Prehistoric men living in caves is an evolutionary concept of ancient times. There is really no such thing as prehistoric, since we have an account of history from the very beginning. (Genesis 1:1 In the beginning.) So then, how do we explain the evidence for men living in caves, carving and painting animals on the cave walls. There are numerous paintings and carvings of dinosaurs on these walls, showing they saw and lived with dinosaurs. Immediately following the flood, and dispersion at Babel a great ice age forced men living in cold climatic regions to live in caves because of the weather conditions. These groups of people were isolated and some, like the Neanderthals died out because of the severe conditions. Since Adam and Eve were intelligent and had language there is NO reason to assume they grunted or were primitive. The ancient civilizations that existed further South have high levels of technology. The Egyptians and Mayans built pyramids that would challenge our building methods today.
Recommend reading:
Buried Alive by Dr. Jack Cuozo
Life in the Great Ice Age by Michael & Beverly Oard
After The Flood by Bill Cooper