How can we know anything about the origin of life?

Imagine we really could build a time machine and go back to the origin of life on Earth. Where should we go and what should we look for? Few researchers could agree about that. Some would visit hot springs on land, others would embark on a voyage to deep sea hydrothermal vents, and a few would look to the heavens, seeking delivery of organic molecules, or even whole cells, from outer space.

Let’s say that we did happen to go to the right place and found some green slime. Is it alive? Is it on the path towards life? It would be very hard to say unless we had a good idea exactly what we were looking for: we would need a specific hypothesis about the origin of life.

We don’t have a time machine, so we’ll never know what actually happened. But we can construct a detailed hypothesis, linking each step from the first stirrings of prebiotic chemistry to the emergence of genes and information. We can test each proposed step in the lab, to see whether or not it seems to be plausible. We can build an intellectual framework which shows how a sterile, inorganic planet could spring to life.

In this talk I will use life as a guide to its own origins. I will show that the most important properties of life are energy flow, the synthesis of new organic matter, and genetic information. All three have interesting quirks that might give insights into how they first arose. Energy flow takes place across the flimsy membranes that surround cells, giving them an electrical charge. Organic synthesis uses this electrical charge to drive the difficult reaction between carbon dioxide and hydrogen, to form the carbon skeletons that make up living matter. And the genetic code conceals deeply enigmatic patterns that suggest there were once direct interactions between amino acids (the building blocks of proteins) and the first genes (short strings of genetic information called RNA). Taken together, these quirks point to a specific environment which holds particular promise for the emergence of life: deep sea hydrothermal vents. I will outline some of our own active research on how life might have started in this environment and show how each step could be joined up to give an exciting and testable hypothesis for origin of life on Earth.