Friesen) (05/15/85)
In article <1901@ut-sally.UUCP> riddle@ut-sally.UUCP (Prentiss riddle) writes: >There are several very different examples of this which come to mind. One >which I can (fuzzily) recall from high school biology is sickle cell anemia, >which is deadly when an individual has two of the genes in question but >highly beneficial (in tropical climates) to those who only have one, as it >reduces susceptibility to malaria. In this case, the gene has very >different consequences in heterozygous and in homozygous form. > Actually, the heterozygote(only one copy) sickle cell advantage is restricted to tropical Africa, and it is due to immunity to African Sleeping Sickness not malaria. -- Sarima (Stanley Friesen) {trwrb|allegra|cbosgd|hplabs|ihnp4|aero!uscvax!akgua}!sdcrdcf!psivax!friesen or {ttdica|quad1|bellcore|scgvaxd}!psivax!friesen
emigh@ecsvax.UUCP (Ted Emigh) (05/20/85)
In article <452@psivax.UUCP> friesen@psivax.UUCP (Stanley friesen) writes: > Actually, the heterozygote(only one copy) sickle cell >advantage is restricted to tropical Africa, and it is due to >immunity to African Sleeping Sickness not malaria. Actually, the heterozygote sickle cell advantage is to malaria (Plasmodium falciparum). While the major occurence of sickle cell anemia gene is in Central Africa, it is also found in other malarial environments (Persian Gulf, Central India, etc). Another abnormality also is associated with malaria -- Thalassemia major, which occurs in relatively high frequencies in the Mediterranean countries (also where malaria had a high incidence). -- Ted H. Emigh Genetics and Statistics, North Carolina State U, Raleigh NC USENET: {akgua decvax duke ihnp4 unc}!mcnc!ecsvax!emigh ARPA: decvax!mcnc!ecsvax!emigh@BERKELEY
mccann@sjuvax.UUCP (mccann) (05/23/85)
>>There are several very different examples of this which come to mind. One >>which I can (fuzzily) recall from high school biology is sickle cell anemia, >>which is deadly when an individual has two of the genes in question but >>highly beneficial (in tropical climates) to those who only have one, as it >>reduces susceptibility to malaria. In this case, the gene has very >>different consequences in heterozygous and in homozygous form. >> > Actually, the heterozygote(only one copy) sickle cell >advantage is restricted to tropical Africa, and it is due to >immunity to African Sleeping Sickness not malaria. Sickle cell animea does provide an advantage against malaria. The parasite which causes malaria attacks the hemoglobin in the red blood cell, destroying it and thus reducing the amount of oxygen carrying cells in circulation (after the parasite degrades the Hemoglobin, it reproduces and lysis the cell). Being heterozygous for the sickle cell trait causes half of a persons hemoglobin to be different from the 'normal' hemoglobin. If this person contracts malaria, only half of the hemoglobin in his/her blood is susceptable to the parasite and they therefor mearly become ill (instead of dying) until a sufficient immune response is triggered. I don't know about the African Sleeping Sickness. M. McCann
carter@gatech.CSNET (Carter Bullard) (05/24/85)
In article <452@psivax.UUCP> friesen@psivax.UUCP (Stanley friesen) writes: > Actually, the heterozygote(only one copy) sickle cell >advantage is restricted to tropical Africa, and it is due to >immunity to African Sleeping Sickness not malaria. > Nope. Sickle cell does give immunological advantage against malaria. -- Carter Bullard School of Information and Computer Science Georgia Institute of Technology Atlanta, Georgia 30332 CSNet:Carter @ Gatech ARPA:Carter.Gatech @ CSNet-relay.arpa uucp:...!{akgua,allegra,amd,ihnp4,hplabs,seismo,ut-ngp}!gatech!carter