I'm just reading up a little on how evolution works and I have a quick and simple question. My grasp on the subject is very limited, so you might have to be a little patient. Please point out obvious fallacies.
How are genetic mutations that benefit post-menopausal (as in: after an organism loses the ability to procreate) diseases "filtered out"?
Let's assume there's a genetic mutation that benefits cancer in infants. As this mutation prevents them from procreating, it will be "filtered out" rather quickly.
A mutation that has the same effect but occurs a little later in life, right before sexual maturity will be filtered out even more quickly, as - thinking in terms of group selection - a dead "almost-adult" is a bigger detriment to the group, having taken more nurturing from the group without providing an evolutionary benefit.
It's thus obvious that evolution filters out genetic constellations that benefit deadly diseases before the procreation-period is over.
Which brings me to my point:
How are genetic mutations that benefit diseases that occur in old organisms, such as elderly people, filtered out?
There's two solutions I could come up with that make some sense sense to me, but both aren't really satisfying:
1. I feel like the answer lies in group selection, as there might be a benefit to have elderly people or animals in your pack / peck / herd / group / village etc., but I fail to see what that benefit is. Then again, gayness doesn't seem to have an obvious benefit to group selection and the "gay gene" (lol) must have been around for millennia.
2. Maybe my initial assumption that they are indeed filtered out is simply wrong and that's why there's a million diseases that only affect old people and the only reason you see them around is how advanced medicine has become.
Cheers guys!
Elderly people are useless? Whether its for humans or other animals, these are the ones who hold most if not all knowledge (for example, to lead them to water in times of drought). Gay gene?
But ok.
Name me one disease that only affects elderly people and can't occur for younger people in a similar physical condition?
No need to be so aggressive, as has been pointed out, "the elderly" i. e. post-"menopausal" specimen of a species are almost exclusive to humans.
The "gay gene", which I deliberately put into inverted commas, is discussed here:
Alright, I'll bite.
I like how the trailer opens with "Where only evidence matters" but then all he's bringing up are theories about how ancient tribes could have worked. Here's some actual evidence on the topic:
Dr. Richard Lippa in the BBC Internet study (published 2007) with over 200000 participants found a very high correlation between the interests of gay men / gay women and that of straight women / straight men respectively. Those correlations is consistent across all the 50+ countries present in his study.
Simon LaVey published a book in 1996 about a brain cluster which has a very different structure in both men and women. Interestingly he also found that gay men show an identical pattern in that specific cluster as straight women, the exact same is true for gay women and straight men, providing strong evidence for a biological difference in the brain in general.
Gerulf Rieger did a video study in 2006 where he let a random sample try and guess the sexual orientation of men and women both in their childhood and their adulthood. In his sample about 75% of the guesses for both adults and children turned out to be correct, hinting at sexual orientation establishing itself way before puberty.
Glenn Wilson published a book called "Born Gay: The Psychobiology of Sex Orientation" (2005) in which he compares sexual attraction to something similar to left- and right handedness, showing among other things that the hormone levels between the 8th and 12th week of pregnancy are highly different when comparing later gay people compared to their straight counterparts.
If you look at e.g. twin studies if you're a man with a gay brother the chance of being gay yourself is about 4-5 times higher than average, when looking at identical twins there is about a 50% chance that the second one is homosexual as well which interestingly is a similar, albeit stronger, correlation than between handedness and twins (here we're talking closer to 2-3 times higher than average), indicating it's something that occurs rather early in the pregnancy.
Overall most of the evidence points towards a largely biological disposition towards sexual attraction but also against a single "gay gene". What can be determined in summary from the above and other studies is that the external factors like upbringing, social environment, personal choice etc. etc. are much much smaller indicators for sexual orientation than biological factors.
To bring it back towards the initial topic: It's highly possible that for certain things, which technically are not directly beneficial to reproduction, the genetic factors can simply "stick around" because there is no specific single factor that can easily be eliminated by natural selection. Also there might be secondary beneficial effects, e.g. gay & bisexual men are more likely to have more siblings than straight men which we didn't fully explore yet.
Time to figure out if there's a correlation between having more siblings and heart attacks at 60+ =P
I'm just reading up a little on how evolution works and I have a quick and simple question. My grasp on the subject is very limited, so you might have to be a little patient. Please point out obvious fallacies.
