Reappraisal of the Morphological Affinities of the Maba 1 Cranium: New Evidence From Internal Cranial Anatomy.

OBJECTIVES

Maba 1 is a critical fossil from the late Middle Pleistocene Asia. It is well-known for the Neanderthal-like face, while its neurocranium shows affinities with many hominin taxa, which makes the taxonomic status of Maba 1 controversial. Beyond the limited information from the external surface, we investigate in detail its internal structures, which are largely unexplored.

MATERIALS AND

METHODS

We reconstructed and described its frontal sinuses, diploic vessels, endocast, and bone thickness, using micro-CT data. Linear measurements were applied for the frontal sinuses and endocast, and the latter was also analyzed through geometric morphometrics. A comparison is made after considering the preservation of Maba 1 and the availability of comparative specimens.

RESULTS

The linear discriminant analyses for the frontal sinus cluster Maba 1 with Homo neanderthalensis. The Maba 1 diploic vessels anastomosed with the parietal foramen, a rare trait among H. neanderthalensis. The Maba 1 endocast differs from Homo erectus in the frontal lobe, but it was generally closer to H. erectus than to H. neanderthalensis and Homo sapiens. Generally, Maba 1 shares higher resemblances with other debated specimens, including LH18, Djebel Irhoud, and Broken Hill 1. The bregmatic thickness of Maba 1 differed from most H. erectus, while patterns in other areas share similarities with H. neanderthalensis and some H. erectus.

DISCUSSION: The internal structures of Maba 1 show a combination of morphological features found in various species. These findings further evidence the high morphological variability among Asian hominins in the late Middle Pleistocene. Maba 1 currently cannot be definitely classified in any known hominin taxon.