Life's Increasing Complexity Spurred Evolution of Human Brain

Whether it be a week ago, or a couple of thousand years ago, humans have always needed split second thinking to avoid life threatening situations. Whether it would be a sudden and cataclysmic encounter with a semi-truck, or a similar encounter with a disgruntled lion, quick thinking has always been necessary.

But we don’t always need split second thinking; sometimes we just need to take in all the information, and process it. Slowly.

According to new research from the University of Bristol, lead by Pete Trimmer, and published Tuesday in the Proceedings of the Royal Society B., those two types of thinking are completed by two separate areas of our brains.

For a long time scientists have believed that mammals have two decision making systems in their brains, each one operating at different speeds depending on the situation around them. Trimmer’s research shows that the older, more instinctual and thus less accurate thinking may have helped shape the more recent, methodical thinking.

"If we compare the brain of a human with that of a reptile, we find they are very similar except that mammals have a large 'outer cortex' around the outside of the existing 'sub-cortical' brain, that is common to other vertebrates," Trimmer said. "The fact that lizards make decisions indicates that the sub-cortical brain in humans is also likely to be used in decision-making. However, fMRI (Functional magnetic resonance imaging) scans now reveal that parts of the outer cortex (which developed more recently in our evolutionary past) are also used when making decisions."

Trimmer’s team set about understanding the need for two decision making aspects by building theoretical models representing the two systems. In their models they assumed that the sub-cortical system acted very quickly, but inaccurately, and the cortex slower but more precise, thought out.

Their modeling results showed that when the threat level is higher, it is useful to have the fast acting aspect of the brain. However, when dealing with situations that don’t occur very often, or scenarios which are more complex and less instinctual, the cortical system is more useful than the sub-cortial system.

"As life became more complex, the benefit of gathering information before making a decision put an evolutionary pressure on the early brain," Trimmer commented. "This may have led to the rapid development of the cortex in mammals. So if humans continue to live in a world of dangers such as wild animals or fast-moving cars, there will still be an evolutionary benefit to maintaining the sub-cortical system, and it is unlikely to atrophy in future humans."

Posted by Josh Hill.

Source:
http://www.eurekalert.org/pub_releases/2008-07/uob-wof070708.php

Comments

[jer35mx]

I'd like the scientists to find the part of the brain that process the signals of the taste of chocolate, and "apply pressure" to it to enhance a thousand times. Je. I know, I know it'll take hundreds of thousands of years.