Neil Shubin, Paleontologist, University of Chicago

Is Tiktaalik, the fossil you found, technically a fish?

You might recognize it as a fish—it has fin webbing and scales on its back.

What makes you think it’s related to the first vertebrate animals to walk on land?

It has a head that’s shaped like some of the earliest land-living creatures. It has a neck—the head can move separately, unlike any fish but very similar to land animals—and an upper arm, a forearm and even parts of a wrist. It blurs the distinction between fish and land-living animals. We think this animal was able to support its body on the ground, whether that ground is underwater, or in the shallows, or even on land for brief periods.

Tiktaalik lived about 375 million years ago. What was its world like?

You would see some of the earliest forests and some invertebrate animals—centipede-like things. In the water you’d see a pretty hostile place, with lots of predatory fish with giant fangs.

Is that why Tiktaalik—or its descendants—left the water?

That’s a compelling explanation, but there’s also the fact that some of the invertebrates on land were large, pretty defenseless and probably nutritious.

You found these fossils in Nunavut Territory, in Arctic Canada. Why there?

We were actually looking for a fossil like this. By looking at maps and geological publications, we saw that the rocks were of the right age and the right type—they were formed in ancient stream environments. Another thing that’s special about the Arctic is the rocks are at the surface. They’re not hidden under plants or buildings or miniature golf courses.

But Nunavut wasn’t cold 375 million years ago?

What is Nunavut today was straddling the Equator 375 million years ago. You see glaciers and musk ox there today, but when you look inside the rocks at your feet, you find a tropical world.

Was this discovery a fluke?

No, it wasn’t. As we learn more about the history of life, and as we learn more about what rocks are preserved in different parts of the world, we can make these kinds of predictions.

Some scientists dislike the term “missing link.”

When people call Tiktaalik “the missing link,” it implies there is a single fossil that tells us about the transition from water to land. Tiktaalik gains meaning when it’s compared with other fossils in the series. So it’s not “the” missing link. I would probably call it “a” missing link. It’s also no longer missing—it’s a found link. The missing links are the ones I want to find this summer.

Laura Helmuth | | READ MORE

Laura Helmuth is the science and health editor at Slate. Previously, she was a senior science editor at Smithsonian magazine.