Modern phylogenetics studies look at variations in animals that are known to be related, and from those can work out when specific structures evolved.

BBC: Language universality idea tested with biology method

Since that time, more advanced cloning technologies have evolved, including the iPS system of induced pluripotent stem cells, which can be grown from nearly any skin cell.

FORBES: July 5th: Interdependence Day

But Prof Hoekstra added that the "modular" nature of the different behaviours that evolved separately in the two is the most suggestive finding: seemingly complex habits and actions may be built up from smaller, genetically-controlled behaviours.

BBC: Mouse burrowing 'in their genes'