In an interview at Columbia University, where she’s dean of social science, Nelson described DNA as containing a social power as well as a biological one.

“We think it offers a lot of answers on things that ail us,” Nelson said. She wanted to expand the kinds of problems DNA could answer beyond those of individual health or biology to include “social and political problems, which have their historical roots in slavery”.

That may seem like a broad statement, and Nelson understands that some may doubt her. She herself admits that she only came to believe in DNA’s potential for racial progress “reluctantly”. She worried it seemed like buying into a long history of “scientific racism [used] to make claims about fundamental differences between people, which are deleterious for communities of color and become justifications for inequality”.

So when she started to study how black people were using DNA, Nelson said she had to suppress an urge “as an activist to wag my finger and say, ‘You are wrong! Put that DNA down and stop doing that!’”

But she still found herself wanting to understand the research, knowing that researchers’ intentions were often noble. “These were smart people, college-educated people, who know about Henrietta Lacks and the Tuskegee experiments,” she said, referring to two infamous cases where African Americans’ bodies were used for scientific experimentation without their consent.

So Nelson began studying black people who are engaging in “recreational genealogy” – the act of finding out about one’s history through genetic ancestry testing. Nelson believes that recreational DNA testing “may not just dwell in that domain”, with data sometimes leaking into medical research or criminal databases. There are documented cases where a voluntary DNA test inadvertently led to someone, or their relative, becoming a suspect in a crime.

In this era of mass incarceration, Nelson points out, there are already many African Americans whose DNA is recorded in the genetic databases used by law enforcement. In fact, the supreme court has approved DNA collection simply from routine police stops, before any conviction. It happened, for example, to Black Lives Matter activist Netta Elzie, raising the question whether it is wise for black people to voluntarily give such an intimate part of themselves when it can easily become a tool used for surveillance.

Nelson has also documented how black activists used DNA for explicitly political and historic reasons in technologically creative ways. She laughed when she admitted to being “the great, great grandmother of Afrofuturism” who started the Afro-Futurism list-serve in the 1990s. Afrofuturism is an Afrocentric intellectual concept which critiques and reimagines the black past, present and future. It can do so through cultural ideas of science or science fiction alike – indeed, through DNA itself, or through the ways it affects the public imagination.

“DNA,” Nelson writes in her book, is being “leveraged to raise awareness of blacks’ experiences and, in so doing, contribute to today’s racial politics, which are too often marked by historical amnesia.” She chronicles the story of Deadria Farmer-Paellmann, a reparations activist who organized a class-action suit by descendants of slaves in 2002. Although reparations had recently been granted to Japanese Americans who had been interned during the second world war, a judge denied the suit, arguing that “the plaintiffs did not demonstrate a precise connection to former slaves, and thus – could not sue for injury as their descendants”. The plaintiffs then turned to DNA to try to persuade the court that they could, in fact, trace back their ancestry to slaves.

This allowed them to “deal with the court on its own terms”, as Nelson put it, “if you can even imagine the US court system considering reparations”. Indeed, it’s something the most left presidential candidate won’t consider. Just last month, the writer Ta-Nehisi Coates chided Senator Bernie Sanders for calling theoretical payments to descendants of slaves “very divisive”, and for having a “political imagination [which] is so active against plutocracy, but so limited against white supremacy”.

Yet, as controversial as calls to study reparations are within the United States, pressure is mounting from outside. Finishing a visit to the US just last week, the United Nations Working Group of Experts on People of African Descent wrote it was “extremely concerned about the human rights situation of African Americans” and encouraged Congress to “examine slavery and discrimination in the colonies and the United States from 1619 to the present and recommend appropriate remedies”.

Nelson herself finds it “stunning” that HR 40, Congressman John Conyers’ call to just study reparations, has never made it out of committee – which she equates to “being in a relationship for 300 or 400 years, and your partner has been saying for the past 40 years, ‘Can we just talk about this?’ And you saying, ‘ No, I don’t want to talk about it.’

“It’s fascinating and sad,” she added.