David Epstein - The Sports Gene: Inside the Science of Extraordinary Athletic Performance

Superbaby, Bully Whippets, and the Trainability of Muscle

T he baby boy was born around the turn of the millennium, and it was the twitching that grabbed the nurses eye. Sure, the boy was slightly on the heavy side, but nothing jaw-dropping for the nursery at Charit hospital in Berlin. But those jitters. The little ticks and shudders that started just a couple of hours after he was born. The doctors worried that he might have epilepsy, so they sent him to the neonatal ward. Thats where Markus Schuelke, a pediatric neurologist, noticed his pipes.

The newborn had slightly bulging biceps, as if he had been hitting the womb weight room. His calves were chiseled, and the skin over his quads was stretched a bit too taut. Soft as a babys bottom? Not this baby. You could bounce a nickel off these glutes. Ultrasound examination of his lower body showed that the boy was beyond the top of the baby charts in the amount of muscle he had, and beneath the low end of the charts in terms of fat.

The boy was otherwise normal. The functioning of his heart was ordinary, and the jitters subsided after two months. Perhaps the baby was the Benjamin Button of bodybuilding, and would gradually lose muscle. Not quite. By the age of four, he had no trouble holding 6.6-pound dumbbells suspended horizontally at arms length. (Imagine toddler-proofing that household.)

Monstrous strength ran in the family. The boys mother was strong, as were her brother and father. But her grandfatherhe was acclaimed on his construction crew for unloading 330-pound curbstones from truck beds with his bare hands.

Fully clothed, the boy did not stand out from his peers. You wouldnt ogle his puerile pecs if you passed him in the street. But the muscles in his upper arms and legs were roughly twice the size of other boys his age. Double muscle. It reminded Schuelke of something.

In the early 1990s, Johns Hopkins geneticist Se-Jin Lee had begun searching for muscle in his lab on North Wolfe Street in Baltimore. Not the finished muscle tissue itself, but the protein scaffolding that builds it. The purpose of the search was to find treatments for muscle-wasting diseases, like muscular dystrophy. Lee and a group of colleagues targeted a family of proteins known as transforming growth factor-. They cloned genes that coded for the proteins and then set off like kids with new toys, trying to figure out what the heck each gene did.

They gave the genes prosaic namesgrowth differentiation factor 1 through 15and then bred mice that lacked working copies of each gene, one at a time, so they could see what would happen and thereby deduce each genes function. The mice without GDF-1 had their organs on the wrong side. They didnt survive long. The mice without GDF-11 had thirty-six ribs. They, too, died quickly. But the mice without GDF-8 survived. They were freak show rodents of a different kind. They had double muscle.

In 1997, Lees group named GDF-8, a gene on chromosome two, and its protein myostatin. The Latin myo-, meaning muscle, and -statin, to halt. Something that myostatin does signals muscles to cease growing. They had discovered the genetic version of a muscle stop sign. In the absence of myostatin, muscle growth explodes. At least it did in the lab mice.

Lee wondered whether the gene might have the same effect in other species. He contacted Dee Garrels, owner of the Lakeview Belgian Blue Ranch in Stockton, Missouri. Belgian Blue cattle are the result of postWorld War II breeding that sought more meat to accommodate the increased demand of Europes postbellum economy. Breeders in Belgium crossed Friesian dairy cows with stocky Durham shorthorns and got cattle with heaps of muscle. Double muscle, to be precise. Belgian Blues look as if somebody unzipped them and tucked bowling balls inside their skin. Hotline, Garrelss 2,500-pound prize Belgian Blue bull, once ripped a steel restraining gate off its hinges and flicked it aside en route to a cow in heat.

Lee asked Garrels for blood samples from her double-muscled cattle. Sure enough, the Belgian Blues were missing eleven of the DNA base pairsout of more than six thousandfrom the myostatin gene. It left them without a stop sign for their muscles. Another breed of double-muscled cattle, Piedmontese, also had a genetic mutation that resulted in no functional myostatin.

So Lee went hunting for human subjects. First stop: the grocery store, where he loaded his cart with muscle mags, the kind with cover photos of bulging-veined men in itty-bitty skivvies. Lee has jokingly been called the skinniest man in the world by a colleague, and he still remembers the sideways look from the cashier. Nonetheless, he placed an ad in Muscle and Fitness and was immediately swamped with willing volunteers, many of whom mailed him photos of themselves flexing and scantily clad, or not clad at all. He took samples from 150 muscular men, but found no myostatin mutants.

He put the work aside until 2003, when Markus Schuelke called to talk about the bulging baby boy who was born at Charit hospital three years earlier and whose development he was monitoring. The following year, Schuelke, Lee, and a group of scientists published a paper that would introduce the world to the Superbaby, as the media would name him. The German boy, whose identity has been carefully guarded, was the human version of a Belgian Blue. Mutations on both of his myostatin genes left him with no detectable myostatin in his blood. Even more provocatively, Superbabys mother had one typical myostatin gene and one mutant myostatin gene, leaving her with more myostatin than her son but less than the average person. She was the only adult with a documented myostatin mutation, and she was a professional sprinter.

Double muscle might seem like an unconditional blessing, but myostatin exists for a reason. It is, in evolutionary terms, highly conserved. The gene serves the same function in mice, rats, pigs, fish, turkeys, chickens, cows, sheep, and people. This is probably because muscle is costly. Muscle requires calories and specifically protein to sustain it, and having massive muscles can be a massive problem for organismslike ancestral humansthat dont have steady access to the protein necessary to feed the organs. But that is a diminishing concern in modern society.

In Superbabys case, doctors initially worried that the boys lack of myostatin might cause his heart to grow out of control. So far, though, no major health concerns have been reported in him or his mother. Thus, it seems unlikely that an individual with a myostatin mutation would ever even think to get tested. The result is that nobody has any idea just how rare the myostatin mutation is, other than that most people (and animals) dont have it. But the facts that the one boy with two of the rare myostatin gene variants has exceptional strength, and that his mother had exceptional speed, are no coincidence. Superbaby and his mother fall precisely in line with racing whippets.