It was not only Darwin who influenced Haeckel’s creation. He was also inspired by a linguist who was his colleague and friend in Jena. “As early as 1863, the linguist August Schleicher created a first ‘family tree’ to represent the development of Indo-Germanic languages,” says Prof. Uwe Hoßfeld of Friedrich Schiller University Jena in Germany. “Ernst Haeckel eventually adopted this form of visualization.”
No better method has been devised to date for illustrating biodiversity. New techniques and methodologies may have come into use, and trees of life are now presented as cladograms, diagrams, etc., but the principle remains the same. “It is quite simply the best and clearest way of representing the results of biological research in this area,” notes Hoßfeld.
“The idea of visually representing species and their development was already known at the time,” says Dr. habil. Georgy S. Levit. “However, earlier ideas never took into account the principle of monophyly and natural selection in speciation.”
This connection first emerged when British naturalist Charles Darwin sketched in his diary an idea for a tree of life in 1837 and presented it in the form of a diagram in his ground-breaking work ‘On the origin of species’ in 1859. Haeckel took up Darwin’s theory of evolution in his 1866 book, ‘General morphology of organisms’, and drew the first phylogenetic ‘family tree of organisms’, or tree of life.
“Phylogeny is the evolutionary history of organisms,” explains Hoßfeld. “Because Haeckel was the first actually to define this term, in that same work, he was also the only person capable of representing the first tree of life of this kind.”
To be more precise, Haeckel designed the monophyletic tree of life, because it shows all three kingdoms – animals, plants and Protista (organisms that cannot be classified as a plant, animal or fungus) – arising from a common root (‘Moneren Radix’).
Citation: Hoßfeld, U.&Levit, G. S. (2016): 'Tree of life' took root 150 years ago. Nature 540, 38, 1 December 2016, DOI: 10.1038/540038a