The Human Brain :: essays research papers fc

The humans Brain     Through the use of molecular biology it is thought that the family Hominidae family first appe bed about 5 million years ago. Based on this time frame it is believed that an African Hominoid lineage was present shortly in the first place that time, approximately 10 myp, which contained the common ancestor to both the chimpanzee and human. The develop into proto-chimpanzee and proto-human occurred during the last million years of the Miocene epoch. (Changeux and Chavaillon pg. 61). The fossils, especially those of the skull, from this time frame are limited. This leads to difficulty in proving differences in thought formation.      Fossils of the hominoid cranium are not available until 2 million years after the proto-human lineage begins. The wishing of cranial fossils for 2 million years is a problem. We do not know what took place during this time. The first available cranial fossils are those of A. afarensis. The misbegot endo cranial dexterity was 413.5 cm3, which means that its mavin size was that of todays African great apes (Changeux and Chavaillon pg. 65, table 4.1). With the limited fossils available and the apparent brain size of todays African great apes there is no proof of significant differences in brain functionality.      One study through with(p) by Ralph Holloway on the endocaste of the Hadar AL 162-68 skull fragment lead to a diametric theory regarding significant differences in brain functionality. Hadar concluded that the lunate sulcus would fuddle had to be, according to the office staff of the interparietal sulcus, in a more posterior position than in Pan brains. This means that A. afarensis had an expansion of the parietal association cerebral mantle and consequently a brain reorganization (Changeux and Chavaillon pg.106). Brain reorganization implies that A. afarensis had a significant difference in brain functionality.     &nb spThe cranial capacity of A. africanus has a mean of 440 cm3, A. robustus a mean capacity of 530 cm3 and A. boisei a mean capacity of 463.3 (Changeux and Chavaillon pg.65, table 4.1). When the limited sample size is taken into account, is there a significant difference? The modern human inter-racial mean is of the order of 1350 cm3, which is 3.52 measure that of the chimpanzee, 2.68 times that of the gorilla value, and 3.33 times the orang-utan value, the comparative inter-hominoid index values for genus Australopithecus species are seen to have hardly increased at all (Changeux and Chavaillon pg. 67). If we correspond the modern chimpanzee, as modern humans closest musical accompaniment ancestor, to the australopithecines we find that they show a small but definite produce over the chimpanzee in both absolute and relative brain size (Changeux and Chavaillon pg.