Book review of Neil Shubin

Neil Shubin:
"The Universe Within" (2013)
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This book is de facto an expansion of Shubin's previous (excellent) book, "Your Inner Fish" (2009). The book is basically a history of life on Earth, starting 3.5 billion years ago. However it is mainly notable for the numerous trivia, especially the brief biographical information about the scientists who wrote that history. The book also indirectly explains how scientists can track down what happened in such a distant past. And so at the beginning of the book we get a page on the "Harvard computers", women who were the human computers of the Harvard observatory in the early 1900s. In particular, the astronomer Henrietta Leavitt, who in 1912 discovered a way to measure the distance of stars, so that in 1918 Hubble discovered Andromeda, another galaxy far away from the only one known at the time, the Milky Way. Shubin takes a long astronomical detour via Arno Penzias's and Robert Wilson's discovery in 1965 of the cosmic microwave background radiation, the remnants of the Big Bang, via the early theories on the formation of the solar system (Emanuel Swedenborg in 1734, Immanuel Kant in 1755, Pierre-Simon Laplace in 1796), to get to the beginning of life on Earth: DNA analysis points at a common ancestors of all life forms living about three billion years ago, and that's the age of the oldest fossils on rocks yet found. Then we get another lengthy detour to show us that clocks and calendars abound in nature, and scientists can use them to pinpoint dates. Doug Macdougall's book "Nature's Clocks" (2008) is a great introduction to this concept. We also get an introduction to the circadian clock, and to Seymour Benzer's molecular theory of circadian clocks, which feels like a short summary of John Palmer's book "The Living Clock" (2002). In 1954 Elso Barghoorn and Stanley Tyler announced their discovery of Precambrian life forms (in the Gunflint Iron Formation of the Canadian Shield). The earliest life forms that we know of are dated from 3.4 billion years ago. Shubin writes that for three billion years life was confined to microorganisms but later states that the first "big" life forms emerged about one billion years ago. Another detour, via Antonie van Leeuwenhoek's microscope (and how he made his lenses), takes us to the importance and implications of the size of animals and his theory that size depends on the availability of oxygen. Each of these scientific discoveries is accompanied with short bios and anecdotes. We get many more in the following pages. Preston Cloud was the first scientist to explain that the existence of multicelled creatures depends on the availability of oxygen ("Atmospheric and hydrospheric evolution on the primitive earth", 1968). In 1861 Eduard Suess, having found glossopteris in different continents, came up with the idea that much of the land of Earth (South America, Africa, India, Australia) used to make up a supercontinent, Gondwanaland (in 1885 he summarized his ideas in the book "The Face of the Earth"). In 1912 Alfred Wegener argued that the continents are slowly drifting ("The Formation of the Continents", 1912). The idea of continental drift was proven by Marie Tharp's oceanic maps in 1952 (and publicized by her boss Bruce Heezen). In 1929 Arthur Holmes had already explained how continental drift could happen, but back then not many believed in Wegener's idea, and in 1962 Harry Hess used a similar explanation and in 1966 John Tuzo Wilson perfected it with the notion of plate tectonics ("Did the Atlantic close and then re-open?", 1966). In 1984 NASA measured the continental drift (e.g. Europe and North America are moving apart 1.5 cms per year). This lengthy detour serves Shubin to explain why large animals (for example mammals) began to emerge 200 million years ago: the continental drift began 200 million years ago and one side-effect was the creation of oxygen. See also Nick Lane's book "Oxygen - The molecule that made the world" (2003). The advantages and disadvantages of size have been discussed by many scientists, from JBS Haldane in "On Being the Right Size" (1926) to Stephen Gould ("Allometry and size in ontogeny and phylogeny", 1966) and Frits Warmolt Went (“The Size of Man”, 1968); from William Calder's book "Size, Function and Life History" (1996) to John Tyler Bonner's book "Why Size Matters" (2011).

