Extra: Did Life Start Twice On Earth?
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What is the main topic discussed in this episode?
Future Proof with Jonathan McCrae
on News Talk. Proudly supported by Research Ireland. Despite the mathematics, perhaps the only thing that keeps us doubting the existence of aliens elsewhere in the universe is that on this planet, over a span of four and a half billion years, life only emerged once. As far as we know, but could there have been multiple origins of life on Earth? Bill Martin is an evolutionary biologist and head of the Institute of Molecular Evolution at Heinrich Heine University in Düsseldorf. He joins me now. Bill, welcome to the program. Uh the the thing that I think about at night when I wake up at three o'clock in the morning because I can't sleep for one reason or another, is that our best theory right now, and it's like we're pretty certain about this, is that we came from rock.
Why do scientists think life on Earth may have started only once?
And I find that such a crazy idea. So there was a period where we were rock, and then there was a period where we were living things that we we all know and sometimes love and sometimes hate. Um the fascinating thing is that transition is how something that was inert became something that was living. And that's what we wanted to talk to you a little bit about about. So how do we figure out the question of how that happened?
Jonathan, you wake up at night with very difficult questions. I suggest you go for simpler questions in the middle of the night. It makes it easier to go back asleep. Uh everything does point at the moment to the notion or the idea or the theory that life arose from rocks, not just rocks themselves, but from rocks and water, rock-water interactions. Of course, there had to be carbon involved. And there had to be nutrients involved. And I guess most of us would say life arose once, uh, because we look at the attributes that are common to all cells. For example, the genetic code. The genetic code arose once. That's a the information processing program that converts information in genes into information in proteins.
That's the same in all cells. It's the best the best evidence we have for a single origin. But there are at the most basic level, if we take complicated cells like our own eukaryotes that arose very late in evolution. We go down to the cells, the kinds of cells that existed on the early Earth maybe four billion years ago. There are two kinds, very distinct kinds. There are and these have been known since the nineteen seventies. There are bacteria, the standard sorts of things that gives us infections and that That uh colonize our gastrointestinal system and help us live. And then there are other cells called archaea, which were discovered by Coller Wolves and colleagues in the 1970s and uh George Fox.
And archaea are very different. They have different kinds of lipids in their membrane that surrounds the cell. They have different kinds of uh cell wall that compartmentalizes them from the environment. And so one of the questions has been, is did one evolve did bacteria evolve from archaea? Did Archaea evolve from bacteria? Or did they evolve from something simpler that did not have cell walls and membranes and therefore was not a free living cell?
Yeah. People may have heard on the program this term Luca, the last universal common ancestor. And and and and this idea that there was at one point the springing out of life somehow from rocks and nutrients and pressure and temperature that the the beginning of something living began. W when you look at your research, what what is your take on Luca?
Okay, on the early earth there was a time when there was no life, and there was a time when there were free living cells, bacteria and archaea. That's life. Okay, life as we know it, cells that divide and propagate.
And and and so just to just to just to drill down that, you're talking about w once once you get something that can live on its own, um, divide cells, that has a cell, that has a structure, you know, that i it can have its parts inside, it can respirate, it can re reproduce, it creates weight, it uses energy, this is this is something that we can definitely say, this is separate, this is this is now something we definitely call living.
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Chapters
4 chapters
1
What is the main topic discussed in this episode?
0:01–0:49
2
Why do scientists think life on Earth may have started only once?
0:49–9:25
3
What is the evidence that the universal genetic code points to a single origin?
9:25–11:37
4
How do bacteria and archaea differ and what does that tell us about early evolution?
11:37–14:59