I have been thinking about the impact of AI on health and what that will do to the concept of age.  Usually when we talk about longevity, we think about how much longer people will live.  Those of us who are more sophisticated about this topic break it down into health span and sick span, hoping we will have not only more days but better days.

We may wonder if we will reach 100 or 120 or perhaps live even longer. This may be the least interesting question.  It assumes that we will just slow down our aging, but otherwise things will remain the same.  I don’t think it will be that simple, and the results might redefine who we actually are.

Today we define aging as a simple process. I am 81. Next year I will be 82. If I am fortunate enough to be around ten years from now, I will be 91. That is chronological age, and there is nothing to be done about it. Time marches on. As the joke goes, “aging is better than the alternative.”

But there is another concept: biological age.  This is an estimate of how old your body is functionally and physiologically, rather than how many years have passed since you were born.  There are a number of ways it is estimated. I will not go into that here.  Frankly, the various methods are still very primitive.  Most provide a single age.  I had my biological age measured by TruDiagnostic about three years ago. I was delighted that my biological age was computed as 15 years younger than my chronological age.  But I do not give this test or the other commercial tests much validity. They do not deal with the complexity of our bodies, and giving  age one number is where the biggest mistake starts.

An essential issue of age is that not every part of us has the same life expectancy.  This has great implications. Imagine an 80-year-old whose body functions like that of the average 70-year-old. Now suppose medicine becomes increasingly effective at slowing aging. Ten years later that person is chronologically 90 but biologically 75. That would be quite an accomplishment.  At some point his life expectancy would increase by a year every year.  This is what is referred to as longevity escape velocity.  But as I said, just living longer does not really communicate what is likely to happen.

So far the focus has been on slowing down the aging process.  But it is likely that we can actually reverse aging at some point. Now take it one step further. What if we become capable not merely of slowing biological aging but of reversing some of it? Our 80-year-old who was biologically 70 reaches 90 chronologically and has become biologically 60.

Chronological age went up ten years. Biological age went down ten years.I imagine a graph showing this, but the more I thought about it, the more I realized it was the wrong graph.  It was one-dimensional because we are not a uniform age already.  Some of us have hearts five years younger than our chronological age but knees that are ten years older.

We Have Never Been One Age

There probably isn’t any such thing as one biological age. My liver could function like that of an average 60-year-old while my kidneys function like a 70-year-old’s. My cardiovascular system might be another age, my muscles another, my immune system another, my brain another.

This isn’t science fiction. Human aging has always been heterogeneous. Different organs and systems age at different rates, and researchers are now developing ways to measure those differences. So perhaps we shouldn’t talk about our biological age. We should talk about our biological ages. We have always been mosaics of age.

What AI and biotechnology will do is make those differences much greater. Suppose we become very good at rejuvenating muscle but nowhere near as good at rejuvenating skin. I might look 70 and have the strength of a 40-year-old. Suppose we also become extraordinarily good at maintaining cognition. I could have an 80-year-old face, 70-year-old kidneys, a 50-year-old cardiovascular system and a brain performing like a 40-year-old’s.

So how old am I really?

The question itself begins to lose its meaning. Knowing one’s chronological age is a recent development.  But it has become a big factor. It has been remarkably useful shorthand. It is important data with respect to understanding someone’s personal history and the things they may have experienced, but it does not tell you their biological age. Tell me someone is 20, 50 or 80 and I immediately have some idea of what that person looks like, how strong they are, what they are physically capable of and, to some extent, what their health risks are. Those things have always travelled together. Perhaps they won’t anymore.

We May Be as Old as Our Weakest Part

There is another way I think about aging, particularly when I think about myself. I sometimes say that we are as old as our oldest critical part. More precisely, we are as old as our most vulnerable critical part.

I can be in excellent shape. My muscles can be strong, my brain can function beautifully, and my heart can be doing its job. But my kidneys are giving out. If one essential system is deteriorating rapidly, that system may determine how long I live. The average doesn’t help when a single critical component fails.

