Significance Patterns of pairwise correlations in sequence alignments can be used to reconstruct the network of residue-residue contacts and thus the three-dimensional structure of proteins. Less explored, and yet extremely intriguing, is the functional relevance of such coevolving networks: Do they encode for the collective motions occurring in proteins at thermal equilibrium? Here, by combining coevolutionary coupling analysis with a state-of-the-art dimensionality reduction approach, we show that the network of pairwise evolutionary couplings can be analyzed to reveal communities of amino acids, which we term “evolutionary domains,” that are in striking agreement with the quasi-rigid protein domains obtained from elastic network models and molecular dynamics simulations.