Final answer:
Differences between chimpanzee and human genomes are due to genetic variations, such as an inversion on chromosome 18 affecting genes ROCK1 and USP14, which may have contributed to significant evolutionary changes in humans, including larger brain size.
Step-by-step explanation:
The differences in chimpanzee and human genomes mainly stem from genetic variations and evolutionary adaptations. Gorillas, chimpanzees, and humans share over 97% of their DNA, indicating close genetic relationships. Despite this high percentage of shared genetics, there are significant anatomical differences, such as the protrusion of the jaw and the relative lengths of arms and legs. One notable genetic change involves an inversion on chromosome 18, where two genes, ROCK1 and USP14, are positioned differently in humans compared to chimpanzees. This repositioning may have altered gene expression and cellular function, contributing to the evolutionary divergence of humans, including the development of a much larger brain size in humans compared to chimpanzees.