Final answer:
The discovery of Paranthropus boisei and footprints of bipedal individuals in the Eastern Rift Valley led the Leakeys to engage in extensive research at Olduvai Gorge in East Africa.
Step-by-step explanation:
The event that led the Leakeys to search for clues to human past at Olduvai Gorge in East Africa over 20 years was the detection of hominid fossils in the Eastern Rift Valley. Notably, the discovery of Paranthropus boisei in 1959, classified as Zinjanthropus boisei, by Louis Leakey and his wife, Mary Leakey, sparked their interest. This was followed by Mary Leakey’s finding of a 75-foot trail of footprints by bipedal individuals in the 1980s, which provided significant evidence of early hominid bipedalism.
Following these discoveries, they dedicated their efforts in the Olduvai Gorge, leading to more significant revelations about early hominid species and their evolution.
Learn more about Leakeys' Archaeological Efforts