Downloaded fromwhen approaching the HOMO or LUMO resonance of the molecular wire (28). The increased conductance at higher bias voltages then compensates for the molecular wire length increase in Fig. 4B (a factor of 40 is not sufficient for the achieved current increase). Thus, such a setup allows the determination of the small conductance (8.6 × 10 -13 S) of a single and the same molecular wire with 20 nm length (the conductance at small bias voltages cannot be measured over such a large distance, due to the extremely low current-below the detection limit-passing through the polymer in this case). In this regard, it would be interesting to prepare and study conjugated polymers with smaller HOMO-LUMO gaps. Such molecular wires should exhibit higher conductances and allow charge transport to be determined over even larger distances. Hominin footprints offer evidence about gait and foot shape, but their scarcity, combined with an inadequate hominin fossil record, hampers research on the evolution of the human gait. Here, we report hominin footprints in two sedimentary layers dated at 1.51 to 1.53 million years ago (Ma) at Ileret, Kenya, providing the oldest evidence of an essentially modern human-like foot anatomy, with a relatively adducted hallux, medial longitudinal arch, and medial weight transfer before push-off. The size of the Ileret footprints is consistent with stature and body mass estimates for Homo ergaster/erectus, and these prints are also morphologically distinct from the 3.75-millionyear-old footprints at Laetoli, Tanzania. The Ileret prints show that by 1.5 Ma, hominins had evolved an essentially modern human foot function and style of bipedal locomotion. Bipedalism is a key human adaptation that appears in the fossil record by 6 million years ago (Ma) (1). Considerable debate continues over when and in what context a modern human-like form of bipedalism evolved, because of a fragmentary record and disagreements over the functional interpretations of existing fossils and footprints (2-7). Modern human footprints reflect the specialized anatomy and function of the human foot, which is characterized by a fully adducted hallux, a large and robust calcaneus and tarsal region, a pronounced medial longitudinal arch, and short toes (2). Footprints reflect the pressure distribution as the foot makes contact with the substrate, but also the sediment's geomechanical properties (8). During normal walking, the weight-bearing foot undergoes a highly stereotypical movement and pressure distribution pattern in which the heel contacts the ground first, making a relatively deep impression on the substrate. This is followed by contact with the lateral side of the foot and metatarsal heads, after which weight transfers to the ball of the foot with peak pressure under the medial metatarsal heads, and finally ending with toe-off pressure under the hallux (9, 10). As a consequence, the deepest part of a footprint often occurs beneath the first and second metatarsal heads, that along with a deep hallucal impression cor...

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Carbon-isotope values of bulk organic matter from high-altitude lakes on Mount Kenya and Mount Elgon, East Africa, were 10 to 14 per mil higher during glacial times than they are today. Compound-specific isotope analyses of leaf waxes and algal biomarkers show that organisms possessing CO2-concentrating mechanisms, including C4 grasses and freshwater algae, were primarily responsible for this large increase. Carbon limitation due to lower ambient CO2 partial pressures had a significant impact on the distribution of forest on the tropical mountains, in addition to climate. Hence, tree line elevation should not be used to infer palaeotemperatures.

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Cholera epidemics have a recorded history in the eastern Africa region dating to 1836. Cholera is now endemic in the Lake Victoria basin, a region with one of the poorest and fastest growing populations in the world. Analyses of precipitation, temperatures, and hydrological characteristics of selected stations in the Lake Victoria basin show that cholera epidemics are closely associated with El Niño years. Similarly, sustained temperatures high above normal (T(max)) in two consecutive seasons, followed by a slight cooling in the second season, trigger an outbreak of a cholera epidemic. The health and socioeconomic systems that the lake basin communities rely upon are not robust enough to cope with cholera outbreaks, thus rendering them vulnerable to the impact of climate variability and change. Collectively, this report argues that communities living around the Lake Victoria basin are vulnerable to climate-induced cholera that is aggravated by the low socioeconomic status and lack of an adequate health care system. In assessing the communities' adaptive capacity, the report concludes that persistent levels of poverty have made these communities vulnerable to cholera epidemics.