Can someone think of an example of a scientific theory that got superseded by a better one and then got re-incorporated into scientific consensus again?
In my field, I can name only one such theory: Lamarckism - the notion that an organism can pass on to its offspring characteristics that the parent organism acquired through use or disuse during its lifetime.
It became superseded by Darwinian notion of evolution but since discovery of epigenetics, it became more and more obvious that things are not nearly as simple and cracking the genetic code of the individual would tell only a fraction of information about it's genetic expression.
All the genes' expression are influenced by epigenetics which is in part influenced by the lifestyle of the progenitors.
@biomedmax Alchemy posited that one metal could be turned into another. Chemists then discovered that the metals were distinct elements which precluded this transmutation, but nuclear reactions were later discovered in which one metal did become another.