Chellean Man
Olduvai Hominid number 9, known as the Chellean Man, is a fossilized skull cap of an early hominin, found in LLK II, Olduvai Gorge by Louis S. B. Leakey in 1960. It is believed to be ca. 1.4 million years old. Its cranial capacity is estimated at greater than, the largest value among all known African Homo erectus specimens. OH 9 is significant because of the features it carried and its correlation to the species classification it resides in.
Species Classification
Leakey named it "Chellean Man", in reference to the Oldowan tools found at the site, which were then referred to by the now-obsolete name Chellean. Heberer provisionally named a new species Homo leakeyi based on the specimen in honor of Leakey, but most subsequent workers have regarded it as Homo ergaster, or as Homo erectus. Phillip Tobias provisionally named a new subspecies, H. erectus olduvaiensis, in 1968 based on the specimen, but this has not seen continued use. To the extent that proponents of the use of H. ergaster define ergaster as a separate species rather than a pure chronospecies, the assignment of OH 9 to H. erectus sensu stricto by Colin Groves supports subsuming H. ergaster into H. erectus.Because the name Homo leakeyi was proposed conditionally, it is not valid according to the rules established by the ICZN. Kretzoi created the replacement name Homo louisleakeyi, which is valid.
Cranial bone thickness has been widely qualified for Homo erectus but rarely quantified. It’s quite often that throughout craniums found, the thickness varies between those different hominids. Yet in OH 9, compared to other H. erectus, it had the biggest cranial capacity standing at 1,067 cc and one of the largest mid supra-orbital torus thickness of 18.5 mm also known as the brow ridge. OH 9 has a robust brow ridge that allows it to stand out among other H. erectus. The brow ridge made it difficult to determine whether this cranium should be classified as H. erectus or a different species. Cranial bone thickness is key when determining whether a specimen found is H. erectus. The pattern of bone thickness distribution observed in Asian H. erectus, P. paniscus, and possibly in the australopiths, early Homo or African H. ergaster/erectus analyzed appears to be a pleomorphic trait among hominids. Since cranium thickness and the OH 9 cranium capacity is larger than any found, it explored the idea of different forms of H. erectus from different areas due to migration. By the 1980s, the growing numbers of H. erectus specimens, particularly in Africa, led to the realization that Asian Homo erectus, once thought so primitive, was in fact more derived than its African counter-parts, which leads into the Out of Africa hypothesis of humans origins.