In a 2008 paper in this journal, the biologist Paul Ehrlich decried demography's limited focus on narrow technical analysis to the neglect of the big issue before it, “the role of population growth in damaging humanity's life-support systems, and developing policies that will help to prevent the damage.” The charge rings true: indeed, a wider range of neglected issues might be identified. Where demographers hesitated others stepped in. As a result, some of the loudest and most influential voices on population matters have come from outside the field. On global population growth, Ehrlich's voice was especially prominent. In this memoir, written in old age (he was born in 1932), Ehrlich recounts a full and varied life as scientist and public intellectual with attention particularly to man's environmental impact. The science comes first. By training a lepidopterist (he claims more than 40 years of studies of checkerspot butterflies), Ehrlich's interests soon broadened into ecology and evolution. Resisting “the classical structure of university departments” like zoology, entomology, and botany, which he saw as slowing scientific advances in critical areas, he became a pioneer in the interdisciplinary field of population biology. He co-authored the original paper on coevolution and was one of the founders of Stanford's celebrated Program in Human Biology. Disciplinary compartmentalization, he argues, similarly besets the social sciences, impeding their recognition of environmental issues. The paperback bestseller, The Population Bomb (1968), launched Ehrlich into the popular media. Put together in a few weeks drawing on some of his lecture notes from a course on evolution, with a title dictated by the publisher, the book drew an alarming picture of overpopulation and imminent famine and saw an urgent need to rein in future growth. Its breathless opening set the stage: “The battle to feed all of humanity is over. In the 1970s the world will undergo famines—hundreds of millions of people are going to starve to death in spite of any crash programs embarked upon now.” Writings of the ecologist Garett Hardin, agriculturalist Lester Brown, and the Club-of-Rome computer modelers broadly agreed on the dire outlook—together, some have argued, giving support for the more intrusive birth control measures adopted in a number of countries. There were contrary views too, in what became a vociferous public debate. Beyond the opponents of contraception, usually on religious grounds, there were those—fellow biologist Barry Commoner for one, but economists in the main—who denied any problem of population numbers, even in this period when the world's annual growth rate had risen above 2 percent. Julian Simon was such a figure. He should have merited a mention in the memoir, especially as he was counterparty in a famous wager with Ehrlich on whether the prices of some specified nonrenewable resources would rise over the next decade (Ehrlich lost). The wager is not mentioned in the memoir; nor is Simon himself, except namelessly, in a dismissive endnote that must mean him, as “a mail order marketer who claimed the human population could grow for billions of years.” Statistician Bjørn Lomborg, the Skeptical Environmentalist, is another absentee. The simple narrative that has taken hold in the press goes that in the 1960s and 1970s, works like The Population Bomb and The Limits to Growth were soon falsified by the Green Revolution in crop yields and by a family-planning-led fall in birth rates; hence the worry was and is needless—or worse, as it may have led to the excesses of China's one-child policy and India's Emergency sterilization campaign. A closer reading reveals a less facile story—one that emphasizes both the continuing perilous fragility of the world's food system, with its monocultures and heavy reliance on chemical inputs, and the mix of influences that brought about the rapid fertility decline in some regions, stalled or lagging change in others. Ehrlich's revisiting of The Population Bomb in his memoir concedes regret for its overdramatic scenarios (too easily misread as predictions), a mellowing of views on population policy (putting store now on girls' education), and a reluctant recognition of a possible further world population increase of two or three billion, but with promise of a subsequent decline from the peak. The fall will have to go far: the sustainable population level, he judges, “is somewhere between one and a half billion and two and a half billion, the size of the population in the early twentieth century” (p. 290). Ehrlich's long Stanford career includes other notable contributions of demographic significance. The IPAT equation, proposed in a 1971 paper with John Holdren, is a widely influential heuristic for assaying population and consumption effects, not of immediate statistical value in assigning shares but the stimulus for a raft of later research. Ehrlich was in the group of scientists in the early 1980s who first publicized the risks and implications of nuclear winter. A 1986 study with Peter Vitousek and others yielded the first estimate of the proportion of the world's net primary production appropriated by humans—that is, in effect, the food unavailable for all of nondomesticated animal life. And his books on ecology and evolution (many coauthored with Anne Ehrlich, his wife, and research colleague) have brought population issues home to generations of students. In 1990 Ehrlich together with E.O. Wilson was awarded the Crafoord Prize, the biosciences' and geosciences' Nobel. Major threats to humanity's life-support systems, of course, are now evident to all, the subject of successive dire reports from UN agencies and often the stuff of the daily news. The approach of binding environmental constraints points to the need for a smaller human appropriation of nature—a striking indicator is the estimate that livestock now makes up 15 times more of the world's mammalian biomass than all wild animals. Social scientists have a necessary part in the deliberations responding to this predicament, economists perforce. Ehrlich's disdain for many in that profession has allowed for distinguished exceptions: Kenneth Arrow and Partha Dasgupta in particular, with both of whom he has been associated at Sweden's Beijer Institute of Ecological Economics. Demographers might be thought to have a policy role here as well, in that there might be much to be gained from trying to attain a lower world population peak than is currently anticipated; oddly, however, population policy in still-high-fertility regions has dropped well down the development agenda. In that tiny three-hundred-year stretch in its roughly three-hundred-thousand-year history, modern Homo sapiens expanded some fifteenfold in numbers, fouled the air so that it often became lethal to breathe, began to disrupt greatly the climate on whose stability the human food supply rested, wiped out most of the other large animals and replaced them with domesticates, depleted much of our planet's soils and underground freshwater stores, spread novel poisons everywhere, managed to kill in a single war more than five times the number of people that existed on the planet when our species invented agriculture, and developed and used weapons with the potential to kill everyone. The sociologist and demographer Kingsley Davis put his own, not dissimilar view even more concisely (in a 1989 oral-history interview): “The failure to control population is the greatest tragedy that ever hit humanity.”