The Price of Human Intelligence

By FreelanceCat, 28th Jul 2011 | Follow this author | RSS Feed | Short URL http://nut.bz/20ap_b87/
Posted in Wikinut>News>Health

Humans may be smarter than chimps, in the long run however their brains fail them. Scientists explain why.

Although the human brain is unusually large compared to that of other species, it also has the tendency to shrink as years go by.

This shrinking which is accompanied by a degeneration of cognitive functions, does not occur at all to elderly chimpanzees, as a new study reveals. The causes of this difference remain unknown, however researchers speculate that dementia is probably the price to be paid for human intelligence.

An abundance of previous studies have shown that the human brain is especially vulnerable to time. Homo sapiens appears to be the only species the brain of which suffers from neurodegenerative diseases such as Altzheimer’s and Parkinson’s. Even the elderly that do not suffer from dementia, constantly lose a percentage of brain mass, especially in the areas associated with memory and learning.

Studies on the subject of brain shrinking are scarce on other primates, however recent experiments showed that in rhesus monkeys brain shrinking due to ageing is minimal.

The same result was given by a new study that was conducted on chimpanzees and was published at the Proceedings of the National Academy of Sciences.

The analysis showed that the mass of brain areas that were examined did not differ significantly between young and elderly chimpanzees.

In humans however the brain loss was significant. Up until the age of 80, some brain areas had shrunk up to 25%. This brain loss appears to accelerate as time goes by, however it is not uniform throughout the brain.

The greatest brain loss was found in the hippocampus and the frontal lobe, areas that play a critical role in memory and learning.

After the age of 70 the brain’s white matter starts shrinking disproportionally faster to the rest of the brain. This is very important as white matter is crucial for all the complex learning functions of Homo sapiens.

The causes of the differences between the two related species remain completely unknown. Researchers suggest the hypothesis that the shrinking is due to the large energy demands of the human brain.

The consumption of energy by the human brain is the equivalent of the 25% of the basic human metabolism while the corresponding percentange in the, proportionally smaller, chimpanzee brain is approximately 10%.

This overconsumption of energy from the human brain has consequences: the production of free radicals that cause cells oxidative stress as well as reduce productivity in mitochondria, the valuable energy factories of cells.