McCann begins with the biology of maize and how it fits into African climates and ecologies. "Africa is distinctive among world regions in that 95 percent of its maize is consumed by humans rather than being used as livestock feed or industrial raw material." It is grown as either a vegetable or a grain crop, sometimes integrated into existing farming practices and sometimes bringing new ones with it.
Chapter two surveys the linguistic evidence from the diverse range of African names for maize. The most common naming conventions involved known grains ("sorghum"), the source ("from the sea", "Egypt"), or both ("India sorghum", "grain of the white man"), while some were based on the form of the plant ("stalk").
In West Africa, maize was one foundation of the 18th century Asante Empire, providing "a transportable forest-based food supply for [its] army that expanded its reach into savanna zones to the north" and motivation for the critical first clearing of primary forest for a subsequent fallow regime. In Nigeria, linguistic evidence suggests introduction from the north rather than the Atlantic coast. Subsequent history has seen a shift from "a forest vegetable crop cultivated alongside root crops and legumes" to "virtual monocropping" in a savanna ecology.
The adoption of maize in Venice's Po Valley region in the 16th and 17th centuries was in contrast to its slower take-up in the Ethiopian highlands. Both were driven as much by the political economy of peasant farming as by agricultural concerns, and decisions by farmers mattered more than government policies. In Italy, "the initiative to adopt maize derived from farm-level decisions by a peasant population chafing under restrictive property law and tenuous access to land", while "in Ethiopia crop choices — whether to plant teff or wheat, sorghum or finger millet — reflected a finely tuned judgment and were controlled only by the farmer himself".
In South Africa, growth in industrialisation and mining in the years around 1900 drove a shift to large-scale cultivation of maize; this and the need for uniformity created a preference for white dent varieties such as Hickory King. And this choice spread across the continent: "Despite the wide variation in localized tastes, traditions, and aesthetic choices among African farmers and consumers, historical serendipity, and the eccentricities of maize genetics, African maize is, at the beginning of the twenty-first century, overwhelmingly white in color."
An "American Rust" fungus was detected in Sierra Leone in late 1949 and by 1952 had spread to East Africa. It disappeared on its own, but not before sparking a global effort to develop a resistant maize strain — which involved international science and other networks, but not African farmers. This "lack of interest in or attention to local knowledge and conditions marked a new era in colonial science", in contrast to an earlier tradition of colonial ecologists.
The 1960 development of the SR-52 maize hybrid, by a little-known research station in the Federation of Rhodesia and Nyasaland, was "a miracle of sorts, one that transformed African landscapes, racial politics, and diets over the next forty years. ... [B]y the end of the first decade of majority rule in Zimbabwe, virtually 100 percent of Zimbabwe's maize fields were planted with the hybrids developed in the 1960s, including the short-season triple-crosses suited to drought-prone areas". The situation was rather different in Malawi, where smallcroppers stuck with older flint varieties.
Exploring links between maize and malaria, McCann focuses on the Ethiopian area of Burie. Experiments show that maize pollen is excellent food for mosquito larvae, while epidemiology clearly links maize to a 1998 malaria epidemic. A key contribution comes from changes in agroecology that have brought maize fields closer to human habitations and mosquito habitats, as well as improving communications with outside malaria reservoirs.
A final chapter looks at the future of maize in Africa. With poorly regulated storage, there are risks to maize consumers from mycotoxins, especially aflatoxin. There is "little if any evidence that GM maize threatens human health or damages local ecologies", but its widespread adoption is likely to have unintended consequences. And periurban agriculture may see a return to market gardening and localised small-scale production of maize.
So ends a fascinating tour of five centuries of African history. Maize and Grace is narrower and more academic than the popular histories of individual products, but it is a far cry from a technical monograph and should attract some general readers as well as students of African agriculture.