I don't understand what Atchley factors are, here's the paper: https://www.pnas.org/doi/full/10.1073/pnas.0408677102 https://www.pnas.org/doi/full/10.1073/pnas.

I don't understand what Atchley factors are, here's the paper: https://www.pnas.org/doi/full/10.1073/pnas.0408677102 https://www.pnas.org/doi/full/10.1073/pnas.0408677102