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Author Topic:   Is there really such a thing as a beneficial mutation?
Omnivorous
Member
Posts: 3851
From: Adirondackia
Joined: 07-21-2005
Member Rating: 2.9


Message 64 of 223 (343095)
08-24-2006 6:24 PM
Reply to: Message 60 by mjfloresta
08-24-2006 6:17 PM


Re: Beneficial mutation environment
A new body plan would be composed of new organs; starting with the generation of new organs then, seems like the place to start.

That is an unwarranted assumption. A new body plan could well, and more probably would, consist of familiar organs (or organ functions) in a new arrangement.


This message is a reply to:
 Message 60 by mjfloresta, posted 08-24-2006 6:17 PM mjfloresta has taken no action

  
Omnivorous
Member
Posts: 3851
From: Adirondackia
Joined: 07-21-2005
Member Rating: 2.9


Message 178 of 223 (343409)
08-25-2006 7:06 PM
Reply to: Message 151 by Percy
08-25-2006 12:18 PM


Re: Trade-offs
I agree with Faith's earlier argument that the genome of the human race is over time becoming less and less robust

I disagree, Percy.

I do agree that technology insulates some individuals from selection pressures that would otherwise impact their reproductive success, but that is quite a different matter.

How would we measure the robustness of the human genome? I would hazard the argument that diversity, more than any other metric, indicates the robustness of any genome.

Surely robustness must reside in both current and potential reproductive fitness; thus, the greater the diversity in the genome, the more likely it is that some members of the species will survive a novel environmental challenge.

I think that the power of culture to maximize genomic diversity suggests one reason the human brain has evolved so rapidly--intelligence trumps almost every other trait when it comes to survival and reproductive success. As intelligence insulates its carriers from other selective pressures, positive feedback ramps up the evolution of intelligence. The fact that we have a greater number, or even a greater percentage, of "flawed" individuals does not impact our genomic robustness--quite the contrary, because a "flawed" individual by definition represents genetic novelty. The power of culture (technology) to mediate between the genome and the environment enlarges the potential genomic "space."

Surely the sickle cell gene existed prior to the malarial challenge, and those who carried it were "flawed." Yet, when the mosquitos began their pathogen delivery, that "flaw" spelled the difference between life and death.

I agree with you on wisdom teeth, however. Having worked many years doing IT inside cardiology departments and groups, I know the deadly potential of caries. Even patients with good teeth can die from a pericarditis seeded by something as apparently innocuous as a dental cleaning: those with leaky valves or other cardiac issues are treated with antibiotics prior to any dental work, because the mechanical removal of plaque can introduce bacteria into the bloodstream, leading to a potentially lethal infection of the pericardium. The practice is known as subacute bacterial endocarditis prophylaxis. On a likely related note, the role of inflammation in coronary artery disease has only recently come to light. On a similar note, it is easy to forget that diarrhea (dysentery) kills more children than any other factor: a mutation that killed you at 30 but resisted dysentery would spread explosively across the undeveloped world.

I'm not so sure about how vital a selective factor vision was in our evolutionary history, though. It is worth noting that our vision seems to have been shaped more by color than acuity: compared to many species, our visual acuity is, at best, mediocre. I suspect that auditory and olfactory sharpness played a greater role; as Crash has suggested, once you see the tiger, it's probably too late. Hearing or smelling a threat probably played a greater role. I agree that the importance of information exchange has increased the role of vision, but I'm not so sure that importance can be projected too far back down the hominid line--else we would have the eyes of raptors.

Edited by Omnivorous, : No reason given.


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This message is a reply to:
 Message 151 by Percy, posted 08-25-2006 12:18 PM Percy has replied

Replies to this message:
 Message 180 by Percy, posted 08-25-2006 8:22 PM Omnivorous has replied

  
Omnivorous
Member
Posts: 3851
From: Adirondackia
Joined: 07-21-2005
Member Rating: 2.9


Message 190 of 223 (343457)
08-25-2006 11:09 PM
Reply to: Message 180 by Percy
08-25-2006 8:22 PM


Re: Trade-offs
Hi, Percy. I welcome the rare opportunity to disagree with you at length.

