Pretty much everyone here either misunderstands how evolution works, or is willfully ignoring it to push their viewpoint.

Humans at this point have very little evolutionary pressure from natural selection. We aren’t getting weaker, shorter, taller, or anything like that from natural selection because those traits aren’t killing people.

The main driving factors for human evolution are sexual selection, random mutation, and genetic drift. There are still some poorer areas disease may still play a not insignificant part, but even that is fairly minimal since people largely live to reproductive age.

Human evolution has been fairly stagnant for quite a while. The differences most people would notice are from changes in diet, environment, and other external forces. For natural selection to pressure evolution we would need to have a significant portion of the population sure before they are able to reproduce.

Same question rephrased: Can seat belts be a threat to humanity long-term by greatly reducing the effects of natural selection? After all, stronger individuals are more likely to survive car crashes.

What about wood stoves? Surely the fittest individuals are able to handle the cold?

We removed ourselves from "natural selection" a long time ago.

No. This is a result of thinking of natural selection as working towards an "absolute" better and away from an "absolute" weaker, as opposed to pushing in directions that are entirely defined by the situation.

Natural selection is this: in populations that make copies of themselves, and have mistakes in their copies, those mistakes that better fit the situation the copies find themselves in are more likely to be represented in that population later down the line.

Note that I didn't say, at any point, the phrase "SuRvIVaL oF ThE FiTtEsT." Those four words have done great harm in creating a perception that there's some absolute understanding of what's permanently, definitely, forever better, and natural selection was pushing us towards that. But no such thing is going on: a human may have been born smarter than everyone alive and with genes allowing them to live forever, but who died as a baby when Pompeii went off - too bad they didn't have lava protection. Evolution is only an observation that, statistically, mutations in reproduction that better fit the scenario a given population is in tend to stick around more than those that don't - and guess what? That's still happening, even to humans - it's just that with medical science, we're gaining more control of the scenario our population exists in.

Now, can we do things with medical science - or science in general - that hurts people? Sure, there's plenty of class action lawsuits where people sued because someone claimed their medicine was good and it turned out to be bad. But if you're asking "are we losing out on some 'absolute better' because we gained more control of the world we reproduce in," no, there is no "absolute" better. There's only "what's helpful in the current situation," and medicine lets us change the situation instead being forced to deal with a given situation, dying, and hoping one of our sibling mutated copies can cope.

Plenty of answers already.

I'd like to point out that it's not medicine alone, but empathy that changes natural selection. We have evidence of our ancestors caring for members of their tribe that would have been unable to survive otherwise.

But while in some edge cases (some diseases) you could make an argument that it's bad for future humanity for some reason, it's overall good, because it enables a larger population. And a larger population has a better chance of mutating to fit changing environments. Or to phrase it differently: diversification comes first, selection can wait.

Hmm, that's an interesting question. I'm not an evolutionary biologist but I am a biologist (more specifically, a microbiogist).

The crux of the misunderstanding, I think, is that the definition of what counts as advantageous or "good" has changed over time. Very rapidly, in fact. The reason many diseases are still around today is because many genetic diseases offered a very real advantage in the past. The example that is often given is malaria and sickle cell anemia. Sickle cell anemia gives resistance to malaria, which is why it's so prevalent in populations that historically have high incidence of malaria.

Natural selection doesn't improve anything, it just makes animals more fit for their exact, immediate situation. That also means that it is very possible (and in fact, very likely) that the traits that we today associate with health will become disadvantageous in the future.

If we remember that natural selection isn't trying to push humanity towards any goal, enlightenment, or good health, it becomes easier to acknowledge and accept that we can and should interfere with natural selection

I feel like the largest threat may be C-sections over natural births. A lot of births in developed countries are C-sections, with a lot of it being because the babies are too large to fit comfortably through their mothers' hips.

As baby size increases and has benefits post birth, there may come a day where some human populations need to rely on C-sections to propagate.

The more varied the sample of individuals you can afford to keep alive in your population, the more chances you have that a subset of them will be able to withstand random changes in the fitness function. If the environment changes abruptly, you will have a hard time adapting as a species if you only ever supported people "within the norm". What happens in those cases is called extinction.

Oh boy, a population genetics question in the wild.

In technical terms what you are asking is:

When a selection pressure is removed for a deleterious allele, what happens to the allelic frequency on the population?

The answer: they remain stable in the population, unchanging from when the selection pressure was removed. Every generation will have the same ratio of affected individuals as the previous one

Look up Hardy-Weinberg Equilibrium for more info.

Yes absolutely. We've already affected our biology and evolution.

Birth control, antibiotics, are examples

Given time, and even greater lifespans, we will have a larger impact on the path of our evolution.

