Today life has conquered every square inch of Earth, but when the planet formed it was a dead rock. How did life get started?
We have probably been wondering for millennia how life started on Earth. At some point we decided that it must have been done by one or more gods, and we’ve elaborated that hypothesis as it evolved over the ages. We’ve never tested it, though. No one has ever done an experiment to see if a god could create life. We just sort of said that they must have because, well, how else could it have happened? The judicious application of exclusion, torture and execution kept the questions to a minimum.
Eventually we reached a point where inquiry could no longer be peremptorily quashed, at least not everywhere all the time, and we began to look at the question in a more naturalistic way. That is, could life have arisen on Earth through the natural workings of physical elements and forces? The linked BBC article is a long, comprehensive look at the evolution of this inquiry over the last two hundred years or so. I strongly recommend reading it, but in the case of TL;DR, here’s the condensed version: We haven’t settled on a single theory yet, but we’ve certainly shown that’s it’s plausible.
From the BBC article:
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 microbes dating back 3.7 billion years.
This means we can define the problem of the origin of life more precisely. Using only the materials and conditions found on the Earth over 3.5 billion years ago, we have to make a cell.
Before the 1800s, most people believed in “vitalism”. This is the intuitive idea that living things were endowed with a special, magical property that made them different from inanimate objects.
… the big biological breakthrough of the 19th Century was the theory of evolution, as developed by Charles Darwin and others.
The idea that life formed in a primordial soup of organic chemicals became known as the Oparin-Haldane hypothesis. It was neat and compelling, but there was one problem. There was no experimental evidence to back it up. This would not arrive for almost a quarter of a century.
The Miller-Urey experiment.
Miller connected a series of glass flasks and circulated four chemicals that he suspected were present on the early Earth: boiling water, hydrogen gas, ammonia and methane. He subjected the gases to repeated electric shocks, to simulate the lightning strikes that would have been a common occurrence on Earth so long ago.
And five more chapters follow. It’s really worth the read. But I think I can safely guarantee that the creationists won’t be convinced. They prefer the age of vitalism.