“Let me point out to you in parentheses, that erect posture – this stance that the human race has chosen and adopted – can have nothing whatsoever to recommend it, when compared to the horizontal stance of the four-footed animals, unless in its achievement we also achieve and maintain an efficient, near-perfect balance. Four-footed creatures balance on their four feet pretty adequately; we balance on our two, for the most part, very precariously. This is a more serious matter than most of us have realised.”
(Taken from “The Centenary Memorial Lecture” given in 1969)