The age of the deposits is estimated to be 15 to 16 million years, and they are especially important for the abundance of primate fossils they contain.

These excavations resulted in a large number of craniodental (crania and teeth) remains of a medium seized cercopithecoid monkey and cranial and postcranial remains of a large anthropoid ape — later to become the holotypes Victoriapithecus macinnesi and Sivapithecus africanus.

Watson returned to Maboko in 1949 to collect a large amount of specimen, including an isolated molar later attributed to Limnopithecus legetet.

Leakey returned again in 1951 and found fossils of new holotypes: Victoriapithecus leakeyi, Mabokopithecus clarki, and Nyanzapithecus pickfordi.

In 1982 and 1983, Martin Pickford searched the deposit dumps left by Owen in 1933 and by Leakey in 1949 and unveiled over 500 isolated specimen of at least five antropoid primates, later assigned to Kenyapithecus africanus.