‘It’s life, Jim, but not as we know it…’

WHAT IS LIFE?

Some questions are so complex that they remain unanswered for centuries. Yet the search for a solution often yields information and wisdom even while the final answer remains out of reach.

The set-up in the lab of 22-year-old chemist Stanley Miller at the University of Chicago was modest–one large five-litre ball-shaped Florence flask and a smaller 500ml flask connected by tubes. The larger flask contained two electrodes together with a mix of methane, ammonia and hydrogen gases. The smaller flask held just water. Things became a bit more spectacular when Miller lit the Bunsen burner under the water flask and charged the two electrodes, so that as steam from the boiling water passed through one of the tubes into the larger flask of gases it was lit up by tiny flashes of ‘lightning’ between the electrodes. Miller left the experiment running, and waited for the results.

After only 24 hours, he could see that a pink liquid had appeared in the tube that led from the gas flask back to the water flask. The system was completely sealed, so these had to be substances formed during the process. Miller let the experiment run for a week, and then analysed the substances. He found what he had almost not dared to hope for: a series of biomolecules, including amino acids, that are important building blocks of all forms of life as we know it.

Miller’s famous experiment, which took place back in 1952, was aiming to create a simplified model of the atmosphere of a young Earth billions of years ago. And he proved that simple chemical compounds can develop into complex biomolecules under those circumstances. Miller had copied the first step towards the formation of life.

But only the first one. Many scientists have since followed in Miller’s footsteps, creating more sophisticated experiments, but it has proven very difficult to take the next critical steps.

If there is only one sort of life on Earth, then perspective is lacking in the most fundamental way.

Indeed the origin of life still remains a big mystery. If we could solve it, we might also answer other universal questions. How unique is life on Earth? Is our existence the result of pure coincidence, or the inevitable result of some law of nature? We might also be able to end the hundreds of years of discussions concerning the nature of life. And that could make life easier to identify if we were to encounter it elsewhere.

The meaning of life

When modern biologists try to define life, they face the same problems that history’s leading thinkers have struggled with