In his book "On the Parts of Animals," Aristotle critiqued Hippocrates, stating that bones do not come after flesh, but rather flesh grows around the bones.

Hippocrates, who studied animal miscarriage embryos, stated that the embryo develops in four stages: the sperm of the male and female, the coagulation of the mother's blood, flesh beginning to form, and then bones growing hard.

Keith Moore claimed that bones come before flesh in embryo development.

In his book "On Semen," the Greek scientist Galen described the human embryo stages as: the two semens, plus menstrual blood, unshaped flesh, bones, and then flesh growing on and around the bones.