The paleoecology of Pleistocene birds from Middle Bed II, at Olduvai Gorge, Tanzania, and the environmental context of the Oldowan-Acheulean transition

Homo heterogenus: Variability in early Pleistocene Homo environments

To understand the ecological dominance of Homo sapiens, we need to investigate the origins of the plasticity that has enabled our colonization of the planet. We can approach this by exploring the variability of habitats to which different hominin populations have adapted over time. In this article, we draw upon and synthesize the current research on habitats of genus Homo during the early Pleistocene. We examined 121 published environmental reconstructions from 74 early Pleistocene sites or site phases to assess the balance of arguments in the research community. We found that, while grasslands and savannahs were prominent features of Homo habitats in the early Pleistocene, current research does not place early Pleistocene Homo, in any single environmental type, but in a wide variety of environments, ranging from open grasslands to forests. Our analysis also suggests that the first known dispersal of Homo out of Africa was accompanied by niche expansion.

Historical dispersal and host-switching formed the evolutionary history of a globally distributed multi-host parasite - The Ligula intestinalis species complex

Studies on parasite biogeography and host spectrum provide insights into the processes driving parasite diversification. Global geographical distribution and a multi-host spectrum make the tapeworm Ligula intestinalis a promising model for studying both the vicariant and ecological modes of speciation in parasites. To understand the relative importance of host association and biogeography in the evolutionary history of this tapeworm, we analysed mtDNA and reduced-represented genomic SNP data for a total of 139 specimens collected from 18 fish-host genera across a distribution range representing 21 countries. Our results strongly supported the existence of at least 10 evolutionary lineages and estimated the deepest divergence at approximately 4.99-5.05 Mya, which is much younger than the diversification of the fish host genera and orders. Historical biogeography analyses revealed that the ancestor of the parasite diversified following multiple vicariance events and was widespread throughout the Palearctic, Afrotropical, and Nearctic between the late Miocene and early Pliocene. Cyprinoids were inferred as the ancestral hosts for the parasite. Later, from the late Pliocene to Pleistocene, new lineages emerged following a series of biogeographic dispersal and host-switching events. Although only a few of the current Ligula lineages show narrow host-specificity (to a single host genus), almost no host genera, even those that live in sympatry, overlapped between different Ligula lineages. Our analyses uncovered the impact of historical distribution shifts on host switching and the evolution of host specificity without parallel host-parasite co-speciation. Historical biogeography reconstructions also found that the parasite colonized several areas (Afrotropical and Australasian) much earlier than was suggested by only recent faunistic data.

Fossil birds from Cooper's D aid in reconstructing the Early Pleistocene paleoenvironment in the Cradle of Humankind (Gauteng, South Africa)

Several large-bodied hominin and nonhuman primates have coexisted in the Cradle of Humankind in South Africa during the Early Pleistocene. Previous paleoenvironmental studies regarding the Plio-Pleistocene of South Africa have focused heavily on mammal assemblages. Here, we conducted a comprehensive taxonomic analysis of the fossil bird remains from Cooper's D, the most fossiliferous locality of the hominin-bearing Cooper's Cave complex in South Africa. Our taxonomic evaluation of 505 remains reveals the presence of 23 bird taxa, two of which are extinct and already reported from the nearby fossil locality of Kromdraai. The taxonomically diverse bird assemblage is dominated by Francolinus sp. and other species associated with open grassland habitats, followed by rock-dwelling species, including Tyto cf. alba and the extinct Corvus bragai, and by woodland species such as Agapornis sp., Accipiter melanoleucos, and the extinct Glaucidium ireneae. The occurrence of these taxa and their respective proportions in the assemblage, in terms of both numbers of bones and individuals, point to the presence of extensive open grassland and/or savannah with rocky outcrops and woodland. These findings corroborate previous analyses of mammals from Cooper's D, with the exception of aquatic species, which are rare in the bird assemblage. Comparison with older deposits from Kromdraai confirms the definitive establishment of open habitats in the Cradle of Humankind during the Early Pleistocene following a transition from woodier habitats during the Late Pliocene. This study constitutes a further step in investigating the fossil bird diversity in the Cradle of Humankind during the Plio-Pleistocene. Our results add to the larger body of work using avian fossils for paleoenvironmental reconstructions in Africa and support the utility of birds as paleoenvironmental proxies. Similar future studies will refine our understanding of the paleoenvironments and landscape transformation during the Plio-Pleistocene, a critical timeframe for hominin evolution in southern Africa.

