A 750,000 year old hominin molar from the site of Nadung'a, West Turkana, Kenya

Aridity, availability of drinking water and freshwater foods, and hominin and archeological sites during the Late Pliocene-Early Pleistocene in the western region of the Turkana Basin (Kenya): A review

Although the Turkana Basin is one of the driest regions of the East African Rift, its Plio-Pleistocene sediments are rich in freshwater vertebrates and invertebrates, providing evidence that freshwater resources were available to hominins in this region during the Plio-Pleistocene (4.2-0.7 Ma). Here we provide an overview of the hydroconnectivity of the Turkana Basin. We then review the period during which freshwater river and lake systems expanded into the western region of the Turkana Basin, where hominin and archeological sites have been discovered in sediments dating back to the Late Pliocene-Pleistocene. Freshwater conditions are reconstructed from river and lake sediments and the flora and micro- and macofauna they contain. Data synthesis suggests that drinking water and freshwater foods prevailed in the western region of the Turkana Basin at 4.20-3.98 Ma, 3.70-3.10 Ma, 2.53-2.22 Ma, then between 2.10 and 1.30 Ma and intermittently from 1.27 to 0.75 Ma. Milestones in hominin evolution occurred in this context, such as the first occurrence of Australopithecus anamensis (4.20-4.10 Ma) and Kenyanthropus platyops (3.50 Ma and 3.30-3.20 Ma), the presence of Paranthropus aethiopicus (2.53-2.45 Ma), early Homo (2.33 Ma), Paranthropus boisei (2.25 Ma and 1.77-1.72 Ma) and Homo ergaster/Homo erectus (1.75 Ma, 1.47-1.42 Ma and 1.10-0.90 Ma). Developments in hominin behavior also occurred during this timeframe, including the first known stone tools (3.30 Ma), the oldest Oldowan sites (2.34 Ma and 2.25 Ma) in the Turkana Basin, the earliest known evidence for the emergence of bifacial shaping in eastern Africa (1.80 Ma), and the first known Acheulean site (1.76 Ma). Our synthesis suggests that, diachronic variation in hydroconnectivity played a role on the amount of drinking water and freshwater foods available in the western region of the Turkana Basin, despite regional aridity.

Structural organization and tooth development in a Homo aff. erectus juvenile mandible from the Early Pleistocene site of Garba IV at Melka Kunture, Ethiopian highlands

OBJECTIVES

The immature partial mandible GAR IVE from the c. 1.7 Ma old Garba IV site at Melka Kunture (Upper Awash Basin, Ethiopia), the earliest human representative from a mountain-like environment, represents one of the oldest early Homo specimens bearing a mixed dentition. Following its first description (Condemi, ), we extended the analytical and comparative record of this specimen by providing unreported details about its inner morphology, tooth maturational pattern and age at death, crown size, and tooth tissue proportions.

MATERIALS AND METHODS

The new body of quantitative structural information and virtual imaging derives from a medical CT record performed in 2013.

RESULTS

Compared to the extant human condition and to some fossil representatives of comparable individual age, the GAR IVE mandible reveals absolutely and relatively thick cortical bone. Crown size of the permanent lateral incisor and the canine fit the estimates of H. erectus s.l., while the dm2 and the M1 more closely approach those of H. habilis-rudolfensis. Molar crown pulp volumes are lower than reported in other fossil specimens and in extant humans. The mineralization sequence of the permanent tooth elements is represented four times in our reference sample of extant immature individuals (N = 795).

CONCLUSIONS

The tooth developmental pattern displayed by the immature individual from Garba IV falls within the range of variation of extant human populations and is also comparable with that of other very young early fossil hominins. Taken together, the evidence presented here for mandibular morphology and dental development suggest GAR IVE is a robust 2.5- to 3.5-year old early Homo specimen.