“I think it’s a valuable reframing of the story,” says Phoebe Cohen, a paleontologist at Williams College. “The more we look at the Cambrian explosion, the less explosion-y it looks.”

The time before the explosion is known as the Ediacaran period. Running from 571 million to 541 million years ago, it marked the appearance of the first big, complex, living things. But what were those things? A weird miscellany of unfamiliar blobs, tall fronds, and ribbed mats, they were entirely unlike today’s animals, and some may not have been animals at all. Whatever they were, based on the fossil record, they seem to have suddenly disappeared when the Ediacaran gave way to the Cambrian period, and more recognizable animals arrived. That stark transition led some researchers to cast the Ediacaran biota as “failed evolutionary experiments” that were outcompeted by the ancestors of modern critters.

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The divide between the Ediacaran and Cambrian has been so heavily mythologized that scientists who study the two periods became divided too. “You have people working on the Ediacaran and people working on the Cambrian, and they don’t really come together,” says Wood. But at a recent conference in the U.K, “a lot of us realized that those boundaries had started to become blurred.”

New fossils, she says, showed that some Cambrian-defining traits were actually pioneered in the Ediacaran. For example, fossilized tracks and burrows suggest that animals were already on the move about 25 million years before the Cambrian explosion. Hard shells and skeletons had also appeared pre-explosion, and some of these had boreholes, which hint that their owners were killed by drilling predators. Mobility, armor, hunting: These innovations were part of “a crescendo that started in the Ediacaran,” Wood says.

Recent finds have also reinforced the continuity between the pre- and post-explosion worlds. New fossils of a Cambrian animal called Stromatoveris showed that it’s related to an Ediacaran group called the petalonamids, named for their petal-like fronds. That connection shows that the Ediacarans were “alive and well over 20 million years into the Cambrian period,” wrote Jennifer Hoyal Cuthill from the University of Cambridge in The Conversation.

The Ediacaran biota wasn’t just a single set of organisms either. They were extremely variable, and appeared in distinct waves. First came the Avalon biota, characterized by stationary, fronded creatures that resembled kelp. Next up: the White Sea biota, which included mobile creatures such as Dickinsonia—a ribbed oval that was recently confirmed as an animal. Then the Nama biota—a so-called wormworld that ushered in tubular animals, including some with hard shells.

When the Cambrian fauna eventually arrived, Wood thinks it appeared in two pulses. The mollusks, for example, evolved just before the explosion, but most of the group’s early members died out in an extinction event 513 million years ago, in the early Cambrian. The lineages that gave rise to today’s mollusks—octopuses, clams, and more—flourished only after that point, in the late Cambrian.