As a thought experiment let's imagine humans that live for 2,000 years. What does this mean for our adaptability to environmental changes? What does this mean for our fertility?

If nothing else changes, the carrying capacity for new humans will decrease, if the average lifespan goes up to 2,000 years.

From an evolutionary perspective, the question is always what is the current selection pressure? Historically it's almost always been intelligence plus something else, melanin in the skin, the ability to metabolize lactose into adulthood, etc...

Oh cool, it's time to find out how much of a burden on humanity I am and whether I should have been left to die. Just hypothetically of course, I wouldn't want anyone to misunderstand. I always enjoy this question with my morning coffee.

I would argue that modern medicine prevents non-selective deaths. We try and keep everyone alive, not just the idiots.

Survival of the fittest just means the most adapted to the current environment. Our current environment has medicine so we're adapted to that. If that suddenly changes then sure it would be an issue, but so would a climate difference of even a few degrees, a slight difference in the chemical make up of air, etc.

i always thought that it was the greater volume of humans, the greater the genetic diversity

I expect gene editing soon to become so cheap that everyone starts customising their children, resulting in a situation analogous to where dogs are now: extreme variability improving the chances for survival by making sure we have the needed people for any situation except gamma ray burst which requires backups far from Earth.

Call me when evolution figures out how to deal with guns and automotive accidents, which likely represent the largest selection factors on modern humans.

Natural selection is an agent that runs contrary to the thing which is currently out-competing natural selection, that being big brain thinkering

E.g., if a cancer research scientist dies from a weak heart, that will reduce future life expectancy more than it will increase it

If genetic research gets to a point where we can beat any mutations, then probably not.

I can, will and has. Push back would be on what it means to be "weaker".
When we say evolution selects for strength, we mean strength in terms of environmental fitness with regards to propagation, not anything specific to health, well-being or survival.

Our earliest "medical" advances actually left us significantly less robust over time.
Techniques like "not leaving the sick or injured to die", "blankets", "carrying food and water" and things like that.
Over time, that led is to continue with bigger brains, longer gestation, more care for the mother and infant before and after birth, and old people.
This led to a spiral of smarter, more educated, more cared for people who were able to pass on knowledge between multiple generations.
None of that could have happened if we hadn't started caring for less robust people, like old man Greg with the bad leg, scary stories about snakes and knows all the berries, or Jane who is somehow so pregnant she can barely walk and who's last kid was born with a massive cone head and no kneecaps.

What makes us unique as a species is that we have a much larger ability to influence what exactly defines environmental fitness than others.
When we develop new medical treatments, we are potentially making ourselves less robust going forwards, but we're also making it so that particular thing has less weight in determining what "fitness" means for a human, and more weight is put on "clever" and "social".
Natural selection selected for a creature that can't opt out of the game, but can bump the table.

So we will inevitably allow a genetic condition that's currently awful to become benign and commonplace.
We'll also keep selecting for smart, funny, social and dump truck hips.

My biggest contenders are diabetes, gluten intolerance and hemophilia. They all used to be death sentences, and now they're just "not". There's also the interesting possibility of heritable genetic treatment becoming possible, which puts a lot of what I said into an interesting position.
We'll probably keep selecting for those big hips though.

The entire point of medicine is to give nature the finger. The goal is to make natural selection obsolete. We can certainly screw it up enough to wipe us out though or be unfair with it.

Yes, but I'd argue that capital has a more profound impact than "modern medicine".

There is a massive MASSIVE selection pressure against reproduction for if you can afford kids or not.

You can look around the world and see countries with amazing health outcomes, beyond anything our ancestors even a few generations back could have dreamed of...

... And yet these countries no longer even have children at a replacement rate.

I'm not saying medicine isn't a factor... Just saying that in terms of evolutionary pressure, capitalism is even greater a pressure.

I don't think so.

For one, natural selection selects the "fittest", but what the "fittest" means, changes over time.

Also, there's lots of other factors that you may have overlooked, such as sexual selection probably playing a bigger factor.

A quite different approach: modern medical practice uses a whole lot of medicine, which ultimately ends up in (waste) water, and becomes an environmental problem, including a health hazard to humans. https://www.sciencedirect.com/science/article/pii/S2772427122000390

Also, a point I don't see others mentioning, is religious people often tend to have more children, and whilst religion isn't actually hereditary, children often do have more likelihood to follow the same religion as their parents, the population is likely to tend to more extremist religious people, unless the rate of conversion away from those religions drastically increases.

Yes. Without the selection pressures to minimize disease, we observe more disease in the population over time. This reduces our fitness for any environment without the artificial benefit of modern medicine.

People don't want to understand because it is difficult and challenges their worldview. Is this an existential risk? Yes. Can we do anything about it? Yes.