Figure 9.

The position of birth for six placental mammals relative to the event scale (x-axis); the age of each mammal in PC days can be read for birth (or any event scale value) on the y-axis. The five placental mammals are chosen to represent close to the full range of the dataset and include one highly precocial mammal, the guinea pig. For an example, in the mouse at birth cortical neurogenesis is still underway and synaptogenesis in the forebrain is only beginning, while in the guinea pig at birth, cortical neurogenesis, cortical cell migration, and basic axonogenesis is entirely complete, and the point of peak synaptic density has passed (human (blue dot), macaque (red dot), cat (yellow cat), guinea pig (green dot), and mouse (black dot).