Brain size and the ability to walk upcenter efficiently are twoofthe main attributes that sete humanity from the apes.Nowresearchers say learning to walk millions years ago was notwithoutits trials.

• 美国研究人员通过对早期原始人类的踝关节进行重新研究后发现，早期人类的步态并非如同此前人们认为的那么稳健。