I have always liked to think I have an understanding of the basic process of natural selection, but one thing I have never fully understood was how life first began on earth. Can someone please explain to me in terms I can understand how single celled organisms first appeared and then flourished? Specifically, how was it that they were able to survive in the environment that was at that point, aside from them, completely devoid of life?

Hi Taylor,

You have asked perhaps the toughest question in biology - we really have no clue as to how life got started.

What are claimed to be the earliest fossils of life on Earth are actually just blobs of Carbon (they are not well preserved) and it is still debatable as to whether they are really biotic (the products of living organisms) or abiotic (the product of some naturally occurring chemical process that is non-biological in nature).

What we do know is that life remained very simple for 2-3 billion years until about 600 million years ago when the 'Ediacarans' appeared, but they were just a precursor to a more important event often termed the 'Cambrian Explosion'. It was then that all of the modern Phyla (Animal groups) appeared and bigger, more complex life forms became possible.

One way we could answer the question of how life started from non-life is by generating it ourselves in the lab. Unfortunately so far none of our attempts have been successful despite the enticing carrot of a dead cert Nobel Prize!

Of course it is also possible that life is spontaneously arising all around us and that it simply dies out before anyone notices. It would have to be very small and would probably get swamped by pre-existing life forms, killing it off very quickly - so this might not be as crazy as it sounds!

To conclude, it is probably pertinent to point out that the most startling conclusion of Darwin's theory is that all life (literally everything from you and me to plants, fungi and bacteria) stems back to a single common ancestor.

However many times life may have started we are all the descendants of just one successful individual.

Last edited by Graeme Lloyd (4th Mar 2007 20:13:51)