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.

　　結(jié)構(gòu)分析:句子的框架是The point…is…when…and when…。兩個(gè)when引導(dǎo)的從句為并列的表語(yǔ)從句。at which tool using and tool making acquire evolutionary significance為定語(yǔ)從句修飾主語(yǔ)the point;第二個(gè)when引導(dǎo)的表語(yǔ)從句中也有that引導(dǎo)的定語(yǔ)從句修飾a brand-new problem。ability to manipulate objects譯為“操縱物體的能力”;…a brand-new problem that without the use of a tool would prove insoluble中without和insoluble為雙重否定可譯成肯定句。

　　譯文：當(dāng)一種動(dòng)物能夠使自己操縱物體的能力適用于更廣泛的目標(biāo)范圍，并且能夠自發(fā)地使用物體解決只有通過(guò)工具才能解決的嶄新問(wèn)題時(shí)，工具的使用和制造就肯定達(dá)到了具有進(jìn)化意義的階段。