Radiocarbon Revolution Chris Turney Applauds a Book on Carbon-14 and Its Key Applications

JAMES KING-HOLMES/SPL JAMES

A human femur, thought to be from medieval times, being sampled for carbon dating.

GEOSCIENCE Radiocarbon revolution Chris Turney applauds a book on carbon-14 and its key applications.

t is nearly 80 years since the discovery — whose discoveries the carefully gathered sample and found that of carbon-14, a radioactive isotope of made possible the it was measurably radioactive. The story of the sixth element. Because its decay can theory, practice and 14C thus began with a dose of high drama. Ibe used to track the passage of time, radio further findings we Originally expected to have a half-life of carbon has made myriad contributions now take for granted. just minutes or hours, this heavy form of car- across the Earth, environmental, biological There’s enough to sat- bon was considered a low research priority. and archaeological sciences. In the wonder- isfy the most insatiable But Kamen and Ruben’s efforts proved that fully engaging Hot Carbon, oceanographer informavore. it would be stable over millennia, opening up John Marra takes this story much further, Hot Carbon starts a breathtaking number of research avenues exploring not just the science, but why we with the extraordi- (its half-life of 5,730 years was determined should care about it. nary story of chemist Hot Carbon: some years later). Kamen never received the Carbon-14 and Radiocarbon is scarce in nature, formed in Martin Kamen, born a Revolution in credit he deserved, becoming a victim of the the upper atmosphere through the interaction in Canada to Russian Science US anti-communist fervour of the 1940s and of cosmic rays with nitrogen. It is rapidly immigrants. In Febru- JOHN F. MARRA 1950s. Those who applied his insight, such as converted to carbon dioxide, and filters into ary 1940, Kamen was Columbia University chemists Willard Libby and Melvin Calvin, a host of carbon reservoirs in the biosphere trying to produce a Press (2019) reaped the scientific reward. and ocean. Living organisms constantly take new isotope of carbon We follow the 14C trail through a number up 14C, and after they die, the isotope decays at the Berkeley Radiation Laboratory at the of disciplines, learning, for instance, how at a known rate. By measuring the amount University of California. Sleep-deprived Calvin and his team used the isotope to left in a carbon-based sample, it is possi- after three nights of collecting sufficient trace the way in which plants convert CO2 ble to calculate its age. Since the 1940s, the irradiated graphite to measure the hoped-for into sugar, revealing the intricate processes technique has been used to date materials isotope, he stepped outside. His bedraggled underpinning photosynthesis. We see how as much as 60,000 years old, capturing eve- appearance caught the attention of police; radiocarbon was deployed by labs in Britain, rything from the early migration of modern worse, he fitted the description of an Switzerland and the United States to date the humans out of Africa, by dating bones and escaped convict who had gone on a murder flax used to weave the Turin Shroud (believed charcoal from ancient hearths, through to the spree. Hauled to the police station, Kamen by some to be the burial cloth of Jesus) to incredibly slow growth rates of mosses living was finally released when a survivor of the between 1260 and 1390. Radiocarbon dating on the fringes of Antarctica. In retelling these bloodbath confirmed he was not the suspect. has shown that Ötzi — the corpse retrieved facts, Marra offers compelling stories about Kamen returned to the laboratory to find from melting alpine ice on the Austrian–Ital- the great researchers — many long forgotten that his colleague Sam Ruben had analysed ian border in 1991 — is more than 5,000 years