This is one reason I spend so much time trying to understand what is happening inside my own body. I look at blood tests, MRIs, heart data, sleep data and anything else I can measure. I am particularly interested in trends. I don’t simply want to know whether today’s measurement falls within some population’s definition of “normal.” I want to know whether something is changing. I stay alert.

In a real sense, I am hunting. I am trying to identify, as early as possible, what is going to try to kill me. I don’t think of that as morbid. I think of it as sensible. If something is going to become a serious problem, I would much rather discover it five years too early than six months too late.

Cancer is a good example. I have already dealt with it three times: prostate cancer, melanoma and bladder cancer. I don’t think that means I have won my war with cancer. I have won three battles, and I assume there could be others.

Surveillance is part of staying alive.

This is one of the areas where AI will make an enormous difference. Today medical information is fragmented. One specialist looks at one system. Another physician looks at something else. Blood tests are taken occasionally, imaging is done occasionally, and wearables produce still another stream. Each provides a piece of the picture. But who is continuously looking at the whole?  I have now integrated all my medical information into an AI agent—an agent that has access to 30 years of my medical data and knows my blood chemistry, imaging, medications, genetics, exercise, sleep, heart rhythms, blood pressure, cognitive performance and hundreds of other measurements, as well as my genetic information. More importantly, it knows me. It can see patterns most, if not all, doctors would miss. Instead of asking whether today’s kidney measurement is normal for an 81-year-old man, it asks whether something has changed from what has been normal for Avram over the last fifteen years. Perhaps no individual change is alarming. But the agent sees five subtle changes occurring together and says: something is happening here. Let’s find out what it is. It can also make suggestions about the things that I can do to improve my longevity.

This will transform medicine. We would move from waiting for disease to reveal itself toward continually searching for the next weak link. Fix the cardiovascular problem and perhaps the kidneys become the limiting factor. Fix the kidneys and perhaps it is cancer. Control cancer and perhaps neurodegeneration becomes the problem. Then we go after that. Longevity becomes an ongoing process of finding and repairing the next weakest link as well as strengthening the others.

What if we don’t grow old together?

There is another consequence I hadn’t thought about until recently. We assume that people grow old together at the same rate.

Imagine a couple who are five years apart when they marry. Fifty years later they are still five years apart. Chronologically, that will always be true. Biologically, perhaps it won’t. Suppose a new rejuvenation treatment becomes available. One partner responds extraordinarily well because of some combination of genetics, immune function and biological circumstance. The other doesn’t. Ten years later they might be chronologically 85 and 90, but one functions like someone who is 50 while the other functions like someone who is 85. A five-year difference has effectively become a 35-year difference.

What does that do to a marriage? One person may want to travel, work, ski, start a company or begin another entire chapter of life. The other may increasingly need care. We have always talked about growing old together. Perhaps some couples won’t.

And then it gets stranger. Suppose their children are in their sixties. The rejuvenated 90-year-old parent could be biologically and functionally younger than their 65-year-old child. Who is the old person? Who takes care of whom?

We are accustomed to generations moving through life in a predictable order. Parents get old. Children become middle-aged. Eventually the children may care for the parents. But what happens when biological age no longer respects generations? Two people born on the same day might eventually be biologically separated by decades.

If we want to have children at a later age, we will be able to.  So it will not be so uncommon to have parents with children younger than their grandchildren.  Yes, another breakdown in what we have considered to be normal.

Human relationships are based partly on the fact that we move through life together. Changing the rate at which individuals age could therefore change marriage, friendship, caregiving and the relationship between parents and children. One of the strangest consequences of defeating aging may be discovering that we no longer age together.

What happens to the stages of life?

That raises an even larger question. Our entire civilization is organized around the assumption that a human life follows a predictable curve. We grow up. We go to school. We work. We raise families. We retire. We grow old. Eventually we die. We can divide life into three ages: the first is where we learn, the second is where we apply, and the third is where we retire.

