Early steps towards life

Imagine an RNA molecule that can replicate … this is already quite life-like.

I have a really exciting story for you today, especially if you are interested in the origin of life and evolution.

RNA
A section of double-stranded RNA

A recent article in the magazine Science reports that Thomas Carell, a chemist at Ludwig Maximilian University in Munich, Germany, has outlined a process that can generate all four of the building blocks of RNA from compounds and conditions present on the pre-biotic Earth.

Why is this significant?

To understand, we need to grasp the importance of RNA. Its cousin, DNA, is the molecule used by most living things on Earth to store the genetic information that controls their form and function. RNA is also capable of storing genetic information, and some viruses use it in exactly this way. RNA is also essential in all living forms because it acts as a go between in the production of proteins from the DNA genetic material. RNA is less stable than DNA and copying errors are more likely. For this reason, DNA is a better long-term genetic store than RNA, but RNA is more dynamic. Think in terms of DNA as a library of printed recipe books, while RNA is like hand-copied notes on scraps of paper that enable the recipes to be taken to the kitchen.

But RNA has additional tricks up its sleeve. No only can this molecule store genetic information, it can also catalyse biochemical reactions, including the synthesis of simple proteins. RNA is a bit of an all-rounder, and it’s not so hard to imagine that quite soon after being randomly synthesised by Carell’s process, RNA molecules might be formed as the dissolved RNA bases came into contact with tiny rock templates that could act to stabilise the process.

RNA also has the potential to self-replicate. Imagine an RNA molecule that can replicate (albeit with occasional errors). This is already quite life-like. Now image the population growing in places where the Carell process was providing reliable supplies of the four bases. Some of those RNA molecules will have errors, sooner or later an error, or a combination of errors will provide a version that replicates more efficiently, or gets trapped inside a lipid membrane that protects it from breakdown, or catalyses the production of a protein that makes the RNA more efficient in some way. If all of those things happen you have something that might be regarded as an early living form – an enclosed lipid membrane with a self-replicating genetic system that can mutate and evolve. Nothing more that that would be needed to kick of an expanding array of related forms.

Voila!

The story as I describe it here is not complete and likely incorrect in many ways. I accept that. But though it’s a simplistic view, it’s also likely to be broadly correct as a bare outline. Over the next few years and decades I expect much more detail will become clear, especially detail about what is or is not possible. And I expect to see many of the steps to be experimentally demonstrated. Watch this space…