THE DEMOGRAPHIC FATE OF intelligent SPECIES: 1/7. Will our 200,000-year-old species endure until the death of the whole universe, tens of billions of years away?

1/7. Will our 200,000-year-old species endure until the death of the whole universe, tens of billions of years away?

What are we in this boundless universe? With current technology, it would take at least 19,000 years to send a human to Proxima Centauri, the star closest to our Sun at just 4.24 light years away. For a quick star count, there may be up to (200 billion stars per galaxy) times (200 billion galaxies) within the observable universe. And if one existed in each galaxy, there would be around sentient civilizations alive across this universe. If all stars, planets, and living things appear then disappear obeying the same laws of nature, does every cosmic civilization follow the natural birth-death course, here or ten billion light years away? Are intelligent species just wildflowers in the cosmic desert, forever fading here and blooming there? As humanity had no say in its own emergence on this specific Earth, being but evolved wild nature, are we also headed for an inescapable natural ending? How could a highly evolved society of aware individuals consciously fade away?

An aware species on a deterministic extinction path won’t surprise if you recognize how important things in the world - from your smelly, aging carcass to the whole dissipating universe - just run their own courses, against which your cute awareness is powerless. All things age and die: youthful bodies and memories, the Sun and every other star up there... Even the whole of everything also dies. All cosmic civilizations are faced with this hard reality: the universe, the entire physical world that hosts us, is irreversibly heading for demise. Our ever-dispersing universe is not static since forever. At the end of its ongoing, relentless expansion, started at the Big Bang 13.8 billion years ago, the whole thing will die out. It will be one of those hellish futures, none realistically allowing for life's continuation: absolute coldness (the Big Chill), complete disintegration (the Big Rip), terminal inferno (the Big Crunch) or being suddenly sucked down a wormhole (the Big Trip). In a Big Crunch scenario, the universe may follow an eternal cycle of death and rebirth where, in a new Bang, it all restarts again after the collapse phase, which unfortunately we can't survive. While our inquiring minds may learn about the course of the world, there is nothing we can do to alter it. In energy terms, humans are to the expanding universe what germs are to the circling Earth. Even if our species manages to move elsewhere to avoid the Milky Way's slated collision with the Andromeda galaxy in 3 billion years or the Sun's programmed death in 6 billion years, there is nowhere we can go to escape the scheduled end of everything.

With the ultimate fate of all life forms already sealed by the laws of physics, the remaining question is how a sentient civilization will collectively approach something all individuals must face: death. Will humanity, and other intelligent species out there, try hard to endure until the very end of all worlds, expected no sooner than tens of billion years from now? Or are these clothed apes, like other kings of their day: t-rex dinosaurs, megalodon sharks..., set to naturally vanish long before the end date of the whole universe? Will we fade away willingly or unwillingly? In fun or in pain?

For the end of humanity, wild and serious theories have been proposed for millenniums. Most are doomsday prophecies where God's anger, natural disasters, nuclear war, environmental collapse, super-virus, ET invasion, AI rebellion… force us into an unwanted and painful extinction, precisely the type of fate befalling nature's lower species. Many of these threats are all too real. Like an individual's car crash or alcohol addiction, a species may die young because of abrupt, unlucky accident (an asteroid from space did the dinosaurs in) or slow-burning lifestyle issues (consumerism-induced environmental destruction). Genetic research on human history indeed points to a perilously exposed moment some 70,000 years ago, when a severe "population bottleneck" of unknown origin saw our species hanging precariously at a few thousand individuals. Mankind's existence and its unique brainpower - something we hold dear - have a lot to do with luck: no big asteroid has been Earth-bound since our species' emergence in Africa 200,000 years ago. If we are here by good luck - 200 quiet millenniums aren't much on the billions-of-years timescale of the universe - we may as well disappear by bad luck. Regardless of luck, humanity's very own idiocy can also lead to a youthful demise; an ecological suicide might be forthcoming if we keep senselessly disrupting the biosphere's delicate balance. As with each of us, a premature end is always possible for our species.

If a youthful death doesn't occur, will humanity, and other intelligent societies in the universe, still face the equivalent of an individual's "getting old and die"? Everything dies eventually in the grand scheme of things. Do high-tech species grow old and die naturally, like their home stars, my body, and yours? Will a peaceful and consensual fading away await humanity at the end of the road, exactly the kind of serene conclusion preferred by many humans for their own biological lives?

As population aging spreads around the planet, one such scenario may be unfolding at this very moment, right before our eyes. Does high median age conclude the natural life cycle of an intelligent species the way old age ends all individual lives? In more than 80 countries - almost entirely the upper half of the UN Human Development Index - birthrates have fallen below 2.1 per female lifetime, which is the minimum needed to keep a constant-sized population. Apart from a shrinking society, as below-replacement fertility makes the new generation smaller than its predecessor, it also lowers the percentage of youth in total population. As median age rises, society becomes increasingly dominated by seniors. According to UN projections, due to the remaining momentum in the low-income countries, world population will peak above 9 billion at the end of the 21st century before climbing down, as sub-replacement fertility spreads to more places. The demographic descent from the top would be steep if all countries followed Japan's current lead: Earth's third largest economy is now losing more than 200,000 people every year. At present birthrate, this ancient nation would see its citizenry halved over the next hundred years. And, even more importantly, Japan's median age would be well above 60 by 2100. Will this first hyper-aged society be the prelude to a high-median-age humanity later on? From its projected 9.x-billion peak at the end of this 21st century, let’s assume for the whole species the slightly below 2.1 birthrate of envied Sweden or Denmark and world population would easily drop by half by the year 2500.

