because it's associated with stone tools.因为他们擅于使用石制工具

associated with 与…相联系，与 ... 有关

I associated with him in business.

我过去和他合伙经商。

He was briefly associated with that organization.

他同那个组织有过短时间的联系。

and a smaller face that's tucked up under the skull.颅骨下方的脸 ，则变小了

tuck up掀起，折起，卷起

Please tuck up the chair and put it side.

请把椅子折起来放在一边。

Please help me tuck up my sleeves.

请帮我卷起袖子。