Why should education be concentrated in the first twenty or twenty-five years of life if you might remain cognitively vigorous for a century? Why have one career? Perhaps people will have five. Why retire at 65 if you are biologically 45? Why accumulate money for a retirement that may last longer than your entire working life once did? Why inherit your parents’ money at 60 if your parents are biologically younger than you?

Longevity could require us to redesign institutions we don’t normally think of as having anything to do with biology: education, careers, retirement, marriage, inheritance, pensions, politics. The stages of life themselves may begin to disappear.

Youth may become a luxury good

There is also an uncomfortable economic dimension to all of this. The first really effective rejuvenation technologies are unlikely to be cheap, and wealthy people will probably get them first. That could create an entirely new way of displaying wealth.

Today we recognize wealth through houses, cars, clothes and travel. In the future we may recognize it by looking at the person. You meet someone who is chronologically 85 but looks 60, moves like someone who is 45 and has the energy and cognitive ability of someone decades younger. You immediately know something about them: they can afford it.

But there is another possibility. People may change what they choose to spend their money on. Suppose you aren’t extraordinarily wealthy, but you have accumulated some savings. You can buy a bigger house. You can buy an expensive car. Or you can buy another ten healthy years. What do you choose?

I suspect a lot of people will choose the years. The ultimate luxury may turn out not to be something you own. It may be time. Or, more precisely, the ability to remain capable while time passes.

Politics Without a Single Age

Politics could get particularly strange. Today an aging politician inevitably faces questions about age. But imagine an 82-year-old candidate saying: “Yes, I am chronologically 82. But my cardiovascular age is 58, my cognitive age is 52 and my physical performance is equivalent to the average 55-year-old.”

Candidates might release biological-age reports alongside their medical records. Of course, we would immediately begin arguing about the measurements. Which test counts? Who administers it? Can campaigns choose whichever biological clock makes their candidate look youngest?

But the fundamental political question could change. Instead of asking whether this person is too old to be president, we might ask which parts of this person are actually old.

And there is a more uncomfortable possibility. If rejuvenation is expensive, wealthy politicians might be biologically younger precisely because they can afford treatments unavailable to many of the people voting for them.

The geopolitics of youth

The same paradox exists between countries. Many of today’s richest countries are also among the oldest. Birth rates are low and populations are aging. Meanwhile, many poorer countries possess something rich countries increasingly lack: young people.

But what happens if wealthy countries learn how to make old people young? Not chronologically young; an 80-year-old remains 80. But suppose that 80-year-old has the cardiovascular system of someone who is 50, the muscles of someone who is 45 and the cognitive capabilities of someone considerably younger. Suddenly an aging population doesn’t necessarily mean a declining population.

We could have two kinds of young countries. One is young because its people were recently born. The other is young because its people can afford not to become biologically old. Which has the greater advantage? I don’t know.

A young African country might have millions of energetic people entering the workforce. A wealthy European or Asian country might have scientists, physicians, engineers and entrepreneurs remaining highly productive into their eighties and nineties. Imagine a scientist with sixty years of experience and the cognitive capabilities we currently associate with middle age. Experience itself begins to compound.

And eventually rejuvenation technologies may become inexpensive. Then the balance changes again, as countries with large populations of naturally young people acquire the same technologies. Perhaps someday we won’t simply ask how many people live in a country or what their median age is. We will ask how old those people are biologically, and who can afford to keep them young.

Why stop at just younger?

But there is an assumption buried in everything I have written so far that I increasingly question. Why is youth the objective? Why should I be satisfied if, at 90, I have the cognitive capabilities I had at 40? Why shouldn’t I be smarter than I was at 40?

I think of myself as a cognitive athlete.  I believe cognitive training has played an important role in my own cognitive development. I have never been interested simply in holding on. I want to get better: to learn faster, recognize patterns better, improve memory and attention, understand complicated things more easily. I don’t merely want to avoid becoming less capable as I get older. I want to become more capable.

