This page is for postings to newsgroups of a less contentious variety and any resulting email. Especially on groups such as alt.memetics, sci.bio.evolution and talk.origins
Genes whose deleterious effects are not manifest until after reproductive maturity are not as effectively selected against as those manifest before reproductive maturity. Alleles increase in a population when they are subject to positive natural selection, and by genetic drift if they are not subject to negative selection. [Chuck Dunn in sci.bio.evolution]
That is about the size of it. If it doesn't kill you before you breed it is invisible to evolution. My father has a heart condition, by the time anybody, including any evolutionary pressures, found out he had seven grandchildren. He has been a genetic success, and may have spread a late acting lethal genetic condition.
It is in the nature of nature to do just enough to get by. For us breeding is the finishing line. After that any illnesses that we have or bad things that happen to us have no effect on the evolution of us as a species unless they impact on the lives or success of our children, or perhaps our tribe. Actually living until about 70, long enough to help the grandchildren a bit and passing on our culture to other generations is about as far as our usefulness goes. If we limped on to 150 we would be more of a handicap to our children than an asset. So basically that is what happens, our bodies repair themselves well up to the point we have reached full breeding age then they slacken off, they succumb to entropy.
A good question to ask is about the evolution of the menopause, think about that one. It pays your genes to stop the risky project of trying to pass an object the size of a human baby through such an obviously inadequate passage once the woman would be better off looking after grandchildren than putting her life in great danger trying to have another child herself. Human babies are right on the limit of what is possible to give birth to without the female pelvis being too wide for bipedalism. As it is the human baby is born effectively prematurely, incapable of walking or even riding on its mother's back. A gorilla mother is twice the human size and her baby is half the size, but much more capable. It is all down to our enormous brains. We have to be born when we are or mother and child would be killed by the expanding head. In contrast there is no big risk for the elderly father, apart from the increased risk of genetic mutation in his senile testicles.That explains why female reproductive capacity dries up and male capacity just gradually declines, with the rest of his body.
Any quest for the secret of eternal youth is doomed to failure. The only way to do it would be to select for long life over many generations, only breeding from the long lived. It would probably work to some degree but the question will have to arise as to why bother? The desire to live for ever is one thing, but where would the desire for our great great great grandchildren who we may never meet to live for ever come from? Apart from some dodgy pseudo-religious / destiny vision.
Which is the stronger evolutionary trait?
1. The desire of the organism to replicate (Mechanisms for reproducing the organism)
2. The desire of the organism to stay alive (Mechanisms for keeping the organism alive)
Any comments?
[moderator's comment: Sure, I'll bite. When I was a wee sprat I was fortunate enough to be taught from a NSF-developed curriculum titled "Man - A Course Of Studies" (which I initially thought was something titled "manacoursive studies", but when I couldn't find manacoursive in the dictionary...), where I was taught the three rules, in order, which guide a critter's life:
1) Eat,
2) Avoid being eaten,
3) Reproduce.
Three of the four F's of animal behavior. I suppose one might roll two of 'em into number three there. - JAH]
Which is the strongest evolutionary trait? It has got to be an optimum trade-off between the two. An organism [NEVER use the word critter, a terrible folksy abbreviation of creature, a thing that has been created, presumably by Our Lord Jesus's dad urghh, ban both these words] sorry, where was I? Yeah, an organism must strike the optimum trade off between eating, sex and everything else. It does no good for an organism to be eating all the time and growing but not reproducing. At least it does no good for the genes of that organism. Although it can benefit the genes of parasites of that organism.
