Perhaps the most important of all the epochs is when life first emerged from the early seas - the primordial 'soup' as it is sometimes called. What do we know about the chemistry of this stage? The first 'life' might have been very different from today's simplest cell or bacteria. Current thinking is that once a suitably complex molecule formed - one that could copy and replicate itself - then essentially life had also started [2].

In 1952 Stanley Miller and Harold Urey wanted to investigate how the basic building blocks of complex biological molecules might have been created on the early Earth. They setup a sterile glassware apparatus and introduced water, methane, ammonia and hydrogen to represent the Earths early atmosphere (Note: it is thought that an oxygen rich atmosphere appeared much later). To simulate lightening in the primitive Earth's atmosphere an electrical spark was continuously maintained. What they found surprised them. Within a day the flask had turned pink and in a week 10% of the carbon was found to be in organic compounds. Even in this short time quite large / complex molecules had been created including sugars, lipids and simple amino acids such as glycine. In 2007 a box of some of the original samples were rediscovered. Modern analysis revealed an even greater range of structures to be present, including many amino acids [3].

From the starting materials many pathways are possible, for glycine for example:
H₂O → H₂ + O (e.g. by UV radiation)
CH₄ + NH₃ → HCN + 3H₂
CH4₄+ 2O → CH₂O + H₂0
CH₂O + HCN + NH₃ → NH₂CH₂CN + H₂0
NH₂CH₂CN + 2H₂0 → NH₃ + NH₂CH₂COOH (glycine)

Of course the film does not go into these technical details but what we see beautifully presented in these haunting scenes is an intriguing and unique Hollywood account of Earth's evolution.

References and Links
[1] Tree of Life, 20th Century Fox, 2011
[2] The History of Life, M J Benton, OVSI, 2008. ISBN 978 0 19 922632
Also see Keosians classic work 'The Origin of Life', 1965
Also see 'The TNA world before RNA', Chemistry World, Feb. 2012
[3] Miller's legacy: new clues to origins of life, Chemistry World, Oct. 2008


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