So Explaining the Cambrian Explosion Is All About the Oxygen, Is It?

A news article at Nature, "Oxygen fluctuations stalled life on Earth," is remarkable for skirting the main issue, the primary enigma, in the geologically sudden rise of complex animal life. Certainly, animals need oxygen and the article is at pains to show how oxygen levels on the early Earth were "dynamic" rather than stable, sometimes leaving the planet starved of the vital gas.

Oxygen concentration spiked once about 2.3 billion years ago, then again at 800 million years ago, well before the...