Explain the "saber-tooth curriculum" and why it became ineffective.

The text explains that the saber-tooth curriculum was effective when environmental conditions were stable. However, an approaching ice age caused a glacier to melt, turning the clear creek water muddy. This made the traditional skill of fish-grabbing-with-the-bare-hands obsolete, as fish could no longer be seen, and the remaining fish became more timid. Even highly trained individuals found the skill useless because the changed environment no longer supported it.