BOOKS & ARTS COMMENT

old. And we discover how candidate drugs, labelled with 14C at specific parts of the mol- ecule, can be followed through phases of the Books in brief body’s metabolism to test the drugs’ safety and efficacy. There is so much more. Marra Life Finds a Way explains, for instance, how, shortly after 14C Andreas Wagner Basic (2019) was discovered, dissolved CO2 in seawater From gut microbes to elephants, the embodiments of evolution are was used to track the movement of currents in marvels of innovation. So writes biologist Andreas Wagner, whose the deep ocean, revealing connections around eloquent study finds the “augmented” view of Darwinian evolution the planet considered unfathomable before. echoed in the ‘landscape thinking’ of human creativity — the mental Carbon-14 may be the star, but scientists, exploration of possibility. Wagner meshes research into areas such institutions and happenstance have valuable as genetic drift with theories on aspects of the creative process supporting roles. Take Libby, winner of the (such as serendipity) seen in luminaries from radioimmunoassay 1960 Nobel Prize in Chemistry for his work inventor Rosalyn Yalow to artist Pablo Picasso, and shows how such developing radiocarbon dating. At one point, a mindset can solve real-world problems. his team waded into the sewers of Baltimore, Maryland, collecting methane produced from human waste to demonstrate unequiv- The Trouble with Gravity ocally that it contained considerably more Richard Panek Houghton Mifflin Harcourt (2019) 14C than did archaeological samples and a Gravity is, scientifically speaking, an enigma. We know that it is a precisely dated piece of redwood heartwood. weak force with infinite reach, pulling at matter to form bodies from Marra also reveals, in vivid detail, the diffi- black holes to galaxies — but that is what it does, not what it is. culties faced by early researchers in acquiring Science writer Richard Panek follows the evolution of gravitational precious samples of plankton, which opened theories through time, from Aristotle (arguably the first to question up a new perspective on ocean productivity why things fall on Earth but heavenly bodies stay aloft) through the and, ultimately, carbon sequestration. His momentous discoveries of Galileo Galilei, Isaac Newton and Albert own experience in this area illuminates the Einstein. He also touches on insights from the likes of poet Dante researchers’ pioneering spirit in the face of Alighieri and philosopher-physicist Ernst Mach. wild conditions, cramped spaces and some- times surly ships’ captains. The technologi- cal limitations were progressively overcome The Last Butterflies by dogged perseverance and a belief that the Nick Haddad Princeton University Press (2019) work would help them to understand the Terrestrial ecologist Nick Haddad studies the beleaguered denizens oceans’ potential for incorporating inorganic of liminal lands: the world’s rarest butterflies. Far from niche research, carbon into organic compounds — still the he argues, findings on species and subspecies such as the St Francis’ focus of fierce investigation. satyr (Neonympha mitchellii francisci) and crystal skipper (Atrytonopsis Mysteries remain in the Earth sciences, quinteri) offer a valuable lens on the biodiversity crisis. Yet Haddad such as the effectiveness of the carbon cycle does not just gather data on habitat loss and other drivers of decline and the ramifications of human activity, — although he does that with crystalline acuity. He emphasizes including our seemingly insatiable hunger that measures such as restoring ecological systems can protect for fossil fuels. Importantly, Marra shows populations of these fragile “ambassadors of nature”, against the odds. how 14C can be used to tease out processes across a range of timescales. He explains why the Southern Ocean is the ‘gatekeeper’ to the The Fate of Food planet’s ocean circulation, and how abrupt Amanda Little Harmony (2019) changes in the formation of deep water and As Earth’s human population tips towards 8 billion, is our food the position of the overlying wind belts can system up to it? In this tour of the brave new world of adaptive drive dramatic shifts in the carbon cycle. production, environmental journalist Amanda Little encounters Soberingly, a doubling of atmospheric levels robot weeders, aquaponics innovators, permaculture farmers, toilet- of 14C — arising from mid-twentieth-century to-tap water recyclers and other players in the field — both high- nuclear-bomb testing — is preserved as a tech innovators and eco-traditionalists. That balanced viewpoint spike in annually formed natural archives, extends to broader discussions of debates over genetically modified including tree rings. That marker could be crops in Kenya and cultured meat production in the United States. chosen to delineate the start of a new geologi- Witty, nimble and timely, this is a gem of crack reporting. cal epoch: the Anthropocene. Hot Carbon offers a timely perspective on how mind-bogglingly connected our Giants of the Monsoon Forest planet is — and how 14C will continue to Jacob Shell W. W. Norton (2019) be important in helping us to understand In this thought-provoking study, geographer Jacob Shell probes what lies ahead. ■ an unusual interspecies alliance: the relationship between people and the working elephants of Indonesia, Myanmar and India. Never Chris Turney is professor of climate change selectively bred, the night-roaming pachyderms are essentially wild, and Earth science, and director of the yet engage in cognitively demanding tasks such as rescue work Chronos 14Carbon-Cycle Facility, at the during floods. Examining everything from the muscular miracle of University of New South Wales in Sydney, the beast’s proboscis to the species’ wartime work, Shell also charts Australia. His website is christurney.com the threats facing Asian elephants, and the dearth of local voices in e-mail: [email protected] relevant policymaking. Barbara Kiser