Episode 6 of The Story of Life on Earth follows life out of the water. It starts with simple mosses, which broke down bare rock into the first soil, and ends with four-limbed animals hauling themselves across Devonian mudflats.
Early plants like Cooksonia, only a few centimeters tall, were among the first to stand upright on land. Animals followed the plants. Pneumodesmus, a small millipede-like creature from Scotland, is one of the oldest known air-breathing animals, and it breathed through spiracles much as millipedes still do.
The move from water to land was not one fish crawling up a beach. Tiktaalik had a fish’s body with a neck and sturdy, wrist-like fins. Acanthostega had eight fingers on each hand and still lived mostly in water. The episode describes these animals as years of experiments with different hands, and the one bone, two bones, wrist and digits pattern they tested is the same one inside every human arm today.
By the Carboniferous, the forests that plants built were home to giants. Arthropleura, a millipede relative, reached about 2.6 meters long, and dragonflies grew to the size of hawks.
The same move from sea to land is one of the central turns in Martin Jenkins’s 2019 book Life: The First Four Billion Years, illustrated by Grahame Baker-Smith.
Watch Episode 6 on YouTube, go back to Episode 5, continue to Episode 7, The Great Dying, or see the full series on the YouTube Series page.