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Dave W.
Info Junkie
USA
26022 Posts |
 Posted - 09/02/2004 : 19:58:40 [Permalink]
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Actually, some aspects of "developed" civilizations can have genetic effects. As I read recently, at least some anthropologists consider ancient people to have lived to "old age" if they survived until they were about twice the age of puberty. Call it 24 years old.
People in the U.S. (at least) are often putting off child-rearing until well past that age, giving at least a few diseases a chance to rear their ugly heads prior to reproducing. Psoriasis, for example, has a peak age-of-incidence in the late 20s. And since psoriasis leaves ugly patches of red skin and/or big scaly build-ups, it's also quite possible in this largely-shallow nation that finding a mate would be a royal pain (and in fact, there are at least a couple of psoriasis dating services out there now).
I don't believe there are any statistics on this, but such a situation could conceivably lead to more psoriatics dying childless than the rest of the population, resulting in an evolution towards having fewer psoriasis genes in the pool (psoriasis has at least a half-dozen genes associated with it). Or, it could lead to more couples who both have psoriasis getting together and having lots of kids, who themselves may reproduce before showing any symptoms of the disease, and possibly increasing the frequency of the genes in the general population. Or, both effects could balance each other out, which would result in no evolution with regard to those particular genes.
Assuming the effects don't balance, is the result "natural" or "artificial" selection?
Either way, it's important to note, as I said at the start of this post, that thousands of years ago, many fewer cases of psoriasis would have been apparent, as most people would have died prior to showing symptoms of the disease. The genes, back in those dreary times, wouldn't have had much selection pressure at all, except for the 5% or so of gene carriers who displayed symptoms at a very young age. Genes without a heavy negative selection pressure can expand throughout a population even without offering a reproductive advantage. Psoriasis genes, then, may very well have been much more widely prevalent before "civilization" came along and started offering longer lifetimes in which it could become symptomatic. And the fact that psoriasis was once known as "white leprosy" couldn't have helped it maintain the status quo (especially since children could have been ostracized along with their "leper" parent[s]).
People with symptomatic psoriasis account for about 2% of the world's population. People who've got the genes but who aren't symptomatic may account for another 4%. The more I think about this, the more I bet that the former number was much lower, and the latter number higher, several millenia ago. |
- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too. |
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BigPapaSmurf
SFN Die Hard
3192 Posts |
Posted - 09/03/2004 : 05:48:41 [Permalink]
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| Thanks for the example I couldnt provide. |
"...things I have neither seen nor experienced nor heard tell of from anybody else; things, what is more, that do not in fact exist and could not ever exist at all. So my readers must not believe a word I say." -Lucian on his book True History
"...They accept such things on faith alone, without any evidence. So if a fraudulent and cunning person who knows how to take advantage of a situation comes among them, he can make himself rich in a short time." -Lucian critical of early Christians c.166 AD From his book, De Morte Peregrini |
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Dave W.
Info Junkie
USA
26022 Posts |
Posted - 09/03/2004 : 06:52:07 [Permalink]
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Well, as has already been noted, evolution is directionless. "Devolution" implies that evolution has a goal, when it doesn't. Whether psoriasis genes have become more or less prevalent due to longer lifespans doesn't matter - either way would be evolution, a change in the frequency of alleles in a population over time. And considering that I think that psoriasis genes are slowly getting weeded out of the gene pool, we're not headed back to some previous state (unless one can identify when the genes first entered the genome, and it was after the evolution of Homo sapiens sapiens), which is another implication of the word "devolution."
And something I was trying to get at in my prior post: should evolution like this be called "natural" or "artificial" selection? I mean, no "higher intelligence" picked my mate for me, so whether or not my child will survive with my (and my wife's) genes to reproduce himself will not be an artificially-decided event.
Heck, is gang violence an example of natural or artificial selection? Is the propensity to join a gang - and thus lower your own chances of reproduction - even genetically influenced? |
- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too. |
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Dr. Mabuse
Septic Fiend
Sweden
9688 Posts |
Posted - 09/03/2004 : 21:15:52 [Permalink]
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quote:
Originally posted by Dave W.
[Heck, is gang violence an example of natural or artificial selection? Is the propensity to join a gang - and thus lower your own chances of reproduction - even genetically influenced?
I always figured that it was a genetic disposistion with the purpose of population-control. Perhaps I'm wrong, and gangs are just some weird expression of the socio-economic decline in the urban areas.
Edit: By the way, great piece about psoriasis, Dave.
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Dr. Mabuse - "When the going gets tough, the tough get Duct-tape..."
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"Equivocation is not just a job, for a creationist it's a way of life..." Dr. Mabuse
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Send them unarmed civilians for target practice..
Collateralmurder. |
| Edited by - Dr. Mabuse on 09/03/2004 21:18:22 |
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Dave W.
Info Junkie
USA
26022 Posts |
Posted - 09/03/2004 : 21:31:47 [Permalink]
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Dr. Mabuse wrote:quote:
Edit: By the way, great piece about psoriasis, Dave.
Thanks, Mab. Comes from having devoted five years, more or less, of my spare time to the disease after I finally found out what the patches were on my elbows. The psoriasis web site I linked to is my own - now rather neglected - contribution to trying to correct a lot of psoriatic misinformation out there. And this is why, when offered a moderator position here on the SFN, I jumped at the opportunity of moderating the Health folder, at the very least. It was my self-taught area of "expertise," such as it is, within the much-larger field of critical thought. |
- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too. |
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