But the simple fact that we have evolved highly visible eyes, to which infants attune even before language, supplies at least one small piece of the puzzle of how.

• 人类在进化中形成了可以轻易被追随目光的双眸，即使不会说话的婴儿也能利用这一特点，这至少为揭示人类进化之谜提供了一点线索。