Does Ontogeny Recapitulate Ontogeny? (Nope, It Doesn't)

Most people who have taken a biology course that touched on reproduction have come across the claim by Ernst Haeckel that “ontogeny recapitulates phylogeny”—that is, that the development of an individual repeats or at least is similar to stages in the development of the species that individual belongs to. Haeckel’s statement was based on the observation that in the course of development of the human embryo, the embryonic individual will temporarily resemble the embryos of other species whose members are less complicated and developed than human beings are. For example, at one stage, the human embryo has gill slits like those of embryonic fish; at another stage, the human embryo has a tail that will be lost as development proceeds. For Haeckel, the stages of embryonic development recapitulate or repeat the stages through which the ancestors of human beings evolved, although actually it’s probably more accurate to say that the stages through which the human embryo develops are periods in which the developing individual resembles embryos of other species.

The idea of recapitulation, so exciting to 19^th-century biologists, has also proved exciting to alternative psychotherapists. They applied the idea to ontogeny, individual development, itself, and not simply to the resemblance of a developing human embryo to embryos of other species. As is common in pseudoscientific thinking, these people jumped from Haeckel’s principle to the idea that they can make recapitulation of early development happen by imitating some of the events that might have been present during an original early developmental stage. Magically, the imitation of the past makes the consequences of earlier events vanish, and they are replaced by the consequences of the imitation. Rituals of imitation—like handfeeding a child in imitation of early feeding experiences—are said to return the child’s development to “square one”, to take a detour around any previous problems or bad experiences, and to deliver the child to a good developmental status, as if previous problems had never been.  

This treatment claim, based on a partial analogy with embryonic development, would require nonexistent empirical support before it could be acceptable. It’s also weakened by alternative psychotherapists’ tendency to forget that child development is driven by two major forces, experience and maturation (genetically determined growth and change), and that although experience is the only factor under the therapists’ control, the power of maturation is essential to developmental change. Alternative therapists like to reference the brain’s plasticity, but when they forget maturation, they omit experience-expectant plasticity—time-limited sensitivity to experience like that seen in the development of vision, or language, or emotional attachment.

For example, Bruce Perry, in a 2006 publication ( “Applying principles of neurodevelopment to clinical work with maltreated and traumatized children”, Chapter 3 in N. Boyd Webb (Ed.), Traumatized youth in child welfare, New York: Guilford), claims that the fetal brainstem’s neurology is shaped by the heart rate of the mother and the rhythmic beat that impinges on the fetus.  ( This claim ignores the maturational factor in the development of any part of the brain.) From this claim, Perry goes on to propose that the brainstem, the part of the brain responsible for functions like temperature control, can be changed by exposing the individual to rhythmic stimuli, drumming, music, dance, and so on; he suggests that EMDR treatment uses this rhythmic reshaping function, and although I have not seen that he expects “tapping” treatments to follow the same pattern, that would make sense within his framework. Many alternative therapists have followed Perry’s pseudoscientific claims and used them to argue that somatic treatments are essential for all forms of mental disorders. Perry’s ideas are the basis of, or supports for, various alternative psychotherapies that use re-enactment of early childhood events with the intention of recapitulating ontogeny.

Did Perry, or any of his colleagues, invent the idea that ontogeny can recapitulate ontogeny (but make it come out right)? No, in fact most of Perry’s ideas go back to somewhere around Haeckel’s time. 

John Hughlings Jackson, a 19^th century neurologist, developed the idea that the nervous system is hierarchically organized, using his work on patients with brain injuries or diseases. He saw that when the cortex was damaged, the patient’s behavior reflected the functioning of lower areas of the nervous system—functioning that had been present in that individual before the cortex was fully developed. Jackson gave this phenomenon the name “regression”, and the term and an analogous concept, psychological regression, were promulgated by Sigmund Freud. Freud’s colleague (and later rival) Sandor Ferenczi, suggested that psychological regression and recapitulation could be accomplished  by “babying” a patient. This proposal has been repeated right into modern times by some transactional analysts, “primal scream” therapists, dance and music therapists, holding therapists, rebirthers, and so on and on. Claims about brain plasticity have been used to support the idea that it should be possible to repeat and correct development.

For all the advocacy, however, we still see no systematic evidence that ontogeny can recapitulate ontogeny. It would be rather surprising if re-enactments could cause recapitulation, because the more developed person is a different individual today than he or she was years ago. Both maturation and experience have done their developmental work, and any new experience—even am imitation of an old one—must interact with that work in order to have an impact. You can’t step into the same river twice, and you can’t learn something for the first time more than once, because the river changes while moving, and you, the individual, are not the same person after that first experience.