At the last meeting we heard a superb talk by Dr Geoff Steele on the origins of life.
Even the oldest rocks on Earth have traces of life. They date from the early Archaen, about 3.8 billion years ago. Hence to search for life’s origins we are forced back into the Hadean. The name means “Hell” and it‘s a good description. Huge volcanic eruptions, burning ultraviolet radiation, noxious gases, enormous tides and constant bombardment by meteorites and comets do not sound like a good place to start.
No fossils survive from the Hadean. But the biochemistry of our own cells, and that of all other living organisms, preserves a remarkable record of our earliest times. It has given us a new kind of fossil hunting. In particular the DNA and RNA that store and manipulate our genes can be read like a book, complete with the copying errors and editing errors that tell so much about previous owners. They prove to us that all life on Earth is indeed related, as Charles Darwin proposed, and even allow a reasonable reconstruction of our common ancestor (a simple prokaryote). But where did that come from?
If our quest is the origin of life then we need to think carefully about what we’re looking for. What exactly is life? How is it defined? It seems that replication and metabolism are the minimum requirements, and if they are confined within an enclosed space such as a membrane then that object is perhaps “living”. Could such a thing have formed naturally in Hell? Research suggests that the conditions were right for RNA molecules to form. And they can act as both genes and enzymes giving both replication and metabolism. Hence the simplest life may have begun with just RNA, wrapped in the lipid membranes that form naturally when oil and water are shaken together. And it is astonishing to discover that one of our most basic enzymes, crucial to all modern life, appears to be a living fossil from that time.
The next meeting will be held on Wednesday 19th March when Keith Nicholls will give a talk entitled “The Late Ordovician Ice Age: a mass extinction”