Gobekli Tepe's Pillars

The origin of Life

Growth and fissioning (reproduction) of SALR clusters as the concentration of SALR particles is slowly increased.

Okay, this is off-topic, but I thought I'd share the other research highlight of my career. Most biological molecules, like amino acids and nucleobases (the building blocks of proteins and DNA/RNA respectively), are 'SALR'. This means they are attracted to each-other at short range (the short-range attraction, or SA, part), but because they are typically also charged in solution, they repel each other at much larger separations (the long-range repulsion, or LR, part).

I have been researching the behaviour of  SALR particles in solution for the last 6 years or so. Last year, I discovered [1] that in a solution of SALR particles in which the concentration is slowly increased, the SALR clusters that form will gradually grow and then split, or fission. The above set of snapshots from a 3-D simulation shows this happening many times in succession. Each square image above is a 2-D projection of the 3-D simulation. The simulation progresses from top left to bottom right. BTW, there are 'periodic boundaries' in these simulations - which means that particles that move off to the left of the cubic simulation box will reappear on the right, those that move off the bottom will reappear at the top, and so on. We do this to mimic an infinite system without interfaces within a small simulation. It's fine.

So in the image top-left there is just one SALR cluster - but it appears to be split across the top/bottom boundary. It isn't. It is really just one cluster.

Anyway, we can see this cluster slowly grows, elongates into a  dumbbell shape, and then fissions. And this keeps happening. Effectively, the clusters are 'reproducing'. It's very likely this process is going on right now inside every cell of your body. Within each cell are structures known as 'membraneless organelles'. I have published a paper recently [2] that suggests that these membraneless organelles are just different types of SALR cluster, formed from specific types of protein and RNA.

Now, while this SALR clustering behaviour was known already, this fissioning behaviour was not. It is brand new physics for SALR particles in solution. But it makes sense. In Prehistory Decoded I compare these SALR clusters with human communities. I suggest early human communities show the same kind of growth and fissioning behaviour - they split in winter when resources are hard to find, and merge in spring when they are easier to find.

Anyway, the key thing is that this physics is almost certainly going on inside every cell of your body, and because of this it might have driven chemical evolution of clusters at the very origin of life. In other words, before the biological evolution of biological organisms, there might have been chemical evolution of SALR clusters - 'survival of the fittest cluster'. Those clusters that can fission more quickly, and with the best 'fidelity', will propagate and out-compete the other clusters. It's a kind of cluster optimisation process. By 'fidelity' I mean the cluster chemistry is reproduced accurately. Biological organisms achieve this through an immensely complex auto-catalytic reaction network involving proteins, lipids, RNA, DNA and minerals.

I suggest that as soon as an SALR cluster evolves, purely by chance, a very basic auto-catalytic reaction network, life is practically inevitable. Basically, I am arguing in favour of Darwin's 'warm little pond', in which evaporation and condensation cycles of the warm pond drove the origin of life. This SALR-world idea explains how this might have happened. The really useful thing about this idea is that it allows reproduction to be driven by physics. The specific chemical pathway is no longer important. In other words, the origin of life is a problem in chemical physics, not organic chemistry [3].

[1] M.B. Sweatman 'Giant SALR cluster reproduction, with implications for their chemical evolution', Molecular Physics, Vol 116, 1945-1952 (2018).
[2] M.B. Sweatman and R. Insall 'Assembly of the Actin Catalyst WASP by Giant SALR Cluster Formation', Advanced Theory and Simulations, accepted (2019).
[3] M.B. Sweatman and L. Lue 'The giant SALR cluster fluid: a review', Advanced Theory and Simulations, accepted (2019).