The course of human events: predicting the timing of primate neural development

A recent model of the timing in which neural developmental events occur in a variety of mammals has shown high predictability of the order and duration of these events across species when appropriately computed. The model, originally derived to study the developmental mechanisms of evolutionary change in the nervous system, is adapted in this paper to predict the course of those events in the developing human, a sequence that has been difficult to determine using non-invasive neuroanatomical techniques. Using a modified version of our original regression model, we generate predicted times of occurrence for a large number of developmental events in the human embryo and fetus, and include a chart of comparable events for macaque monkeys. We discuss a bidirectional variability in the original model which allowed us to identify limbic and cortical primate neural events that are significantly deviant from the general mammalian norm, but which also proved predictable following modification. We test the modified model against empirically derived values for neural events not included in the original model, as well as through comparisons with human developmental sequences inferred by other methods. In view of the remarkable stability in the course of development across species, knowledge of the timing of human neural events need not be entirely restricted to the limited existent embryonic and infant data. Although the primate neural development sequence is somewhat more complex than that for other mammals, primate data continue to support a theory of developmental conservation across evolution.