Living hominoids are distinguished by upright torsos and versatile locomotion. It is hypothesized that these features evolved for feeding on fruit from terminal branches in forests. To investigate the evolutionary context of hominoid adaptive origins, we analyzed multiple paleoenvironmental proxies in conjunction with hominoid fossils from the Moroto II site in Uganda. The data indicate seasonally dry woodlands with the earliest evidence of abundant C4 grasses in Africa based on a confirmed age of 21 million years ago (Ma). We demonstrate that the leaf-eating hominoid Morotopithecus consumed water-stressed vegetation, and postcrania from the site indicate ape-like locomotor adaptations. These findings suggest that the origin of hominoid locomotor versatility is associated with foraging on leaves in heterogeneous, open woodlands rather than forests.
Finding Homo nearly 3 million years ago The fossil record of humans is notoriously patchy and incomplete. Even so, skeletal remains and artifacts unearthed in Africa in recent decades have done much to illuminate human evolution. But what is the origin of the genus Homo ? Villmoare et al. found a fossil mandible and teeth from the Afar region in Ethiopia. The find extends the record of recognizable Homo by at least half a million years, to almost 2.8 million years ago. The morphological traits of the fossil align more closely with Homo than with any other hominid genus. DiMaggio et al. confirm the ancient date of the site and suggest that these early humans lived in a setting that was more open and arid than previously thought. Science , this issue p. 1352 , p. 1355
Lake sediments in 10 Ethiopian, Kenyan, and Tanzanian rift basins suggest that there were three humid periods at 2.7 to 2.5 million years ago (Ma), 1.9 to 1.7 Ma, and 1.1 to 0.9 Ma, superimposed on the longer-term aridification of East Africa. These humid periods correlate with increased aridity in northwest and northeast Africa and with substantial global climate transitions. These episodes could have had important impacts on the speciation and dispersal of mammals and hominins, because a number of key events, such as the origin of the genus Homo and the evolution of the species Homo erectus, took place in this region during that time.
The Olorgesailie basin, southern Kenya Rift, is a renowned prehistoric site that preserves evidence of hominin behavior over the past ~1 million years. During this period the basin experienced environmental variability in response to orbitally controlled climate changes and tectonic forcing, which together influenced preservation of evidence for early human behavior and technological innovations. Palaeobotanical data from phytoliths extracted from outcrop paleosols show that vegetation cover varied subtly across the landscape and through time, shifting between wooded grasslands and open grasslands. Low-resolution outcrop data and a sedimentary hiatus between ~500 ka and ~320 ka hinder understanding of when important vegetation changes may have occurred and how these influenced mammalian species turnover or major transitions in hominin technology and behavior.         Here we report vegetation data analyzed from a well-dated and continuous 139 m sedimentary core spanning the last ~1 million years, drilled from the southern area of the Olorgesailie catchment known as the Koora basin. Phytolith data from 270 samples show that climate largely controlled vegetation variability in the basin. These changes appear to have influenced mammalian assemblages and corresponded with changes in human behavior and technological transitions in the southern Kenya rift. Our record shows a significant shift towards more C4-short-Chloridoideae grasslands associated with increased variability in available fresh water, corresponding to the technological transition from Acheulean to Middle Stone Age around 320 ka. In addition, phytolith indices indicate increased vegetation variability 330-220 ka, corresponding to high variability in terrestrial and freshwater conditions resulting from tectonic, hydrological and ecological changes. The sediment core thus provides a unique, high-resolution opportunity to evaluate vegetation dynamics of the Olorgesailie-Koora region, providing new insights on how vegetation may have influenced our ancestors’ behavioral changes over the past ~1 million years.
Although it is widely acknowledged that the Corsica‐Sardinia microplate rotated counterclockwise with respect to Europe during Oligocene‐Miocene time, the precise timing of this event has yet to be determined. We have measured the age and degree of rotation of a single ‘tie‐point’ in the rotation history of the microplate. Biotite and sanidine 40 Ar/ 39 Ar age determinations of the 200m‐thick Monte Furru volcanic succession indicates that most of the volcanic pile accumulated within less than 200 ky. The paleomagnetic pole obtained for the 12 volcanic flow units comprising this succession indicates that by 18.2 Ma Sardinia remained 13° shy of its final rotation angle. These results demonstrate that the movement of the Corsica‐Sardinia block and the opening of the liguro‐provençal basin terminated later than previously estimated based on paleomagnetic and geochronologic studies of Sardinian volcanic rocks, in agreement with paleomagnetic data from Sardinian sediments.