AI could make that idea enormously more powerful. Imagine an AI that understands precisely how I learn, that knows my strengths and weaknesses and continually develops experiences and exercises designed to improve my cognition. Combine that eventually with advances in neuroscience, pharmacology, neurostimulation, brain-computer interfaces and things we haven’t yet imagined. Then perhaps the objective isn’t maintaining intelligence. It is increasing it.

Could we turn ordinary people into what we would today call geniuses? Why not at least ask the question? We accept that years of training can transform an ordinary human body into that of an extraordinary athlete. Why assume the brain must remain permanently limited to whatever nature happened to give us?

And why stop with the brain?

I have never thought of myself as a physical athlete. It simply hasn’t interested me very much. But it interests lots of other people.

Imagine someone who has spent a lifetime running. Today, success at 80 means running remarkably well for an 80-year-old. Perhaps someday that qualifier disappears. Suppose regenerative medicine restores muscles, joints and tendons. Cardiovascular treatments improve oxygen delivery. AI continually optimizes training, nutrition and recovery for that particular individual. At 85, that runner might not merely run as well as she did at 60. She might run faster than she did at 35. A swimmer might set a personal record at 90. Someone might become stronger at 75 than they ever were at 30. Then the familiar human life curve of growth, peak and decline no longer describes us. Perhaps your best memory occurs at 75. Your greatest intellectual achievement at 90. Your fastest running time at 80. Your most creative period at 100.

“Longevity” seems an inadequate word for that. This isn’t simply living longer. It is continuing to develop.

How old would you feel?

There may also be an age that has nothing to do with biology.

Suppose I am chronologically 110. My body functions like that of someone who is 50. My cognitive abilities are better than they were when I was 40. But I still have 110 years of memories. I have watched people be born and die. I have experienced relationships, successes, failures, grief, love and perhaps several completely different careers.

Would I feel 50? I doubt it.

We might create people who are physically young and cognitively extraordinary but psychologically unlike any humans who have ever existed. Imagine possessing the physical vitality of middle age with a century of lived experience. We have no idea what that person would be like.

Just speculation

Almost everything I have described may prove wrong in timing or degree. Measuring aging is not the same as reversing it. AI may give us increasingly sophisticated maps of how our organs are aging long before medicine gives us reliable ways of making those organs young again. Some forms of aging may prove extraordinarily difficult to reverse. Some interventions may work only for certain people. Some may have consequences we didn’t anticipate. There is no guarantee that an 80-year-old will ever be able to become biologically 50.

But I don’t think we need to know that these things will happen to think seriously about what would follow if even some of them do. The direction of travel is already interesting. We are getting better at measuring biology. We are getting better at manipulating biology. And AI is getting better at finding patterns in complexity that human beings could never hope to understand unaided.

Put those three things together and it seems reasonable to ask some very unreasonable-sounding questions.

We created AI. Will AI create us?

And that brings me to the strangest thought of all.

Humans created AI. But perhaps AI will create the humans of the future.

We created artificial intelligence with the brains evolution gave us. Now AI may help us understand those brains well enough to improve them. Those improved brains may then become better at creating AI. That more powerful AI becomes better at improving us. And around we go.

Smarter humans create smarter AI. Smarter AI creates smarter humans.

For hundreds of thousands of years, evolution determined the basic capabilities of Homo sapiens. We didn’t choose our memory capacity. We didn’t choose how quickly we learn. We didn’t choose how long our muscles remain strong or how our brains age. We inherited all of that.

Perhaps that is about to change. For the first time, intelligence itself may participate in designing its successor. And that successor may be us.

Which means that perhaps I started this essay with the wrong question. The question isn’t how long humans will live. It isn’t even how young we can remain. The question is: what will a human being be?

I have no idea. But I increasingly suspect that the humans living at the end of this century will not simply be longer-lived versions of us. They may be something we have never seen before.  And at 81 there is even a small possibility that some form of me will be around to observe it.

Humans created AI. The great irony may be that AI’s most important creation turns out to be the next version of humans.