Strange Piece of Ass SyndromeThe Strange Piece of Ass Syndrome was first introduced to me as a graduate student working on the evolutionary genetics of fruitflies. Some of my readings involved studies on what had been called, rare male mating success in Drosophila. At the same time during this period, I made the acquaintances of two fellow female graduate students that were both doing research on various aspects of sex, genetics, and behavior. One was Patty Gowaty, working with sexual selection in bluebirds. Patty now is a distinguished professor at the University of Georgia (Athens). She majorly expanded my views on this subject, and being a feminist of the 70's helped clean up my primitive West Texas thinking and verbage about women. Thank you, Patty! Sue's story is not so happy. She was doing some innovative research on macaque monkeys at the Yerkes Primate Center in Atlanta. Her research was the first to show that the alpha males were not doing all the mating in a troop of macaques. The alpha males are at the top of the pecking order, or Top Horse, in the troop. They get first shot at food and mates. However, Sue's research showed that the females were mating with subordinate males at a significant frequency. Many of the young were offspring from these subordinate males. Sue later was killed by a deranged Viet Nam vet at a research station in SC. What a tragedy. I miss her. This webpage is a based on a lecture I used to give in my genetics course at Clemson University on sexual selection. I would usually give it in the spring, the human mating season, especially on college campuses. High SchoolI can remember back in my high school days, often times when a new guy would transfer into the school, the girls were all curious and abuzz about him--unless of course he was an obvious geek. What is this all about?I had better luck dating the good-looking honeys from the high school across town, than I did the ones from my own high school. Why was this? I stumbled onto a partial answer to these two questions while working on my PhD at the University of Georgia... Fruitflies (a.k.a. Drosophila)Rare male Mating Success--a number of studies showed that when "strange" male fruitflies were introduced into a vile containing female fruitflies, the strange male's had a mating advantage over the old males that were there. The females would prefer to mate with these strange males. It was not that they were strange, but rather that they were different and rare--that is, there were not very many of them. As soon as their numbers increased in the population, they lost this mating advantage. This rare male mating advantage effect was seen even if the males were genetically identical to the females and other males, as long as the rare males came from a different vial.Fish and other beasties (but not primates or humans yet)Fish, amphibians, and reptiles all have been found that females often mate with multiple males. Females in some species will actually store sperm from more than one male. So much for being the alpha male. This phenomenon relates to the rare male mating success seen in fruitflies...and in high school. (Although, back in my high school days, I not sure they were actually mating. At least I wasn't.)Point: females were being nearly as promiscuous as the males. Primates (non-humans)As Sue Bernstein's studies showed, macaque females were sneaking around behind the alpha male's back and mating with other males in the troop. Studies with other primates have shown similar results with some species being more promiscuous than others.Maybe this is a good time to also introduce monogamy as a closely related concept--and long term pair bonding. You see these in birds and other mammals too. (For a wonderful review and delightful read on a lot of this, I highly recommend two books by Helen Fisher,Why We Love: The Nature and Chemistry of Romantic Love  and Anatomy of Love: A Natural History of Mating, Marriage, and Why We Stray .)We do find monogamy and long term pair bonding in other primates and birds. Not all, but for some species. Mongamy refers to what we would call marriage in humans. It refers to only mating with one mate. Of course this is only myth in many cases. Likewise, we see long term pair bonding in birds, primates, and even occasionally in humans. This means a mating pair stays together through more than one mating season. Mating season in humans is all year long but for other critters not necessarily so. Let's move on to humans now... HumansThe short version is that overall humans are pretty promiscuous too. Some cultures/ tribes can be very promiscuous. Fisher talks about these.So how does the strange piece of ass play into all this and what is its relation to all this fooling around (promiscuity)? It is all about evolutionMore specifically, it is about genetic variation and optimizing the sexes' evolutionary strategies. Again, the object of the evolutionary game is survival and