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On The Origins & Evolution of Life

It is generally thought that all life on earth evolved from a single lifeform approximately 3,900 million years ago. Chemical evolution is theorised to have preceded biological evolution, ribonucleic acid worlds leading to protein worlds. In this lecture, we will tell a story that begins with the earliest likely lifeforms and the evolution of amino acids, phospholipids, nucleotides and the basic biomolecules of life. We will study the fossilised microorganisms found in hydrothermal vents in Quebec, and stromatolites housing fossilised cyanobacteria. We will study the work of Stanley Miller and the now famous Miller-Urey experiments with ammonia, hydrogen and methane; we will also recount Sidney Fox's experiments in abiogenesis, which supported the proposition that peptides could emerge from the "primordial soup". Thomas Gold posited that life may have developed deep beneath the surface of the earth and so we review the deep-hot biosphere model. To conclude, we will evaluate the relative validity of the RNA world hypothesis compared with the protein-metabolism hypothesis, before briefly considering the theory of panspermia - the likelihood that life evolved elsewhere in the universe and came to earth transported by spores. For those who have ever wondered how life came to be, this lecture is intended to provide some delicious food for thought!

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