#513 Why We Age and How to Stop It | Dr. Steven Austad

Steven Austad (0:00)

It's so counterintuitive, how evolution could have produced animals that age, and then how they could age at such different rates. Thought is that not that longer life or shorter life is selected for, it's the reproductive pattern that is selected for, but a consequence of becoming an adult rapidly and breeding very rapidly is that you age rapidly as well.

Siim Land (0:27)

Dr. Austad, welcome to the show.

Steven Austad (0:29)

Thank you. It's nice to be here.

Siim Land (0:31)

Yeah, I'm excited to have you on the podcast. You've been in the field of Lingerit and aging research for decades, and we're going to go into all the details of that in our talk today. But it's very interesting to always hear where people get into the field of aging research and you have a very interesting background, that you were initially like a lion tamer in Hollywood, which is completely like a different field, but how did you go from being a lion tamer into starting to research biology of aging?

Steven Austad (1:04)

Yeah, it was a very complex journey, let me say that. So when I was training lions, I got very interested in the science of animal behavior because of self preservation. And when I decided I didn't want to spend the rest of my life in Hollywood, I decided that I would like to study animal behavior more formally in an academic situation. So I went to graduate school, got a PhD in behavior, still had no thoughts about aging research. But as part of a postdoc, I was working in South America, and I got involved in a project studying opossums, which are small marsupials about the size of a house cat. And I discovered quite by accident, even though the project was not involved with aging, that they aged really fast, that these things that were the size of a house cat, aged as fast as a mouse. And that was such a shock to me because I just assumed they would live 10 or 15 years like a house cat, that it captured my interest immediately. And I decided, and in fact, the project I was working on did very, very well. I ended up publishing it in Nature, but by the time it got published, I had completely lost interest in that topic and it had shifted my interest to aging. And it was mainly an evolutionary issue. I thought it's so counterintuitive, how evolution could have produced animals that age, and then how they could age at such different rates. That's a question that still attracts and intrigues me. So that's been a long, long time.

As soon as I thought I'd figured out a topic, I lost interest in it.

So after these many decades in the field, I still don't feel like I've really figured out everything about aging. So it keeps my interest. It's endlessly fascinating.

Siim Land (3:21)

Yeah. I mean, as you said, there's so many different life spans in animal species. There's bowhead whales that live over 200 years, shark, Greenland sharks up to 500 years, and then there's mice who live only a few years or less than that. So there's a huge, I guess, inequality or imbalance in how long some animals live. So maybe we can start with that.

Why do opossums then live a bit shorter?

Steven Austad (3:49)

Well, there's a couple of ways to answer that. There's a couple of levels at which to answer that. One is at an evolutionary level.

What we know from a lot of comparative research is that animals that live in particularly hazardous environments, environments where they're quite likely to get killed by predator or climatic catastrophe, those animals age quickly. And conversely, animals live in safe environments where they're unlikely to be killed by random forces tend to age slowly. And opossums are vulnerable to an enormous amount of predation. In the natural world, about 80 percent of them die from predators. And so, I think that that is a pretty complete explanation about why they're so short-lived. They just don't have the weaponry, they don't have the escape capability of a lot of other animals that are about the same size. Now, on the level of mechanistically, what goes wrong, that we don't really know about. We just know that it happens fast and it happens early. They actually do seem to have a fairly robust immune system, which is surprising to me. For instance, opossums are resistant to the bites of venomous snakes. So rattlesnakes, they can get bitten by them and they're just fine.

So we're not really sure why they get cataracts and cancer and arthritis and all the other things that happen to aging mammals so quickly.