The face and jaws are distinctive characteristics of humans and animals,and are evolutionary innovations for vertebrates. The cartilages and bones of the face and jaws are generated from cranial neural crest mesenchyme (NCM),which arises from the dorsal neural tube, but what remains unclear is how these skeletal elements acquire their species-specific differences in size and shape. Now, Eames and Schneider demonstrate, by transplanting neural crest cells from quails into ducks, that the NCM controls both the size and shape of cartilage (see ). By exploiting the marked differences in maturation rate and jaw anatomy between these two birds, the authors show that quail NCM, when transplanted into ducks, imparts species- and stage-specific information about the rate and time of cartilage formation. The NCM does so by regulating FGF signalling and downstream target expression. Thus, these findings reveal an autonomous function for the NCM in generating cartilage size and shape, and highlight the importance of developmental programs in the process of morphological evolution.
