[1][2] He was born in London the son of Hugh Barker, an engineer, and Joye, a concert cellist.
At Oundle School, he developed an interest in Natural History and was given special access to the biology classrooms to study his finds.
The Natural History Museum later asked him to mount an expedition to collect plant specimens from the Icelandic offshore island of Grimsey.
In 1969, with a grant from the Medical Research Council, Barker moved with his family to Uganda, to research Mycobacterium ulcerans infection ("Buruli ulcer"), demonstrating that it was caused, not by mosquitos, but by wounds caused by the razor-sharp reeds growing near the River Nile.
There he made the observations on the geographical relationship between neonatal and post-neonatal mortality and heart disease.