The Vital Question

Life arose around half a billion years after the earth’s formation, perhaps 4 billion years ago, but then got stuck at the bacterial level of complexity for more than 2 billion years, half the age of our planet

Some 350 years after the discovery of cells, we still don’t know why life on earth is the way it is.

All complex life on earth shares a common ancestor, a cell that arose from simple bacterial progenitors on just one occasion in 4 billion years.

On the contrary, a population of morphologically complex eukaryotic cells arose on a single occasion – and all plants, animals, algae and fungi evolved from this founder population. Any common ancestor is by definition a singular entity

Over the past two decades, we have learned from their genome sequences and detailed biochemistry that none of the archezoa is a real missing link, which is to say that they are not true evolutionary intermediates. On the contrary, all of them derive from more complex eukaryotes,

Over hundreds of millions of years, complexity gradually increased, as cells learned not only to deal with oxygen, but also to profit from its reactivity: they evolved aerobic respiration, giving them far more power.

This view implicitly underpins the textbook history of the earth. We tend to think of oxygen as wholesome and good, but in fact from the point of view of primordial biochemistry it is anything but: it is toxic and reactive.

Life, as biochemist Albert Szent-Györgyi observed, is nothing but an electron looking for a place to rest.

Carbon comes in two stable forms, or isotopes, which have marginally different masses.2 Enzymes (proteins that catalyse reactions in living cells) have a slight preference for the lighter form, carbon-

Genomes do not predict the future but recall the past: they reflect the exigencies of history.