Evolution is very rarely about maximizing anything, the key is always the optimum trade-off. A bird whose courtship dance is so spectacular than everything within a quarter of a mile notices will probably have its genes consigned to the stomach of a passing predator. Moderator: for the crime of using that terrible word I suggest you copy out the whole of Darwin's Origin of Species as a pennance ;-)
Martin
The following is in response to a posting that was effectively a republishing of the evolution page. |
Very nice note. Thank you for taking the time to write and post it. If you could answer a few question I would be grateful. I've tried to keep the format simple and short, in the hopes you will answer the questions. This is not a test, I will not grade you. These questions reflect my own gaps in information on evolution. And though you may or may not be an expert, I hope a series of responses to this questionnaire will be somewhat self correcting. Please delete the response that least matches your opinion. Leave the one response that most closely approximates your opinion. Thank you for your time. Homo sapien sapiens (modern man) have been an individual group for about 130,000 years.strongly disagree disagree I don't know slightly agree strongly agree Humans descended from a single female born at that time.strongly disagree disagree I don't know slightly agree strongly agree This primary female human, lived in southern Africastrongly disagree disagree I don't know slightly agree strongly agree The human race migrated from this area to spread to the rest of the world through migrationstrongly disagree disagree I don't know slightly agree strongly agree These humans migrated along the continuous beach that stretches from southern Africa to the bearing straightstrongly disagree disagree I don't know slightly agree strongly agree Racial features are the result of small groups of humans becoming isolated geographically for several millennia and then reinforcing certain superficial physical traits within the group through descendants.strongly disagree disagree I don't know slightly agree strongly agree Humans are 99.9% the same genetically. strongly disagree disagree I don't know slightly agree strongly agree The most diverse genetic "pool" (the genes with the largest number of genetic variations) of humans, is in Africa, then in descending order of complexity progresses through the middle east, Asia and the Americas.strongly disagree disagree I don't know slightly agree strongly agree
Thank you for your time. I hope you found this survey interesting. writer@ime.net Richard Rust |
I don't like forms. My medium is words, not options. I don't agree with the simplistic idea of African Eve as a single female that gave birth to us all. That is a misunderstanding of the African Eve mitochondrial DNA evidence. There has to be a single latest common universal female-line only direct ancestor to us all, that is elementary evolutionary logic. What is open to question is how far back she lived; was she an ape, a fish, a four foot high early hominid, an African shoreline scavenger or the Queen of Atlantis? Another equally valid question is why should you assume that the latest common human ancestor was
It is far more likely that our latest common ancestor was male and from a mixed-sex line of direct decent. Males have a much higher chance of having many or no descendants, females have much less variation in the number of offspring. While it does not necessarily follow that our most recent common ancestor must have been especially fertile it would seem to be a not unreasonable assumption. As an exercise contemplate OUR most recent common ancestor. [assuming we are both white and British] Chances are we have one a lot closer to home than Africa 130,000 years ago. He or she probably lived in Europe within the last thousand years or two. I read once that there was a Mr Willett who lived in London in 1640 or so and had 11 surviving children, and he is an ancestor of a substantial proportion of the British population. That may or may not be true. But if we had to trace the female only line of common descent we might have to go back ten times further into the roots of our family trees. Or try this one, your father's brother's daughter is your first cousin, by definition. How far back is your latest common ancestor? You share a grandmother or grandfather and maybe both. But how far back is your latest FEMALE LINE ONLY relative? Chances are you and I could be as closely related by that route as you and your first cousin. I don't fall for this nice easy we-are-all-relatives idea. It is too convenient. Always ask yourself who benefits. Who benefits from science that proves that races are trivial artefacts of no underlying significance? Scientific researchers. They stay employed. Homo sapien sapiens (modern man) have been an individual group for about 130,000 years. I don't know Humans descended from a single female born at that time. slightly agree This primary female human, lived in southern Africa This statistical nonentity probably did live in Southern Africa, yes. Who knows where the latest common ancestor of us all lived? Probably in the same place as his great-great-great-great grandmother, "Eve". The human race migrated from this area to spread to the rest of the world through migration strongly agree. Where they met other people and did what comes naturally... Kill, drive off, shag or eat depending on how different the people were and how much they resisted. To what degree they followed each strategy I don't know, but I am curious. These humans migrated along the continuous beach that stretches from southern Africa to the bearing straight Agree. Seashore is seashore, a habitat that does not require much adaptation, if you've survived on one beach you are fitted to survive on most beaches. Racial features are the result of small groups of humans becoming isolated geographically for several millennia and then reinforcing certain superficial physical traits within the group through descendants. Racial features could come from sexual selection (isn't red hair sexy?), founder effect within small semi-isolated populations, regular natural selection and the effect of interbreeding with other (earlier) populations. I doubt whether any one of those explains more than 90% of the phenomenon. Humans are 99.9% the same genetically. I don't know, I would not be surprised. The most diverse genetic "pool" (the genes with the largest number of genetic variations) of humans, is in Africa, then in descending order of complexity progresses through the middle east, Asia and the Americas. I don't know, but I see no reason to doubt it. Martin |