How are genetic mutations that benefit post-menopausal (as in: after an organism loses the ability to procreate) diseases "filtered out"?
Let's assume there's a genetic mutation that benefits cancer in infants. As this mutation prevents them from procreating, it will be "filtered out" rather quickly.
A mutation that has the same effect but occurs a little later in life, right before sexual maturity will be filtered out even more quickly, as - thinking in terms of group selection - a dead "almost-adult" is a bigger detriment to the group, having taken more nurturing from the group without providing an evolutionary benefit.
It's thus obvious that evolution filters out genetic constellations that benefit deadly diseases before the procreation-period is over.
Which brings me to my point:
How are genetic mutations that benefit diseases that occur in old organisms, such as elderly people, filtered out?
There's two solutions I could come up with that make some sense sense to me, but both aren't really satisfying:
1. I feel like the answer lies in group selection, as there might be a benefit to have elderly people or animals in your pack / peck / herd / group / village etc., but I fail to see what that benefit is. Then again, gayness doesn't seem to have an obvious benefit to group selection and the "gay gene" (lol) must have been around for millennia.
2. Maybe my initial assumption that they are indeed filtered out is simply wrong and that's why there's a million diseases that only affect old people and the only reason you see them around is how advanced medicine has become.
Cheers guys!
Elderly people are useless? Whether its for humans or other animals, these are the ones who hold most if not all knowledge (for example, to lead them to water in times of drought). Gay gene?
But ok.
Name me one disease that only affects elderly people and can't occur for younger people in a similar physical condition?
No need to be so aggressive, as has been pointed out, "the elderly" i. e. post-"menopausal" specimen of a species are almost exclusive to humans.
Gerulf Rieger did a video study in 2006 where he let a random sample try and guess the sexual orientation of men and women both in their childhood and their adulthood. In his sample about 75% of the guesses for both adults and children turned out to be correct, hinting at sexual orientation establishing itself way before puberty.
This might sound impressive, but is not the slightest bit meaningful without mentioning the baseline. I can guess the sexual orientation of a random sample of people with more than 95% accuracy, simply by assuming everybody is heterosexual.
On June 14 2013 00:46 Sablar wrote: There's no right or wrong answer to selection theories based on evolution. If it makes sense, then maybe it is so, but it's often surprisingly easy to argue for diametrically opposed views of how evolution has come to benefit a trait.
Overall I'm thinking that throughout human evolution, people never really got old enough to no be able to reproduce, so it's never really been an issue. Maybe a few of the high-status individuals were able to do so, but just a few hundred years ago people simply died young.
People didn't all die at the age of thirty in the past. The low life expectancy in poorer societies is primarily a result of high mortality among infants and children.
Upper Paleolithic, 33, Based on data from recent hunter-gatherer populations, it is estimated that at age 15, life expectancy was an additional 39 years (total age 54).
Classical Rome[14], 28, At age 15, life expectancy an additional 37 years (total age 52).
Medieval Britain[17][18], 30, At age 21, life expectancy an additional 43 years (total age 64).[19]
Menopause occurs around the age of fifty, and women generally live longer than men.
So a few years of age past menopause, as theorized in this very theory heavy field, means that post-menopause women played an impactful role in evolution?
If you look at e.g. twin studies if you're a man with a gay brother the chance of being gay yourself is about 4-5 times higher than average, when looking at identical twins there is about a 50% chance that the second one is homosexual as well which interestingly is a similar, albeit stronger, correlation than between handedness and twins (here we're talking closer to 2-3 times higher than average), indicating it's something that occurs rather early in the pregnancy.
This could just as well be used to claim that sexual orientation is purely based on socialization, as identical twins more likely than not have a very similar social background and spend a significant amount of time together, much more so than normal siblings.
I'm not saying you're wrong, but I don't buy that example.
Well it's obviously the case of 2 imo. Don't we simply "die of old age" at about 110 because our genetic material is to deteriorated by that point for new healthy cells to be produced ? There are species who don't, who developed ways to keep that genetic material relatively intact or to resist better to that alteration and can live more than thousands of years. Also there are plenty of "old people only" diseases, Alzeimers comes to mind ( pun wasn't actually intended ) but also a whole lot of other diseases have a way higher chance of affecting old people or only affect old people.
