ダウンロード American Scientist [US] November - December 2020 (単号) epub 本

American Scientist is an illustrated bimonthly magazine about science and technology. Each issue is filled with feature articles written by prominent scientists and engineers, reviewing important work in fields that range from molecular biology to computer engineering. < featured topic> Paranthropus boisei, a little-known member of the hominin family, lived in East Africa from about 2.3 to 1.3 million years ago. Neither an ape nor a direct ancestor of modern humans, P. boisei shared the landscape with several of the earliest species of the genus Homo. The relatively few fossils that have been found so far indicate an unusual combination of physical features: upright posture together with adaptations for climbing, a braincase approximately one-third the size of our own but molar and premolar teeth several times larger than ours, and tiny canine and incisor teeth. This dental pattern suggests a diet consisting mainly of tough grasses and seeds, a notion that is corroborated by stable-isotope analysis of the thick enamel coating on P. boisei teeth.