What caused the Cambrian explosion, 'biology's Big Bang'? The Economist explores.

Starting about 542 million years ago, a huge diversity of new animals appeared in the Earth's oceans, continuing over a 20-million-year stretch known as the Cambrian Period. "The Cambrian explosion was really biology's Big Bang," Andrew Parker, a professor of life science at London's Natural History Museum, tells The Economist in the video below. "Life literally exploded." And nobody is quite sure why.

In just under 11 minutes, The Economist provides a crash course on the Cambrian explosion, talking to Parker and two other experts in the field, trying out different theories: A sharp increase in oxygen levels in the water, new nutrients from melting glaciers, evolutionary innovation in nervous systems and vision, the rise of more capable predators, perhaps some catastrophic explosion that wiped out the shell-less creatures who lived before. But "from the human point of view," The Economist notes, "the significance of the Cambrian explosion is that homo sapiens wouldn't be here if it hadn't happened." If you're curious, watch the video below. Peter Weber

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