Phillip Tobias provisionally named a new subspecies, H. erectus olduvaiensis, in 1968 based on the specimen, but this has not seen continued use.

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.

The brow ridge made it difficult to determine whether this cranium should be classified as H. erectus or a different species.

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.

Which implied that major differences in the development of cognitive capabilities existed between H. erectus and anatomically modern humans.

[12] These new traits like the robust brow ridge and skull thickness confirmed that H. erectus in different areas kept evolving.