Rhizome of Life

Certain images die slowly or are kept alive way beyond their usefulness by ideological image-support systems. We seem to have been stamped with ineradicable imprints when it comes to certain metaphorical models or schemata we use, or are told & taught to use, to represent our understanding of various aspects of the world — even if this use has become little more than alibis for the status quo. Maybe most persistent has been the tree image, as a descriptor of any number of structures, mythological, biological, cultural, familial, political, cosmological, scientific — what Deleuze & Guattari have called and criticized as the “arborescent model.” This proudly erect unitary tree has pervaded Western thinking for several millennia (think of even the cross as a dead tree) and has been at the center of our imaging imagination most forcefully at least since the Renaissance to explain and impose hierarchical orders on our universe.

It was thus not surprising that in the nineteenth century, Charles Darwin (his 200th birthday is coming up on 12 February, and thus a flurry of activity has been developing around his name & work) would draw on that model to represent his ideas of evolution — trying to turn an earlier “tree of life” image into a new, scientifically correct and verifiable tree of life image. Up until today scientists have tried to fill in this image, to add branches, etc. as they discover new data. But it seems that the latest data from various fields can no longer be so easily added to an arborescent structure, that we may have to change that old, all-pervasive schemata — and imagine other, more web-like structures to make sense of our world.

The picture above shows Darwin’s early attempt to draw a model for his discoveries — a “spindly sketch of a tree of life” much closer, I submit, to a non-hierarchical rhizome model than to the hierarchy-heavy arborescent tree model — even if Darwin would try, again and again, to fit his data into the more constraining and ideologically laden image of the latter.

A fascinating article in this week’s New Scientist, entitled “Why Darwin was wrong about the tree of life,” goes a long way to vindicate the rhizomatic view of the world, even if the authors do not use that term, preferring expressions such as “web-like.” Oh how I wish that D&G’s Mille Plateaux was compulsory reading not only for scientists but also for scientific journalists. It might make the inevitable, though much-resisted paradigm shift from an arborescent to a rhizomatic model of the world somewhat easier.

You can the full story here and the opening section of said article right below:

IN JULY 1837, Charles Darwin had a flash of inspiration. In his study at his house in London, he turned to a new page in his red leather notebook and wrote, “I think”. Then he drew a spindly sketch of a tree.

As far as we know, this was the first time Darwin toyed with the concept of a “tree of life” to explain the evolutionary relationships between different species. It was to prove a fruitful idea: by the time he published On The Origin of Species 22 years later, Darwin’s spindly tree had grown into a mighty oak. The book contains numerous references to the tree and its only diagram is of a branching structure showing how one species can evolve into many.

The affinities of all the beings of the same class have sometimes been represented by a great tree. I believe this simile largely speaks the truth…

The tree-of-life concept was absolutely central to Darwin’s thinking, equal in importance to natural selection, according to biologist W. Ford Doolittle of Dalhousie University in Halifax, Nova Scotia, Canada. Without it the theory of evolution would never have happened. The tree also helped carry the day for evolution. Darwin argued successfully that the tree of life was a fact of nature, plain for all to see though in need of explanation. The explanation he came up with was evolution by natural selection.

Ever since Darwin the tree has been the unifying principle for understanding the history of life on Earth. At its base is LUCA, the Last Universal Common Ancestor of all living things, and out of LUCA grows a trunk, which splits again and again to create a vast, bifurcating tree. Each branch represents a single species; branching points are where one species becomes two. Most branches eventually come to a dead end as species go extinct, but some reach right to the top – these are living species. The tree is thus a record of how every species that ever lived is related to all others right back to the origin of life.

…The green and budding twigs may represent existing species, and those produced during each former year may represent the long succession of extinct species

For much of the past 150 years, biology has largely concerned itself with filling in the details of the tree. “For a long time the holy grail was to build a tree of life,” says Eric Bapteste, an evolutionary biologist at the Pierre and Marie Curie University in Paris, France. A few years ago it looked as though the grail was within reach. But today the project lies in tatters, torn to pieces by an onslaught of negative evidence. Many biologists now argue that the tree concept is obsolete and needs to be discarded. “We have no evidence at all that the tree of life is a reality,” says Bapteste. That bombshell has even persuaded some that our fundamental view of biology needs to change.

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