Origin of Life

Is this how life began?

All life on Earth is thought to be related to a type of single-celled organism called the 'Last Universal Common Ancestor', or LUCA. But LUCA was not necessarily the first cell to exist. Imagine the very first cell. It would still have been too complex to simply have formed spontaneously. Much more likely, before the very first cell we would recognise, there was another 'cluster' of complex chemicals that would be unreconisable to us as a cell. And yet it must too have evolved from earlier clusters of chemicals. Therefore, it must also have been 'alive', just not as we know it.

Now, go back further in time and imagine what the very first cluster of chemicals that could be considered 'alive' looked like? Difficult isn't it. However, in order for chemcial evolution to occur, even this most primitive cluster of chemcials, that can still be considered to be alive, must have been able to reproduce.

Nobody knows what this cluster of chemicals looked like. Conventionally it is thought that reproduction requires complex chemical reaction networks. The paradox at the heart of studies of the origin of life and synthetic life is this question; 'How can a cluster of chemicals be sufficiently complex to reproduce and evolve, and yet sufficiently simple that its parent formed spontaneously?' Its parent must have been able to form spontaneously, becuase if it could not, then the parent exhibits 'death' and must therefore be alive, and hence the daughter cluster is not the first living organism.

My new work just published provides a potential answer to this paradox. It shows that even the simplest cluster imaginable, without any chemistry at all, can reproduce. Instead of complex chemistry, all that is needed is simple physics, i.e. particles should have a long-range repulsion. As most biochemicals exhibit a long-range repulsion through becoming charged in water (e.g. through protonation or deprotonation), reproduction of simple clusters is likely to be ubiquitous. Quite possibly, it is happening right now in every cell of your body, and it might also have happened within the earliest ponds of 'primordial soup' as soon as Earth was cold enough for these clusters to form. Therfore, perhaps life began soon after these very simple 'SALR' clusters formed, with chemical evolution leading, eventually, to us today.

The video above shows that clusters of a single type of particle (or chemical) with a long-range repulsion (and a short-range attraction) can reproduce. There are no chemical reactions involved. Why hasn't this behaviour been seen before? In fact, it probably has, around 50 years ago, but that work by Sidney Fox has largely been ignored.

Proteins and other biological molecules are already known to form stable clusters in solution. There is now good evidence, from Jan Sefcik's group at Strathclyde, that amino acids, the building blocks of proteins, also form giant clusters in solution. Given their similar chemical structure, it is possible that nucleobases, the building blocks of DNA and RNA, might also form clusters in solution. But, until now, it wasn't realised that these clusters, which are probably all forms of giant SALR cluster, can spontaneously reproduce. However, around 50 years ago, Sidney Fox, an American chemist, showed that what he called 'proteinoid microspheres' could reproduce. He observed their reproduction directly under an optical microscope. At the time, he argued in a series of papers that his proteinoid microspheres were precursors to life, but few other people agreed, and with the advent of genetics the search for the origin of life took a different direction.

This work is available online in the journal 'Molecular Physics'. It potentially opens a new avenue in the search for the origin of life and in studies of synthetic life.

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