In 1983 it was hypothesized that an exaggerated hypertensive response to salt in black Americans might be traced to selective mortality during the period of Atlantic slavery. If mortality from salt and water deprivation, accompanied by excessive electrolyte loss from sweating, diarrhea and vomit during the brutal voyage across the sea, was reduced in those with the genetic good fortune to retain sodium, it was reasoned, might not descendents of these survivors fare worse in a high sodium environment in which this trait would become disadvantageous? This explanation soon became known as the "Slavery Hypothesis," and became intimately linked to its primary proponent, Clarence Grim.

Grim's 1988 conference presentation of this hypothesis attracted considerable media attention, with headlines such as "Black Slave Heritage Linked to Hypertension," and "High Blood Pressure, Most Deadly Among Blacks, Is Inherited." In 1990 a detailed account of the hypothesis made its first appearance in a clinical textbook, and a year later appeared for the first (and last) time as the subject of a peer-reviewed scientific paper. Media response remained energetic. In a medical news column, JAMA reported on the hypothesis declaring "African Lineage, Hypertension Linked." Another headline declared "Gene Linked to Hypertension," even though no genetic variants were identified or measured. Moreover, the unspecified "gene" was portrayed as a foreign villain: "Researchers…have found a genetic link that may explain why blacks in the Western Hemisphere suffer abnormally from high blood pressure. A 'salt retention' gene or genes of African origin may be the culprit," explained one article. This nonsensical description of the putative variant was echoed by an article in Science News: "The African Gene? Searching Through History for the Roots of Black Hypertension." Popular science writer Jared Diamond published an adulatory treatment in a 1991 issue of Natural History, including what appeared to be compelling historical data on African salt-scarcity and high slave-trade mortality.

As the Slavery Hypothesis grew in popularity in professional and popular circles, some researchers began to voice skepticism, arguing against the theory on the basis of population genetics, details of the physiology of hypertension, and basic evolutionary biology. The most scathing rebuttal, however, came from Philip Curtin, an historian of the slave trade on whose work Grim had drawn heavily. Curtin denied any historical validity to the proposition that Africa had traditionally been salt-scarce, and asserted that his own work had been misunderstood or misquoted on this point. He also disputed the mortality estimates cited by Grim, noting that these figures were not only incorrect or outdated, but cited so poorly that their original source could not be identified. Indeed, he disparaged Diamond’s impressive statistics as "numbers of unknown provenance." Further, Curtin argued that Grim's proposition that a majority of deaths were due to diarrheal disease was equally baseless. He concluded that the Slavery Hypothesis not only lacked supporting evidence, but that what little evidence did exist directly contradicted the theory.

Grim has largely avoided responding to specific criticisms, and in reply to these arguments he countered vaguely that Curtin had "failed to grasp several key physiological and epidemiological principles underlying the hypothesis." Other defenders of the hypothesis have been similarly oblique in print. The editor of the journal Psychosomatic Medicine, for example, dismissed critics of the Slavery Hypothesis as "left-thinking" people, and followed with the admonition that race and ethnicity are "too important to be ignored or politicized."