What Are The Weirdest Types Of Life? - Carl Zimmer | Modern Wisdom Podcast 394

Let's put it this way. There are other species that can recognize things that are alive and are not alive. That doesn't mean that they have, like, a deep conceptual understanding of life. But, you know, you could argue that we don't really either. (laughs) You can see different behaviors that animals have in response to living and dead things. You can see that, uh, that some animals are, are very good at recognizing biological motion, that is the movement of living things, and can distinguish that from the movement of things, you know, like rocks or something that are moving but are not alive. And that's really important for a lot of species.

Carl Zimmer, welcome to the show.

Thanks for having me.

It's an interesting thing talking about life and what it constitutes, right? Because I think a lot of people have heard about discussions to do with euthanasia and assisted suicide, and is this person really alive, what does it mean, philosophical arguments to do with is somebody in a coma, uh, discussions around abortion, what constitutes life during, um, childbirth and, and beforehand. And yeah, it's an interesting, an interesting area. It seems like it sort of coalesces a lot of big questions that people have.

Uh, it really does. Um, a- and, but at the same time, uh, for as important as it is, um, there hasn't been really all that much, um, thinking among scientists about, you know, life with a big capital L. I mean, when we talk about life, w- what do we really mean? Um, and so what's really astonishing is that, you know, you can find plenty of definitions of life, uh, in the scientific literature, um, but there are different definitions. And I find if I, if, uh, I start talking about life with a scientist, um, they might very well have a definition and it's different from the one I heard from the last person. Um, so y- you have this situation wh- which is really strange. I mean, imagine like in chemistry people didn't agree on what an atom is. I mean, (laughs) that would be kind of problematic. And yet we're in this situation where scientists who study life, life in different forms, they just, they really don't agree on what it is they're talking about.

Why is it so messy?

Um, you know, that's a good question. I think, uh, part of the problem is that, uh, i- is, is that sometimes we're trying to get at different things when we use the same word. So, you know, um, there are these, uh, issues about end of life, you know. So, um, is someone who's on a ventilator, are, are they alive? Um, and so we start to talk about, um, uh, you know, brain death as being sort of the definition of the end of life. Um, but that's really the end of one person's life, um, you know, their state of being alive. Um, whereas other people want to say, "Okay, um, you know, a snake and a tree and me, we, we all have something in common that's different than a rock. Um, what am I gonna call that?" And people will say, "Well, that's life." And so it's a, and so it can be a way of trying to pull things together into s- and trying to figure out what they have in common. Um, but, you know, e- but even then you get yourself into trouble because then, you know, you think you kind of have a nice little category of things that are alive and then someone comes along with something else, like a virus, and then everyone starts yelling all over again. Um, so, so it's, it, it's a, it's marvelously prone to lead to big arguments.