Early anthropogenic impact on Western Central African rainforests 2,600 y ago

A potential human footprint on Western Central African rainforests before the Common Era has become the focus of an ongoing controversy. Between 3,000 y ago and 2,000 y ago, regional pollen sequences indicate a replacement of mature rainforests by a forest–savannah mosaic including pioneer trees. Although some studies suggested an anthropogenic influence on this forest fragmentation, current interpretations based on pollen data attribute the ‘‘rainforest crisis’’ to climate change toward a drier, more seasonal climate. A rigorous test of this hypothesis, however, requires climate proxies independent of vegetation changes. Here we resolve this controversy through a continuous 10,500-y record of both vegetation and hydrological changes from Lake Barombi in Southwest Cameroon based on changes in carbon and hydrogen isotope compositions of plant waxes. δ¹³C-inferred vegetation changes confirm a prominent and abrupt appearance of C4 plants in the Lake Barombi catchment, at 2,600 calendar years before AD 1950 (cal y BP), followed by an equally sudden return to rainforest vegetation at 2,020 cal y BP. δD values from the same plant wax compounds, however, show no simultaneous hydrological change. Based on the combination of these data with a comprehensive regional archaeological database we provide evidence that humans triggered the rainforest fragmentation 2,600 y ago. Our findings suggest that technological developments, including agricultural practices and iron metallurgy, possibly related to the large-scale Bantu expansion, significantly impacted the ecosystems before the Common Era

Is the bilateral cochlear implantation necessary for avoidance of auditory deprivation in deaf children?

The aim of the paper is to investigate the influence of the cochlear implantation in prelingual deaf children on maturation of the auditory pathways. Auditory deprivation may result in morphological and physiological changes in the central auditory nervous system. In prelingual deaf children, some of these deafness-induced changes may be preventable or partially reversible by application of a cochlear implant (CI). It is without doubt that an early cochlear implantation in prelingual deaf children shows good evidence of speech reception and language development as well as speech production. In some studies, there is a clear benefit from binaural versus monaural hearing aid amplification in children with apparent auditory deprivation caused by a bilateral severe hearing impairment. Hence, there is the question whether, besides the expected benefits in directional hearing and improvement in speech recognition in noise, there is really a need for a bilateral cochlear implantation in prelingual deaf children to prevent or avoid a disturbance in auditory pathway on the otherwise not implanted side. We are reporting on a congenitally bilaterally deaf boy who received a CI at the age of 3. His acquired audio-oral communication went very well. Unfortunately, at the age of 7, he suffered a heavy otitis media, which was resistant to intensive treatment with antibiotics, so that in the end an explantation of the cochlear implant and, then, an implantation in the opposite ear was necessary. The monitoring of effectiveness of rehabilitation was performed by the Kiel Children Profile. Contrary to general opinion, after a small interval of stagnation, the boy fortunately did very well and had even better scores in the profile than before. In our opinion, this report may indicate that if there is only one ear supplied with a cochlear implant there is no absolute must for a cochlear implantation on both sides to prevent or avoid an auditory deprivation on the otherwise not implanted auditory pathway. It may be an indication that we are not missing or losing a possible time window for the non-implanted ear in respect of a bilateral cochlear implantation