In 2013 Esposito and collaborators published a paper, when for the first time, scientists demonstrate that the babies calming response to carrying is an evolutionary trait of mother-child relationship.
They demonstrate that infants under 6 months of age, when carried by a walking mother, immediately stopped crying and show a rapid heart rate decrease. A similar behavior was evident also in mice mothers and their pups.
The calming response is regulated by central, motor and cardiac signals.
mothers, if your babies are crying, carry them, maybe pacing the floor and walking a little. This will help out little cubs calm down.
For further information: “Infant calming response during maternal carrying in human and mice”, Esposito et al., Current Biology 23, 739-745, 2013. https://doi.org/10.1016/j.cub.2013.03.041