Chemists discover plausible recipe for early life on Earth
Their experiments, described today in the journal Nature Communications, demonstrate that key chemical reactions that support life today could have been carried out with ingredients likely present on the planet four billion years ago.
The new study outlines how two non-biological cycles—called the HKG cycle and the malonate cycle—could have come together to kick-start a crude version of the citric acid cycle. The two cycles use reactions that perform the same fundamental chemistry of a-ketoacids and b-ketoacids as in the citric acid cycle. These shared reactions include aldol additions, which bring new source molecules into the cycles, as well as beta and oxidative decarboxylations, which release the molecules as carbon dioxide (CO2).
Paper. (public access) The experiment is interesting but it says a lot about the (lack of) progress in a field when the best that can currently be said of a scenario is that it is plausible. On the other hand, the concept tested deserves a lot of respect, in these times, for not just being another what-if, of which we seem to go through dozens around here every year.
Curiously, we read,
“The chemistry could have stayed the same over time, it was just the nature of the molecules that changed,” says Krishnamurthy. “The molecules evolved to be more complicated over time based on what biology needed.” More.
How did “biology” come to “need” anything, such that molecules “evolved to be more complicated”? Something unacknowledged lurks there, something J. Scott Turner touches on in Purpose and Desire: What Makes Something “Alive” and Why Modern Darwinism Has Failed to Explain It, that life forms seek to remain alive.
See also: What we know and don’t know about the origin of life