4.竖立肌竖立肌。当人类还长满毛发时,皮肤上的竖立肌能使毛发竖立起来,使人显得更威猛害怕。但是现在只能让我们起鸡皮疙瘩。5.尾骨尾骨为人类进化后的“尾巴”所残留的部分。其实,尾骨还有一定作用。研究表明,这小小的一节骨头是帮助内脏保持在必要位置的盆腔肌的支点。如将“退化无用” Erector muscle erect muscles. When humans are still covered with hair, the erected muscles on the skin can erect the hair, making it even more mighty and scary. But now it can only make us goose bumps. 5. The coccyx coccyx is the part of the “tail” after human evolution. In fact, there is a certain role in the coccyx. Research shows that this tiny section of bones is the fulcrum of the pelvic muscle that helps keep the viscera in the necessary position. If “” useless "