First, I want to make sure you are aware of genetic drift. A bit on what scientists think about the importance of drift:
Random Genetic Drift
The two most important mechanisms of evolution are natural selection and genetic drift. Most people have a reasonable understanding of natural selection but they don't realize that drift is also important.
Genetic drift - Wikipedia, the free encyclopedia
Many scientists consider [genetic drift] to be one of the primary mechanisms of biological evolution. Others, such as Richard Dawkins (borrowing from Ronald Fisher), consider genetic drift important (especially in small or isolated populations), but much less so than natural selection.
A bit on what genetic drift is:
Quote: Genetic drift - Wikipedia, the free encyclopedia
In population genetics, genetic drift is the accumulation of random events that change the makeup of a gene pool slightly, but often compound over time. More precisely termed allelic drift, the process of change in the gene frequencies of a population due to chance events determine which alleles (variants of a gene) will be carried forward while others disappear. It is distinct from natural selection, a non-random process in which the tendency of alleles to become more or less widespread in a population over time is due to the alleles' effects on adaptive and reproductive success.
I think of genetic drift as a near mathematical inevitability in genetics.
A decent analogy/ little experiment you can perform to demonstrate this is here - Basic concept of drift - wikipedia
This is evolutionary change; often a particular gene either becomes fixed in the population, or goes extinct. Given enough time, speciation follows as genetic drift builds up.
So part of what we are and what characteristics we have is probably due to genetic drift, as well as natural selection. Also, even if we seem
to thwart adaptive evolution in the short term
, since we are made of cells governed by genes we can be pretty sure that we haven't completely thwarted all evolutionary processes. The reason I say "seem
" is because even though many modern humans don't deal with the same selection pressures our ancestors did millions of years ago, there might be different selection pressures of some relevance that we now face, as well as the fact that some humans, in parts of Africa for example, do actually still deal with many of the selection pressures that were adaptively imporant in our evolutionary past. The reason I say "short term
" is b/c things can change quickly. Think about the impact that earthquakes, hurricanes, volcanic eruptions, asteroid impacts, and nuclear war could potentially have on our species. We are but a blink of an eye in the face of life on this planet. No matter how easy things seems for us now, things could change quickly. Just look at the dinsosaurs, they dominated the Earth for FAR longer than humans have so far, and in general were amazingly well adapted for life on this planet, yet when faced with a couple of natural catastrophes such as major volcanic activity and an asteroid impact, they were largely eliminated from the face of the Earth.
So now that I've said all that, I'll return directly to the points in your OP.
But for those who subscribe - at least in some part - to these theories, I have some questions for you predicated on two ideas:[INDENT]Premise 1: Human beings have stopped, stunted and thwarted the natural evolutionary process of their human race through medical care, preventive medicine and the gadgets we've come up with (everything from pace-makers to glasses). This is fine, this is good, yee haw and have a happy.[/indent]
In Premise 1, I personally think it would be more accurate to say that we seem to have stunted adaptive
evolution in the short term
; this is somewhat semantic, and I do get your point, but it's important to note that we have NOT stopped evolution in humans. Most evolutionary change that is even slightly significant usually takes place over extremely long periods of time, especially in species with life spans as long as ours. Just b/c we have come up with extensive medical care over the last couple 100 years doesn't, at this point anyway, necessarily mean that much in terms of processes that typically take hundreds of thousands, and millions of years to to do their work in a significant way.
[INDENT]Premise 2: Yet today, what robustness there is in our bodies - the stamina, ability to adapt, immuno-systems, etc., are a product of natural selection. As changes, climate and mutations occurred over eons, what was weak wasn't able to pass along its genome. Any 'health' or 'fortitude' we have now, we owe - to the largest extent - to natural selection. [/INDENT]
I have little quarrel with Premise 2.
Does this now mean that any evolutionary processes we might have since enjoyed since the industrial revolution, age of enlightenment and information age simple won't happen? Are we destined to become more and more hopelessly reliant on the very gadgets and systems we've created? Are we to become less robust, less able to withstand? In short, have we sapped our future by short-circuiting the very evolutionary systems that have enabled us to survive this long? And of course the kicker: Does it matter?
Here I would change "any evolutionary processes" to "any adaptive evolutionary change" and also go back to the point about how long major evolutionary change usually takes to happen. (since you mentiond periods of time within the past few hundred years) I assume that if things keep going the way they currently are for a long time, we will become increasingly reliant on our gadgets and systems; our way of life and environment. This is the way it is for most species. If they live in one environment with certain circumstances for a long time, then they become reliant on those circumstances, and find themselves unable to survive in the face of abrupt changes, should they occur. So when you ask if we are to become less able to withstand, if you mean less able to withstand in the face of environmental/ circumstantial change, then yes, the more control we become accustomed to in our environment, the less we will be able to withstand a sudden lack of control in this regard. We haven't "short circuited" the system IMO, b/c the system is still all there; we are still made up of cells governed by genes, and evolutionary processes still govern life. If our environment is to drastically change in the future, well, we'll just have to see how far our bodies and ingenuity take us. Just like 99% of the species that have ever lived on this planet, our future will likely be extinction. If anything, we might be MORE able to withstand change however, due to genetic engineering.
Are we missing out on any evolutionary change that we might have experienced should we have not developed medical care? Well, first consider that we may have all died by now if it wasn't for medical care, which would make the question moot. Next, consider that this is how evolution works. Major evolutionary change tends to cease as long as a species is well adapted to it's enviroment, and the enviroment doesn't change much. Look at many deep sea animals; their world has seen little change over hundreds of millions of years, and those that have been well adapted to their enviroment haven't changed in any significant ways for many millions of years. Things are essentially no different for humans.
So I would say that no, we have not "sapped our future".
Would it matter if we had though? Well, if
you value the preservation of our species, and if
we've made ourselves less robust and/or able to survive in the future, then yes, it would matter. But let's consider the alternative to doing what we can to help members of our species survive and overcome past selection pressures; to let the "weak" suffer and die. We would have less reproducing individuals and if we weren't lucky, the process could runaway and be more likely to completely kill us out. So I'd say it matters if it makes us less able to survive, but overall, I'd say that it probably doesn't. It does perhaps make the average individual less robust and physically capable, but it also helps to keep us alive as individuals and as a species, as well as to reduce suffering.