The universe is enormous on a scale beyond comprehension. In the Milky Way alone, there are ~100 billion stars, with an equal number of planets. And this is just in our backyard. Across the entire universe, there are an estimated 100-200 billion galaxies. If each galaxy, on average, is the Milky Way's size, there are a mind-numbing number of stars and planets. Our caveman brains aren't equipped to understand just how big the universe is.
On the other hand, exoplanets that can sustain life are, in fact, pretty rare. They must be the right distance from their host star, have suitable atmospheric composition, have the right gravity, etc. But even if finding a host star with a habitable exoplanet capable of sustaining life is rarer than winning the Powerball (or 1 in 292 million), there should still be trillions and trillions of habitable earth-like planets in the universe. In reality, the odds are much better. Just looking in the Milky Way, NASA's best guess is that there should be a few hundred million habitable planets. With many of these stars and planets being much older than our solar system, why are there no signs of life? Why are we seemingly alone? In a nutshell, this is the main question the Fermi Paradox asks.
Many hypotheses attempt to answer the Fermi Paradox, but the one I find most interesting is the idea of a "Great Filter". This states that on the way to colonizing the stars, all life runs into an inevitable "Great Filter", leading to the end of said lifeform, or at least ending that specie's progression up the Kardashev Scale. This "great filter" could be ahead of Humans, or if we're really, really lucky (fall out of an airplane without a parachute, get hit by lightning on the way down, survive, and then win the Powerball later that day), it could be behind us. It's also worth mentioning that, however improbable, humans may be the first species to colonize the stars.
Let's explore the scenario where we have yet to hit the great filter. Standard proposals for "great filter" endings include things like man-made superweapons ending life on Earth, life-ending natural disasters like a supervolcano / asteroid / megatsunami, super viruses, alien invasions wiping out life, etc.
I'd like to propose another category that is more subtle and less spectacular. It's the empathy of a species. On an evolutionary timeline, we've only just started to climb the intelligence ladder. For a quick perspective check, in the US at the turn of the 20th century, only 50% of households had indoor water and electricity. We are much, much more primitive than we like to think.
What do I mean by the empathy of a species? I'm talking about the period of time when a species moves away from "survival of the fittest" based on the sheer difficulty of existing in a species' environment to the period where they have "conquered" their environment. That species (humans) can then take their foot off the evolutionary accelerator and begin changing their environment to adapt to their genetics instead of continuing to naturally allow their gene pool to evolve with the environment in the name of comfort. In the short term, this is sustainable, but in the long-term, I suspect nature always wins out.
Before I continue, I'd like to clarify that this section may come across as unfairly critical to the state of healthcare today. To be fair, these are extremely challenging problems that minds far brighter than mine are working towards solving. The problem is we don't have the technological breakthroughs that enable our species to make, evolutionarily speaking, meaningful progress in healthcare yet. Until very recently, the most significant breakthroughs in healthcare consisted mainly of accidentally discovered treatments (antibiotics), vaccines (ex: smallpox treatment found through cowpox), or butchering tissue and hoping the body repairs itself in the right way (surgery). Not sure what I'm talking about? Watch a video of an orthopedic surgeon replacing a hip. Most early-stage human cancer trials are a shot in the dark. Chemo is the equivalent of firebombing a city, trying to kill all the weeds but spare the buildings. Collateral damage is immense. I acknowledge I'm vastly oversimplifying here, and on the cutting edge, we are starting to get "smarter" with our treatments. Still, even these solutions are closer to "tricking" our immune system into doing our bidding rather than directly intervening. To give an analogy, we're dressing up as a robber and running to the bank, hopeful that the police show up to arrest us and the actual criminal instead of telling the police, "go to the bank and arrest the bad actor".
