Insights into the palaeobiology of an early Homo infant: multidisciplinary investigation of the GAR IVE hemi-mandible, Melka Kunture, Ethiopia

Abstract

Childhood is an ontogenetic stage unique to the modern human life history pattern. It enables the still dependent infants to achieve an extended rapid brain growth, slow somatic maturation, while benefitting from provisioning, transitional feeding, and protection from other group members. This tipping point in the evolution of human ontogeny likely emerged from early Homo. The GAR IVE hemi-mandible (1.8 Ma, Melka Kunture, Ethiopia) represents one of the rarely preserved early Homo infants (~ 3 years at death), recovered in a richly documented Oldowan archaeological context. Yet, based on the sole external inspection of its teeth, GAR IVE was diagnosed with a rare genetic disease–amelogenesis imperfecta (AI)–altering enamel. Since it may have impacted the child’s survival, this diagnosis deserves deeper examination. Here, we reassess and refute this diagnosis and all associated interpretations, using an unprecedented multidisciplinary approach combining an in-depth analysis of GAR IVE (synchrotron imaging) and associated fauna. Some of the traits previously considered as diagnostic of AI can be better explained by normal growth or taphonomy, which calls for caution when diagnosing pathologies on fossils. We compare GAR IVE’s dental development to other fossil hominins, and discuss the implications for the emergence of childhood in early Homo.

Experimental Evidence of Bone Lesions Due to Larder Beetle Dermestes maculatus (Coleoptera: Dermestidae)

“…In the case of pupation chambers observed on an extensive set of bone remains or a whole skeleton, our results suggest the presence of several corpses at different decomposition stages, or the addition of new corpses while others were already skeletonized [ 30 ]. In such a situation, bones with pupation chambers should be considered to be the oldest, as they were already dry and served as refuges, while other corpses provided the flesh required for larval development.…”

“…Larder beetles and their larvae are most active during the hot and dry summer months, when rapid desiccation of carrion is more likely and larval development is fast [ 1 , 3 ]. Consequently, the presence of pupation chambers could indicate the seasonality and a narrow temperature range during the period of larval activity [ 18 , 30 ].…”

Early Homo erectus lived at high altitudes and produced both Oldowan and Acheulean tools

“…3) have identified affinities with various early Homo species such as H. habilis, H. rudolfensis, H. ergaster, and H. erectus (13). Although GAR IVE had been described as struck by a rare genetic disorder affecting its enamel (amelogenesis imperfecta) (14), this was recently refuted with synchrotron imaging, and features previously interpreted as pathological were instead shown to result from taphonomic processes (15). On the basis of medical computed tomography (CT) scans, Zanolli et al (3) expanded on previous assessments to examine the sequence of dental development, tooth crown-tissue proportions, tooth size in the unerupted permanent dentition, and corpus cortical-bone thickness.…”

Une vue d’ensemble sur Melka Kunture, grand complexe de sites pléistocènes dans la vallée supérieure de l’Awash (Éthiopie)

“…Leur cheminement re ´gulier et re ´pe ´te ´en direction de leurs pa ˆturages, qui a finalement creuse ´une sorte de tranche ´e peu profonde, indique un comportement identique a `celui des hippopotames actuels. Les restes d'hominine ´s les plus anciens sont ceux d'un tre `s jeune Homo erectus de ´couvert dans le niveau oldowayen de Garba IVE (Zilberman et al, 2004 ;Le Cabec et al, 2021). Un hume ´rus attribue ´a ùn Homo sp.…”