what do you understand by recapitulation theory

The Recapitulation Theory, also known as the biogenetic law, is a historical hypothesis that the development of an animals embryo goes through stages resembling or representing successive adult stages in the evolution of the animals remote ancestors. The theory was first formulated in the 1820s by Étienne Serres based on the work of Johann Friedrich Meckel. Ernst Haeckel later formulated the theory as "Ontogeny recapitulates phylogeny," meaning that the developmental history of an organism from the zygote stage until it is ready for hatching or gestation repeats the history of the evolution of the ancestors. However, 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. Despite its discreditation, analogies to recapitulation theory have been formulated in other fields, including cognitive development and music criticism. The theory had a strong influence on social and educational theories of the late 19th century.