The Violinist's Thumb: And Other Lost Tales of Love, War, and Genius, as Written by Our Genetic Code (32 page)

Einstein had unusual wrinkles and ridges in the cortex of his parietal lobe, a region that aids in mathematical reasoning and image processing. This comports with Einstein’s famous declaration that he thought about physics mostly through pictures: he formulated relativity theory, for instance, in part by imagining what would happen if he rode around bareback on light rays. The parietal lobe also integrates sound, sight, and other sensory input into the rest of the brain’s thinking. Einstein once declared that abstract concepts achieved meaning in his mind “only through their connection with sense-experiences,” and his family remembers him practicing his violin whenever he got stuck with a physics problem. An hour later, he’d often declare, “I’ve got it!” and return to work. Auditory input seemed to jog his thinking. Perhaps most telling, the parietal wrinkles and ridges in Einstein’s lobes were steroid thick, 15 percent bigger than normal. And whereas most of us mental weaklings have skinny right parietal lobes and even skinnier left parietal lobes, Einstein’s were equally buff.

Finally, Einstein appeared to be missing part of his middle brain, the parietal operculum; at the least, it didn’t develop fully. This part of the brain helps produce language, and its lack might
explain why Einstein didn’t speak until age two and why until age seven he had to rehearse every sentence he spoke aloud under his breath. But there might have been compensations. This region normally contains a fissure, or small gap, and our thoughts get routed the long way around. The lack of a gap might have meant that Einstein could process certain information more speedily, by bringing two separate parts of his brain into unusually direct contact.

All of which is exciting. But is it exciting bunkum? Einstein feared his brain becoming a relic, but have we done something equally silly and reverted to phrenology? Einstein’s brain has deteriorated into chopped liver by now (it’s even the same color), which forces scientists to work mostly from old photographs, a less precise method. And not to put too fine a point on it, but Thomas Harvey coauthored half of the various studies on the “extraordinary” features of Einstein’s brain, and he certainly had an interest in science learning something from the organ he purloined. Plus, as with Cuvier’s swollen brain, maybe Einstein’s features are idiosyncratic and had nothing to do with genius; it’s hard to tell with a sample size of one. Even trickier, we can’t sort out if unusual neurofeatures (like thickened folds) caused Einstein’s genius, or if his genius allowed him to “exercise” and build up those parts of his brain. Some skeptical neuroscientists note that playing the violin from an early age (and Einstein started lessons at six) can cause the same brain alterations observed in Einstein.

And if you had hopes of dipping into Harvey’s brain slices and extracting DNA, forget it. In 1998, Harvey, his jars, and a writer took a road trip in a rented Buick to visit Einstein’s granddaughter in California. Although weirded out by Grandpa’s brain, Evelyn Einstein accepted the visitors for one reason. She was poor, reputedly dim, and had trouble holding down a job—not exactly an Einstein. In fact Evelyn was always told she’d been
adopted by Einstein’s son, Hans. But Evelyn could do a little math, and when she started hearing rumors that Einstein had canoodled with various lady friends after his wife died, Evelyn realized she might be Einstein’s bastard child. The “adoption” might have been a ruse. Evelyn wanted to do a genetic paternity test to settle things, but it turned out that the embalming process had denatured the brain’s DNA. Other sources of his DNA might still be floating around—strands in mustache brushes, spittle on pipes, sweated-on violins—but for now we know more about the genes of Neanderthals who died fifty thousand years ago than the genes of a man who died in 1955.

But if Einstein’s genius remains enigmatic, scientists have sussed out a lot about the everyday genius of humans compared to that of other primates. Some of the DNA that enhances human intelligence does so in roundabout ways. A two-letter frameshift mutation in humans a few million years ago deactivated a gene that bulked up our jaw muscles. This probably allowed us to get by with thinner, more gracile skulls, which in turn freed up precious cc’s of skull for the brain to expand into. Another surprise was that
apoE,
the meat-eating gene, helped a lot, by helping the brain manage cholesterol. To function properly, the brain needs to sheathe its axons in myelin, which acts like rubber insulation on wires and prevents signals from short-circuiting or misfiring. Cholesterol is a major component of myelin, and certain forms of
apoE
do a better job distributing brain cholesterol where it’s needed.
ApoE
also seems to promote brain plasticity.

Some genes lead to direct structural changes in the brain. The
lrrtm1
gene helps determine which exact patches of neurons control speech, emotion, and other mental qualities, which in turn helps the human brain establish its unusual asymmetry and left-right specialization. Some versions of
lrrtm1
even reverse parts of the left and right brain—and increase your chances of being left-handed to boot, the only known genetic association
for that trait. Other DNA alters the brain’s architecture in almost comical ways: certain inheritable mutations can cross-wire the sneeze reflex with other ancient reflexes, leaving people achooing uncontrollably—up to forty-three times in a row in one case—after looking into the sun, eating too much, or having an orgasm. Scientists have also recently detected 3,181 base pairs of brain “junk DNA” in chimpanzees that got deleted in humans. This region helps stop out-of-control neuron growth, which can lead to big brains, obviously, but also brain tumors. Humans gambled in deleting this DNA, but the risk apparently paid off, and our brains ballooned. The discovery shows that it’s not always what we gained with DNA, but sometimes what we lost, that makes us human. (Or at least makes us nonmonkey: Neanderthals didn’t have this DNA either.)

