Yet, as you get closer to humans on the evolutionary tree, tails disappear ... gives us a huge advantage Because unlike four-legged animals, which have to pour energy into every step they take ...

Why don't humans have tails? Since tails first evolved at least ... Now, walking like this gives us a huge advantage Because unlike four-legged animals, which have to pour energy into every ...

Instead, Hersh and her colleagues suggest that dog tail-wags made people happy, so humans tended to select for that trait ...