Percy writes:

Omnivorous writes:

How would we measure the robustness of the human genome? I would hazard the argument that diversity, more than any other metric, indicates the robustness of any genome.

I'm not so sure it's as simple as this. If we use the example of vision and accept, merely for the sake of argument, that the vision of civilized peoples has declined in terms of visual acuity (i.e., resolution) and the ability to focus, then genomic diversity for vision was less in the distant past than it is today. In other words, a lesser percentage of people had bad vision in the past than today. Would a greater diversity in visual acuity and focal ability be a sign of robustness? In other words, is the fact that more people are born today with bad vision a sign of robustness?

Again, I'm not trying to sneak in my stance on vision, it's just for the sake of argument.

I don't think it is simple at all. I was arguing from first principles: we know that traits that were deleterious at their emergence, like sickle cell, ultimately proved to be advantageous.

We will not recognize an adaptive mutation until the environmental pressure that selects it emerges.

In passing, let me say that I see no reason to believe that ancient peoples had better visual acuity, nor do I see any reason to believe that modern peoples have poorer visual acuity.

But for the sake of argument, let's presume that is so: we do not see as well as our progenitors. Why is that? Is there some entropic principle in evolution such that an advantageous trait will deteriorate in the absence of its originating selective pressure? I suppose so, if the biologic cost is high. Is the cost of excellent human vision higher than poor human vision? I don't see why it would be.

I am familiar with genetic drift, but that seems like a gentle force compared to the degree of change you propose. If visual acuity was so adaptive, why was its lack--like, say, the relatively rare condition of congenital blindness--not largely purged from the genome long ago?

Rather, I suspect that the differences we detect in visual acuity are largely a factor of our ability to detect them, and they are made manifest to us by our ability to correct them.

From your earlier remarks, I assume you see no causal agent for this deterioration earlier than agriculture--do you believe this deterioration occurred in a span of 10,000 years? Do you believe that the Third World has clearer eyes? I don't: I think they lack ophthalmologists, optometrists, and the means to purchase lenses.

Rather, I think good enough vision was good enough. The myth of the Golden Age pervades many areas of modern thought: the clear-eyed hunter, the noble savage, the clean-limbed and mighty Grecian wrestler, the etc. But, in fact, our biggest and strongest seem to be bigger and stronger than theirs were.

I think there is strong evidence for the possibility that intelligence continued to evolve after the emergence of our species. Even in scant centuries, the studies involving populations of Asjkenazi Jews suggest that intelligence-focused bottlenecks--e.g., that in Bohemia only a single scion could obtain a marriage license, and that lottery was won by the most successful child in a hostile environment--can measurably shift a population's average intelligence.

More fundamentally, I want to make clear my central idea here. What determines a genome's robustness? Clearly, the reproductive fitness of its members in the current environment is one determinant. But if that genome's extant population is a monoculture--say, clones of elm planted after the clear-cutting of an ecologically complex forest--then the potential survivors of a dramatic challenge to the genome are fewer than if the genome has greater variability: if every individual shares the same genetic vulnerability to Dutch Elm disease, the species is toast.

But we didn't know that until the disease arrived. Intelligence and its child, culture, permit an increase in the diversity of the genome. That will include bets that become losses (i.e., never pay off), but you cannot win if you do not play. You could be right about visual acuity, but you are still wrong about the deteriorating robustness of our genome.

Diversity is the insurance for the genome; a higher number of currently less adaptive individuals is the current premium paid; intelligence raises the capital on hand to afford that premium.

If I were to guess, I'd say that you and Crash see our modern technology as an indication that we're superior to ancient man. I don't see it that way. Our modern technology is just an inevitable development of thousands of years of gradually accumulating knowledge and expertise made possible through language and writing.