How and how quickly DNA spreads through a population can reveal which genes contribute to intelligence. In 2005 scientists reported that two mutated brain genes seem to have swept torrentially through our ancestors,
microcephalin
doing so 37,000 years ago,
aspm
just 6,000 years ago. Scientists clocked this spread by using techniques first developed in the Columbia fruit fly room. Thomas Hunt Morgan discovered that certain versions of genes get inherited in clusters, simply because they reside near each other on chromosomes. As an example, the
A, B,
and
D
versions of three genes might normally appear together; or (lowercase)
a, b,
and
d
might appear together. Over time, though, chromosomal crossing-over and recrossing will mix the groups, giving combos like
a, B,
and
D;
or
A, b,
and
D.
After enough generations, every combination will appear.

But say that
B
mutates to
B
₀
at some point, and that
B
₀
gives people a hell of a brain tune-up. At that point it could sweep through a population, since
B
₀
people can outthink everyone else. (That spread will be especially easy if the population drops very low, since the novel gene has less competition. Bottlenecks
aren’t always bad!) And notice that as
B
₀
sweeps through a population, the versions of
A
/
a
and
D
/
d
that happen to be sitting next to
B
₀
in the first person with the mutation will
also
sweep through the population, simply because crossing over won’t have time to break the trio apart. In other words, these genes will ride along with the advantageous gene, a process called genetic hitchhiking. Scientists see especially strong signs of hitchhiking with
aspm
and
microcephalin,
which means they spread especially quickly and probably provided an especially strong advantage.

Beyond any specific brain-boosting genes, DNA regulation might explain a lot about our gray matter. One flagrant difference between human and monkey DNA is that our brain cells splice DNA far more often, chopping and editing the same string of letters for many different effects. Neurons mix it up so much, in fact, that some scientists think they’ve upended one central dogma of biology—that all cells in your body have the same DNA. For whatever reason, our neurons allow much more free play among mobile DNA bits, the “jumping genes” that wedge themselves randomly into chromosomes. This changes the DNA patterns in neurons, which can change how they work. As one neuroscientist observes, “Given that changing the firing patterns of single neurons can have marked effects on behavior… it is likely that some [mobile DNA], in some cells, in some humans, will have significant, if not profound, effects on the final structure and function of the human brain.” Once again viruslike particles may prove important to our humanity.

If you’re skeptical that we can explain something as ineffable as genius by studying something as reductive as DNA, a lot of scientists are right there with you. And every so often a case like that of savant Kim Peek pops up—a case that so mocks our understanding of how DNA and brain architecture influence
intelligence that even the most enthusiastic neuroscientist seeks the consolation of a stiff bourbon and starts to think seriously about going into administration.

Peek, a Salt Lake City native, was actually a megasavant, a souped-up version of what’s impolitely but accurately known as an idiot savant. Instead of being limited to poignantly empty skills like drawing perfect circles or listing all the Holy Roman Emperors in order, Peek had encyclopedic knowledge of geography, opera, American history, Shakespeare, classical music, the Bible—basically all of Western Civ. Even more intimidating, Peek had Google-like recall of any sentence in the nine thousand books he’d memorized, starting at eighteen months old. (When finished with a book, he returned it to his shelf with the spine upside down to indicate he’d knocked it off.) If it makes you less insecure, Peek did know loads of useless crap, too, like the complete U.S. zip code system. He also memorized
Rain Man
, a movie he inspired, and knew Mormon theology in lobotomizing detail.
^*

Trying to get some, any, sort of measure on Peek’s talents, doctors in Utah began scanning his brain in 1988. In 2005, NASA got involved for whatever reason and took complete MRI and tomography scans of Peek’s mental plumbing. The scans revealed that Peek lacked the tissue that connects the brain’s right hemisphere to the left. (Peek’s father remembered, in fact, that Peek could move each eye independently of the other as an infant, probably because of that disconnect between the right and left halves.) The left hemisphere, which focuses on big-picture ideas, also seemed misshaped—more lumpen and squished than normal brains. But beyond these details, scientists learned little. In the end, then, even NASA-level technology could reveal only abnormal features,
problems
with Peek’s brain. If you wanted to know why Peek couldn’t button his own clothes or why he could never remember where to find the silverware, despite living
at his father’s house for decades, there you go. As to the basis of his talents, NASA shrugged.

But doctors also knew Peek had a rare genetic disorder, FG syndrome. In FG syndrome, a single malfunctioning gene can’t flick the on switch for a stretch of DNA that neurons need to develop properly. (They’re very picky, neurons.) And as with most savants, the fallout from these problems clustered in Peek’s left brain, possibly because the big-picture-oriented left hemisphere takes longer to develop in utero. A malfunctioning gene therefore has more time to inflict injury there. But in a strange twist, injuring the normally dominant left hemisphere can actually coax out the talents of the detail-conscious right brain. Indeed, the talents of most savants—artistic mimicry, perfect musical regurgitation, feats of calendary calculation—all cluster in the brain’s less-vulnerable right half. Sadly, then, it may be true that those suppressed right-brained talents can never surface unless the domineering left hemisphere suffers damage.

Geneticists have made similar discoveries using the Neanderthal genome. Scientists are currently mining Neanderthal and human DNA for evidence of hitchhiking, trying to identify DNA that swept through humankind after the Neanderthal-human split and therefore helped distinguish us from Neanderthals. They’ve found about two hundred regions so far, most of which contain at least a few genes. Some of these human-Neanderthal differences are real yawners about bone development or metabolism. But scientists have also identified a handful of genes related to cognition. Paradoxically, though, having certain variants of these genes—far from being linked to Nobel Prizes or MacArthur grants—increases the risk of Down syndrome, autism, schizophrenia, and other mental disorders. It seems that a more complicated mind is a more fragile mind; if these genes did uplift our intelligence, taking them on also introduced risk.