Arthur Thomson (21 March 1858, Edinburgh – 7 February 1935, Oxford) was a British anatomist and anthropologist. He is best remembered for his formulation of Thomson's Nose Rule, which states that ethnic groups originating in cold, arid climates tend to have longer and thinner noses, while those in warm, humid climates tend to have shorter and thicker noses. The underlying physiological explanation for Thomson's Rule is that noses help warm and humidify inhaled air; a longer and thinner nose increases the relative contact area between the air flow and the nasal cavity, and as such it becomes a highly selected trait in colder climates.