Is the developmental order of fetal behaviors self-organized in an uterine environment?

Developmental order is one of the fundamental issues of developmental science. de Vries et al. 1982 observed fetal behaviors and suggested that the orders of the timing of first appearance of the behaviors are consistent among fetuses in utero. We have investigated the fetal behavioral development by a computer simulation that has a whole fetal musculoskeletal body, a uterine environment and a nervous system. In this paper, we analyzed data of our simulated fetal behaviors from a perspective of the first appearance. The analysis shows that the order is consistently same as the observation by de Vries et al. 1982 regardless of the value of a nervous system model parameter. The result indicates that physical constraints, including musculoskeletal system, tactile cell distribution, and uterine environment, induce the self-organization of the developmental order.