The bamboo woods man told Zhang Tie about a simple way to complete his first evolution in his ancestral bloodline of precise throwing, namely — keep practicing! Practice precisely throwing with javelins of different sizes!
Now that he knew he could precisely throw a 1.4 m javelin, how about throwing a 1.3 m javelin? And when he can precisely throw a 1.3 m javelin, how about throwing a 1.29 m one and then try throwing a 1.28 m one...
As long as he kept practicing by constantly extending the applicable range of precise throwing and shortening the sizes of the javelins, Zhang Tie would definitely be able throw a knife, a bolt, a piece of stone, or a javelin head, which was only several inches in length, as precisely as he threw out a javelin. When he could accomplish this, he would finish his first round of evolution of his ancestral bloodline.