Our lack of advanced cancer treatment isn't a threat, per se, to the long-term survival of humans, however. The real problem is that we as a species have become very good at finding band-aids for medical problems. Let's take food allergies, for example. We haven't figured out how to repair faulty genetic code to instruct your immune system not to trigger a massive response when you ingest food you're allergic to. However, we have invented a wonderful band-aid to suppress that immune response via epinephrine autoinjectors (aka EpiPens). If we were "smart", we'd fix our genetic code and eliminate the need for Band-Aids in the first place. Nature's solution was that someone whose genetic expression triggered a life-threatening reaction to certain stimuli (i.e., peanuts) would quickly have their genes removed from the human gene pool, making it much less likely for these genetics to persist.
Had we as a species mastered the fundamental building blocks of life, we should be able to engineer organic material to do exactly what we want. After all, the ~37.2 trillion cells in your body all originated from just one diploid cell. Talk about an insanely complex instruction set. Why couldn't we engineer genetic material to go in and repair the genetic code in your existing bad hip to repair and regrow it good as new?
While we're on the topic, why don't we continuously regenerate and live forever? The reason is evolution. Evolution wants continual change in a species. This may seem like a "bug" but it's really a feature. Survival of the fittest. Cycling of genetic combinations to create species fitter for an environment than the last generation. That's how a species adapts to a constantly changing environment. 99.9% of species that have ever existed on Earth are now extinct because they couldn't keep up. Evolution works because nature is very good at purging bad genetic code from the gene pool of life. Despite all the species that didn't make it, life is still incredibly prolific on Earth.
Our band-aid approach to being comfortable as a species becomes problematic when these tiny genetic imperfections, which are relatively easily treated via modern medicine, compound over time. Just 10 generations ago, or in a blink of an eye on an evolutionary timeline (26.9 years avg / generation or 270 years ago), you would have 512 7th great-grandparents and a total of 1022 "unique" ancestors when summing all "parents" that contributed to your genes from your generation to 10 generations ago (assuming no inbreeding within the same gene pool; unlikely at this scale but a topic for another time). Another way of putting this is 10 generations from TODAY, children will be born with parts of DNA from 512 different people living now. This means that keeping just a tiny fragment of harmful genetic code around could have a significant impact down the genetic line.
Before we had "modern" medicine, if there was a combination of genes not well-suited for their current environment, that human was unlikely to make it to reproductive age to pass on said "faulty" genes. Times were tough. In the 1500s, you had roughly a 50/50 shot of reaching the age of 15. What a horrendous experience for parents, where you could expect only half of your children to make it (and this partially contributed to why parents had so many kids back then). While many of these deaths were completely preventable and not gene-related, nature was weeding out a massive percentage of genes that were non-optimal for their current environment.
You might be thinking, "so what, you're proposing to ignore modern medicine for the survival of our species?" No, not at all. If my child has a severe peanut allergy, they will have an EpiPen 24x7. Nor am I saying anyone should have to suffer for "the good of the gene pool". What I am saying though, is that if we don't get smart fast and learn how to deeply understand and repair the human gene pool, future generations are in for a very bad time.
What we've accomplished with our modern medicine Band-Aids is to enable many genes that would otherwise not persist to be passed on to future generations and remain in the human gene pool. It's easy to imagine a future society hundreds of generations from now, where humans cannot function in any semblance of a natural "environment" and rely heavily on modern medicine and an indoor artificial environment just to exist. I imagine "natural" living, or living without medical intervention, will become exceedingly rare. We as a species are making an unconscious tradeoff between short-term comfort (on the timescale of your life) with long-term species-wide suffering. This will set up our species to exist in a highly fragile state, where a futuristic "dark ages" that knock out modern medicine for some time would cause mass death and send us back to the stone age. While this sounds all doom and gloom, I don't think our species would go extinct from a medical "dark ages", as small clusters of humans will almost always persist. This does have a good chance of turning back the clock of progress for our species. Every time we start to build up our society and approach becoming a next-level civilization, a great reset will occur.
Unfortunately, it's the way we're wired. We're empathetic creatures, and we're very good at finding the path of least resistance. We're not going to withhold medical treatments for "the good of the gene pool". Presumably, as every species progresses towards becoming a "Type 2" civilization, they too will go through a period of "modern medicine" where they are really good at making band-aids but haven't quite cracked the genetic code of life yet. The question is, what comes first, cracking the code or the band-aid apocalypse?