The Hadropithecus conundrum reconsidered, with implications for interpreting diet in fossil hominins

Abstract

The fossil 'monkey lemur' Hadropithecus stenognathus has long excited palaeontologists because its skull bears an astonishing resemblance to those of robust australopiths, an enigmatic side branch of the human family tree. Multiple lines of evidence point to the likelihood that these australopiths ate at least some 'hard', stress-limited food items, but conflicting data from H. stenognathus pose a conundrum. While its hominin-like craniofacial architecture is suggestive of an ability to generate high bite forces, details of its tooth structure suggest that it was not well equipped to withstand the forces imposed by cracking hard objects. Here, we use three-dimensional digital reconstructions and finite-element analysis to test the hard-object processing hypothesis. We show that Archaeolemur sp. cf. A. edwardsi, a longerfaced close relative of H. stenognathus that lacked hominin convergences, was probably capable of breaking apart large, stress-limited food items, while Hadropithecus was better suited to processing small, displacement-limited (tougher but more compliant) foods. Our suggestion that H. stenognathus was not a hardobject feeder has bearing on the interpretation of hominin cranial architecture; the features shared by H. stenognathus and robust australopiths do not necessarily reflect adaptations for hard-object processing.

Phylogenetic, Ecological, and Allometric Correlates of Cranial Shape in Malagasy Lemuriforms

“…; Dumont et al. ). The broadest view of lemur cranial diversity was provided by Viguier (), who argued that craniofacial structure in lemurs primarily reflects functional adaptation to diet based on an analysis of 2D craniofacial landmarks using a broad taxonomic sample (in agreement with the nonphylogenetic analyses presented here).…”

“…The H1 analysis reflects a dietary reconstruction of hard‐object feeding for Hadropithecus , which is controversial (e.g., Dumont et al. ). A similarly weak relationship between cranial shape and ecology when phylogeny is taken into account was also documented for guenon monkeys (Cardini and Elton ) and New World monkeys (Perez et al.…”

Dietary Reconstruction of Pliocene Parapapio whitei from Makapansgat, South Africa, Using Dental Microwear Texture Analysis

“…It has been previously established that food items in the upper canopy exhibit fewer abrasive mineral particles than dietary resources found at lower levels [Ungar et al, 1995]. Still greater loads are found on foods at ground level, particularly in xeric habitats where leaves, fruit and herbs can be superficially coated with grit [Sanson et al, 2007;Dumont et al, 2011]. Grit is also found on hypogeous foods where extraneous mineral particles with mechanically resistant properties adhere to the outer plant tunic [Daegling and Grine, 1999;Catlett et al, 2010].…”

Dietary proclivities of Paranthropus robustus from Swartkrans, South Africa

“…The terrestrial foraging of P. robustus in mixed C 4 habitats would likely deliver a heavier grit load than observed in tropical forests. This would be particularly evident in relatively arid habitats where a layer of grit covers food items (Sanson et al 2007;Galbany et al 2009;Dumont et al 2011). Grit adheres to hypogeous organs (Daegling and Grine 1999) and can be inadvertently ingested when bulbs or corms have outer skins that are not easily removed or cleaned with the mouth or hands.…”