I was simpley pointing out, FM, that the phenomenon to which TTF was referring related to malaria. I know nothing of the mechanism, apart from its relation to the quaternary stage of malaria. Slaves in the American South most commonly came from the West Indies, and the west African negroes had already become the "slave of choice" there. By the by, even Chinese were brought to the West Indies and Cuba in an attempt to find the "ideal" sugar cane worker--as though there ever were such a critter.
you are understood set and my little rail was against the "selected against" concept that TTF used. That is not the standard of how science views natural selection. Anyway, the evolved protection against malaria has a bitter consewquence in the native land . The little kids with both parents carrying the gene have a 2X greater frequency of sporting the lethal gene set.
It can be said another way favored by Mayr
Natural selection is where everything that favors survival is passed on and that which doesnt is extinguished. (Actually what most people say now is that favorable traits are selected since they confer "fitness" wrt the environment at hand. it gets close to sounding neo Lamarkian but wat the hell,
An aside, I always like a thread where a bunch of different people see the phenomena from a bunch of different perspectives.
Asherman wrote:....Evolution continues, though we have largely frustrated its direct effect on our own species. Our technology gives us some control over our environment, but it is a limited control as Mother Nature so often reminds us. Our grasp of medical science and biology has given us longer lives and mitigated many of the illnesses that beset us. But, again our grasp and control is neither perfect, nor universal.........
but of course, you are correct; i was referring to evolution of the human species.
And the only effective way to divest ourselves of the threat of 'biology', is to divest ourselves of biology, itself.
The next itteration of the human animal will not be an 'animal', but a machine 'born of beast' but emulating the stars!
I've always been irked, FM, by the continued popularity of Spencer's "survival of the fittest" claptrap. As the ordinary person, despite intelligence and education, usually does not learn much about the mechanisms, even when religious fervor does not interfer in study--it tends to lend itself to the exploitation of demagogues and peddlars of self-interested half-truths. Adaptations which provide a greater probability of producing viable offspring means survival for a putatively "more fit" species. Any individual surviving is fit by definition, so "survival of the fittest" says nothing. The crucial determinant is passing on one's genetic make-up, and the most egregious horse apples have been widely distributed by an exploitation of people's ignorance of even the most simplistic explanation of the mechanisms.
Farmerman, Natural Selection is not adaptive, it is opportunistic. The adaptability of a species is a side effect to the statistical nature of the process. Adaptability implies directionality which is anything but the case.
BoGoWo,
I focused on the evolution of viruses and disease causing organisms because they make such a pretty example. One of the reasons that they present such a terrible risk to our species is not because we've "stopped evolving", but rather because our evolution makes us more vulnerable. Our species is evolving to meet the requirements of survival in the environment it finds itself. Immunity to many diseases is lost as our bodies no longer encounter the threat. We've evolved in just a few short generations to rely more upon vaccines than on natural defenses. The disease organisms continue to evolve to survive our vaccines, and they may be becoming more lethal as well.
There are other examples of continuing human evolution. We are larger today than our great-grandparents, and compared to people living a thousand years ago we might almost be giants. As nutrition becomes less risky, the organism (in this case, humans) get larger. When food becomes more difficult and scares, species become smaller.
Our species may be losing diversity as isolated populations become more rare. We are interbreeding much more than in the distant past. Genetic traits that improved the survivability of small human populations in extreme environments are lost. We are evolving as a whole species toward the genetic requirements to survive only in the highly controlled environment of modern technology. As we adapt to Urbanism, we lose our already limited capacity of smell. Almost certainly primitive human hunters had a greater ability to "sniff-out" predator and prey. If, as the Farmer has pointed out, a catastrophe were to wipe out the artificial environment we've adapted to, how many of the species would survive a return to "primitive" conditions? If we evolve away from physical strength and agility as not being necessary for survival, we would be mal-adapted to being returned to the natural environment. Our manipulation of the evolutionary process might well be a dead-end, and a contributing cause to our extinction.
What could destroy our artificial environment? Overpopulation is perhaps the greatest threat and the most likely engine for destruction. Overpopulation is one of the root causes for famine. If the earth underwent a world wide drought for a few years, our billions might easily be reduced to under one billion. The densely populated and impoverished nations of Asia and Africa are most at risk for famine. Both India and China have long histories of famine that had extremely high mortality rates, and there is no reason to suppose that those conditions will not occur again, perhaps even in the next 20 years. Human interaction with the planet's ecosystem can be very dangerous. Destruction of the rain-forests, and use of soft coal as a fuel are especially worrisome. Almost as dangerous is the use of petroleum products for energy.
