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00:00 When we are cold, the hairs of our body straighten up.
00:03 But how is this phenomenon explained?
00:05 The scientific term is "horripilation".
00:08 It refers to the hair erection when the body is exposed to cold or intense emotion.
00:14 It is a legacy of the ancestors of Homo sapiens, which was covered with long hair.
00:18 Under the effect of the cold, they stood up to trap an insulating layer of air near the skin.
00:24 Our hair then shrunk and shortened, but the erection reflex remained.
00:29 The skin of the chicken is therefore one of the body's defense manifestations exposed to the cold.
00:34 Teeth cracking and shivers are rapid muscle contractions
00:38 commanded by the hypothalamus and intended to produce heat by movement.
00:43 (upbeat music)