We are then introduced to John Phillips, the British geologist who in 1841 published a map of rock layers and fossils in Britain and identified and named three major geological eras: Palaeozoic ("old life"), dominated by fish fossils, Mesozoic ("middle life"), the age of reptile fossils, and Caenozoic ("new life"), the age of mammals. The book then introduces Georges Cuvier (unfortunately the biographies are not in chronological order) who in two 1796 papers (notably "Memoir on the Species of Elephants Both Living and Fossil", 1796) identified mammoths as extinct animals and in general argued that many animals went extinct. In "Essay on the Theory of the Earth" (1813) Cuvier proposed that extinctions were caused catastrophes, i.e. that catastrophes shaped the biosphere. He became the most influential defender of "catastrophism" in geology. His "catastrophism" lost to the theory of gradual change, but he was vindicated 167 years later when geologist Walter Alvarez and his physicist father Luis Alvarez discovered concentration of iridium (rare on Earth but common in asteroids) in geological layers of the same age as the time as the Cretaceous–Paleogene mass extinction event during which three-quarters of the plant and animal species (including dinosaurs) disappeared from Earth, about 65-66 million years ago. Hence they concluded that the mass extinction was caused by a catastrophe, the impact of a large asteroid ("Extraterrestrial cause for the Cretaceous–Tertiary extinction", 1980). A student of Stephen Jay Gould, John Sepkoski created a vast database of paleontology, from which one could see that there had been several other mass extinctions, and then, in collaboration with David Raup, he argued that the Cretaceous–Paleogene mass extinction was part of a cycle of mass extinctions, one every 26 million years ("Periodicity of extinctions in the geologic past", 1984). We now know that there were five big extinctions before that famous one: the Ordovician-silurian Extinction 440 million years ago, the Devonian Extinction 375 million years ago, the Permian-triassic Extinction 250 million years ago, and the Triassic-jurassic Extinction 200 million years ago. David Jablonski pointed out that surviving a mass extinction event requires depends on different factors than surviving during normal times ("Lessons from the past - Evolutionary impacts of mass extinctions", 2001), and Shubin argues that spreading all over the Earth is one key away to avoid extinction. That's precisely what our ancestors did millions of years ago.

Shubin's narrative also includes a brief detour into Antarctica, which underwent a massive transformation in a few million years. To explain what happened, Shubin first introduces us to the Swedish chemist Svante Arrhenius, who in 1896 discovered that increases in atmospheric carbon dioxide cause "global warming" through a "greenhouse effect", although he didn't use these modern terms ("On the influence of carbonic acid in the air upon the temperature of the ground", 1896). In 1969 Edwin Colbert discovered a 220-million-year-old fossil of a dinosaur in Antarctica, a sign that Antarctica was once a warm continent thriving with life (until about 40 million years ago). Twenty years later Maureen Raymo, William Ruddiman and Philip Froelich argued that the continental drift was responsible for cooling the Earth and covering Antarctica with ice, and that a major triggering event was the rise of Tibetan plateau following the collision of India with Asia, the so-called "Uplift-Weathering Hypothesis": the mountains of the Tibetan plateau acted as a giant vacuum that sucked carbon dioxide from the atmosphere, the opposite of the greenhouse effect ("Influence of late Cenozoic mountain building on ocean geochemical cycles", 1988). Shubin argues that the cooling of the planet created a whole new environment in which color vision was crucial to identify the most nutritional plants, and in fact the genes needed for color vision originated about 30-40 million years ago.

Shubin now takes back in time to Louis Agassiz, who in 1837 hypothesized an "ice age" during which glaciers extended from the North Pole to the Mediterranean and covered North America. From that theory, one could deduce that the Earth is cooling. However, in 1864 James Croll proved that changes in the Earth's orbit change the amount of heat that his the Earth and therefore cause ice ages at regular intervals, sometimes in the northern and sometimes in the southern hemispheres The Serbian astrophysicist Milutin Milankovitch developed a mathematical theory of global climate based on the motion of the Earth around the Sun: variations in the shape of the Earth's orbit (more or less oval), variations in the angle of the Earth's axis and variations in the Earth's gyration affect the duration and intensity of the seasons ("Mathematical Climatology and the Astronomical Theory of Climatic Changes", 1930). He died before his theory could be prove true. A more accurate way to date glaciers (by measuring oxygen-18 and deuterium) was discovered by Willi Dansgaard. In 1949 Willard Libby invented radiocarbon dating, realizing that the amount of carbon-14 in bones can be used for dating the bones. The dating of dramatic fossil changes matches the dates of ice ages. And this brings us to the first human societies, that came about after the end of the latest ice age about 12,500 years ago. Shubin only mentions Dorothy Garrod's discovery of the Natufian culture that existed 15,000 to 11,500 years ago. (Ironically, this is the least convincing part of the book).

Overall, the book is a collage of biographical sketches that indirectly tells the story of the Earth, of climate on Earth and of life on Earth. It is also a tribute Shubin's own profession, to all the great paleontologists who discovered where we come from.

It is a pity that notes are confined at the end of the book. Most readers will never check the notes, which instead contain valuable information.