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Hello, scientists have named 1.5 million species of a living organism on the land, in the

skies and in the ocean of planet Earth's.

And a new one's classified every day, estimates of how many species remain to be discovered vary widely.

But science accepts one categorical point. All living matter on our planet from the nematode to the elephant,

from the bacterium to the blue whale is derived from a single common

ancestor. What was that ancestor? Did it really emerge from a primordial soup and what

did in the explanation of evolutionary science provide the

catalyst to start turning the cycle of life. With me to explore the scientific

explanation for the origin of life is Richard Dawkins, the Charles Simoney, professor of the

public understanding of science at Oxford University, and author of The Ancestors

Tale, a pilgrimage to the Dawn of Life. Richard Corfield, visiting senior lecturer at the Center for Earth, planetary, space,

and astronomical research at the Open University and author of the silent landscape, and Linda Partridge,

Biology and Biotechnology Research Council Professor at University College London.

Richard Corfield, can we start with the time the earth was formed?

What time scale was that and what were the conditions of Earth then?

Well the Earth accreted out of the primordial solar system disk about 4.5 billion years ago. The Convention in Geology is that we call a billion GA. And so you might

hear me refer to it as GA from time to time. A more helpful analogy though when you think

about the span of geological time is to consider one single day, 24 hours, and midnight is taken as 4.5 GA, 4.5 billion years. That's when the Earth formed.

From then on, the first Aon of the history of the Earth is called the Heidian,

so called because the Earth and the other planets which were forming at the same time,

...