As a biology student, I often think about evolution and how it works. Having recently watched a topical documentary, the subject of human intelligence has been on my mind a lot. Of course, it is a well-known fact that all organisms around today exist due to random genetic mutations, and ‘survival of the fittest.’ No shark has been able to write a book and no cat can solve equations. But if this theory of evolution is applied to all organisms in existence, then why is it that Homo sapiens have far superior intelligence to that of any other mammal? Although there is no clear-cut explanation, there are a few ideas that researchers have come up with that may explain this.
We consider our knowledge extreme; however, we are not the only extreme species. Whales are extreme with regard to their size; hummingbirds are extreme with regard to the speed at which they can flap their wings, and giraffes are extreme in terms of the length of their necks. This tells us that gene mutations occur in all species resulting in abnormal traits: one of ours is our intelligence. We consider ourselves to have intelligence, but remember this is by our own definition.
So why are we so clever?
Firstly, the way in which humans age, is believed to have a profound affect on their intelligence. Studies at Washington University have been made, comparing the cleverness of a 3-month-old monkey, and a baby of the same age. These tests were done examining their ability to recognize object permanence. You would expect that, due to the greater intelligence of Homo sapiens, the baby would do better in this test, and therefore it is surprising that the results of the experiment showed the monkey understood where the baby did not. Monkeys develop at a much faster rate than humans, meaning the length of human childhood is considerably greater than that of primates; we become sexually mature much later than any other species. This even takes into consideration the comparison in length of lives. Although a lengthened childhood may seem like a fundamental flaw in evolution (leaving humans more vulnerable for longer) this actually might not be the case. In fact, this may be the key to humans’ superior intelligence compared to any other animal. A large, complex brain takes a lot of time to develop, and in humans most of that time must happen after birth. David F. Bjorkland has suggested that a larger period of development does confer advantages; for example, the behavioral flexibility we possess that has contributed to our success as a species. This long period of time that it takes for the human brain to develop may mean that it can be used more efficiently and is therefore more intelligent.
The evolutionary perspective on our intelligence runs something like this: the environment was set up so that our ancestors, who could use signs and symbols for example, were able to survive and reproduce better than those who could not. So, as a result, those traits spread throughout the population, and other traits were lost as fewer and fewer people reproducing had them. Different animals live in different environments and different niches and therefore need different characteristics in order to survive and flourish as a species. Therefore, when one mutation leads to a change in characteristic that will support that animal, and enable it to live longer, the animal will be more likely to reproduce and spread that new allele, and so on and so forth until it becomes normal to have the gene or allele. If there was nothing that weeded out humans with less ability to solve puzzles, then the trait would not have spread.
Finally, to take a more physiological look at the origins of intelligence: Steve Goldman, from the University of Rochester Medical Centre in New York has done an experiment, transferring immature glial cells from human fetuses into the brains of mice. These glial cells developed into astrocytes in the mouse brains and, within a year, the mouse glial cells had completely been taken over by the human cells. Astrocytes help to strengthen the synapses (connections in the neurons) in nerves. As human astrocytes are 10 times the size of mouse astrocytes, they can coordinate neural signals much better than mouse ones can. The mice underwent many tests, allowing the medical centre to see the difference in these altered mice, and those with normal brains. It came about that the humanised mice had a memory four times greater than the normal mice. Goldman came to the conclusion that “they were statistically and significantly smarter than control mice.” This experiment shows that the efficiency of human brains may well be down to both the size and quality of their neural cells.
The way our brains have developed, due to evolution over millions of years, has resulted in intelligence far greater than any other species and ultimately domination over our environment. Although the intelligence of some humans is greater than others, this is comparatively marginal: we all owe a lot to evolution.