Saturday, November 06, 2010

First Life - David Attenborough

Shown on BBC 2 at 9 p.m. last night.

This was the first programme in a series about the evolution of life and constituted a masterclass in how to do popular science on TV. The hour-long episode covered the period from the first life on the planet about 3.5 billion years ago, to the Cambrian explosion around 530 million years ago which originated the basic body plan of virtually all animals alive today.

TV lends itself to 'show, not tell' and Attenborough visited fossil beds around the world to make his points. Around fifteen minutes in he set up the first puzzle: for three billion years life was just single cells floating around in the sea - what on earth caused the sudden emergence of multi-cellular creatures leading to the complex life-forms we see today?

The answer is snowball earth. During an extreme ice-age 650 million years ago the entire earth froze with single-celled life hanging on only at the margins. But as the ice retreated (due to volcanic carbon dioxide emissions) nutriments flooded the oceans and a new wave of photosynthesising, oxygen-generating bacteria flourished. Oxygen allowed new proteins such as collagen to be synthesised, vital for glueing cells together.

The first round of multi-cellular creatures, the Ediacarans were a dead-end, never developing a complex body-plan. However soon afterwards there developed an array of species from which we ourselves are descended (this event is termed the Cambrian explosion).

The program was big on big ideas and skirted over all the details plus the many controversies underlying this simple narrative. However as a roadmap for this period of life's history it could hardly be bettered: I do hope they show it in America.

Next week it's the invasion of the land.