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For a primate of its body size, the relative size of the brain and that of the digestive tract is rather unexpected; the digestive tract is smaller than expected for a primate of a human body size. In 1995, two scientists proposed an attempt to solve this phenomenon of human evolution using the Expensive Tissue Hypothesis.
The size of the brain is a frequent topic of study within the fields of anatomy, ... Research measuring brain volume, ... Primates, for a given body size, ...
[1] [2] This number was first proposed in the 1990s by Robin Dunbar, a British anthropologist who found a correlation between primate brain size and average social group size. [3] By using the average human brain size and extrapolating from the results of primates, he proposed that humans can comfortably maintain 150 stable relationships. [4]
After all of the data, all observations concluded that the main development that occurred during evolution was the increase of brain size. [52] However, recent research has called into question the hypothesis of a threefold increase in brain size when comparing Homo sapiens with Australopithecus and chimpanzees. For example, in an article ...
Recent research indicates that, in non-human primates, whole brain size is a better measure of cognitive abilities than brain-to-body mass ratio. The total weight of the species is greater than the predicted sample only if the frontal lobe is adjusted for spatial relation. [19]
The claim that large brains are linked to large social groups in primates and cetaceans, on which the Machiavellian intelligence hypothesis is based, is criticized by a number of researchers for overlooking the availability of food as a common limiting factor for brain size and social group size. [citation needed] Among primates as well as ...
Similarly sized brains, such as a cow or chimpanzee, might in that scenario contain very different numbers of neurons, just as a very large cetacean brain might contain fewer neurons than a gorilla brain. Size comparison between the human brain and non-primate brains, larger or smaller, might simply be inadequate and uninformative – and our ...
Another theory of brain size in vertebrates is that it may relate to social rather than mechanical skills. Cortical size relates directly to pair-bonding lifestyle and among primates, cerebral cortex size varies directly with the demands of living in a large complex social network. Compared to other mammals, primates have significantly larger ...