The Future of the Mind (26 page)

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With my mentor David Haussler leaning over my shoulder, I looked at the top hit, a stretch of 118 bases that together became known as human accelerated region 1 (HAR1),” she recalled.

She was ecstatic. Bingo!

“We had hit the jackpot,” she would write. It was a dream come true.

She was staring at an area of our genome containing only 118 base pairs,
with the largest divergence of mutations separating us from the apes. Of these base pairs, only eighteen mutations were altered since we became human. Her remarkable discovery showed that a small handful of mutations could be responsible for raising us from the swamp of our genetic past.

Next she and her colleagues tried to decipher the precise nature of this mysterious cluster called HAR1. They found that HAR1 was remarkably stable across millions of years of evolution. Primates separated from chickens about three hundred million years ago, yet only two base pairs differ between chimps and chickens. So HAR1 was virtually unchanged for several hundred million years, with only two changes, in the letters G and C. Yet in just six million years, HAR1 mutated eighteen times, representing a huge acceleration in our evolution.

But what was more intriguing was the role HAR1 played in controlling the overall layout of the cerebral cortex, which is famous for its wrinkled appearance. A defect in the HAR1 region causes a disorder called “lissencephaly,” or “smooth brain,” causing the cortex to fold incorrectly. (Defects in this region are also linked to schizophrenia.) Besides the large size of our cerebral cortex, one of its main characteristics is that it is highly wrinkled and convoluted, vastly increasing its surface area and hence its computational power. Dr. Pollard’s work showed that changing just eighteen letters in our genome was partially responsible for one of the major, defining genetic changes in human history, vastly increasing our intelligence. (Recall that the brain of Carl Friedrich Gauss, one of the greatest mathematicians in history, was preserved after his death and showed unusual wrinkling.)

Dr. Pollard’s list went even further and identified a few hundred other areas that also showed accelerated change, some of which were already known. FOX2, for example, is crucial for the development of speech, another key characteristic of humans. (Individuals with a defective FOX2 gene have difficulty making the facial movements necessary for speech.) Another region called HAR2 gives our fingers the dexterity required to manipulate delicate tools.

Furthermore, since the genome of the Neanderthal has been sequenced, it is possible to compare our genetic makeup with a species even closer to us than the chimpanzees. (When analyzing the FOX2 gene in Neanderthals, scientists found that we shared the same gene with them. This means that
there is a possibility that the Neanderthal could vocalize and create speech, as we do.)

Another crucial gene is called ASPM, which is thought to be responsible for the explosive growth of our brain capacity. Some scientists believe that this and other genes may reveal why humans became intelligent but the apes did not. (People with a defective version of the ASPM gene often suffer from microcephaly, a severe form of mental retardation, because they have a tiny skull, about the size of one of our ancestors, Australopithecus.)

Scientists have tracked the number of mutations within the ASPM gene and found that it has mutated about fifteen times in the last five to six million years, since we separated from the chimpanzee. More recent mutations in these genes seem to be correlated with milestones in our evolution. For example, one mutation occurred over one hundred thousand years ago, when modern humans emerged in Africa, indistinguishable in appearance from us. And the last mutation was 5,800 years ago, which coincides with the introduction of the written language and agriculture.

Because these mutations coincide with periods of rapid growth in intellect, it is tantalizing to speculate that ASPM is among the handful of genes responsible for our increased intelligence. If this is true, then perhaps we can determine whether these genes are still active today, and whether they will continue to shape human evolution into the future.

All this research raises a question: Can manipulating a handful of genes increase our intelligence?

Quite possibly.

Scientists are rapidly determining the precise mechanism by which these genes gave rise to intelligence. In particular, genetic regions and genes like HAR1 and ASPM could help solve a mystery concerning the brain. If there are roughly twenty-three thousand genes in your genome, then how can they possibly control the connections linking one hundred billion neurons, containing a quadrillion total connections (1 with fifteen zeros after it)? It seems mathematically impossible. The human genome is about a trillion times too small to code for all our neural connections. So our very existence seems to be a mathematical impossibility.