reproduction. (Woops, I just realized I haven't written these webpages yet. I will add them to my list.) He or she that does both of these best, i.e. survives and reproduces, wins.Genetic variationWhat we learned decades ago is that, in general, genetic variation is good. A population with a lot of genetic variation is healthier, more viable, and has higher reproduction. Again, the early studies were done with fruitflies, but the story appears to be the same for all other species. So genetic variation increases your survival and reproduction.Even Darwin, as in Charles, the father of evolution, realized that you had to have genetic variation for natural selection to work and the evolutionary process to work in general. He had only a very rudimentary, and unfortunately pretty off the mark, understanding of genetics. Gregor Mendel had published his work on genetics in peas and Darwin had a copy of the manuscript in his library. But he did not understand it. It had math in it and math, to Darwin, had nothing or little to do with biology. What do we mean by "genetic variation"? Genetic variation refers to more than one allele for a specific gene being present in the population. (See page on Basic Genetics) As an example we can refer to the ABO blood types in humans. Each of these blood types is due to a different allele for the alpha hemoglobin gene. So there are three alleles in the human population for this gene, an A allele, a B allele, and an O allele. Any individual in the population will carry a maximum of two of these alleles. One he gets from his mother and the other from his father. As an example of how genetic variation increases survival, let us look at hybrid vigor. When you have a hybrid between two different strains, in agriculture for example, the hybrid offspring often carries a lot more genetic variation than either of the parental strains. Hybrid crops are examples of this. Likewise, the mule is a hybrid between a horse and a donkey (two different species, not strains). Mules are very hardy animals. It is because the hybrids have so much genetic variation. Unfortunately, the two parental species are two different and the poor mule is sterile, but very healthy. One of the ways genetic variation increases survival and reproduction is by masking or covering up deleterious alleles and mutations. We can also look on the opposite end of this spectrum, called inbreeding. Inbreeding is the mating between closely related individuals. Inbreeding does two things. First, it reduces genetic variation because closely related individuals carry many of the same alleles. Second, it tends to uncover deleterious alleles because, since closely related individuals carry many of the same deleterious alleles, they don't have alternative alleles (variants) to cover up those bad alleles. (Clear as mud, right?) The short of all this is that by being promiscuous, both sexes are maximizing their genetic variability and thus their survival and reproduction. But the sexes strategies differ... The Males Evolutionary GameFor males there is very little cost for being promiscuous. Sperm is cheap, easy to produce. It takes very little energy to make a lot of sperm. So the male's optimal evolutionary strategy is to go around inseminating any available females. He thus maximizes his reproduction.Back when it was only males that studied this stuff, e.g. Charles Darwin and the boys, we thought this was the end of it. It was just too costly for females to be promiscuous. A female, if she becomes pregnant, pays a very high reproductive cost. She carries the baby for nine months, has to nurse it for say two years, provide for it and herself, etc. Very costly So all these male evolutionary biologist argued, see, girls, you should sit at home, behave yourselves, and not be promiscuous. Right? Wrong. Enters female evolutionary biologists like Patty Gowaty... The females counter strategyIt turns out that females can optimize their reproduction by being promiscuous too. Why put all your proverbial eggs in one basket? In a tribe, like primitive man and modern primates, by mating with more than one male in the tribe, none of them knew who the kid belonged to. Who was its father? (This was of course before the days of DNA analysis and CSI episodes.) Therefore, females could get the care and protection of several males in the tribe, thus increasing both her reproduction and survival and that of her offspring. Cool, no?Back to the Strange Piece of Ass SyndromeNow before you all go out and get hot, horny, and promiscuous, there are tradeoffs, one of which in humans is STD's. Evolution/natural selection seems to have balanced the advantages of monogamy and long term pair bonding with the advantages/disadvantages of promiscuity. So in general, human populations tend to be more toward the monogamy/long-term end of the spectrum...as opposed to the screw-everyone-you-can end.Amen |
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