These folks' Nature Geoscience paper appears [1] to say nothing more than that, if you take methane and squeeze it a lot under high temperature and pressure, so

These folks' Nature Geoscience paper appears [1] to say nothing more than that, if you take methane and squeeze it a lot under high temperature and pressure, some of it becomes ethane, propane, and butane: Here we use in situ Raman spectroscopy in laser-heated diamond anvil cells to monitor the chemical reactivity of methane and ethane under upper-mantle conditions. We show that when methane is exposed to pressures higher than 2 GPa, and to temperatures in the range of 1,000–1,500 K, it partially reacts to form saturated hydrocarbons containing 2–4 carbons (ethane, propane and butane) and molecular hydrogen and graphite. Although, of course, when you continue to squeeze the ethane, propane, and butane some of it turns back into methane: Conversely, exposure of ethane to similar conditions results in the production of methane, suggesting that the synthesis of saturated hydrocarbons is reversible. That's equilibrium for you. It's hard to believe that any of this is really news to organic chemists, but maybe it is. Or maybe this paper got reviewed by the scientists' best friends. Whatever. I'm neither a geologist nor an organic chemist. In any case, I really admire the phrasing of the final sentence of the abstract: Our results support the suggestion that hydrocarbons heavier than methane can be produced by abiogenic processes in the upper mantle. Very judiciously stated. But this is like saying that the fact that engineers can make diamonds in the laboratory "supports the suggestion" that many of the diamonds under South Africa could have been made in ancient underground laboratories. Yes, A is a necessary condition for B, but the fact that A is true doesn't really say much about the extent to which B is true. Better evidence, please. Preferably in a journal I can actually read. --- [1] I can't read it, of course, without paying $18. Because why should the public be allowed to read the results of the research that we pay for? For-profit journals delenda est.