The answer may be that nature takes numerous shortcuts in creating the brain. First, many neurons are connected randomly, so that a detailed blueprint is not necessary, which means that these randomly connected regions
organize themselves after a baby is born and starts to interact with the environment.

And second, nature also uses modules that repeat themselves over and over again. Once nature discovers something useful, she often repeats it. This may explain why only a handful of genetic changes are responsible for most of our explosive growth in intelligence in the last six million years.

Size does matter in this case, then. If we tweak the ASPM and a few other genes, the brain might become larger and more complex, thereby making it possible to increase our intelligence. (Increasing our brain size is not sufficient to do this, since how the brain is organized is also crucially important. But increasing the gray matter of our brain is a necessary precondition to increasing our intelligence.)

APES, GENES, AND GENIUS

Dr. Pollard’s research focused on areas of our genome that we share with the chimpanzees but that are mutated. It is also possible that there are areas in our genome found only in humans, independent of the apes.
One such gene was discovered recently, in November 2012. Scientists, led by a team at the University of Edinburgh, isolated the RIM-941 gene, which is the only gene ever discovered that is found strictly in
Homo sapiens
and not in other primates. Also, geneticists can show that the gene emerged between one and six million years ago (after the time when humans and chimpanzees split about six million years ago).

Unfortunately, this discovery also set off a huge firestorm in science newsletters and blogs as misleading headlines blared across the Internet. Breathless articles appeared claiming that scientists had found a single gene that could, in principle, make chimpanzees intelligent. The essence of “humanness” had finally been isolated at the genetic level, the headlines shouted.

Reputable scientists soon stepped in and tried to calm things down. In all likelihood, a series of genes, acting together in complex ways, is responsible for human intelligence. No single gene can make a chimp suddenly have human intelligence, they said.

Although these headlines were highly exaggerated, they did raise a serious question: How realistic is
Planet of the Apes
?

There are a series of complications. If the HAR1 and ASPM genes are
tweaked so that the size and structure of the chimp brain suddenly expand, then a series of other genes would have to be modified as well. First, you would have to strengthen the chimp’s neck muscles and increase its body size to support the larger head. But a large brain would be useless unless it could control fingers capable of exploiting tools. So the HAR2 gene would also have to be altered to increase their dexterity. But since chimps often walk on their hands, another gene would have to be altered so that the backbone would straighten out and an upright posture would free up the hands. Intelligence is also useless unless chimps can communicate with other members of the species. So the FOX2 gene would also have to be mutated so that humanlike speech would become possible. And lastly, if you want to create a species of intelligent apes, you would have to modify the birth canal, since it is not large enough to accommodate the larger skull. You could either perform caesarians to cut the fetus out or genetically alter the birth canal of the chimps to accommodate the larger brain.

After all these necessary genetic adjustments, we are left with a creature that would look very much like us. In other words, it may be anatomically impossible to create intelligent apes, as in the movies, without their also mutating into something closely resembling human beings.

Clearly, creating intelligent apes is no simple matter, then. The intelligent apes we see in Hollywood movies are actually monkey suits with humans inside, or are computer-generated graphics, so all these issues are conveniently brushed under the rug. But if scientists could seriously use gene therapy to create intelligent apes, then they might closely resemble us, with hands that can use tools, vocal cords that can create speech, backbones that can support an upright posture, and large neck muscles to support large heads, as we have.

All this raises ethical issues as well. Although society may allow genetic studies of apes, it may not tolerate the manipulation of intelligent creatures that can feel pain and distress. These creatures, after all, would be intelligent and articulate enough to complain about their situation and their fate, and their views would be heard in society.

Not surprisingly, this area of bioethics is so new that it is totally unexplored. The technology is not yet ready, but in the coming decades, as we identify all the genes and their functions that separate us from the apes, the treatment of these enhanced animals could become a key question.

