Which means they had all the less time to develop:
The first animals evolved towards the end of the Ediacaran period, around 580 million years ago. However, the fossil record shows that after an initial boom, diversity declined in the run-up to the dramatic burgeoning of biodiversity in the so-called “Cambrian explosion” nearly 40 million years later. Scientists have suggested this drop in diversity is evidence of a mass extinction event roughly 550 million years ago—possibly caused by an environmental catastrophe—but previous research has not investigated the structure of these ancient ecological communities…
The first animals evolved towards the end of the Ediacaran period, around 580 million years ago. However, the fossil record shows that after an initial boom, diversity declined in the run-up to the dramatic burgeoning of biodiversity in the so-called “Cambrian explosion” nearly 40 million years later. Scientists have suggested this drop in diversity is evidence of a mass extinction event roughly 550 million years ago—possibly caused by an environmental catastrophe—but previous research has not investigated the structure of these ancient ecological communities…
The results point to competitive exclusion, rather than mass extinction, as the cause of the diversity drop in the late Ediacaran period, the authors say. The analysis indicates that the features of ecological and evolutionary dynamics commonly associated with the Cambrian explosion—such as specialization and niche contraction—were established by the first animal communities in the late Ediacaran.
Public Library of Science, “First animals developed complex ecosystems before the Cambrian explosion” at Phys.org (May 17, 2022)
Mitchell adds, “We found that the factors behind that explosion, namely community complexity and niche adaptation, actually started during the Ediacaran, much earlier than previously thought. The Ediacaran was the fuse that lit the Cambrian explosion.”
One can claim that the Cambrian explosion was nothing new only at the risk of shortening the time to establish complex ecologies, which should begin to create doubt about random processes in an active mind.
The paper is open access.
You may also wish to read: Stasis: Mating behavior unchanged from Cambrian era Researcher: And it provides strong evidence to suggest that a Limulus, or horseshoe crab-like behavior, already existed in the Cambrian completely by convergence. So, it really helps us to get a sense of how these animals were actually living millions of years ago.”