Celebrating Forgotten Scientists: Onesimus

In 1721, after a ship from Barbados arrived with passengers infected with smallpox, the inhabitants of Boston, USA found themselves in the middle of a smallpox outbreak. With almost half of the 11,000 people in the area affected by the disease, this rapidly became one of the worst smallpox epidemics the city has ever seen. 

A breakthrough in the epidemic only occurred when physician Zabdiel Boylston introduced the idea of inoculation – achieved by introducing pus from an infected individual’s pustules into a healthy patient to prevent future smallpox infections. This treatment method significantly reduced the rates of death from smallpox. However, Boylston was not the one who came up with the idea of inoculation, as was previously believed. He was introduced to the method of inoculation by a New England Puritan minister named Cotton Mather, who was himself introduced to the method by Onesimus – his slave.

African slave Onesimus (his true name at birth unknown) was gifted to Mather by his congregation and was subsequently renamed. Unfortunately, much of what is known about Onesimus comes from Mather’s personal diary, an obviously biased source. Mather referred to Onesimus’s ethnicity as “Guaranmantee”, likely a reference to the Coromantee (also known as the Akan people of modern-day Ghana). Whilst we will never know his true birthplace, it is likely that Onesimus was born in Western Africa, since he had been inoculated against smallpox in a way that is traditional for this area. Inoculation was already a relatively common practice in both Asia and African communities. It is believed that at some point during his enslavement, Onesimus informed Cotton Mather about this process of inoculation.

These experiments were important in inspiring similar experiments by Lady Mary Wortley Montagu during a smallpox outbreak in London, as well as being a stepping-stone for efforts in developing the smallpox vaccine. Fast forward to 1980 and smallpox would be declared officially eradicated worldwide thanks to the efforts of scientists and healthcare professionals. For a long time, Zabdiel Boylston was incorrectly credited with being the ‘first’ to introduce the practice to America, overlooking the fact that the idea originally came from Onesimus. Despite being the source of information that would ultimately save hundreds of lives, Onesimus remained a slave for many years before saving up the money to buy his freedom.

Whilst there has been some recent progress towards Onesimus receiving the recognition he deserves (in 2016 he was named one of the “100 Best Bostonians of All Time” in the Boston Magazine), this pales in comparison to the acclaim that Boylston and Mather have been granted over the years. Therefore, it is important that we continue to shed light on the hidden figures of history who deserve to have their contributions recognized and celebrated.