We should not rule out the effect of climate change. For most of human history the earth's climate has been conducive to the rise of large human populations. However, we know that the planet does periodically undergo rather dramatic natural climatic extremes. The after-effects of a spasmic exchange of nuclear weapons, like the entire Soviet/US stockpiles, might trigger such a change. Major volcanic eruptions have been known to lower global temperatures for years after the event. If we witnessed a large increase in volcanic activity, and eruptions were very violent significant changes in the weather might result. Being struck by a large, massive bit of space debris is a third "artificial" trigger to climate change that might severely test our genetic ability to survive. We may be facing global warming, or a return to the Ice Ages. Either may be a challenge to human survival, especially to those whose genetic codes will not tolerate extreme environmental conditions.
Overpopulation coupled with almost universal rapid transit, also makes us very vulnerable to epidemics. Deadly diseases spread most quickly in dense populations, especially if sanitary conditions are poor and public health systems weak. A highly lethal disease might emerge and spread world-wide almost before it is fully recognized. Such a disease might be air-borne with an incubation period of around 14 days, during which the disease could still be transmitted on the breath of the infected. Existing vaccines and anti-biotics would be ineffective, and the mortality rate would be somewhere between 30 and 40%. We are unlikely to face higher mortality rates, because the disease organisms are unlikely to suddenly develop a degree of lethality that it would cause the extinction of the disease itself.
Asherman wrote: There are other examples of continuing human evolution. We are larger today than our great-grandparents, and compared to people living a thousand years ago we might almost be giants. As nutrition becomes less risky, the organism (in this case, humans) get larger. When food becomes more difficult and scares, species become smaller.
That is not evolution, that is simply a morphological response to the environment - available nutrition. Homo Erectus males were probably six feet or more in hight, and we have not improved on that in the succeeding 2 million years.
The one area where natural selection is probably at work on our species is the size of the jaw, it is getting smaller. That is why many people need to have their wisdom teeth removed. It is speculated that this is a response to cooked food, which hominids have been doing for about a million years.
Adaptation is a consequence so, I can certainly agree with you acquiunk. You too set , Im even surprised I said that old Herbieism, but I did , it was early this AM, so I have to carry it around my neck for a week or two
.
In my own defense however, ole Herbie actually, when quoted, is often only given credit for the last 4 words, when, what he actually said was
"Evolution is merely the survival of the fittest",
so he wasnt really talking about some property of an organism , but of survival-favoring attributes. Thats why Darwin glommed on to this as a fairly reasonable statement when quuoted in its entirety. Darwin, in his many pubs was really fussy about his language .
In my estimation this statement, in full, isnt a real tautology as an earlier thread in afuzz stated. I was sidebarred at a presentation by a friend who is a Darwin scholar and he pointed out the full quotes of H SPencer and I backed off the tautology truck.
Thank you for that background, FM, i appreciate the clarification . . .
I think my problem with terms like 'adaptation' and 'selection for' is that to my students they see design in those terms.
Random mutation and selection against I will continue to use - and I think I have been explaining it properly.
FM - I agree (and could not have explained it so technically) I was simply attempting to give my tac and this post attempts to explain why I use that particular line.
TTF
http://www.talkorigins.org/faqs/evolphil/tautology.html
By the way I found this post that gives a little more grist to what FM is saying.
TF
I like the comparison to an equation .
Asherman wrote:BoGoWo,
I focused on the evolution of viruses and disease causing organisms because they make such a pretty example. One of the reasons that they present such a terrible risk to our species is not because we've "stopped evolving", but rather because our evolution makes us more vulnerable. Our species is evolving to meet the requirements of survival in the environment it finds itself. Immunity to many diseases is lost as our bodies no longer encounter the threat. We've evolved in just a few short generations to rely more upon vaccines than on natural defenses. The disease organisms continue to evolve to survive our vaccines, and they may be becoming more lethal as well............
as usual your comments are insightful; but i must disagree with this, your first point.
The human animal does not evolve noticeably by random genetic mixing to be less resistant to current diseases; but is more commonly affected by consuming various chemicals - antibiotics, etc. - in our food supply dulling the bodies reaction to their being administered for the purpose of battling a specific infection. Our lack of exposure limits the degree to which natural antibodies are formed, to protect against reinfection, and our foolish excessive hygiene practices dull the bodies natural protective strategies by not allowing them to function (flex their muscles, as it were). The 'bugs' do indeed evolve, as their life cycles are a fraction of ours, and we are killing of the less virulent competitors in their midst, quite compliantly, with our chemistry.
Genetic mixing from interracial breeding is not evolution, but natural gene pool 'stirring' (it does, non the less, confer advantages, and disadvantages on the recipient); evolution results from the testing of random mutations, your disease remarks are tending toward lamarckian ideas.