A population drop from 9 billion to 90 million and a rise in median age from 25 to 72 don't automatically mean that such aged and small species can't monkey around for another 20 billion years, in a prolonged demographic winter. With enough luck, anything can happen. Living a fortunate life of no big disease or unhealthy habits, some humans can last until their 120th birthday. No one lives eternally, however. There are no fixed rules for how long a species could survive, yet none of the life forms that roamed the Earth when life started here some 3.7 billion years ago is still around today, with the same DNA. No species exists since forever and none will last forever. As evolution has set us distinctly apart from other creatures in terms of brainpower, will our eventual ending be in a category of its own? While no species has ever given up on life, all blindly multiplying until being wiped out by unfavorable conditions, would mankind go the unique way of a conscious and apathetic fading? An increasingly higher median age for the whole of humanity, caused by our low enthusiasm for offspring, might lead us down this unprecedented extinction path.

Rather than immediate death, a species-wide demographic aging simply creates a pint-size high-median-age society that will be much more vulnerable to adverse events. For the rest, we have Murphy's Law: whatever can go wrong will. Like a fragile 80-year-old body that can be easily finished off by some trivial cold, an aged humanity must face a long list of things that can go wrong: pandemic outbreaks, asteroid strike (it has been a while!), machine malfunctioning… For all our scientific brilliance, microscopic viruses are still, for one thing, mankind's deadliest predators. Common flu, not steel weaponry, brought to the Americas by immune Europeans might have decimated up to 90% of the native population (is this why ETs avoid us?). Nowadays, Ebola, West Nile, H1N1... are all incurable viruses that can get us k.o.'ed, pending a few random mutations. Adapting scarily fast to man's best-laid medical schemes, they are always out there testing human weaknesses. Immunologically, the smaller a population gets, with a less diverse gene pool, the weaker its chance to withstand a pandemic outbreak.

With or without external shocks like deadly viruses, AI rebellion, random asteroid... with most of its members over 70 and tired, a hyper-aged society may see its very appetite for life greatly diminished. The end of mankind might not even require adverse events, just a computer-sustained society full of senile half-present VR/TV/pot fans who don't care anymore. If he/she/humanity in the future no longer care about the species, who am I to judge, here and now? In an anti-climax ending, the last humans, surrounded by robotic attendants, could calmly code for the lights to turn off after them. They could also opt to set the machines free, which may lead to a new era of sentient machine civilization, just like the Transformers'. Or a complete and total stop, if the robots can't really handle living without human input.

Is this graying of humanity the late stage in a natural life cycle common to all intelligent societies in the universe? Do smart species just bloom and fade wildly across infinity, like those improbable flowers in an endless barren desert, surreal yet so real? Even with the infinitesimal odds of, say, only one high-tech society for every galaxy, there would still be 200 billion concurrent civilizations throughout this 200-billion-galaxy universe? And our observable universe may be just one of endless bubble universes in existence? How likely can this scenario of high-median-age extinction be for other intelligent species out there? The aliens could be so different from us that none of our concepts would apply to them? ETs will be truly different if they are immortal. Biologically, however, there may be no immortal life anywhere, as this impermanent universe is relentlessly expanding towards a scheduled demise. Without immortality, all intelligent beings in the universe should intimately understand dying and their societies must all have a measurable median age. Getting old may be a truly universal experience. Like your home star, you're born, you change then you die. You can live for 1000 Earth/Pluto/whatever years, all you have is your being in this moment and the knowledge that your existence is not forever. There are a before-you and an after-you. In this sense, time may unify all creatures of the universe. All lives – you, me, the gooey aliens ten billion light-years away… - are indeed equal before time.

Accidents aside, is there a natural ending common to all intelligent societies in the universe, past, present, and future? Are we seeing here on Earth, in our rising median age, the immutable law of nature that deprives us of (or saves us from) an ET visitor? Such questions may not be easily answered, yet at least we now have this elegant empirically-based theory of demographic aging to disprove. As population aging and atrophy are widely observed in the only alien civilization we can examine so far, our own, would this simple scenario be, methodologically, the most-substantiated hypothesis until proven otherwise by more real-world cases? 

So this human species, too, shall pass? Is that good, bad, or just neutrally natural? Can we make a value judgment of this trend towards an older and smaller humanity? While a complete disappearance of our species in the very far future might be natural and neutral, a reduction in human number over the next few centuries could give us an unexpected break. Though most people have fewer kids for selfish reasons other than the environment, those self-interested reproductive decisions can, in aggregate, give the environment an unintended but much needed relief. As human population exploded from 1 billion in 1816 to 7 billion in 2016, the pressure on Mother Nature has intensified immensely. What if she fights back for her other offspring who are being massacred by our aggressive multiplication? What if 3 or 4 billion humans would die from the coming total loss of antibiotic effectiveness, because Big Agriculture massively abuses those drugs to produce enough meat for glutton consumer societies? A loss of one half of a species being so common in natural history, it doesn’t even mean inexorable extinction, just an ordinary correction. Historically, as recently as the 14th century, the Black Death killed around 40% of European population. The loss of 40% of today’s humanity, nearly 3 billion deaths in this era of intercontinental flight, would only bring world population back to the 1960s level. Given the serious danger we may have stupidly brought ourselves into, wouldn’t it be better to have a soft landing where, thanks to a shrinking humanity, environmental pressure gradually drops over a few centuries than to suffer a quick, hard correction where 2/3/4 billion die in just a few years from an untreatable viral mutation? The difference between the two scenarios would be all the saved lives that might otherwise be lost in a dramatic reset. Will we have enough time – a few hundred years - for a demographically-enabled ecological renaissance or a correction will strike before then, that is another question. Will we be lucky enough?

Let’s think about all these on the last steps up the population peak, a watershed moment in human history that many of us may witness in our own lifetime, in this very 21st century.

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