The point at which tool using and tool making acquire evolutionary significance is surely when an animal can adapt its ability to manipulate objects to a wide variety of purposes，and when it can use an object spontaneously to solve a brand-new problem that without the use of a tool would prove insoluble.

　　结构分析:句子的框架是The point…is…when…and when…。两个when引导的从句为并列的表语从句。at which tool using and tool making acquire evolutionary significance为定语从句修饰主语the point;第二个when引导的表语从句中也有that引导的定语从句修饰a brand-new problem。ability to manipulate objects译为“操纵物体的能力”;…a brand-new problem that without the use of a tool would prove insoluble中without和insoluble为双重否定可译成肯定句。

　　译文：当一种动物能够使自己操纵物体的能力适用于更广泛的目标范围，并且能够自发地使用物体解决只有通过工具才能解决的崭新问题时，工具的使用和制造就肯定达到了具有进化意义的阶段。