Alex McColgan

When these pathways loop around on themselves, they are known as autocatalytic sets.

These are nascent forms of metabolism.

Crucially, these metabolisms are spontaneous and can exist without the need for evolved enzymes.

We have seen how the molecules present on early Earth interact and produce lifelike behaviours without the need for the highly specialised cellular control.

Much of life's chemistry may indeed be spontaneous.

metabolism, chemical selection, division, information transfer, but in order for life to emerge and for all these processes to come together, we need time.

But incredibly, not much time at all.

The Earth formed around 4.54 billion years ago.

The Moon was created 4.5 billion years ago.

There were liquid oceans around 4.4 billion years ago,

and the earliest life is present potentially as early as 4.3 billion years ago.

For something regarded by many as unlikely, it's curious, don't you think, that almost as soon as it is given the chance, life emerges.

Maybe life is inevitable.

At least, it was on the early Earth, because Earth has a lot of free energy and is, in effect, a giant battery.

Some 4 billion years ago, our ocean was acidic and lacking in electrons, while the molten mantle just below it was alkaline and rich in electrons, a huge chemical charge imbalance that has been shown to be used to power chemical reactions that are evolving towards life.

There is a consensus that somewhere on this world, where the inside of the Earth meets the outside,

where the two ends of the battery meet, there was a spark of some sorts.

There are deep sea hydrothermal vents, gas filled caves, hot springs, evaporating pools and volcanic areas totally devoid of oxygen.

All have all the elements that we think are required for life to emerge to harvest this free energy source, and all would have killed us if we were able to travel back in seconds.

It is proposed that Luca was a methanogen, originating at one location like these, an organism that reacted hydrogen with carbon dioxide to make methane.