Hello everyone and welcome to the Mindscape Podcast.

I'm your host, Sean Carroll, and like most of you, I am getting older.

When I was your age, we didn't even have podcasts.

If we wanted to listen to this American life, we had to turn on the radio and listen to

it coming over the airwaves, and that's how we liked it.

As a physicist, I studied the arrow of time, the fact that the past is different from

the future.

So of course, there is aging in the sense that we are all older now chronologically

than we used to be.

But in the world of biology, there's also aging in the sense that our bodies are changing

as we get older.

In a very uniform, monotonic way, we all had certain qualities when we were babies, we

all have certain features and characteristics when we were elderly, and in between we move

from one to the other in a more or less predictable fashion.

But the interesting thing about aging is that it's not really inevitable.

In a sense, aging is a choice.

It's not a choice that we make as individual organisms.

It's a choice that evolution has made for us.

If we want to have evolutionary progress, then you have certain organisms giving birth

to others, trying new combinations of DNA, occasional mutations.

But then the old ones have to die off.

They have to give way to make room for the new generations.

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