eli5: What will aging look like in the future?

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If in the past, life expectancy was 50ish, and is now expected to rise to 100, would this mean that signs of aging (grey hair, wrinkles, bones and muscles becoming weaker) would happen later in life at around 70-80?

In: Biology

It depends on how the change in life expectancy is achieved. If it’s done via a change in daily behaviors and habits, then you may see people who are still fit and healthy at older ages than typical. If it’s done via medical intervention for conditions associated with aging, then there won’t be a change in when signs of aging show up, and just a delay in death; more elderly people who are still infirm, but aren’t getting sick or as sick.

Human aging has always progressed at the same rate. A few millenia are nowhere near enough for such profound biological changes to happen as a matter of evolution. We live so much longer nowadays because we get sick much less, and when we do we have access to massively better treatment.

It’s difficult to envision how aging might be slowed and the human *healthspan*, as it’s called, lengthened. Advances in technology might eventually allow it, to some degree, but anything more would just be wild speculation.

Past life expectancy numbers were mainly brought down by lots of childhood deaths, childbirth, and warfare. People weren’t older at 50 than they are now, although you can argue they were on average a bit less healthy due to poor diet and medical care. Surviving to 90 or 100 was rare but not unheard of among those with healthy finances.

If you look to some healthy, long-living groups in the modern day, that’s about as much as you can hope to get out of human aging. Lifespan naturally caps out at about 100 or so regardless of medical care.

There are theories that there is an upper limit to natural human aging, that ~125 is just about as old as you can go, no matter how ideal your health and environment get. As it is, signs of aging aren’t delaying – we’re still all starting to gray in our 30s, etc.

That said, of course we are trying to extend life well beyond natural boundaries, and there’s nothing known that is inherently preventing us from artificially extending life. I think it’s a bit optimistic, but some like Aubrey de Grey say the first person to live 1,000 years has already been borne. Listening to him talk about it, he says all the big problems with essentially indefinite aging have been solved, there’s now just a lot of little problems.

If we’re going to live this long, we’re going to want to deal with all the degradations of our various tissues. No one wants to be a brittle old man for a thousand years. And in such a long lifetime, you’ll lose your teeth, you’ll probably lose eyes, or fingers, and so we’ll want to be able to repair damage that is statistically unavoidable and otherwise permanent. What would you do for a thousand years missing your arms?

Aging to death isn’t inherent to life, it’s actually an evolutionary strategy. It’s both offensive and defensive. Offensive, in that future generations can adapt to take advantage of their environment and be more competitive. Defensive, in that by dying, you make space for those future generations, and the population isn’t essentially static and vulnerable to mutating and evolving competitors – viruses and bacteria, principally. One good pandemic could wipe out the whole species if it wasn’t in a state of constant, fast paced evolution. And indeed, there are species that are effectively immortal – some jellyfish are very famous for this property. We speculate many species of sharks can be immortal, as well. Yes, they breed and reproduce as well, but their populations don’t see endless growth like ours do, and they have different selection pressures on them that long life is an effective strategy for them, and has been for millions of years.

Average life expectancy is an average. This is something that people often forget.

If a family walks in, including a mother (31), a father (33), a baby (1), a toddler (3), and a grandpa (67), the average age of that group is 27. If they all died together in a car crash, the average life span of that family was 27. Do you see how that kind of number works?

In times past, we lost lots of people in infancy and early childhood. Ages 0-5 were the danger years. About 45% of babies died.

If you survived those years, and childbirth if you were a woman (around 1 in 30 births were fatal) then you had a pretty good shot at making it to 65.

65 was the average life expectancy for a human being who survived infancy for most of history.

Then came three amazing innovations:

Antibiotics

Vaccinations

The Sanitation Movement

These three things have extended the average life expectancy by 20 years.

(The Sanitation Movement is the reason we have sewer systems, the reason we do not have public spittoons, the reason we wash our hands after going to the loo, the reason we have food safety standards, and the reason we have PSAs right now about keeping a safe distance and wearing your mask.)

So, ageing in the future will likely continue to look like ageing has looked in the past. We have not prevented ageing. We have allowed it to happen. And that’s great, because dying young sucks.