You are in the marshlands of Greenland, 365 million years ago.

The water was shallow, barely deep enough to submerge a man’s knee, and thick with tangled roots and decaying detritus. The air hummed with a strange silence—no birds, no mammals, just the rustle of primitive ferns and the occasional splash of a lobed-fin fish. You froze as a shadow moved through the murk just ahead.

It wasn't a fish, not truly. It was about two feet long, with a flat, crocodile-like skull and large, pale eyes staring upward. This was an Acanthostega.

The salamander-like creature was holding onto a sunken branch with its front limbs—limbs that possessed eight distinct, webbed digits, appearing more like hands than fins. It didn't walk on the bank; it was deeply aquatic. Instead of walking, it used these digits and its limbs to navigate through the dense weed-choked swamps, pulling its long, slender body through the mud, a "wheelbarrow" motion with its rear-wheel-drive legs.

As it turned its head—a flexibility that fish lack—you saw the distinct gap between the skull and shoulder girdle. It wasn't breathing air, not yet. Instead, its throat pumped, a motion you recognized from fish, as it used internal gills to breathe the water.

Suddenly, it froze, sensing my presence.