If you donate DNA, what should scientists give in return? A 'pathbreaking' new model

Anthropologist Carla Handley is sitting cross-legged in a mud-walled house in a Kenyan village called Merti. She's meeting with a man dressed in a flowing blue robe and a woven cap of red and white. His name is Wario Bala and he's a member of Kenya's Borana ethnic group, a nomadic people who raise cattle across Kenya's northern regions.

Handley introduces herself, then adds that she's "known locally as Chaltu Jillo Hanti" – the Borana language name bestowed on her by elders in the community. An interpreter translates and Wala laughs approvingly.

Then Handley points to a poster she's brought with pictures on it.

"You see here we have this small brush?" she says. Bala – who never went to school and doesn't know how to read – peers closely at the picture and nods.

"So do you remember in 2017," continues Handley, "when I was here, I was using a brush to rub the inside of people's cheeks? This was the brush I used."

Handley, a research associate with Arizona State University, is doing this presentation to fulfill a promise she made seven years ago, when she teamed up with some geneticists at her university for a study requiring the collection of DNA samples from nearly 600 people.

Back then, says Handley, the elders in the community had made a request that's almost