Monthly Marvel: Tree of Life

On the first Saturday of each month for at least the next little while I intend to share here one of the Weekly Wonders from that previous project. This time I want to share the Tree of Life: as a nod to Darwin’s birthday I focus mostly on Darwin’s use of the metaphor, but I also look at other places in which it shows up.


TREE OF LIFE

This week’s idea is the tree of life. The image of a tree of life—axis mundi, if you prefer—is a common one in mythology around the world, but I’m referring specifically to Charles Darwin’s metaphor for all living things on Earth in an evolutionary relationship going back to the origins of life itself. In On the Origin of Species, Darwin’s only  illustration was tree-like branched diagram, and the book includes a passage which compares “the great Tree of Life” with a growing tree, saying that the former “fills with its dead and broken branches the crust of the earth, and covers the surface with its ever-branching and beautiful ramifications.” Other biologists have used this image, updating it with genetic data. For instance, the Tree of Life Web Project is a collaborative project providing information about biodiversity and phylogeny.

Source: Leonora Enking at flic.kr/p/9GQuCD

Source: Leonora Enking at flic.kr/p/9GQuCD

Other trees of life include arbor vitae, the branching pattern between the grey matter and white matter of the brain; the Tree of Life in Genesis’s Garden of Eden, of which Adam and Eve are said to have eaten before they chose to eat of the Tree of Knowledge of Good and Evil instead; a central symbol in the Kabbalah of Jewish mysticism, which consists of ten interconnected nodes; Yggdrasil, a massive yew or ash tree which supported the worlds; a cipher for the Elixir of Life and the Philosopher’s Stone in European alchemy; the Bo or Bodhi tree under which the Buddha attained enlightenment; an acacia tree in Egyptian mythology from which Isis and Osiris emerged, which encloses both life and death and, more literally speaking, contains a psychedelic drug associated with spiritual experiences; and many others.

But let’s return to Darwin’s metaphor. It was more politically charged than it might first appear. He was writing On the Origin of Species during the abolition movement, and at the time there were two competing theories about human origins: monogenists, who argued that there was a single origin for all humans, and the polygenists, who argued that there were multiple origins for all humans, one for each race (source). For the most part, monogenists cited the Bible, while polygenists cited scientific theories, mostly based on cranial measurements, which suggested Europeans and Africans were separate biological species. Supporters of slavery mostly used these polygenist scientific theories, while abolitionists relied on Biblical monogenist theories. However, the intellectual climate of the era was leaning more heavily to science than to religion, and it looked as though the slave owners were going to win the argument. They had science on their side, after all. That is, they had science on their side until Darwin, the product of strongly abolitionist families, published On the Origin of Species. Darwin argued that all humans were the same species, tied together in one branch of the Tree of Life; the polygenist theory lost scientific support, giving the monogenist theory the scientific grounding it needed to win the argument in that era.

Posted by Christian H.

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