Although it would be tempting to speculate that AA taste receptors may be optimized to sense digestion of the AA composition of the milk of their own species, the trends seen in our results are not convincing, because the aliphatic AA are generally found at equivalent or higher frequencies in human compared with rodent, contrary to this hypothesis (Figure 1, Supplemental Table S1; http://dx.doi.org/10.3168/jds.2013-7317)