We can see, therefore, that it is only a matter of time before all the tiny genetic differences between us and the chimpanzees are carefully sequenced, analyzed, and interpreted. But this still does not explain a deeper question: What were the evolutionary forces that gave us this genetic heritage after we separated from the apes? Why did genes like ASPM, HAR1, and FOX2 develop in the first place? In other words, genetics gives us the ability to understand how we became intelligent, but it does not explain why this happened.

If we can understand this issue, it might provide clues as to how we might evolve in the future. This takes us to the heart of the ongoing debate: What is the origin of intelligence?

THE ORIGIN OF INTELLIGENCE

Many theories have been proposed as to why humans developed greater intelligence, going all the way back to Charles Darwin.

According to one theory, the evolution of the human brain probably took place in stages, with the earliest phase initiated by climate change in Africa. As the weather cooled, the forests began to recede, forcing our ancestors onto the open plains and savannahs, where they were exposed to predators and the elements. To survive in this new, hostile environment, they were forced to hunt and walk upright, which freed up their hands and opposable thumbs to use tools. This in turn put a premium on a larger brain to coordinate tool making. According to this theory, ancient man did not simply make tools—“tools made man.”

Our ancestors did not suddenly pick up tools and become intelligent. It was the other way around. Those humans who picked up tools could survive in the grasslands, while those who did not gradually died off. The humans who then survived and thrived in the grasslands were those who, through mutations, became increasingly adept at tool making, which required an increasingly larger brain.

Another theory places a premium on our social, collective nature. Humans can easily coordinate the behavior of over a hundred other individuals involved in hunting, farming, warring, and building, groups that are much larger than those found in other primates, which gave humans an advantage over other animals. It takes a larger brain, according to this theory, to be able to assess and control the behavior of so many individuals.
(The flip side of this theory is that it took a larger brain to scheme, plot, deceive, and manipulate other intelligent beings in your tribe. Individuals who could understand the motives of others and then exploit them would have an advantage over those who could not. This is the Machiavellian theory of intelligence.)

Another theory maintains that the development of language, which came later, helped accelerate the rise of intelligence. With language comes abstract thought and the ability to plan, organize society, create maps, etc. Humans have an extensive vocabulary unmatched by any other animal, with words numbering in the tens of thousands for an average person. With language, humans could coordinate and focus the activities of scores of individuals, as well as manipulate abstract concepts and ideas. Language meant you could manage teams of people on a hunt, which is a great advantage when pursuing the woolly mammoth. It meant you could tell others where game was plentiful or where danger lurked.

Yet another theory is “sexual selection,” the idea that females prefer to mate with intelligent males. In the animal kingdom, such as in a wolf pack, the alpha male holds the pack together by brute force. Any challenger to the alpha male has to be soundly beaten back by tooth and claw. But millions of years ago, as humans became gradually more intelligent, strength alone could not keep the tribe together. Anyone with cunning and intelligence could ambush, lie or cheat, or form factions within the tribe to take down the alpha male. Hence the new generation of alpha males would not necessarily be the strongest. Over time, the leader would become the most intelligent and cunning. This is probably the reason why females choose smart males (not necessarily nerdy smart, but “quarterback smart”). Sexual selection in turn accelerated our evolution to become intelligent. So in this case the engine that drove the expansion of our brain would be females who chose men who could strategize, become leaders of the tribe, and outwit other males, which requires a large brain.

These are just a few of the theories about the origin of intelligence, and each has its pros and cons. The common theme seems to be the ability to simulate the future. For example, the purpose of the leader is to choose the correct path for the tribe in the future. This means any leader has to understand the intentions of others in order to plan strategy for the future. Hence simulating the future was perhaps one of the driving forces behind the evolution
of our large brain and intelligence. And the person who can best simulate the future is the one who can plot, scheme, read the minds of many of his fellow tribesmen, and win the arms race with his fellow man.