User:Smith609/Cambrian explosion
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, organisms were on the whole simple, comprised of individual cells occasionally organised into colonies; Over the subsequent 70-80 million years, the rate of evolution would accelerate by an order of magnitude,[1] and the diversity of life would begin to resemble today's.[2]
The Cambrian explosion has generated extensive scientific debate. The seemingly rapid appearance of fossils in the "Primordial Strata" was noted as early as the mid 19th century,[3] and Charles Darwin saw it as one of the principal objections that could be lodged against his theory of evolution by natural selection.[4]
The long-running puzzlement about the appearance of the Cambrian fauna, seemingly abruptly and from nowhere, can be distilled into three key points:
- Was the “explosion” real?
- What does it tell us about the origin and possible evolution of animals?
- What were its causes?
A limited supply of evidence, based mainly on an incomplete fossil record and chemical signatures left in Cambrian rocks, makes interpretation difficult; consequently, a wide variety of answers to these three questions have been touted. Further discoveries continue to bolster our knowledge, marking previously well-supported hypotheses as inaccurate, and allowing new ideas to crop up in their place.
Key Cambrian explosion events | ||||||||||||||||||||||||||||||
−590 — – −580 — – −570 — – −560 — – −550 — – −540 — – −530 — – −520 — – −510 — – −500 — – −490 — – | "Stage 2" "Stage 3" "Stage 4" "Stage 5" "Stage 10" * * * * * * * * * * * * * * * * * * * * * * * * * Baykonur glaciation * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * |
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