Why do human have such a great intelligence compared with other creature? Which parts of brain that set a part of the cognitive ability? Are there any evolutionary cost associated with it? Briefly I will elucidate that confounding questions on this essay. My writing is based on the TED talk about the evolution of human brain (for detailed information, please refers to the web-link below).
One of the proposed idea of the reason behind human’s intelligence is due to the size. However, the research shown that our brain isn’t the biggest brain on earth. If it is compared with elephant, our brain only accounts for thirds of the elephant’s brain (human was 1.5 kg, whereas the elephant bumped to 4.5 kg). In addition, It is seemingly true that the body size in line with the brain size. By writing that, I mean that the larger animal, the bigger its brain is.
If the size isn’t the case, what about the number of the cells instead. Popular believe said that we human have approximately 100 million neurons. This fact couldn’t be traced back into its original scientific literature and no one knows where the number comes from. Recent research shown that we overestimate the actual number of the brain cells, the figure is actually stands just under 70 million of cells. The research method to reveal the brain cells is quite innovative as it involves creation soup of brain cells, where the protein linker between brain cells treated with enzyme, hence the cells doesn’t remain intact and dissolved like a soup. At this stage, the calculation is getting easy as the scientist can count the number under the microscope. Scientist calculate the actual number of brain from various range of organism and again, the number of cells also seem do not correlated with the extent of the intelligence. As the organisms getting more intelligent, it doesn’t mean that the animal also possess more brain cell.
The striking finding is actually coming from the distribution of the cells. In primate, human particularly, has large proportion of the total neuron located on region namely as celebral cortex. It has been long known that this area responsible for the cognitive ability. On average, sixty million of neurons were calculated in this area, accounting for more than 80 per cent of the total. Thus, the number of neurons in celebral cortex in celebral cortex which correlate with the cognition and neither the size or total neuron in entire brain.
If it is the brain metabolism is concerned, the facts also merit an attention. Having a big size of brain is actually costly as the brain on average needs of 500 kCal of calorie supply which amount a fourth of the normal daily energy intake, even tough the brain only contributes to 2 per cent of the whole body weight. Thus, should be there trade off between the energy for body-related work purpose and the one that directed into the brain or generally speaking that the combined energy allocated both for body and brain shall not exceeded the total energy intake. Considering that human has large brain capacity and active works at the same time, if that the case we human should have been facing the metabolic limitation which hinder our brain develop further. Thankfully, it wasn’t happened and to date we are the forefront in fields of brain’s evolution. Expert proposes the reason behind this fact is owing to the advent of cooking hundreds years ago. Human is solely species who don’t eat all their diet in raw and invent the way to make it calorie-dense by cooking it before served. If it is plotted again the geographic time scale of human’s evolution, the intelligence is markedly increased after human starting to cook their diet which surely corroborate with the thought.