The theory of recapitulation, also called the biogenetic law or embryological parallelism—often expressed using Ernst Haeckel's phrase "ontogeny recapitulates phylogeny"—is a historical hypothesis that the development of the embryo of an animal, from fertilization to gestation or hatching (ontogeny), goes through stages resembling or representing successive adult stages in the evolution of the animal's remote ancestors (phylogeny). It was formulated in the 1820s by Étienne Serres based on the work of Johann Friedrich Meckel, after whom it is also known as Meckel–Serres law.
Since embryos also evolve in different ways, the shortcomings of the theory had been recognized by the early 20th century, and it had been relegated to "biological mythology" by the mid-20th century.
Analogies to recapitulation theory have been formulated in other fields, including cognitive development and art criticism.
Since embryos also evolve in different ways, the shortcomings of the theory had been recognized by the early 20th century, and it had been relegated to "biological mythology" by the mid-20th century.
Analogies to recapitulation theory have been formulated in other fields, including cognitive development and art criticism.
Embryology
Meckel, Serres, Geoffroy
The idea of recapitulation was first formulated in biology from the 1790s onwards by the German natural philosophers Johann Friedrich Meckel and Carl Friedrich Kielmeyer, and by Étienne Serres after which, Marcel Danesi states, it soon gained the status of a supposed biogenetic law.
The embryological theory was formalised by Serres in 1824–26,
based on Meckel's work, in what became known as the "Meckel-Serres Law".
This attempted to link comparative embryology with a "pattern of unification" in the organic world. It was supported by Étienne Geoffroy Saint-Hilaire,
and became a prominent part of his ideas. It suggested that past
transformations of life could have been through environmental causes
working on the embryo, rather than on the adult as in Lamarckism. These naturalistic ideas led to disagreements with Georges Cuvier. The theory was widely supported in the Edinburgh and London schools of higher anatomy around 1830, notably by Robert Edmond Grant, but was opposed by Karl Ernst von Baer's ideas of divergence, and attacked by Richard Owen in the 1830s.
George Romanes's 1892 copy of Ernst Haeckel's controversial embryo drawings
Haeckel
Ernst Haeckel (1834–1919) attempted to synthesize the ideas of Lamarckism and Goethe's Naturphilosophie with Charles Darwin's
concepts. While often seen as rejecting Darwin's theory of branching
evolution for a more linear Lamarckian view of progressive evolution,
this is not accurate: Haeckel used the Lamarckian picture to describe
the ontogenetic and phylogenetic history of individual species, but
agreed with Darwin about the branching of all species from one, or a
few, original ancestors. Since early in the twentieth century, Haeckel's "biogenetic law" has been refuted on many fronts.
Haeckel formulated his theory as "Ontogeny recapitulates
phylogeny". The notion later became simply known as the recapitulation
theory. Ontogeny is the growth (size change) and development (structure change) of an individual organism; phylogeny is the evolutionary
history of a species. Haeckel claimed that the development of advanced
species passes through stages represented by adult organisms of more
primitive species.
Otherwise put, each successive stage in the development of an
individual represents one of the adult forms that appeared in its
evolutionary history.
For example, Haeckel proposed that the pharyngeal grooves between the pharyngeal arches
in the neck of the human embryo not only roughly resembled gill slits
of fish, but directly represented an adult "fishlike" developmental
stage, signifying a fishlike ancestor. Embryonic pharyngeal slits, which
form in many animals when the thin branchial plates separating
pharyngeal pouches and pharyngeal grooves perforate, open the pharynx to the outside. Pharyngeal arches appear in all tetrapod embryos: in mammals, the first pharyngeal arch develops into the lower jaw (Meckel's cartilage), the malleus and the stapes.
Haeckel produced several embryo drawings
that often overemphasized similarities between embryos of related
species. Modern biology rejects the literal and universal form of
Haeckel's theory, such as its possible application to behavioural
ontogeny, i.e. the psychomotor development of young animals and human
children.
Contemporary criticism
Drawing by Wilhelm His of chick brain compared to folded rubber tube, 1874. Ag (Anlage) = Optic lobes, matching bulges in rubber tube.
Haeckel's drawings misrepresented observed human embryonic
development to such an extent that he attracted the opposition of
several members of the scientific community, including the anatomist Wilhelm His, who had developed a rival "causal-mechanical theory" of human embryonic development.
His's work specifically criticised Haeckel's methodology, arguing that
the shapes of embryos were caused most immediately by mechanical
pressures resulting from local differences in growth. These differences
were, in turn, caused by "heredity". His compared the shapes of
embryonic structures to those of rubber tubes that could be slit and
bent, illustrating these comparisons with accurate drawings. Stephen Jay Gould noted in his 1977 book Ontogeny and Phylogeny
that His's attack on Haeckel's recapitulation theory was far more
fundamental than that of any empirical critic, as it effectively stated
that Haeckel's "biogenetic law" was irrelevant.
