‘It is mere rubbish thinking, at present, of the origin of life,’ Charles Darwin wrote to his friend Joseph Hooker in 1863. But that didn’t stop him speculating to Hooker just eight years later about a ‘warm little pond’ containing a prebiotic soup from which the first life emerged. And it hasn’t stopped us since from accumulating theories about the origin of life in almost embarrassing profusion, at a rate that far exceeds our capacity to test or eliminate any.
Among those theories, I’ve never felt very attracted by the ones that bob in Darwin’s soup, which focus on how the basic molecular ingredients of living organisms – amino acids, sugars, nucleotide bases – might have been made before life emerged. This must evidently have happened somewhere in the universe, but it leaves us a very long way from anything even close to being alive. Neither am I a fan of the obsession with making molecular systems that replicate, as if this alone crosses the threshold for life.
I’m excited, then, by the notion highlighted in recent work on the nature of the last universal common ancestor (Luca), the putative progenitor of all the biosphere, which suggests that Luca could have had the key ingredients of life (genetic information and metabolism) before it was even truly alive and autonomous.1 That picture frees us from seeing the beginning of life as a sudden all-or-nothing affair.
Amino acids, sugars and nucleotide bases
Another reason to be more relaxed about locating that Darwinian pond on the prebiotic Earth is that we no longer have any particular reason to suppose that the basic molecules were created in situ. Just about all of the ingredients could plausibly have arrived from space, ready-made in astrophysical environments for dusting newly-formed planets. Amino acids have long been known to be present in carbon-rich meteorites.2 So have sugars,3 and recent work has revealed one – erythrulose – in the interstellar medium,4 thought to be formed from simpler molecules on the surfaces of dust grains.
You might think that the nucleotide bases adenine, guanine, cytosine, thymine and uracil would be less likely to form spontaneously in space. But all of them have been found in meteorites, and scientists in Japan recently detected the complete set in samples collected by the Japanese space agency’s Hayabusa2 mission that landed on the asteroid Ryugu in 2018.5
There are also extraterrestrial examples of those prebiotic resources joining up to form oligomers – the first stage in the formation of complex large molecules like those in biology. In general, such reactions need an energy source, such as ultraviolet light. But it doesn’t take much.
Earlier this year a team at Xiamen University in China reported that amino acids such as alanine and arginine can be linked into dipeptides on the surface of the olivine mineral forsterite in the presence of low doses of ionising radiation.6 The same environment could also couple the nucleotide base adenosine to phosphate, making the biologically important molecules adenosine monophosphate (AMP) and adenosine triphosphate (ATP). Forsterite is a source of phosphorus compounds that can activate peptide bond formation. The radiation was simply that in the cosmic environment: the experiments were conducted on board the Chinese Space Station in 2024.
Of course, none of this means that life’s basic components did indeed arrive from space
While many of the putative prebiotic reactions in space environments happen in aqueous conditions, such as on the surfaces of ice grains, those peptide-forming reactions were solvent-free, in the solid state. This could be significant, because irradiation – for example, by high-energy ions like those in the solar wind – might also cause peptide hydrolysis in the presence of water.
At any rate, simple dipeptides like the dimer of glycine have never been detected in astronomical observations. But a new report, suggests that this glycylglycine dipeptide can indeed be made within icy particles by irradiation, without any need for catalytic activation by a mineral. A team in Denmark, Hungary and the UK has shown that this peptide is formed when glycine ice is zapped with a high-energy beam of protons, simulating cosmic rays or the solar wind.7 Just how widespread glycine is in the cosmic environment remains unclear, but there are arguments why it might be fairly common. Peptides are themselves known to be catalysts of peptide synthesis, raising the prospect of an autocatalytic process.8
Of course, none of this means that life’s basic components did indeed arrive from space. And I can’t help suspecting that life didn’t begin within a sprinkling of prebiotic cosmic dust over the planet. But if instead it started deep in the oceans, did the first organisms emerge to find the surface of the planet already primed for making more?
References
1 N Mrnjavac et al, Sci. Adv., 2026, DOI: 10.1126/sciadv.aef3128
2 K Kvenvolden et al, Nature, 1970, 228, 923 (DOI: 10.1038/228923a0)
3 Y Furukawa et al, PNAS, 2019, 116, 24440 (DOI: 10.1073/pnas.1907169116)
4 I Jiménez-Serra et al, Nat. Astron., 2026, DOI: 10.1038/s41550-026-02905-7
5 T Koga et al, Nat. Astron., 2026, 10, 655 (DOI: 10.1038/s41550-026-02791-z)
6 R Ding et al, Nat. Commun., 2026, 17, 3210 (DOI: 10.1038/s41467-026-69575-x)
7 A T Hopkinson et al, Nat. Astron., 2026, 10, 531 (DOI: 10.1038/s41550-025-02765-7)
8 M Gorlero et al, FEBS Lett., 2009, 583, 153 (DOI: 10.1016/j.febslet.2008.11.052)
