information:highlighting, structural:reformatting
Evolutionary theory

Phylogenetic acquisition of imagination was a gradual process. The simplest form of imagination, REM-sleep dreaming, evolved in mammals with acquisition of REM sleep 140 million years ago. Spontaneous insight improved in primates with acquisition of the lateral prefrontal cortex 70 million years ago. After hominins split from the chimpanzee line 6 million years ago they further improved their imagination. Prefrontal analysis was acquired 3.3 million years ago when hominins started to manufacture Mode One stone tools. Progress in stone tools culture to Mode Two stone tools by 2 million years ago signifies remarkable improvement of prefrontal analysis. The most advanced mechanism of imagination, prefrontal synthesis, was likely acquired by humans around 70,000 years ago and resulted in behavioral modernity. This leap toward modern imagination has been characterized by paleoanthropologists as the "Cognitive revolution", "Upper Paleolithic Revolution", and the "Great Leap Forward".