Embryo Project Encyclopedia Articles

Stephen Jay Gould studied snail fossils and worked at Harvard University in Cambridge, Massachusetts during the latter half of the twentieth century. He contributed to philosophical, historical, and scientific ideas in paleontology, evolutionary theory, and developmental biology. Gould, with Niles Eldredge, proposed the theory of punctuated equilibrium, a view of evolution by which species undergo long periods of stasis followed by rapid changes over relatively short periods instead of continually accumulating slow changes over millions of years. In his 1977 book, Ontogeny and Phylogeny, Gould reconstructed a history of developmental biology and stressed the importance of development to evolutionary biology. In a 1979 paper coauthored with Richard Lewontin, Gould and Lewonitn criticized many evolutionary bioligists for relying solely on adaptive evolution as an explanation for morphological change, and for failing to consider other explanations, such as developmental constraints.

Regeneration is a fascinating phenomenon. The fact that many organisms have the capacity to regenerate lost parts and even remake complete copies of themselves is difficult to fathom; so difficult, in fact, that for a very long time people were reluctant to believe regeneration actually took place. It seemed unbelievable that some organisms could re-grow lost limbs, organs, and other body parts. If only we could do the same! Unfortunately, our regenerative capacities are limited to hair, nails, and skin, while the liver and a few other tissues display more restricted regenerative abilities. What if we could grow back lost limbs, or damaged organs? This question has inspired many stories, dating back to Greek mythology, wherein Prometheus was doomed to regenerate his liver after it had been devoured by birds. Regeneration has permeated many imaginations; it has appeared in many literary and religious texts, and has also provoked much interest from the scientific community.

Although educated as a scientist who studied with both August Weismann and Ernst Heinrich Haeckel, Hans Adolf Eduard Driesch was first employed as a professor of philosophy and became a strong proponent of vitalism. Driesch was born on 28 October 1867, the only child of Josefine Raudenkolb and Paul Driesch. He grew up in a wealthy merchant family in Hamburg, Germany, where he was educated at the humanistic Gymnasium Gelehrtenschule des Johanneums that had been founded by a friend of Martin Luther. In 1886 he spent two summers studying with Weismann at the University of Freiburg and then entered the University of Jena, where he received his doctorate in 1889 with a study of hydroid colonies. By 1890 Driesch had lost interest in Haeckel's popular phylogenetic approach to zoology and instead focused on experimental embryology.

This video is composed of a sequence of films created by John Tyler Bonner in the 1940s to show the life cycle of the cellular slime mold Dictyostelium discoideum. As only the second person to study slime molds, Bonner frequently encountered audiences who had never heard of, let alone seen, the unusual organism. He therefore decided to create a film to present at seminars in order to introduce his object of study; the time-lapsed film captivated audiences, indeed Bonner has described that the film "always stole the show." Bonner began working in the biology department at Princeton University in 1947, and although Princeton appears in the opening title, Bonner actually made the film for his senior thesis as an undergraduate at Harvard University with some early assistance from Frank Smith, a photographer. Although unsure of name of the device that was used for filming, he has described it as "the most amazing antique contraption that belonged to my professor, Wm. H. Weston. It consisted of a gigantic and VERY heavy set of brass gears that had numerous possible speeds that turned a crank on the side of an old 16 mm box camera that pointed into the ocular of a microscope. The electric motor that propelled it made such vibrations that the whole apparatus had to be on a separate table and not touching the microscope."

The gradient theory is recognized as Charles Manning Child's most significant scientific contribution. Gradients brought together Child's interest in development and his fascination with the origins of individuality and organization. The gradient theory grew from his studies of regeneration, which were largely based on work he conducted with marine invertebrates, such as the ascidian flat worm, planaria and the hydroid, tubularia. Child observed that regeneration occurred in a graded process along the axis of the organism, with the characteristics of each physiological process seemingly determined by its location along the axis. To explain these observations, Child posited the existence of physiological factors working to guide the regenerative process. He was convinced that these differences along the gradients could be explained quantitatively.

Ontogeny and Phylogeny is a book published in 1977, in which the author Stephen J. Gould, who worked in the US, tells a history of the theory of recapitulation. A theory of recapitulation aims to explain the relationship between the embryonic development of an organism (ontogeny) and the evolution of that organism's species (phylogeny). Although there are several variations of recapitulationist theories, most claim that during embryonic development an organism repeats the adult stages of organisms from those species in it's evolutionary history. Gould suggests that, although fewer biologists invoked recapitulation theories in the twentieth century compared to those in the nineteenth and eighteenth centuries, some aspects of the theory of recapitulation remained important for understanding evolution. Gould notes that the concepts of acceleration and retardation during development entail that changes in developmental timing (heterochrony) can result in a trait appearing either earlier or later than normal in developmental processes. Gould argues that these changes in the timing of embryonic development provide the raw materials or novelties upon which natural selection acts.

Born in Ypsilanti, Michigan, on 2 February 1869, Charles Manning Child was the only surviving child of Mary Elizabeth and Charles Chauncey Child, a prosperous, old New England family. Growing up in Higganum, Connecticut, Child was interested in biology from an early age. He made extensive collections of plants and minerals on his family farm and went on to study biology at Wesleyan University, commuting from his family home. Child received his PhB in 1890 and MS in biology in 1892, and then went on to study in Leipzig after his parents death. He worked for a short time in the psychology laboratory of Wilhelm Wundt, and then pursued studies in zoology under the supervision of Rudolf Leuckhart. His doctoral dissertation investigated morphological aspects of insect sense organs. Leuckhart emphasized the functional purpose of morphological structures and led many of his students to develop and defend the notion of teleology, including Child, who completed his PhD in 1894.

The Spandrels of San Marco and the Panglossian Paradigm:
A Critique of the Adaptationist Programme, hereafter called
The Spandrels, is an article written by Stephen J. Gould and
Richard C. Lewontin published in the Proceedings of the Royal
Society of London in 1979. The paper emphasizes issues with
what the two authors call adaptationism or the adaptationist
programme as a framework to explain how species and traits evolved. The paper
is one in a series of works in which Gould emphasized the
role of development in evolutionary theories. The article suggests
that constraints on how organisms can develop and constraints on how species can evolve from others play a
central role in explaining the how species and traits evolve. The
authors note that organisms from different species develop as
embryos through stages similar across species, genera, and higher
classes. Gould and Lewontin hypothesize that those stages
constrained the possible pathways of evolution and has therefore
guided the history of life. Throughout the paper, the authors rely on analogy of some parts of organisms to architectural structures called spandrels, marked in this image as 'a'."

The biogenetic law is a theory of development and evolution proposed by Ernst Haeckel in Germany in the 1860s. It is one of several recapitulation theories, which posit that the stages of development for an animal embryo are the same as other animals' adult stages or forms. Commonly stated as ontogeny recapitulates phylogeny, the biogenetic law theorizes that the stages an animal embryo undergoes during development are a chronological replay of that species' past evolutionary forms. The biogenetic law states that each embryo's developmental stage represents an adult form of an evolutionary ancestor. According to the law, by studying the stages of embryological development, one is, in effect, studying the history and diversification of life on Earth. The biogenetic law implied that researchers could study evolutionary relationships between taxa by comparing the developmental stages of embryos for organisms from those taxa. Furthermore, the evidence from embryology supported the theory that all of species on Earth share a common ancestor.