Complex organisms seem wired to enable this so-called causal emergence. Emergence refers to the appearance of overall behavior in a complex system of many parts that can’t be predicted or understood by focusing just on what those parts themselves are like.

Philip Ball, How Life Works

The pelvic fins of fish are considered to be the evolutionary precursor to the hindlimbs of tetrapods (four-limbed vertebrates like amphibians, reptiles, birds, and mammals). Does focusing on this component element tell us anything? Or is this focus more like looking at a “three body” system where you only can see one (maybe two) of the bodies.