Homo ergaster
Another species, called "Homo ergaster" was discovered and dated the same age as "A. Boisei" 1.7 million years ago. In 1975 this species was found in northern Kenya, Koobi Fora by Bernard Ngeneo. The same age of 1.7 million years ago means that different species were on the scene in Africa at the same time. Yes, they coexisted. It’s known that a species can survive when they inhabit a specific ecological niche. The morphology was different because of the resources they consumed. The "Homo ergaster" hunted and ate softer foods and more meat. His skull looked more like modern humans. But, "A. Boisei’s" skull was robust and had large temporals muscles that helped crush nuts and hard plants. It’s important to note that these two species coexisted.