Origin of HIV infection discovered in Cameroon

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A population of chimpanzees in south-east Cameroon identified as the source of the original HIV infection in humans. Do other animals have "theory of mind" – the ability to ascribe thoughts and feelings to themselves and others? The effect of positive feedback of high levels of greenhouse gases on global warming, from two points of view. Optical illusion and the possibility of achieving invisibility. The cost of sustainable timber growing in rainforests.