Final answer:
The increase in neocortex ratio is correlated with intelligence and complex social behaviors. The encephalization quotient (EQ) is used to measure brain size relative to body size as an indicator of potential cognitive abilities. The rapid brain size expansion in human evolution suggests a response to environmental challenges and technological advances.
Step-by-step explanation:
The evolution of the large brain, particularly in the genus Homo, and the associated increase in the neocortex ratio, is correlated with a number of cognitive and behavioral complexities. An increased neocortex surface area has been linked to pronounced intelligence and social behaviors across various mammals. This enlargement of the brain over time, particularly the neocortex, has been facilitated by the folding of the cortical sheet, leading to more sulci and gyri which increase the surface area and thereby the space for neural connections.
This brain evolution has occurred relatively quickly in evolutionary terms, expanding rapidly between 800,000 and 100,000 years ago. The encephalization quotient (EQ) has been used as a measure to gauge brain size relative to body size, informing us of the potential for more complex cognitive tasks. While brain size is not the only measure of intelligence, with organization and cortical neuron density also playing critical roles, it remains an important factor in the assessment of cognitive capabilities in different species, including the genus Homo.
It is also worth noting that the rapid increase in brain size in early humans corresponded with periods of significant climate change, suggesting that the need to survive in more challenging and unpredictable environments may have driven this aspect of human evolution. The progression of culture and technology also paralleled the biological development of the larger brain, thereby reinforcing humans' ability to adapt and thrive in diverse habitats.