The sudden appearance of the oldest fossilized remains of complex animals in rocks that are 538 million years old has long been a puzzle for scientists. These ancient animals, including crab-like arthropods, shelled mollusks, and the ancestors of starfish and sea urchins, seemed to emerge out of nowhere in the fossil record, challenging the idea of gradual evolution proposed by Charles Darwin.
A recent paper by palaeontologist Graham Budd and mathematician Richard Mann offers a new explanation for this phenomenon. The traditional molecular clock theory, which relies on the regular accumulation of genetic changes to estimate evolutionary timelines, may not be as precise as previously thought. Budd and Mann suggest that when a new group of organisms first appears, evolution speeds up, causing genes to change more rapidly.
This speeding clock hypothesis could reconcile the discrepancy between the predicted age of the common ancestor of complex animals based on molecular clocks and the sudden appearance of their fossilized descendants. It would explain how diverse animal groups could evolve rapidly from a common ancestor and why there is a gap between the molecular clock estimates and the fossil record.
By proposing that evolution accelerates when new groups of organisms emerge, the speeding clock theory could also help resolve other discrepancies between molecular clocks and the fossil record. It could shed light on the prolonged existence of early flowering plants before leaving fossils and clarify debates about the coexistence of early primates, carnivores, and rodents with dinosaurs.
Overall, the speeding clock hypothesis offers a new perspective on the evolution of complex animals and their ancestors. By suggesting that evolution can occur more rapidly during key periods, this theory provides a potential solution to Darwin’s mystery of gaps in the animal fossil record.
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