BOOKS AND ARTS 31 JULY 2018
The band of biologists who redrew the tree of life
John Archibald praises a compelling guide to the past 3 billion years — and its molecular historians.
John Archibald
Carl Woese discovered the ‘third domain’ of life — the Archaea.
Credit: Jason Lindley/LAS, Univ. Illinois at Urbana-Champaign
The Tangled Tree: A Radical New History of Life David Quammen Simon & Schuster (2018)
In The Tangled Tree, celebrated science writer David Quammen tells perhaps the grandest tale in biology: how scientists used gene sequencing to elucidate the evolutionary relationships between living beings. Charles Darwin called it the ‘great Tree of Life’. But as Quammen reveals, at the molecular level, life’s history is more accurately depicted as a network, a tangled web through which organisms have been exchanging genes for more than 3 billion years. This perspective is indeed radical, and he presents the science — and the scientists involved — with patience, candour and flair.
Centre stage in Quammen’s narrative is Carl Woese (1928–2012), the US microbiologist best known as the discoverer of the Archaea (Archaebacteria) — the ‘third domain’ of life. Inspired by the visionary musings of Francis Crick, Linus Pauling and Emile Zuckerkandl, Woese committed himself to molecular phylogenetics at a time when this powerful approach to the study of evolution was in its infancy. During the 1960s and 1970s, the Woese Laboratory at the University of Illinois at Urbana–Champaign developed and refined techniques for deriving sequence information from molecules of ribosomal RNA (core components of the cell’s protein-synthesizing factory, the ribosome). Sequences were painstakingly obtained from diverse microbes and used as molecular yardsticks to infer how the organisms were related to one another and to animals and plants. Through the following two decades, as molecular sequencing got easier and cheaper, Woese’s ‘three-domains’ tree — comprising archaea, bacteria and the nucleus-containing eukaryotes — served as the definitive road map for the field of comparative genomics. In many ways, it still does.
But life is complicated, and so are the scientists who study it. In his breezy, conversational style, Quammen shepherds us up and down life’s vast timeline, and across 150-plus years of exciting, often controversial discoveries. He handles the complexities with humour and clarity (he’s right: some ribosomes do look like rubber ducks). We learn about the seeds of “tree thinking” in biology, before and after Darwin’s 1859 On the Origin of Species. We learn of a time when a natural classification of microorganisms was considered impossible (they were deemed morphologically too simple, physiologically too variable). We learn how molecular sequencing helped test and eventually prove the endosymbiont hypothesis for the origin of mitochondria and chloroplasts; these eukaryotic organelles are now known to have evolved from once free-living bacteria.
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Woese’s last months and weeks with pancreatic cancer, as revealed by those closest to him, make for painful, albeit illuminating reading. I was surprised, for instance, to learn that Woese believed in a deity.
Around 2010, Woese and Canadian science historian Jan Sapp began to collaborate on a book tentatively entitled Beyond God and Darwin. The project never moved beyond Sapp’s draft introduction, on which Woese wrote: “Jan, you accord Darwin so much more substance than the bastard deserves.”
FREE PDF GRATIS: Nature
