No. Natural selection will always occur for the very simple reason that life replicates at exponential rates and therefore quickly expands to fill all available environmental niches. There is more life produced than can possibly survive. Therefore some must die. The ones that die, die for different reasons. Whatever those reasons are, they are natural selection.

The effect that modern medicine and health care has is to lower the threshold of survival, which only means that more varieties of people can survive. This leads to greater genetic diversity overall, which is a good thing. But we will never reach a point where all people can survive and reproduce equally. There will always be differential survival and reproduction rates.

What has actually occurred is that on top of biological evolution we have developed a capacity for cultural evolution. Cultural evolution occurs much faster than human biological evolution. So, our medicine is evolving faster than our genes. But our genes are still evolving. That will not stop.

In fact, there are good arguments to make that due to our cultural evolution co-evolving with our genetics, we are actually evolving *faster* than we would if we did not have such sophisticated culture. Wars, for instance, are cultural phenomena and tend to kill a lot of people. Likewise, those who are able to 'game the system' better, who can adapt to culture and society in order to gain reproductive success, are able to pass their genes down to the next generation. There are a whole bunch of cultural factors that affect genetic success. Some are even paradoxical, such as poverty. But the point is that our genes co-evolve with our culture, and co-evolution tends to lead to dramatic evolutionary changes.

I think in a way we are. I wear glasses for example and if a thousand years ago I didn't have them, I'd have gotten eaten by a Grizzly or beaten up by somebody else. We've invented firearms, so now even pansies can put up a fight.

I mean look at all these bacterial sprays and such. Never mind the fac that the bacteria are becoming resistant, it's that our immune system is probably getting weaker because we use 5 lysols wipes on our doorknobs.

Ergo we don't get infected in small amounts, and build up the anti-bodies then when a bigger exposure hits, we're sick, or toast, depending on what the germ is. For example, chicken pox is lethal in adults.

The evolution of technology has trumped the evolution of genes.

Depends on who controls the technology. Technology will soon be able to turn on or off all our primal urges, including sex/reproduction. So if someone can control people by controlling their primal instincts, they can do whatever they want with the human race.

That was awesome!  It looks like you've had as much wine to drink as I have...

If it is 'good' that we are screwing with natural selection, does that imply that natural selection doesn't always select those traits which are most beneficial to gene propagating machines?

 I raise my goblet to you, mrjonno!  (unfortunately, that was my last gulp of cheap cab)

By the way, may I have your permission to use the term "Pastafarian?"  Love it!  Can't wait to tell my wife about it...

 The whole "screwing with natural selection" argument makes an interesting mistake -- it steals from religion!

In the Christian mindset, there are things that are natural and things that are unnatural.  Humans disturbed the natural order by sinning.  Homosexuality is unnatural.  Not feeling love for the Warm and Fuzzy Savior is unnatural.  Etc, etc.

Do a thought experiment for a second or two.  If all that exists is the material universe, what is unnatural?  The only possible answer is "that which does not exist" for if a thing exists, it is part of the material universe, and natural.

Actually, it's funny you picked these two topics (morality and medicine) because both fall prey to the same obfuscation through equivocation (clouding the water by using multiple definitions vaguely).  Even though we all think we know what unnatural means, we can't quite put our finger on it -- and that's precisely because everything is natural.  We often use the word to mean things that are far from the ordinary, but that's not unnatural, just statistically rare.  We can also use it to mean things that are morally bankrupt, but that is also quite natural -- just morally bankrupt.

The final nail in the coffin is when we realize that our intelligence isn't special, nor can it possibly cause anything unnatural to happen.  Sure, we are the most intelligent animal on the planet, but the cheetah is the fastest cat, and the blue whale is the biggest animal on the planet, and the dolphin is the best at using sonar.  We like to put intelligence on a pedestal because it's our particular specialty, but other than the fact that it's human, there's no real reason to postulate that it is somehow "outside of natural selection."

Natural selection is the principle that the realities of the universe will influence the survival of genes over time.  There's nothing about modern medicine that stops the realities of the universe from influencing which genes survive and which don't.  Humans are natural, and our influence is part of the realities of the universe.  Organisms influence their own natural selection all the time.  We are just aware of it, and do it purposefully.  So what?  Still natural.

One could make the argument that our selection is partly "artificial" and if they word it correctly, they might have a case.  However, this still doesn't affect the point that even our conscious "artificial" tinkering with our own descent is still within the scope of our natural capabilities.  We are still passing our own genes into the next generation with variation, and that's natural selection.

 The only place where modern medicine could have an appreciable effect on natural selection is infant mortality, which is down considerably over the last couple hundred years, though not nearly as considerable in third world countries.

Currently, the infant mortality rate in the U.S. is about 7 per 1000.  In Afghanistan it's 165 -- more than 20 times higher.   Curiously, though, the decrease of infant mortality adds diversity, which in effect can speed up the process of natural selection, given the right circumstances.

As you point out, most of the applications of modern medicine are most useful after most people have reached reproductive age, so there's that, too.

Finally, contraception certainly has an effect.  Because of contraception, I'm the last of my genetic line, and I will not be reproducing, so modern medicine has certainly had a local effect.  The question is whether the net effect is such that we could say that some fundamental process of natural selection has been altered.  I can't think of any way that we could say it has.  We still reproduce, our children still have a mix of our DNA, and we still compete with each other and against our environment.  It's still the same process.

It's better if you get away from the idea of our preference having much to do with it.  Female sexual selection is the most common in vertebrates, but that doesn't mean that natural selection is reliant on females to make the correct selection.  Female sexual selection is just the path we happen to be on.  If a human female has babies with her husband, her illicit lover, or a rapist, she is still, from the point of view of the genes, getting the job done.  It's nice for human females if they get to choose, but that's only really important to us humans, not to natural selection.

Dolphins, FYI, routinely rape (by human standards) females by ganging up on them, separating them from the pack, and tiring them out until they finally either cannot resist or give in.

It only seems more subtle because we think of things as good that don't matter to natural selection.  Your kid's going to be smart enough to get into Yale?  Bully for you, but if you only produces one kid, and the redneck down the street produces ten between his wife and all his girlfriends, you lose and he wins, genetically.