It has long been thought that the ingredients for life came together slowly, bit by bit. Now there is evidence it all happened at once in a chemical big bang
5 August 2020
WHEN Earth formed 4.5 billion years ago, it was a sterile ball of rock, slammed by meteorites and carpeted with erupting volcanoes. Within a billion years, it had become inhabited by microorganisms. Today, life covers every centimetre of the planet, from the highest mountains to the deepest sea. Yet, every other planet in the solar system seems lifeless. What happened on our young planet? How did its barren rocks, sands and chemicals give rise to life?
Many ideas have been proposed to explain how it began. Most are based on the assumption that cells are too complex to have formed all at once, so life must have started with just one component that survived and somehow created the others around it. When put into practice in the lab, however, these ideas don’t produce anything particularly lifelike. It is, some researchers are starting to realise, like trying to build a car by making a chassis and hoping wheels and an engine will spontaneously appear.
The alternative – that life emerged fully formed – seems even more unlikely. Yet perhaps astoundingly, two lines of evidence are converging to suggest that this is exactly what happened. It turns out that all the key molecules of life can form from the same simple carbon-based chemistry. What’s more, they easily combine to make startlingly lifelike “protocells”. As well as explaining how life began, this “everything-first” idea of life’s origins also has implications for where it got started – and the most likely locations for extraterrestrial life, too.
The problem with understanding the origin of life is that we don’t know what the first life …