<P> The area of the brain with the greatest amount of recent evolutionary change is called the cerebrum, or neocortex . In reptiles and fish, this area is called the pallium, and is smaller and simpler relative to body mass than what is found in mammals . According to research, the cerebrum first developed about 200 million years ago . It's responsible for higher cognitive functions - for example, language, thinking, and related forms of information processing . It's also responsible for processing sensory input (together with the thalamus, a part of the limbic system that acts as an information router). Most of its function is subconscious, that is, not available for inspection or intervention by the conscious mind . Neocortex is an elaboration, or outgrowth, of structures in the limbic system, with which it is tightly integrated . </P> <P> Some animal groups have gone through major brain enlargement through evolution (e.g. vertebrates and cephalopods both contain many lineages in which brains have grown through evolution) but most animal groups are composed only of species with extremely small brains . Some scientists argue that this difference is due to vertebrate and cephalopod neurons having evolved ways of communicating that overcome the scalability problem of neural networks while most animal groups have not . They argue that the reason why traditional neural networks fail to improve their function when they scale up is because filtering based on previously known probabilities cause self - fulfilling prophecy - like biases that create false statistical evidence giving a completely false worldview and that randomized access can overcome this problem and allow brains to be scaled up to more discriminating conditioned reflexes at larger brains that lead to new worldview forming abilities at certain thresholds . This is explained by randomization allowing the entire brain to eventually get access to all information over the course of many shifts even though instant privileged access is physically impossible . They cite that vertebrate neurons transmit virus - like capsules containing RNA that are sometimes read in the neuron to which it is transmitted and sometimes passed further on unread which creates randomized access, and that cephalopod neurons make different proteins from the same gene which suggests another mechanism for randomization of concentrated information in neurons, both making it evolutionarily worth scaling up brains . </P> <P> With the use of in vivo Magnetic resonance imaging (MRI) and tissue sampling, different cortical samples from members of each hominoid species were analyzed . In each species, specific areas were either relatively enlarged or shrunken, which can detail neural organizations . Different sizes in the corticol areas can show specific adaptations, functional specializations and evolutionary events that were changes in how the hominoid brain is organized . In early prediction it was thought that the frontal lobe, a large part of the brain that is generally devoted to behavior and social interaction, predicted the differences in behavior between hominoid and humans . Discrediting this theory was evidence supporting that damage to the frontal lobe in both humans and hominoids show atypical social and emotional behavior; thus, this similarity means that the frontal lobe was not very likely to be selected for reorganization . Instead, it is now believed that evolution occurred in other parts of the brain that are strictly associated with certain behaviors . The reorganization that took place is thought to have been more organizational than volumetric; whereas the brain volumes were relatively the same but specific landmark position of surface anatomical features, for example, the lunate sulcus suggest that the brains had been through a neurological reorganization . There is also evidence that the early hominin lineage also underwent a quiescent period, which supports the idea of neural reorganization . </P> <P> Dental fossil records for early humans and hominins show that immature hominins, including australopithecines and members of Homo, reveal that these species have a quiescent period (Bown et al. 1987). A quiescent period is a period in which there are no dental eruptions of adult teeth; at this time the child becomes more accustomed to social structure, and development of culture . During this time the child is given an extra advantage over other hominoids, devoting several years into developing speech and learning to cooperate within a community . This period is also discussed in relation to encephalization . It was discovered that chimpanzees do not have this neutral dental period and suggest that a quiescent period occurred in very early hominin evolution . Using the models for neurological reorganization it can be suggested the cause for this period, dubbed middle childhood, is most likely for enhanced foraging abilities in varying seasonal environments . To understand the development of human dentition, taking a look at behavior and biology . </P>

Information on evolution of the brain of vertebrates