What do you mean we, kemosabe? :D

I have no doubt that "ancient man" would fit within our modern bell curve of intelligence, though there is certainly some undefinable point where that is not so. Whether that bell has moved would require the testing of both populations. I see neither the possibility nor the necessity.

My single, intense, insisted on point, is that we cannot know now which genetic constellation means reproductive fitness in the future. We do know that genes which have an immediate cost can, in changed circumstances, confer huge benefits. For that matter, we know so little of the complex constellation of our DNA that it may well be that the set of "poor visual acuity" genes includes a subset that will dictate the survivors of the first viral war. Do you suppose that anyone witnessing the agonies of a possessor of a single allele for sickle cell would have bought the argument that their misery paved the road to survival?

The point is that when you do not know what number will win the lottery, and you simply must win the lottery, your best bet is to play as many numbers as you can afford, not to increase your bet on one number. The emergence of intelligence, culture, and technology have increased the number of our genome's bets on the table.

Diversity isn't just a warm and fuzzy ideology; it's what intelligence makes possible, and it promotes our genome's survival.

Edited by Omnivorous, : typos

Edited by Omnivorous, : 'nother typo.


This message is a reply to:
 Message 180 by Percy, posted 08-25-2006 8:22 PM Percy has replied

Replies to this message:
 Message 196 by Percy, posted 08-26-2006 4:43 AM Omnivorous has replied

  
Omnivorous
Member
Posts: 3851
From: Adirondackia
Joined: 07-21-2005
Member Rating: 2.9


Message 203 of 223 (343570)
08-26-2006 11:46 AM
Reply to: Message 196 by Percy
08-26-2006 4:43 AM


Re: Trade-offs
Percy writes:

Does it mean how well the organism is adapted to the present environment, in which case diversity is a disadvantage? Or does it mean how well the organism is prepared to meet unpredictable environmental changes, in which case diversity is an advantage? You anticipated this much further on in your post when you said, "Clearly, the reproductive fitness of its members in the current environment is one determinant."

I think your preferred measure of robustness is to just say robustness==diversity.

No, I recognize that robustness is more complex than that--sorry if I seemed to suggest otherwise.

But the reason I introduced the term robustness was because I specifically did not mean to include diversity. I'm not married to the term robustness and am perfectly content if you'd like to propose another term, but what I had in mind was measuring how well the organism was adapted to the present environment.

Yet that is quite difficult to measure in a static way.

One characteristic of the present environment is mutability. All other things being equal, the more diverse genome seems more robust.

I think you mean hereditary, not congenital. But this is a counterargument? Why not ask why all severe hereditary diseases haven't been purged from the genome long ago?

Mea culpa--it was the wrong word and a lame argument. I know better. It was late, and the beer was cold. Say no more.

While the Third World is poor and underdeveloped, and while there are certainly parts of the third world with primitive peoples, it isn't what I was thinking of when I used the term primitive. I don't recall exactly what I said, but I was referring to primitive peoples who live in direct contact with nature and who are relatively isolated from modern civilization and its conveniences. There are very few parts of the world like this today. But yes, I believe they have better vision. As I mentioned earlier, this was one of Darwin's observations about the native Patagonians, but I by no means consider his lone observation conclusive and await better evidence.

Fair enough, though I remain skeptical that differential selective pressures among hunter-gatherers, farmers, and technological peoples were enough to drive a reduction in visual acuity.

I'm don't recall Darwin's observations on the Patagonians, but I do know that one must learn to see well in a new environment, a learning that includes drawing more information from the same sensory input. Although I am quite short-sighted, I once had to drive without corrective lenses for several weeks.

The first day or two were frightening, but I soon adapted, and learned to extract the data I needed from less acutely defined surroundings.