I don't get why you assume that genes that affect old people are "filtered out" because that doesn't seem to be the case, else there wouldn't be talking about old people crowding hospitals and costing billions in terms of drugs for the state to "allow" them to live.
On June 14 2013 00:46 Sablar wrote: There's no right or wrong answer to selection theories based on evolution. If it makes sense, then maybe it is so, but it's often surprisingly easy to argue for diametrically opposed views of how evolution has come to benefit a trait.
Overall I'm thinking that throughout human evolution, people never really got old enough to no be able to reproduce, so it's never really been an issue. Maybe a few of the high-status individuals were able to do so, but just a few hundred years ago people simply died young.
People didn't all die at the age of thirty in the past. The low life expectancy in poorer societies is primarily a result of high mortality among infants and children.
Upper Paleolithic, 33, Based on data from recent hunter-gatherer populations, it is estimated that at age 15, life expectancy was an additional 39 years (total age 54).
Classical Rome[14], 28, At age 15, life expectancy an additional 37 years (total age 52).
Medieval Britain[17][18], 30, At age 21, life expectancy an additional 43 years (total age 64).[19]
Menopause occurs around the age of fifty, and women generally live longer than men.
So a few years of age past menopause, as theorized in this very theory heavy field, means that post-menopause women played an impactful role in evolution?
We can for instance look at the upper paleolithic statistic in isolation. Note that it only excludes people who died before the age of fifteen, which means is includes the majority of everybody who successfully reproduced.
So, among people who survived to reproductive age, the average life span is estimated at fifty-four years. Let's assume that this goes for both men and women, though women tend to survive longer than men do.
Now, the menopause is defined as the end of a woman's menstrual cycles. The menopause is not a sharp cutoff between childbearing and old age. A woman's fertility declines steeply as the menopause approaches. For illustration - I can't vouch for this graph: http://assets.babycenter.com/i/infertilitygraph.gif Keep in mind this related graph, which should shed some light on the problems associated with reproduction in the forties. Down's syndrome is only one of many defects which grow more likely with increasing maternal age: http://www.aafp.org/afp/2000/0815/afp20000815p825-f1.gif
So, not only do women who reach fertility on average tend to survive menopause, but a significant number (depending on how the distribution is shaped) live somewhere in the order of ten to twenty years of their lives past the point of no reproduction. Note that the reproductive window is, counting generously, the thirty years from fifteen to forty five.
Now, of course I will admit that the numbers and details matter. Perhaps menopause hits women earlier in modern times than in the past? I have no idea why it should be like that, but one could imagine that poor nutrition leads to later puberty and later menopause. Perhaps fertility didn't drop off so early in the stone age. On the other hand, maybe women were infertile by the time they became thirty because of childbearing, STDs and poor nutrition? Who knows. Perhaps the statistics are dead wrong, though there is no obvious reason why they would be exaggerated in favor of long life spans.
Note, though, that medieval Britain, for which church records should provide fairly accurate statistics, is more or less in agreement, and neither medicine nor living conditions were all that great for the majority of the populace at that time. And today, many of those who live to be eighty and ninety, do so without any life prolonging medical care.
My tentative conclusion, though, is that living to the point of declining fertility is not just an artifact of modern conditions, and that post-menopausal women did matter in the evolution of the human species. Exactly how much of an impact they would have made is of course difficult to estimate.
And still, if one finds this hard to believe - menopause is observed, not merely as a curiosity, in a number of species of whale living in the wild. Some details can be found here: http://en.wikipedia.org/wiki/Menopause#In_other_animals
If you look at e.g. twin studies if you're a man with a gay brother the chance of being gay yourself is about 4-5 times higher than average, when looking at identical twins there is about a 50% chance that the second one is homosexual as well which interestingly is a similar, albeit stronger, correlation than between handedness and twins (here we're talking closer to 2-3 times higher than average), indicating it's something that occurs rather early in the pregnancy.
This could just as well be used to claim that sexual orientation is purely based on socialization, as identical twins more likely than not have a very similar social background and spend a significant amount of time together, much more so than normal siblings.
I'm not saying you're wrong, but I don't buy that example.
That's why it's one among many and not presented in isolation. Twin studies in general are a rather explored field so a notable difference between identical twins and normal twins tends to be rather conclusive.
EPT
