From 1935 to 1959, Louis and Mary worked hard in several excavations in Kenya and Tanzania, looking for the remains of early humans. Although they encountered many difficulties, both because of the dangerous and inaccessible terrain and the scarce postwar scientific foundations.
However, the real breakthrough came in 1959, when one morning in the Olduvai Gorge - a region separating the famous National Park from Tanzania's more famous Serengeti National Park - Mary discovered a 1.75 million-year-old hominid skull, later classified as Parantropus boisei.
This finding was a strong argument that hominids evolved in Africa.