Embryology theories of Ernst Haeckel and Karl Ernst von Baer compared
Darwin proposed that embryos resembled each other since they shared a
common ancestor, which presumably had a similar embryo, but that
development did not necessarily recapitulate phylogeny: he saw no reason
to suppose that an embryo at any stage resembled an adult of any
ancestor. Darwin supposed further that embryos were subject to less
intense selection pressure than adults, and had therefore changed less.
Modern status
Modern evolutionary developmental biology
(evo-devo) follows von Baer, rather than Darwin, in pointing to active
evolution of embryonic development as a significant means of changing
the morphology of adult bodies. Two of the key principles of evo-devo, namely that changes in the timing (heterochrony) and positioning (heterotopy)
within the body of aspects of embryonic development would change the
shape of a descendant's body compared to an ancestor's, were however
first formulated by Haeckel in the 1870s. These elements of his thinking
about development have thus survived, whereas his theory of
recapitulation has not.
The Haeckelian form of recapitulation theory is considered defunct.
Embryos do undergo a period where their morphology is strongly shaped
by their phylogenetic position, rather than selective pressures, but
that means only that they resemble other embryos at that stage, not
ancestral adults as Haeckel had claimed. The modern view is summarised by the University of California Museum of Paleontology:
Embryos do reflect the course of evolution, but that course is far more intricate and quirky than Haeckel claimed. Different parts of the same embryo can even evolve in different directions. As a result, the Biogenetic Law was abandoned, and its fall freed scientists to appreciate the full range of embryonic changes that evolution can produce—an appreciation that has yielded spectacular results in recent years as scientists have discovered some of the specific genes that control development.
Applications to other areas
The idea that ontogeny recapitulates phylogeny has been applied to some other areas.
Cognitive development
English philosopher Herbert Spencer
was one of the most energetic proponents of evolutionary ideas to
explain many phenomena. In 1861, five years before Haeckel first
published on the subject, Spencer proposed a possible basis for a
cultural recapitulation theory of education with the following claim:
If there be an order in which the human race has mastered its various kinds of knowledge, there will arise in every child an aptitude to acquire these kinds of knowledge in the same order... Education is a repetition of civilization in little.
— Herbert Spencer
G. Stanley Hall
used Haeckel's theories as the basis for his theories of child
development. His most influential work, "Adolescence: Its Psychology and
Its Relations to Physiology, Anthropology, Sociology, Sex, Crime,
Religion and Education" in 1904
suggested that each individual's life course recapitulated humanity's
evolution from "savagery" to "civilization". Though he has influenced
later childhood development theories, Hall's conception is now generally
considered racist.
Developmental psychologist Jean Piaget favored a weaker version of the formula, according to which ontogeny parallels phylogeny because the two are subject to similar external constraints.
The Austrian pioneer of psychoanalysis, Sigmund Freud,
also favored Haeckel's doctrine. He was trained as a biologist under
the influence of recapitulation theory during its heyday, and retained a
Lamarckian outlook with justification from the recapitulation theory.
Freud also distinguished between physical and mental recapitulation,
in which the differences would become an essential argument for his theory of neuroses.
In the late 20th century, studies of symbolism and learning in
the field of cultural anthropology suggested that "both biological
evolution and the stages in the child's cognitive development follow
much the same progression of evolutionary stages as that suggested in
the archaeological record".
Art criticism
The musicologist Richard Taruskin
in 2005 applied the phrase "ontogeny becomes phylogeny" to the process
of creating and recasting art history, often to assert a perspective or
argument. For example, the peculiar development of the works by
modernist composer Arnold Schoenberg
(here an "ontogeny") is generalized in many histories into a
"phylogeny" – a historical development ("evolution") of Western music
toward atonal styles of which Schoenberg is a representative. Such historiographies
of the "collapse of traditional tonality" are faulted by art historians
as asserting a rhetorical rather than historical point about tonality's
"collapse".
Taruskin also developed a variation of the motto into the pun
"ontogeny recapitulates ontology" to refute the concept of "absolute
music" advancing the socio-artistic theories of the musicologist Carl Dahlhaus. Ontology
is the investigation of what exactly something is, and Taruskin asserts
that an art object becomes that which society and succeeding
generations made of it. For example, Johann Sebastian Bach's St. John Passion, composed in the 1720s, was appropriated by the Nazi regime in the 1930s for propaganda. Taruskin claims the historical development of the St John Passion (its ontogeny) as a work with an anti-Semitic
message does, in fact, inform the work's identity (its ontology), even
though that was an unlikely concern of the composer. Music or even an
abstract visual artwork can not be truly autonomous ("absolute") because
it is defined by its historical and social reception.
