If you were to look around and start counting all the organisms in your line of sight,

flora and fauna, single-celled and multi-celled, macroscopic and microscopic,

the task would far exceed a human lifetime.

A single acre may hold hundreds of millions of individual organisms.

So it's next to impossible to say precisely how many co-inhabitants we have here on Earth.

Perhaps in an effort to determine how we fit into the mix, we've spent hundreds of years attempting

to categorize the living things around us, grouping them by shared traits into a series

of taxonomic ranks, of which the most specific and likely most familiar is species.

But it turns out, even our most precise point of classification

isn't all that well defined. If we don't truly understand species, how can we possibly understand

evolution, conservation, or ourselves? I'm Jan 11, and this is the joy of why, a podcast from Quantum Magazine, where I take turns

at the mic with my co-host, Steve Strogetz, exploring the biggest questions in math and science

today.

In this episode, we take a look at what species means, why it's so hard to pin down, and why it's important to get that definition right.

We're joined by Kevin DeKeruse, a research zoologist and curator of amphibians and reptiles for the National Museum of Natural History of the Smithsonian Institution.

He's been central in the development of a unified concept of species, using an approach

that focuses on phylogenetics, which is to say the evolutionary history and relationships

between groups of organisms.

Kevin, it's great to have you on The Joy of Why.

Thanks very much, Jana. It's a pleasure to be here.

You know, we can't really talk about species without talking about Darwin and without talking about Darwin's on the origin of species.

Can you tell me a little bit, get us anchored in Darwin's thoughts on the topic?

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