Book SummaryLifespan, by David Sinclair

1-Page Summary1-Page Book Summary of Lifespan

For all of recorded history, people have seen aging as an inevitable fact of life. Biologist and geneticist David Sinclair disagrees: He believes that old age is a deadly disease, and he’s dedicated his life to curing it.

In Lifespan: Why We Age and Why We Don’t Have To (published in 2019), Sinclair discusses why aging happens, how we can prevent it, and how we might create a world where nobody has to die of old age. This guide explains Sinclair’s ideas and provides background information to make complex biological concepts more accessible to the average reader.

Sinclair earned his Ph.D. from the University of New South Wales in Australia. He’s currently co-director of the Paul F. Glenn Center for Biology of Aging Research at Harvard University, where he is also a professor of genetics.

Sinclair believes it’s not only possible but inevitable that we’ll learn to overcome the aging process. New medicines and technologies will increase our maximum lifespan and years of health until eventually humans won’t have a maximum lifespan—we’ll stay young and healthy forever. In fact, we’ve already taken steps toward...

Lifespan Summary Part 1: Why Do We Age?

Sinclair says that humans have always accepted aging as a fact of life, but relatively few people have questioned why it has to happen.

The oldest theory, dating back to Aristotle, is that we age and die for the good of the species, to “make room” for the next generation. This is part of the theory of group selection—evolving to benefit the species, rather than the individual—but that theory fell out of favor in the 1950s.

(Shortform note: In The Selfish Gene, Richard Dawkins explains that group selection can’t be correct because we can observe selfish behaviors in nature, such as animals competing over food and mates even when there would be enough to share. In fact, selfish individuals—those who benefit at others’ expense—often have an advantage over altruistic individuals, so they’re more likely to survive and pass on their genes to the next generation. That fact is completely incompatible with the idea that evolution is for the good of the species as a whole.)

**The current theory is that we evolved to survive...

Lifespan Summary Part 2: Treating the Disease

Sinclair says that throughout recorded history, we’ve always accepted aging as something that just happens to people. However, he argues that aging is actually a treatable disease.

In fact, old age shares several key traits with cancer:

• Both diseases are more common in older people (by definition, in the case of old age).
• Both diseases used to be considered impossible to treat, let alone cure.
• Both diseases are eventually fatal if left untreated.

(Shortform note: The similarities between aging and cancer might be even more profound than this. In The Emperor of All Maladies, biologist Siddhartha Mukherjee describes cancer as a corruption of our normal bodily processes—the functions that should keep us alive and healthy instead turn against us to create deadly tumors. If Sinclair’s Information Theory is right, then aging is a similar process: The epigenome starts causing the body to break down, instead of keeping it strong and healthy as it’s meant to.)

**If aging is a disease, Sinclair argues, then things like...

Lifespan Summary Part 3: A World Without Aging

In the final part of Lifespan, Sinclair imagines what it might look like to live in a world where people live forever. He speculates on how we might create such a world, and he discusses the potential pros and cons of doing so.

Causes for Concern

In imagining a world where people never die, Sinclair starts by outlining some of the potential problems. Some of his chief concerns are:

• Stagnating scientific and social advancements. Sinclair says that progress doesn’t happen by winning over the opposition, but because the (usually older) opposition eventually dies off—if people start living for hundreds of years, that won’t happen.
• Widening wealth gaps as rich people live longer and invest more in politics to get even richer at everyone else’s expense. To make matters even worse, the wealthy will almost certainly have access to life-extending treatments long before poor and working class people do.
• Overpopulation leading to starvation, mass poverty, and worsening climate change

Should We Live Forever?

In Antifragile, Taleb says that people living forever would be a [serious detriment to...

Shortform Exercise: What if You Could Live Forever?

Imagine for a moment that Sinclair’s work has already panned out, and that anti-aging treatments work like he imagined in his most optimistic predictions. If you could live forever, would you want to? And what would you do?

Would you want to live 100 years? How about 200? Why or why not?