Rethinking the ecological drivers of hominin evolution.

A central goal of paleoanthropology is understanding the role of ecological change in hominin evolution. Over the past several decades researchers have expanded the hominin fossil record and assembled detailed late Cenozoic paleoclimatic, paleoenvironmental, and paleoecological archives. However, effective use of these data is precluded by the limitations of pattern-matching strategies for inferring causal relationships between ecological and evolutionary change. We examine several obstacles that have hindered progress, and highlight recent research that is addressing them by (i) confronting an incomplete fossil record, (ii) contending with datasets spanning varied spatiotemporal scales, and (iii) using theoretical frameworks to build stronger inferences. Expanding on this work promises to transform challenges into opportunities and set the stage for a new phase of paleoanthropological research.

The Occurrence of Ophidiomyces ophiodiicola in Northern Georgia Wild and Captive Snake Populations.

Ophidiomycosis, or snake fungal disease, is an emerging wildlife disease caused by the Ophidiomyces ophiodiicola fungus. The fungus can result in high mortality rates among infected snakes and has been documented across much of the eastern US, including southern Georgia. However, little is known about ophidiomycosis in northern Georgia. We surveyed wild snake populations in five counties of northern Georgia between March 2019 and March 2020 and swabbed captured snakes (n=27) for the presence of O. ophiodiicola DNA. We followed similar sampling protocols with a group of captive snakes (n=6) at the Elachee Nature Center in Hall County, Georgia. Quantitative PCR confirmed the presence of O. ophiodiicola DNA in 33% (11/33) of snakes. Eight of the confirmed positive samples were collected from wild snakes (30%, 8/27) across our sample region, while three were from our captive group (50%, 3/6). Our results indicated that O. ophiodiicola is present in wild snake populations in northern Georgia, and the pathogen is present in seemingly healthy captive snakes. This knowledge is critical for conservation and management efforts, but more research is needed to fully understand ophidiomycosis and its effect on snake populations in the region.

New hominin remains and revised context from the earliest Homo erectus locality in East Turkana, Kenya.

The KNM-ER 2598 occipital is among the oldest fossils attributed to Homo erectus but questions have been raised about whether it may derive from a younger horizon. Here we report on efforts to relocate the KNM-ER 2598 locality and investigate its paleontological and geological context. Although located in a different East Turkana collection area (Area 13) than initially reported, the locality is stratigraphically positioned below the KBS Tuff and the outcrops show no evidence of deflation of a younger unit, supporting an age of >1.855 Ma. Newly recovered faunal material consists primarily of C4 grazers, further confirmed by enamel isotope data. A hominin proximal 3rd metatarsal and partial ilium were discovered <50 m from the reconstructed location where KNM-ER 2598 was originally found but these cannot be associated directly with the occipital. The postcrania are consistent with fossil Homo and may represent the earliest postcrania attributable to Homo erectus.

Comparative isotopic evidence from East Turkana supports a dietary shift within the genus Homo.

It has been suggested that a shift in diet is one of the key adaptations that distinguishes the genus Homo from earlier hominins, but recent stable isotopic analyses of fossils attributed to Homo in the Turkana Basin show an increase in the consumption of C4 resources circa 1.65 million years ago, significantly after the earliest evidence for Homo in the eastern African fossil record. These data are consistent with ingesting more C4 plants, more animal tissues of C4 herbivores, or both, but it is also possible that this change reflects factors unrelated to changes in the palaeobiology of the genus Homo. Here we use new and published carbon and oxygen isotopic data (n = 999) taken from large-bodied fossil mammals, and pedogenic carbonates in fossil soils, from East Turkana in northern Kenya to investigate the context of this change in the isotope signal within Homo. By targeting taxa and temporal intervals unrepresented or undersampled in previous analyses, we were able to conduct the first comprehensive analysis of the ecological context of hominin diet at East Turkana during a period crucial for detecting any dietary and related behavioural differences between early Homo (H. habilis and/or H. rudolfensis) and Homo erectus. Our analyses suggest that the genus Homo underwent a dietary shift (as indicated by δ13Cena and δ18Oena values) that is (1) unrelated to changes in the East Turkana vegetation community and (2) unlike patterns found in other East Turkana large mammals, including Paranthropus and Theropithecus. These data suggest that within the Turkana Basin a dietary shift occurred well after we see the first evidence of early Homo in the region.

Earliest known Oldowan artifacts at >2.58 Ma from Ledi-Geraru, Ethiopia, highlight early technological diversity.

The manufacture of flaked stone artifacts represents a major milestone in the technology of the human lineage. Although the earliest production of primitive stone tools, predating the genus Homo and emphasizing percussive activities, has been reported at 3.3 million years ago (Ma) from Lomekwi, Kenya, the systematic production of sharp-edged stone tools is unknown before the 2.58-2.55 Ma Oldowan assemblages from Gona, Ethiopia. The organized production of Oldowan stone artifacts is part of a suite of characteristics that is often associated with the adaptive grade shift linked to the genus Homo Recent discoveries from Ledi-Geraru (LG), Ethiopia, place the first occurrence of Homo ∼250 thousand years earlier than the Oldowan at Gona. Here, we describe a substantial assemblage of systematically flaked stone tools excavated in situ from a stratigraphically constrained context [Bokol Dora 1, (BD 1) hereafter] at LG bracketed between 2.61 and 2.58 Ma. Although perhaps more primitive in some respects, quantitative analysis suggests the BD 1 assemblage fits more closely with the variability previously described for the Oldowan than with the earlier Lomekwian or with stone tools produced by modern nonhuman primates. These differences suggest that hominin technology is distinctly different from generalized tool use that may be a shared feature of much of the primate lineage. The BD 1 assemblage, near the origin of our genus, provides a link between behavioral adaptations-in the form of flaked stone artifacts-and the biological evolution of our ancestors.

Skeletal lesions in a population of Virginia opossums (Didelphis virginiana) from Baldwin County, Georgia.

Antemortem skeletal lesions were analyzed in 61 Virginia opossums (Didelphis virginiana) collected as roadkill from Baldwin County, Georgia, USA. As evidenced by bridging fracture calluses, misalignments, bone-surface depressions, perforations, localized superficial calluses, periosteal proliferations, and bony bridges across intervertebral disk spaces, 64% of the individuals had signs of one or more healed injuries. Within the subset of skeletons with bone lesions, 54% had healed rib fractures and 23% had scapular, 21% pelvic, 18% fibular, 18% vertebral, 13% dentary, 10% tibial, and 10% podial lesions. Bone lesions occurred most frequently in the cranial portion of the skeletons and averaged approximately four per individual. The majority of the skeletal injuries appeared to be inconsistent with those caused by falls or automobile collisions. The nature and position of the bone lesions suggested that nonfatal predator attacks, possibly from domestic dogs, may be a significant contributor to bodily injury in this species.