<P> Behaviors such as the "tail - flip" escape reaction in crustacea such as crayfish and lobsters are fixed action patterns that may have evolved from earlier ancestral patterns . </P> <P> There has been a gradual increase in brain volume as the ancestors of modern humans progressed along the human timeline of evolution (see Homininae), starting from about 600 cm in Homo habilis up to 1736 cm in Homo neanderthalensis . Thus, in general there is a correlation between brain volume and intelligence . However, modern Homo sapiens have a smaller brain volume (brain size 1250 cm) than neanderthals; women have a brain volume slightly smaller than men, and the Flores hominids (Homo floresiensis), nicknamed "hobbits", had a cranial capacity of about 380 cm, about a third of the Homo erectus average and considered small for a chimpanzee . It is proposed that they evolved from H. erectus as a case of insular dwarfism . In spite of their threefold smaller brain there is evidence that H. floresiensis used fire and made stone tools as sophisticated as those of their proposed ancestor, H. erectus . Iain Davidson summarizes the opposite evolutionary constraints on human brain size as "As large as you need and as small as you can". </P> <P> Brain evolution can be studied using endocasts, a branch of neurology and paleontology called paleoneurology . </P>

The most recent part of the nervous system to evolve is the