Lunate sulcus

In brain anatomy, the lunate sulcus or simian sulcus also known as the sulcus lunatus is a fissure in the occipital lobe found in humans and more often larger when present in apes and monkeys.

The lunate sulcus lies further back of human brains but has a more frontal location in chimpanzees. The evolutionary expansion of the frontal areas of the lunate sulcus would have caused a shift in the particular location of the fissure. It has been hypothesized that evolutionary pressures resulted in the human brain undergoing internal reorganization to develop the capability of human language. Furthermore, this reorganization must have been implemented during early maturity and is likely responsible for eidetic imagery in some adolescents.

During early development, the neural connections in prefrontal cortex and posterior parietal lobe rapidly expand to allow capability for human language, while visual memory capacity of human brain would become limited. Biological studies have demonstrated that the lunate sulcus is subject to white matter growth, and dental fossil and tomography studies have shown that the brain organization of Africanus is pongid-like.