The remnants of dozens of mammoths whose furs, tissues and internal organs were preserved intact for thousands of years in the ice and permafrost of Siberia have been examined by scientists who autopsied the bodies determined that many of these animals died suddenly as a result of fatal falls into crevices and holes hidden in the terrain. Other are believed to have died during violent blizzards that got the mammoths into a state of hypothermia very quickly.
The development of irrigation systems made farming easier, as water was more easily accessible to crops. This meant that food could be produced more efficiently. More efficient farming techniques meant that food was more plentiful, where people weren't constantly scrambling for their next meal or going days without eating. It also gave people the ability to specialize in certain trades, creating better quality of goods and advancing technology in civilizations.