Malaria and the Mason-Dixon

by |February 2, 2012

Updated Aug. 5, 2015.

By Samuel Barnes

In its nascent centuries, the English colonies of North America were set on two disparate economic, social, and philosophic paths. The first was the way of New England and the north, and the second the way of the Carolinas and the south—our country can be segmented laterally. The differences in early history resonate to this day. When one ponders the root of the essential disparity between those states on opposite sides of what we call today the Mason-Dixon line, one first recalls the Civil War between the Union and the Confederacy: the diverse, urbane, egalitarian North ultimately victorious and the antebellum Southern gentry culture still noble in defeat. One remembers the principle divide that spurred the war, the horror that was African chattel slavery. But what is less recognized—or, rather, is just now coming to light with the help of modern studies in biology and ecology—is that the differing climates, landscapes, and, crucially, fauna which flourished in our country’s north and south went a long way towards deciding the societies that developed, and led in the end to that bloody, bitter, defining war.

This map of the malarious zones in 1943 roughly corresponds to the disease’s extent in early American history—extending north to the Mason-Dixon line.

In the earliest years of English colonization, two principal outposts managed to establish themselves. In 1616, the famous Pilgrims sailed their little Mayflower around Cape Cod and settled Plymouth Rock in what we call today Massachusetts. Almost a decade earlier, an officially backed expedition of the Virginia Company had successfully founded Jamestown, about a hundred miles south of Washington, D.C. and near the mouth of the Chesapeake Bay. Both areas were densely inhabited with native nations unwilling to politely disappear, and both dealt with difficult, hungry early winters. Despite the less-forgiving climate of Massachusetts, though, the survival rates for early Puritan colonists were substantially better than their Anglican counterparts to the south.

It is acknowledged, today, that European superiority over native nations around the world was less racial, philosophical, or moral—it could even be argued that European Christendom was deficient in these categories relative to the indigenous peoples the subjugated and usurped—than it was biological. Europe, crossroads of north and south, sea and land, east and west Eurasia, had a population with great biological redundancy. Blood of all three types were common. New plagues entered from east or south or north every other decade and the survivors were that much more resistant. But Europe, like New England, was largely temperate, and Europeans were unequipped to battle with the myriad microbial life forms that held sway in the torrid zones. In the age of sail, the great scourge of these warmer climes was what they called tertian fever, and we moderns call malaria.

In its first decade, those British (along with a number of Dutch, Germans, and Poles) who secured passage to Jamestown as either full citizens or contracted servants were dying at the amazing rate of almost one-out-of-two within the first year of their arrival. The survivors called the treacherous initial twelve months ‘seasoning’; like other poxes and flus one is largely immune to reoccurrences of malaria after surviving the first. Slowly, the number of landowners expanded into the countryside as the hardiest indentured servants earned their freedom, and a larger population of laborers became eminently necessary. As knowledge of the deadly nature of Virginia’s air spread amongst potential European migrants, these new landowners had nobody to work their hard-won land.

Malaria, a manifestation of the protozoan parasite Plasmodium Falciparum, was wholly new to the Americas, and was equally if not more lethal to the exposed Native Americans as it was to the Europeans. Their susceptibility to malaria (along with other invasive ailments like smallpox) would eventually drive them from the whole of the Eastern seaboard. The alarming death rate prevented European farmers from utilizing Native labor en masse in those first tobacco, cotton, and rice plantations that came to define the pre-revolutionary South. There was only one population known to be immune to the ravages of the fever: West and Central Africans.

The first slave ship arrived in Jamestown in 1619, and within forty years the African population of Virginia would outnumber the Europeans by whom they were bought and sold. The Africans, well suited to the climate, largely immune to malaria, and familiar with the rigors of collectivized labor, lived longer and healthier lives in bondage than did their captors with whip in hand. As colonies proliferated, the plantation-slavery model found success from central Maryland to southern Georgia, while the industrial-economic-urban complex took hold in the north, forming into great hubs in Philadelphia, Boston, and New Amsterdam.

Malaria is a mosquito-borne infectious disease of humans and other animals caused by eukaryotic protists of the genus Plasmodium – Photo by Lukas.S

The line that declared the border between the two was not only of jurisdiction, nor was it one of moral hygiene: it was a line of average temperature, separating the mild-wintered south from the thoroughly seasonal north. Below it (in Dixie) the Plasmodium parasite could live, and above it the vector mosquitoes would survive, but the Plasmodium inside them would die. Slavery wasn’t a factor in the north because Caucasians could survive and eventually thrive in its climate. Their adaptability to the climate made a captive labor force unwieldy and unnecessary—as Adam Smith surmised in The Wealth of Nations, chattel slavery is a most inefficient mode of economic production. When push came to shove, it was a microscopic virus that would draw the frontiers of a nation, and help to decide the life and livelihood of millions upon millions of the Americans who came to live there.

CERC provides a course on the principles of conservation medicine and disease ecology, with an emphasis on the effect of disease on human, wildlife and domestic animal and ecosystem health. It examines the impact of disease on biodiversity and rates of extinction, as well as the rise of emergent diseases as a result of various environmental factors.

This course is part of CERC’s Certificate Program in Conservation and Environmental Sustainability. This first session is free and open to the public. Registration is required to attend the full 10-hour course.

Courses may be taken on an individual basis or you may pursue the full 12-course Certificate. Interested in learning more? Visit our website or contact CERC for more information: or 212-854-0149.

Source: Charles C. Mann, 1493: Uncovering the New World Columbus Created

Samuel Barnes is an intern at the Center for Environmental Research and Conservation.

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Bernard Kaplan
Bernard Kaplan

Excellent article!
“When push came to shove, it was a microscopic virus that would draw …”
Please note that plasmodium is not a virus but a protozoan.
Bernard Kaplan MD.