What similarities will alien life forms have to living things here on Earth? We won't know until we find some, but now there is evidence that at least the basic building blocks will be the same.

All terrestrial life forms share the same 20 amino acids. Biochemists have managed to synthesise 10 of them in experiments that simulate lifeless prebiotic environments, using proxies for lightning, ionising radiation from space, or hydrothermal vents to provide the necessary energy. Amino acids are also found inside meteorites formed before Earth was born.

Paul Higgs and Ralph Pudritz at McMaster University in Hamilton, Ontario, Canada, point out that all these experiments produced a subset of the same 10 amino acids and calculate that these 10 require the least amount of energy to form.
This, they argue, suggests that if alien life exists it probably has the same 10 amino acids at its core.

Universal code?

They show how the other 10 may have been added one by one as early life on Earth became more sophisticated. More controversially, they go on to argue that this process dictated the evolution of the genetic code, suggesting it too is universal.

Darren Griffin, a geneticist at the University of Kent, UK, suggests Higgs and Pudritz are pushing their conclusions too far.

"Laws of physics govern the universe, and it seems reasonable to suggest that there are laws of molecular biology that may also be universal," he says. "But it seems unlikely that the very same genetic code would arise on another planet, even if there are similarities in the fundamental molecules such as amino acids."

Journal reference : Physics arXiv preprint


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