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The History of Human Intelligence

Evolution of Humans

Evolution refers to the changes in a population over successive generations in order to allow the population to better adapt to changing environments. Therefore it would seem with the plethora of scientific advancements the human race has made, we must have gotten smarter than our ancestors However, that may not be the case. Cro-Magnon man who inhabited Europe 20,000 to 30,000 years ago, had the biggest brain of any animal species. Today’s human brain is about 10% smaller meaning we have lost a chunk of brain matter roughly equivalent to a tennis ball.

There are two schools of thought on this trend — some think it might be a dumbing down process, while others are not so pessimistic. David Geary, a cognitive scientist argues that while human society becomes more and more complicated, especially with the infringement of technology and artificial intelligence in the 21st century, we no longer need to be as smart individually to reproduce and survive.

However, another group of scientists argues that a decrease in size may not necessarily indicate that humans are getting dumber. Brian Hare, an anthropologist at Duke University believes that the decrease in brain size is an evolutionary advantage. A smaller brain is a signature of selection against aggression — When a population selects against aggression they are considered to be domesticated. In any domesticated species such as apes or dogs, a signature trait is a more slender skeleton with a flatter forehead meaning decreased brain size. The decrease in brain size as a sign of selection against aggression can be seen in the case of chimpanzees and bonobos. In evolutionary terms, they resemble humans but are physically different from each other. Bonobos are less intelligent than chimpanzees and are also much less aggressive. Both chimpanzees and bonobos possess the cognitive ability to solve a given puzzle. However, chimpanzees are much less likely to succeed in an endeavour if it requires teamwork. This is not the case with bonobos. For example in a real-life scenario where food is sparse, bonobos can share food easily whereas chimpanzees are unable to do so even if they possess the ability to do so. However, Hare does ultimately admit that the shrinking human brain could point to an evolutionary dumbing down process. However, comparing our evolution to those of other animals helps us understand the human condition and the human mind.

Human Brain

Aside from brain size and the decreasing trend in the same, there are other factors to be considered when talking about human intelligence. While IQ scores have been rising at a remarkable rate, the underlying human genetic potential could be on the decline. However, these findings are not without controversy as the fundamental issue with measuring intelligence remains that intelligence cannot be defined as one thing. For example, the intelligence required to survive a night in the African forest or hunt for food is practically useless when it comes to coding an app or understanding the stock market. While it cannot be as simple as whether intelligence is moving up or down, different parts of intelligence could be changing in a lot of ways. The current pace of progress certainly indicates an upwards trend in intelligence since we have achieved a lot from artificial intelligence and heart transplants to smartphones and life-saving drugs. Beyond the technological advances, there is another indicator of an increase in human intelligence known as the Flynn Effect. To observe this, scientists have their volunteers take tests designed for previous generations. The general trend is members of the most recent generation score higher than the original test takers did. There is a very significant increase of around three extra IQ points per decade. Flynn and other researchers suspect that this may also be a reflection of improving modern environments. This is because IQ is part heritable and part environmental. When a child is offered opportunities to learn, they end up having a higher IQ later in life. Therefore things such as better schooling, more mental stimulation, and better nutrition could also be a reason for an increase in IQ points While an increase in IQ points may indicate an increase in intelligence, researcher Crabtree from the Stanford University School of Medicine argues that human intelligence might have peaked around 2000 to 6000 years ago. This assertion was based on genetics — 2000 to 5000 genes control human intelligence ( an estimate). At the rate at which genetic mutations accumulate, Crabtree calculated that in the last 3000 years all humanity has sustained at least two mutations harmful to intellect-determining genes. While not every mutation will cause harm — as genes come in pairs, some weaknesses caused by mutation can be covered by the healthy half of the pair, thus calculation suggests that intelligence is much more fragile than it seems. Crabtree also argues that intelligence is not as significant evolutionarily as it used to be when the species survived by hunting and gathering. While a few thousand years ago learning to anticipate the aerodynamics of a spear might have been a life or death situation, the modern world eliminates the need for such alertness and spontaneity.

A theory called dysgenic mating could also explain the decline in intelligence in human beings. Since the mid-1800s, there has been a negative correlation between IQ and reproduction. This means that people with higher IQs, i.e. more intelligent people have fewer babies. Researchers attest that average human intelligence is decreasing since intelligence is largely genetic and genes play a huge role in human development. However the increase in IQ scores per generation contests the dysgenic mating theory.

While our sedentary lifestyles and technology continue to make everyday tasks easier for us, it seems that the average intelligence of the human race is on the rise. This is despite the shrinkage of brain matter. While most theories and scientists believe that the human race peaked in terms of intelligence a few 1000 years ago it is nearly impossible to quantify our ideal intelligence. This is because it is highly subjective.

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