About 9.2 percent of people are left-handed. In other words, less than 10 percent of humans exhibit left-handedness. However, the proteins in living organisms are 100 percent left-handed. I know proteins don’t have hands, but using the term “handedness” helps to explain how proteins are structured. Proteins are made from amino acids, which fold into left-handed shapes that enable their functions in living beings. These proteins are composed of amino acids, which are also left-handed.
This handedness is more accurately called “chirality.” There are over 500 different amino acids, and they exhibit both left and right chirality. However , only 22 of them are used to make proteins, and their chirality is all left-handed. This creates a mystery. If amino acids existed on early Earth in equal amounts of right- and left-handed forms, and life requires only left chirality, how could life have formed spontaneously? Some thus-far unexplained force would have to select only left-handed amino acids to come together to get life started. Robert F. Service, writing on science. org, called this “an enduring mystery.”
Scientists have proposed several ideas to explain why proteins are left-handed. Some suggest meteorites delivered left-handed amino acids to early Earth. It appears that meteorites are rich in these amino acids, likely due to exposure to polarized light. Another hypothesis is that magnetic fields on early Earth twisted the biomolecules. Robert Service asks, “But even if some external force imparted an initial bias, what propagated it?”
Gerald Joyce, a chemist specializing in the origins of life and president of the Salk Institute for Biological Studies, said, “Perhaps it was just a statistical coin flip that caused an original bias toward building blocks of one-handedness to form. But once that coin flipped, it caused other coins to flip.” Those of us who believe in a Creator are often accused of using a “God-of-the-gaps” explanation for life’s mysteries. To me, this explanation for the left-handedness of proteins sounds like a “coin-flip-of-the-gaps.”
— Roland Earnst © 2025
Reference: science.org and Science magazine, Vol 383, Issue 6686
The cover story of the June (2019) issue of Reader’s Digest lists 50 features of your amazing human body. The article gives some evolutionary guesses as to how some of those features could have developed. We thought it was especially interesting that science has not explained nine of the 50: