The history of evolution came through various theories and concepts trying to solve the question of organisms’ development and reproduction. The scientific debates peaked during the late 18th century when researchers formed the most controversial views. Later, embryologists Baer, Owen, and Carpenter gradually solved the situation by developing new approaches to understanding the nature of their science. Creating debates on the development process, scientists moved the theory of evolution.
Before the 18th century, several concepts prevailed in scientific society. The theory of preformationism was widely recognized from the late 17th to the end of the 18th century. This concept proposed the occurrence of the generation of offspring due to the unfolding and development of preformed parts. The alternative version was epigenesis, the foundation of epigenetics, stating that each embryo is produced from a mass. Another discussion revolved around the linear conception of recapitulation theory. Additionally, in the 1830s, cell theory was provided by Schwann and Schleiden, who implied that cells consisted of protoplasm. Thus, various theories dominated during the late 18th century.
However, the scientific field changed with Baer, who is considered the father of embryology. He discovered the mammalian ovum in 1826, writing, “I shrank back as if struck by lightning, for I clearly saw a minuscule and well-developed yellow sphere of yolk.” Two years later, he argued for a process of divergence from common forms, rejecting the linear theory of the same animal forms’ repetition. Baer’s discovery and his laws of embryology inspired further research. Agassiz was one of Baer’s supporters of resemblances between embryos and adults within a single type. He believed in the contribution of recapitulation to the same process. Combining both theories, Agassiz was recognized by zoologists of the 19th century as an essential addition to natural history. Therefore, many ideas that evoked debates and shifts of views combined and deliberated over time.
A similar process appeared in the development of evolution, driven by evolving embryological and epigenetic research. The first scholar to apply the term was Haller, who connected evolution with the concept of pre-existing miniatures. The perception changed due to Baer’s theory of 1828 about embryo development, which replaced the previous beliefs. Later, Spencer, relying on Carpenter’s research, depicted embryological “evolution” “as an illustration of the ability of organic structures to modify themselves.” Spencer worked on evolution in terms of embryological concepts until he developed the theory in 1852 connected with transmutation. Nevertheless, Baer’s works scientifically affected Spencer’s research; further studies began to decline in the embryological concept.
The modern model of evolution was modified and synthesized from various theories. The concept of transmutation was considerably changed over the decades. However, it reveals an equal divergence of meaning in the embryological and Darwin studies. Before Darwin adopted Owen’s archetypes terminology, he worked with ideas of similarity between an old progenitor and its embryo. Therefore, aspects of research interchanged throughout history still contributed to the overall idea of evolution.
Consequently, scholars developed many theories that tried to explain and structure the understanding of embryos. The most successful development was made by Baer, who created the laws of embryology and inspired later research in the same field. Additionally, it resulted in the development of studies by Darwin and Spencer that later became a foundation of evolutionary theory in the embryological context. The concept was changed, but these contributions forever influenced the history of biology.
Bibliography
Baer, Karl Ernst von and O’Malley, Charles Donald. “On the Genesis of the Ovum of Mammals and of Man.” Isis 47, no. 2 (1956): 117-153.
Bowler, Peter J. “The Changing Meaning of “Evolution.” Journal of the History of Ideas 36, no. 1 (1975): 95-114.
Ospovat, Dov. “The Influence of Karl Ernst von Baer’s Embryology, 1828-1859: A Reappraisal in Light of Richard Owen’s and William B. Carpenter’s “Palaeontological Application of ‘Von Baer’s Law’.” Journal of the History of Biology 9 no. 1 (1976): 1-28.
Sapp, Jan. Genesis: The Evolution of Biology. Oxford: Oxford University Press, 2003.