The correct answer to this open question is the following.
It was difficult for early humans to cultivate land before the end of the last ice age because the weather conditions were not favorable for growing crops, the soil of the earth was not ready for agriculture, and the knowledge of early humans about agriculture techniques were minimum. The soil was cold, without the proper nutrients to be cultivated and used to produce crops. That is why early humans were hunter-gatherers that followed herds to hunt them and feed their families. Humans started to learn agriculture techniques during the Neolithic Revolution.