MARY LOUISE KELLY, HOST:
Our next story is about a contemporary of Charles Darwin and Queen Victoria who is still alive. His name is Jonathan. He's 194 years old, give or take, and he is a giant tortoise who lives on the island of St. Helena in the south Atlantic Ocean. Jonathan is the oldest known living land animal in the world. And according to a study out this week in the journal Science Advances, his genes may yield important clues about why we age and possibly how to slow it down. Justin Gerlach was part of the team behind this research. He is director of biology studies at Peterhouse at the University of Cambridge in England. Justin Gerlach, welcome.
JUSTIN GERLACH: Thank you.
KELLY: So Jonathan the giant tortoise, how giant is he? And what do we know of - do we know anything of his life story and where he came from, what he has been up to for these past nearly 200 years?
GERLACH: Well, we know more about Jonathan than we do most 194-year-olds.
KELLY: (Laughter).
GERLACH: So he stands about 4 feet high.
KELLY: OK.
GERLACH: Five or 6 feet long. We know that he arrived in St. Helena 144 years ago.
KELLY: How do we know that?
GERLACH: Well, records were kept. So he was imported and given to the governor of the island. So he's been living on the island ever since then. He has a pretty good life. You know, he's got a pasture to graze in and watches the world go by.
KELLY: Is it notable that Jonathan is a he? Among humans, it's females who tend to set records for longevity.
GERLACH: The largest giant tortoises tend to be males. So the males grow faster. They put effort into growth, whereas the females put a lot of resources into eggs. The bigger animals tend to get the most notice.
KELLY: Interesting.
GERLACH: So it's really hard to answer whether that affects the age or whether it's just our bias towards these really dramatic big animals.
KELLY: So let's get to the research and the why Jonathan has managed this incredibly long and, it sounds, quite pleasant life. It has to do with his genes. In a few sentences, what did your team learn?
GERLACH: So he has quite a few genes that are slightly different from other giant tortoises, and some of those would relate to long life. So for example, he has genes that make him slightly more resistant to inflammation. But actually, there's something else that is much more important, that is much more unexpected.
KELLY: OK.
GERLACH: And that's to do with the regulation of his genes. So we all have regulators that turn on or turn off our genes at the appropriate times. And over time, those regulators break down. So as you age, your genes start being expressed in not quite the right way, and an obvious consequence of that is cancer. Now, it turns out that Jonathan's gene regulation is very similar to that of a very young animal, so not only is he a bit more resistant to the symptoms of aging, he's actually genuinely aging more slowly than we would expect.
KELLY: Is there any way to know what factors controlled that?
GERLACH: We don't know at the moment whether that's because he is a really exceptional individual or whether actually quite a lot of giant tortoises have this.
KELLY: Have you been able to study any offspring from Jonathan?
GERLACH: No. Unfortunately, Jonathan has not bred in his - well, certainly in the 144 years that he's been on St. Helena. It's quite difficult to successfully breed giant tortoises out of their natural range. And although Jonathan is still interested in the ladies, he's not actually managed to father any offspring.
KELLY: (Laughter) Well, I wish Jonathan long life, and I'm grateful to you for sharing your expertise with us. Justin Gerlach, thank you.
GERLACH: Thank you.
KELLY: Justin Gerlach, director of biology studies at Peterhouse, Cambridge University.
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