Born 1923, Olubummo was the second Nigerian PhD in mathematics (after Chike Obi), with a Yale doctorate in 1955 under N. Dunford on semigroups of bounded linear operators on Banach spaces. He joined the University of Ibadan in 1956 and remained there, with brief sabbaticals, for the rest of his career.
His published work concentrated on operator semigroups, Banach algebras, and the structure theory of $L^1$ algebras — published across the *Proceedings of the American Mathematical Society*, the *Journal of Mathematical Analysis and Applications*, and the *Journal of the London Mathematical Society*.
The institutional point: Olubummo's UI Mathematics Department became, from the late 1950s, the principal venue in West Africa for postgraduate training in mathematical analysis. Students he trained — Ibiyinka Fuwape, S. A. Ilori, J. Olusola Adebayo and the next generation — staffed the mathematics departments of the second-wave universities (Lagos, Ife, Benin, Jos) from the 1970s.
He died in 1992. The University of Ibadan's mathematics journal carries his name on its inaugural editorial board.