Dear Martin Willett, Thank you very much for your very generous answer to my query. You note was very interesting and has helped to clarify several points in my own thinking. You've been of great help. Once again, thank you for taking the time to write back. Writer@ime.net Richard Rust |
I hope you are serious in that reply. I am no an expert, I don't have enough spare time to be so, but I am interested in both evolution and the bastardization of science so I have some idea of what I am going on about. But at any time I would love to be corrected if I get anything wrong, that is a sentiment I share with true scientists. A lot has been made of the study of mitochondrial DNA, which is passed on by female only lines of decent because it is not part of the cell nucleus, it comes from the tamed bacteria that are our mitochondria, and passes down through the cell contents and via the egg cell only, never part of the nucleus of any cell. Studying the variation in m-DNA among people of differing racial backgrounds (using race in the everyday sense) has shown more variation among African people than among any other people, suggesting that they are the most diverse and hence the oldest populations, all other groups show decent from a limited range of African genes. That is consistent with a recent out-of-Africa explanation of racial origins. It is not yet fully vindicated research. I would like to see the equivalent research done on the Y chromosome as well. This shows male line only heritability in the way a surname does. I would anticipate that this research may also show an out of Africa result, with an even more recent date for the latest common universal human ancestor, no doubt to be dubbed African Adam. Such research would have more problems though. Nobody is in danger when their female line of decent is investigated, the identity of your mother is very rarely controversial. This kind of research could prove very alarming, given the rate of false attribution of paternity in our species. I can easily imagine scientists shying away from doing it, or rather, hoping that somebody else does it first. My mind fills with images of hungry penguins desperate to go into the sea but fearing predators, they jostle about on the edge of the ice hoping that they can "accidentally" knock another bird in first to test the waters... Martin |
Dear Martin Willett, Thank you again for writing. My last note was quite sincere. I am always amazed when complete strangers will take time out of their busy lives are willing to write back and answer my unsolicited queries. It is something that confirms my belief that humans are basically good and always looking for the truth as best they can. Below is some information about the male counter part to "Mitochondrial Eve." Normally I take Web sources with a grain of salt, but the note listed below, cites a periodical (November, 2000 issue "Nature Genetics") which can give independent confirmation of the web page's assertion. Once again thank you for your note. writer@ime.net Richard Rust ----------BEGIN FORWARD HERE------------- http://www.academicpress.com/inscight/11012000/graphb.htm DATE: 1-November-2000 The Eden Chronicles:Tracking 'Y Chromosome Adam'The fundamentalists aren't going to like this, but Eve was an older woman--by about 81,000 years. By tracing the lineages of Y chromosomes back through the stone age, researchers have estimated how long ago humans' oldest paternal ancestor lived. The results support the idea that modern humans originated in Africa, and they help track where humans wandered from there. Mutations that accumulate in DNA are like molecular clocks. Over time, harmless mutations accrue and are passed down through generations. By comparing mutations from enough people, researchers can construct family trees with roots that reach back to the earliest modern humans. A decade ago, analysis of mitochondrial DNA, which is passed down through the mother's egg cell, showed that humans' earliest common maternal ancestor lived 140,000 years ago. She was dubbed "Mitochondrial Eve." Now, researchers report that they have traced the Y chromosome lineage to modern humans' earliest common paternal ancestor, "Y Chromosome Adam." The team, led by molecular biologist Peter Underhill of Stanford University, looked at 167 mutations in 1062 men from 21 geographical regions. The researchers calculate that the Y chromosomes carried by modern men are versions of the Y chromosome carried by a common ancestor who lived in Africa about 59,000 years ago, they report in the November issue of Nature Genetics. The Y chromosome lineages also provide a finer resolution of early human migration than mitochondrial DNA analysis. Following the molecular footsteps of males, Underhill says early humans left Africa more than once. Some migrated down the coast of Africa and over to Australia; others to India and Asia; and some migrated from there back toward Europe. The researchers also found that fewer Y chromosome lineages survived to the present day than mitochondrial DNA lineages. Perhaps males were more likely to die before passing along their Y chromosome than females, thus preventing some Y chromosome lineages from making it to the modern age. Alternatively, as Underhill delicately puts it, "nonrandom mating patterns," in which only a few males pass their Y chromosomes to many females, could explain the difference. The Y chromosome lineage will have a big impact on the emerging field of "archaeogenetics," the reconstruction of human history from molecular genetics, says archaeologist Colin Renfrew of the McDonald Institute for Archeological Research in Cambridge, United Kingdom. As more Y chromosome mutations are discovered, he says, researchers will be able to paint an ever higher resolution picture of human prehistory--the when, where, and Y of human evolution. MARY BECKMAN ----------------END FORWARD HERE--------- |
Isn't it wonderful to get your suspicions confirmed? That is exactly what I expected, well, maybe not quite as recent, but certainly that pattern. I couldn't be certain that you weren't setting me up for something but I thought I'd do it anyway, I'm a bit impulsive. Martin |
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