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Engaging anecdotes add intimacy to tales of Earth’s 4 billion years of evolution

Some Assembly Required: Decoding Four Billion Years of Life, from Ancient Fossils to DNA

Neil Shubin
Pantheon
2020
288 pp.
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Each December for decades now, I’ve spent a few days in Pacific Grove, California, attending the Asilomar Chromatin, Chromosomes, and Epigenetics Conference. Before reading Neil Shubin’s Some Assembly Required, however, I never knew that the city’s first female mayor, Julia Platt, was also an accomplished embryologist. Having been shut out of academic positions, which were, at the turn of the 20th century, seldom given to women, she pivoted instead to politics, where her legacy includes the establishment of a marine protected area in California’s Monterey Bay. This anecdote is one of many intimate and thoughtful stories tucked into the pages of this brief overview of Earth’s 4 billion years of evolution.

Shubin, an accomplished paleontologist and evolutionary biologist, begins his history in Victorian England, which, he writes, “was a crucible for enduring ideas and discoveries.” “There is something poetic to the notion that knowing how DNA works in the history of life relies on ideas developed during an age when people didn’t know that genes even existed,” he continues.

Here, he relates the story of St. George Jackson Mivart, apprentice to Thomas Henry Huxley. Mivart, we learn, although initially a supporter of Darwin’s theory of evolution, became a vocal critic, focusing on “the incompetency of natural selection to account for the incipient stages of useful structures.” Darwin would respond to this criticism in the 1872 edition of On the Origin of Species, arguing that “This subject is intimately connected with that of the gradation of the characters, often accompanied by a change of function.” These words, Shubin writes, “contain the seeds for a new way of seeing major transitions in the history of life.”

Among the exciting topics covered in Shubin’s sweeping evolutionary history are the transition to land-living animals, the origins of flight, the race for the double helix, and anecdotes from pioneering work in molecular evolution and gene regulation. He recounts the discovery of repetitive DNA sequences and Barbara McClintock’s transposable elements, and he explores Richard Goldschmidt’s controversial “hopeful monsters” hypothesis of macroevolution. We also learn that Lynn Margulis submitted her dogma-defying endosymbiosis work to 15 journals before her insights were recognized—some assembly required, indeed.

Shubin also recounts the charming story of Susumu Ohno, the Japanese American geneticist whose research confirmed that gene duplication played a critical role in molecular evolution. Ohno, we learn, painstakingly weighed paper cutouts of chromosomes from different mammalian species and found that, although the chromosome numbers differed widely, the estimated total amount of DNA was similar in each case. When he moved on to salamanders, however, he was in for a surprise. Some had genomes far larger than those of humans. “With his cardboard cutouts, Ohno discovered something that billions of dollars of genome projects were to confirm decades later,” writes Shubin.

Shubin argues that if we were to rerun the course of evolution multiple times, the results would most likely be the same. He refers to this as the inevitability of evolution, which stands in opposition to the theory that evolution is based on chance events, the outcome of which is contingent on specific conditions. But the experimental observations on which Shubin bases his argument—some of which originated in his own research—were made at the microscale. As Blount et al. have pointed out, “… repeatability is common when the founding populations are closely related, perhaps resulting from shared genetics and developmental pathways, whereas different outcomes become more likely as historical divergences become greater” (1). Furthermore, no experiments have yet accounted for cataclysmic events such as the Cretaceous-Paleogene extinction event.

One of the book’s best features is a 30-page notes section at the end, in which each note could be fodder for an entire volume. These notes are separated by chapter, and many tell a short, engaging story, often accompanied by annotated suggestions for further reading. Readers will want to peruse this section and follow up on some of those readings.

References and Notes
1. Z. D. Blount, R. E. Lenski, J. B. Losos, Science 362, eaam5979 (2018).

About the author

The reviewer is at the Department of Biology, San Francisco State University, San Francisco, CA 94132, USA.