By Michael Marshall
How did life begin? There can hardly be a bigger question. For much of human history, almost everyone believed some version of “the gods did it”. Any other explanation was inconceivable.
That is no longer true. Over the last century, a few scientists have tried to figure out how the first life might have sprung up. They have even tried to recreate this Genesis moment in their labs: to create brand-new life from scratch.
So far nobody has managed it, but we have come a long way. Today, many of the scientists studying the origin of life are confident that they are on the right track – and they have the experiments to back up their confidence.
This is the story of our quest to discover our ultimate origin. It is a story of obsession, struggle and brilliant creativity, which encompasses some of the greatest discoveries of modern science. The endeavour to understand life’s beginnings has sent men and women to the furthest corners of our planet. Some of the scientists involved have been bedevilled as monsters, while others had to do their work under the heel of brutal totalitarian governments.
This is the story of the birth of life on Earth.
Life is old. The dinosaurs are perhaps the most famous extinct creatures, and they had their beginnings 250 million years ago. But life dates back much further.
The oldest known fossils are around 3.5 billion years old, 14 times the age of the oldest dinosaurs. But the fossil record may stretch back still further. For instance, in August 2016 researchers found what appear to be fossilised microbesdating back 3.7 billion years.
The Earth itself is not much older, having formed 4.5 billion years ago.
If we assume that life formed on Earth – which seems reasonable, given that we have not yet found it anywhere else – then it must have done so in the billion years between Earth coming into being and the preservation of the oldest known fossils.
As well as narrowing down when life began, we can make an educated guess at what it was.
Since the 19th Century, biologists have known that all living things are made of “cells”: tiny bags of living matter that come in different shapes and sizes. Cells were first discovered in the 17th Century, when the first modern microscopes were invented, but it took well over a century for anyone to realise that they were the basis of all life.
Using only the materials and conditions found on the Earth over 3.5 billion years ago, we have to make a cell
You might not think you look much like a catfish or a Tyrannosaurus rex, but a microscope will reveal that you are all made of pretty similar kinds of cells. So are plants and fungi.
But by far the most numerous forms of life are microorganisms, each of which is made up of just one cell. Bacteria are the most famous group, and they are found everywhere on Earth.