Well, not 3, but 1.
Most every living thing on this Planet comes from a single cell. Mom and Pops donate 50% of the DNA and one cell divides and divides until a living thing develops, grows and you know the rest.
Whale bones and little kids all come the same way. One of the first things to develop in living things are the nervous systems. From the tissue that eventually because the nervous system all processes are coordinated. The quality of our development and the quality of our life depends on the quality of your nervous system.