Venki Ramakrishnan

And even within the developing embryo, defective cells are destroyed. So I think this... I thought about why is it that we get old, but when a child is born, it's not born old. So it's as if the biological clock has been reset every generation. And that's because of this combination of protection and against damage for the germ cells and ruthless selection.

And even within the developing embryo, defective cells are destroyed. So I think this... I thought about why is it that we get old, but when a child is born, it's not born old. So it's as if the biological clock has been reset every generation. And that's because of this combination of protection and against damage for the germ cells and ruthless selection.

I think it's that combination that allows us to have an embryo that is, you know, looks, you know, it's gone back to state zero. But of course, all of the little tags on the DNA have been erased. These tags are markers for aging. They've been erased and and then reprogrammed to start from scratch.

I think it's that combination that allows us to have an embryo that is, you know, looks, you know, it's gone back to state zero. But of course, all of the little tags on the DNA have been erased. These tags are markers for aging. They've been erased and and then reprogrammed to start from scratch.

So so it's all this combination of things that goes on to to reset the the biological clock every generation.

So so it's all this combination of things that goes on to to reset the the biological clock every generation.

Yeah, so this has to do, you know, we talked about how some species live only a day or two and others live several hundred years. Well, you know, Jeffrey West, who we both know from Santa Fe, has written a great book called Scale. And in that book, he talks about relationship between lifespan and parameters like size.

Yeah, so this has to do, you know, we talked about how some species live only a day or two and others live several hundred years. Well, you know, Jeffrey West, who we both know from Santa Fe, has written a great book called Scale. And in that book, he talks about relationship between lifespan and parameters like size.

It turns out that large mammals live, on average, much longer than small mammals. Now, why would that be? Well, it's because evolution simply doesn't care how long you live. It cares about fitness, which is how likely are you to pass on your genes? How successful are you going to be at passing on your genes? And so I think...

It turns out that large mammals live, on average, much longer than small mammals. Now, why would that be? Well, it's because evolution simply doesn't care how long you live. It cares about fitness, which is how likely are you to pass on your genes? How successful are you going to be at passing on your genes? And so I think...

If you're a mouse, there's no point in spending a lot of resources to repair and maintenance because we do have sophisticated repair and maintenance mechanisms. Otherwise, we wouldn't even last a year. We would be dead before that. We do have this very sophisticated mechanism, but that takes energy and takes resources.

If you're a mouse, there's no point in spending a lot of resources to repair and maintenance because we do have sophisticated repair and maintenance mechanisms. Otherwise, we wouldn't even last a year. We would be dead before that. We do have this very sophisticated mechanism, but that takes energy and takes resources.

And in a small animal, it's not worth it because the animal is going to be killed off by a predator or die of starvation or some other cause. So there it's more advantageous for evolution to put resources into rapid growth and reproduction. And that's what a mouse does. And at the other end, you have things like a bowhead whale or a Greenland shark, very slow metabolism and

And in a small animal, it's not worth it because the animal is going to be killed off by a predator or die of starvation or some other cause. So there it's more advantageous for evolution to put resources into rapid growth and reproduction. And that's what a mouse does. And at the other end, you have things like a bowhead whale or a Greenland shark, very slow metabolism and

well, especially the Greenland shark has a very slow metabolism, large, and can produce offspring over a long period. So you have these opposite extremes. And the interesting twist on this are bats. So bats weigh about the same as a mouse, the same size as a mouse, but can live 10 to 20 times as long. And the reason is bats can fly, so they can escape predation.

well, especially the Greenland shark has a very slow metabolism, large, and can produce offspring over a long period. So you have these opposite extremes. And the interesting twist on this are bats. So bats weigh about the same as a mouse, the same size as a mouse, but can live 10 to 20 times as long. And the reason is bats can fly, so they can escape predation.

And they also can forage over a much wider area and are less likely to starve. So it makes perfect sense that you would have this evolutionary thing.

And they also can forage over a much wider area and are less likely to starve. So it makes perfect sense that you would have this evolutionary thing.

This is called Pitot's paradox, after Pitot, who was the scientist who first formulated it. Because an animal like a whale or an elephant has thousands of times more cells than a mouse.

This is called Pitot's paradox, after Pitot, who was the scientist who first formulated it. Because an animal like a whale or an elephant has thousands of times more cells than a mouse.