You are in the forested riverbanks of Canada, 375 million years ago.

The water in the slow-moving Devonian stream was murky and warm, smelling of rotting vegetation and thick mud. It was the air, however, that you noticed first—thick and humid, completely unlike the ocean water you usually frequented to explore the majority of creatures there. You crouched low on the muddy bank, watching a shallow, meandering stream. The water was murky, barely deep enough to cover the strange creature resting in the shallows.

It was roughly four feet long, with the sleek, grey-brown scales of a fish and a tail that flicked casually in the water. But it wasn't swimming.

You watched in amazement as it shifted its weight. Unlike any fish you had ever seen, this creature—Tiktaalik—had a flat, broad head reminiscent of a crocodile, with eyes positioned right on top, looking up through the water’s surface. It lifted its head, turning it slowly side-to-side, demonstrating a distinct neck—a feature completely unheard of in its aquatic neighbors.

Slowly, awkwardly, it propped itself up. Its pectoral fins, packed with bones that mirrored an elbow and a wrist, dug into the soft mud. It wasn't quite walking, but it was bridging the gap, pushing its body up to catch a breath of air through its gills and lungs, preparing to leave the water behind. It was a breathtaking moment: our fishy ancestor, taking its first, shaky step onto the land.