What is the main point of the provided text regarding paleolithic education and its effectiveness in changing environments?

here's the text from the image:

12 PART I: CONTEXT OF THE CURRICULUM

dreamed of a far-distant day when some of their descendants would be sixteen hands high, weigh more than half a ton, and be able to pitch their would-be riders into the dirt. They knew they could never attain these goals in a wet, marshy country, so they all went east to the dry, open plains, far from the paleolithic hunting grounds. Their places were taken by little antelopes who came down with the ice sheet and were so shy and speedy and had so keen a scent for danger that no one could approach them closely enough to club them.

The best-trained horse-clubbers of the tribe went out day after day and employed the most efficient techniques taught in the school, but day after day they returned empty-handed. A horse-clubbing education of the highest type could get no results when there were no horses to club.

Finally, to complete the disruption of paleolithic life and education, the new dampness in the air gave the saber-tooth tigers pneumonia, a disease to which these animals were peculiarly susceptible and to which most of them succumbed. A few moth-eaten specimens crept south to the desert. It is true, but they were pitifully few and weak representatives of a once numerous and powerful race. So there were no more tigers to scare in the paleolithic community, and the best tiger-scaring techniques became only academic exercises, good in themselves, perhaps, but not necessary for tribal security. Yet