Bone tools from Beds II-IV, Olduvai Gorge, Tanzania, and implications for the origins and evolution of bone technology

The advent of bone technology in Africa is often associated with behavioral modernity that began sometime in the Middle Stone Age. Yet, small numbers of bone tools are known from Early Pleistocene sites in East and South Africa, complicating our understanding of the evolutionary significance of osseous technologies. These early bone tools vary geographically, with those in South Africa indicating use in foraging activities such as termite extraction and those in East Africa intentionally shaped in a manner similar to lithic tool manufacture, leading some to infer multiple hominin species were responsible for bone technology in these regions, with Paranthropus robustus assumed to be the maker of South African bone tools and Homo erectus responsible for those in East Africa. Here, we present on an assemblage of 52 supposed bone tools primarily from Beds III and IV, Olduvai Gorge, Tanzania, that was excavated by Mary Leakey in the late 1960s and early 1970s, but was only partially published and was never studied in detail from a taphonomic perspective. The majority of the sites from which the tools were recovered were deposited when only H. erectus is known to have existed in the region, potentially allowing a direct link between this fossil hominin and bone technology. Our analysis confirms at least six bone tools in the assemblage, the majority of which are intentionally flaked large mammal bones. However, one of the tools is a preform of the oldest barbed bone point known to exist anywhere in the world and pushes back the initial appearance of this technology by 700 kyr.

Soil and plant phytoliths from the Acacia-Commiphora mosaics at Oldupai Gorge (Tanzania)

This article studies soil and plant phytoliths from the Eastern Serengeti Plains, specifically the Acacia-Commiphora mosaics from Oldupai Gorge, Tanzania, as present-day analogue for the environment that was contemporaneous with the emergence of the genus Homo. We investigate whether phytolith assemblages from recent soil surfaces reflect plant community structure and composition with fidelity. The materials included 35 topsoil samples and 29 plant species (20 genera, 15 families). Phytoliths were extracted from both soil and botanical samples. Quantification aimed at discovering relationships amongst the soil and plant phytoliths relative distributions through Chi-square independence tests, establishing the statistical significance of the relationship between categorical variables within the two populations. Soil assemblages form a spectrum, or cohort of co-ocurring phytolith classes, that will allow identifying environments similar to those in the Acacia-Commiphora ecozone in the fossil record.

New excavations at the HWK EE site: Archaeology, paleoenvironment and site formation processes during late Oldowan times at Olduvai Gorge, Tanzania

This paper reports the results of renewed fieldwork at the HWK EE site (Olduvai Gorge, Tanzania). HWK EE is positioned across the boundary between Lower and Middle Bed II, a crucial interval for studying the emergence of the Acheulean at Olduvai Gorge. Our excavations at HWK EE have produced one of the largest collections of fossils and artefacts from any Oldowan site, distributed across several archaeological units and a large excavation surface in four separate trenches that can be stratigraphically correlated. Here we present the main stratigraphic and archaeological units and discuss site formation processes. Results show a great density of fossils and stone tools vertically through two stratigraphic intervals (Lemuta and Lower Augitic Sandstone) and laterally across an area of around 300 m², and highlight the confluence of biotic and abiotic agents in the formation of the assemblage. The large size and diversity of the assemblage, as well as its good preservation, qualify HWK EE as a reference site for the study of the late Oldowan at Olduvai Gorge and elsewhere in Africa. In addition, the description of the stratigraphic and archaeological sequence of HWK EE presented in this paper constitutes the foundation for further studies on hominin behavior and paleoecology in Lower and Middle Bed II.