It also seems reasonable that persons with more acute vision gravitate to roles that require it, say, warrior chiefs and fighter pilots. Not every job or tribal role requires exceptional visual acuity. Our evolution as a social animal will make it especially difficult to tease out the role of selective pressures in evolving or retaining maximal visual acuity vs. just good enough to find a productive niche in the group.

I'm not a romantic, so it would be unusual for myths to drive my thinking, especially myths I don't buy into.

:) Well, it would be uncivil to argue otherwise but I will note that one thing myths do is inform our conceptions without requiring a purchase.

As to disease resistance: that seems, if anything, more difficult to sort out in a comparative way than visual acuity. Agricultural peoples living in close proximity to their livestock, as Jared Diamond has argued, are exposed to pathogens which can cross species lines (like the poxes, e.g., camel and cow), and so those folks eventually evolve resistance.

We know what happens when those resistance-enjoying people encounter others without that resistance--e.g., smallpox decimating the native Americas. Yet the pathogens also evolve in complex ways--not just to overcome our immune systems or to resist antibiotics, but also to supplant more virulent strains by not killing us outright. Ebola, for example, has never moved very far from an outbreak point because it is so quickly and thoroughly lethal. Ironically, it could become more dangerous by evolving less virulence.

Well, we probably agree more than we disagree.

Yes.

I probably can't go as far as saying that intelligence makes diversity possible, but I certainly agree that diversity is a central factor for a population's adaptation and long term survival.

I should clarify that of course I don't believe intelligence is the sole source of diversity, but I do believe it has greatly increased our genetic diversity, and that the complex interplay between intelligence and genetic diversity was in turn a factor in the evolution of intelligence.

Edited by Omnivorous, : fixed quote


This message is a reply to:
 Message 196 by Percy, posted 08-26-2006 4:43 AM Percy has taken no action

  
Omnivorous
Member
Posts: 3851
From: Adirondackia
Joined: 07-21-2005
Member Rating: 2.9


Message 206 of 223 (343583)
08-26-2006 12:26 PM
Reply to: Message 181 by Faith
08-25-2006 8:37 PM


Re: Visual deterioration
Faith writes:

I find it odd, from my creationist point of view, that an inferior condition such as deficient visual acuity and focal ability could be called "diversity." To my mind it can only be properly called genetic deterioration.

One of the things I've been trying to get at is that an apparently defective genetic endowment may become beneficial when the environment changes. Malaria and sickle cell are, of course, the classic examples.

But the more interesting point, to me, is that because we are a social animal with intelligence and culture, the environment becomes much more complex. This greater complexity permits a wider range of individuals to survive.

Consider the archetypes of the blind sage and the lame artisan.

It is simplistic to merely consider them defective, and it is not just political correctness to point out that difference is a more accurate term. Because we are social, there are roles available which are not closed to those with such differences; the development of alternative sets of skills--the inward-looking, reflective "gaze" of the blind and the greater reliance on manual strength and dexterity of the lame--can produce individuals uniquely suited to particular roles.

The blind certainly listen in a different way, and the lame must work with what is at hand. The brain wires itself in response to stimuli, and cultures have almost universally found merit in the differences.

I don't want to annoy Percy with more myth ;) but the myth of, say, Hephaestus, lame smithy to the gods, suggests both these phenomena and our deep cultural recognition of them. Our individual ability to adapt to constrained parameters, and our social inclination to find a niche for the differently abled, work together to maximize even a "defective" person's opportunities for survival and reproductive success. Because of this, the result is greater genetic diversity.

In a social structure, the individual must be fit enough to find a useful niche, not perfectly suited to every possible task. Because our intelligence, social nature, and transmissible culture maximize the number of adapted individuals, the powerful trait of intelligence has freer rein. I'm not suggesting that blindness or lameness are linked to higher intelligence or other cognitive talents, but rather that when they both occur in the same individual, the intelligence or talent is not lost to that particular society or to future generations.


This message is a reply to:
 Message 181 by Faith, posted 08-25-2006 8:37 PM Faith has taken no action

  
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