Ernst Haeckel,
German scientist, a contemporary and supporter of
Charles Darwin, used this phrase to describe his
embryological observation, which says basically that the development of the individual retraces the
evolutionary steps of the
species --- from its conception to its birth (or hatching, as the case may be), every animal passes through the evolutionary phases identical to the general process of evolution, from one-celled animals to advanced life-forms, over eons of time. In other words, every animal embryo "evolves" from a microscopic mass of cells to a fish, then to an amphibian, then to a reptile, and so on.
In terms of the human brain:
- At 25 days - the embryonic brain resembles the brain of a worm
- At 40 days - the embryonic brain resembles the brain of a vertebrate (fish)
- At 100 days - the embryonic brain resembles a mammalian brain
- At 5 months - the embryonic brain resembles the brains of other primates
Other terms that sound
tongue-twistingly similar are:
Ontology recapitulates
phylogeny
Ontology recapitulates
philology
Technology recapitulates phylogeny