Paul Davies: There’s been a lot of research on the setting in which life on Earth may have begun. And there are various fashions. One of these is that it might have started hot and deep.
Astrophysicist Paul Davies of Arizona State University studies the origins of life on our planet.
Paul Davies: It may well have started one or two kilometers beneath the sea bed near one of the volcanic vents that are so common where the internal heat of the Earth comes up and meets the ocean and creates thermal pandemonium.
Tiny microbes, called extremophiles, have been discovered living in the extreme heat of these sea vents.
Paul Davies: I think that offers a possible setting. Life may have begun deep down under the ground and then only later evolved and adapted to cooler surface conditions on Earth.
Davies added that scientists still know little of how life started.
Paul Davies: Scientifically, we’re no better off now than we were off 30 or 40 years ago. The scientific facts are more or less the same. We still have no theory of how life began. It could be that it is an exceptionally rare thing. Or it could be that it is something that is more or less automatic and what happened where there were the right conditions. So the obvious way to test that is to look for it happening many times on Earth.
Paul Davies said that life on Earth might not have even originated from Earth, but possibly from another planet.
Paul Davies: It could be that life didn’t even start on Earth. It may have started in space. It may have started, in fact, in very cold conditions and have been delivered to Earth in micrometeorites or comet impacts or something of that sort, and then established itself on Earth and evolved to spread to the deep, hot subsurface.
He said that Earth may have been sterilized by enormous, heavy bombardments early in its history.
Paul Davies: Only the things that lived deep underground in the hot temperatures got through that genetic bottleneck. And so it could well be that the descendants of life on Earth descended from these from organisms that survived that impact. But the origin of life, we have no idea, it could have been somewhere else entirely.
Davies said scientists have connected about diverse settings for the origin of life, from raindrops and drying lagoons and deep subsurface pores of rocks.
Paul Davies: Or on Mars, it’s entirely likely life began on Mars and came later to Earth, Mars was actually a more favorable planet for life to get going in the early history of the solar system. Again, we don’t have to be restricted to Earth. But wherever it started, what we’re interested in is, did it start more than once, and how can we best test that? It seems to me the best way is looking for multiple forms of life right here on Earth.
Paul Davies talked more about his investigations of life’s origins and the possible connection with extraterrestrial life.
Paul Davies: We’re all used to the idea of life on other worlds, and think of this as alien life, as having a separate origin, as being weird, different from us, not only what it looks like but also its biochemistry. A lot of thought’s been given to, well, if you find life on Mars or Europa what will we look for? It could be completely different from nucleic acid and protein life that we find here on Earth.
But, he said, this assumes that life is going to form readily in Earth-like conditions all around the universe.
Paul Davies: It could be that it’s a stupendously incredible freak, it could be that life is just confined to Earth, it’s happened only once, and we’re it. So how can we discriminate between these two different extremes?
Jorge Salazar has conducted thousands of in-depth interviews with scientists in the process of creating science content for EarthSky. He also helps host the 90-second EarthSky podcasts. Jorge has a bachelor's degree in physics from the University of Texas at Austin. He knows a lot about a lot of different things. For EarthSky, he has explored subjects as diverse as nanotechnology, ecosystem-based management, climate change, global health, international environmental treaties, astrophysics and cosmology, and environmental security. His penetrating research style, poetic writing, and ability to track down and speak with Nobel prize-winning laureates, all make him a huge asset to EarthSky.