Manthropology Page 2
So muscular, in fact, were the Neandertals that I began to take pity on poor Alexey Voyevoda. Anxious to give this champion of Homo masculinus modernus a fighting chance, I stacked the deck slightly in his favor: I decided that instead of having Voyevoda square up to a hulking, rhino-hunting Neandertal male, I would send him into battle against a girl. A sweet, demure, coquettish Neandertal girl—the five foot, 176-pound beauty with the unfortunate name of La Ferrassie 2 (taken from the French cave site, La Ferrassie, where she was discovered with several other buried Neandertals in 1909).
Comparing their biceps strength was difficult, but not impossible. (It does involve a little calculation, unfortunately, so if that bores you just skip ahead four or five paragraphs.) The force a biceps muscle produces per square inch of cross-sectional area (called CSA and measured perpendicularly across the muscle) is known—it is 62 pounds. Fortunately, this doesn’t seem to vary between men and women, though obviously the total area of their muscle does. Measurements of Alexey Voyevoda’s total biceps CSA are, unfortunately, not available, but the average for a comparable group of modern males, elite bodybuilders, comes in at approximately 3.5 square inches. Multiplied by 62 pounds per square inch, that gives a hypothetical force of roughly 220 pounds for Voyevoda’s biceps. But how, then, to estimate the CSA of La Ferrassie 2’s biceps, given that all that survives of her arm is bone?
Surprisingly, it can be done thanks to a rule known as Wolff’s law. Wolff’s law, named after German military surgeon Julius Wolff, states that bone carries a record of the muscular load placed upon it because it grows larger over time in response to mechanical stress. In crude terms, the size of the muscle can therefore be estimated from the cortical area, or CA (a cross-sectional measure of thickness similar to muscle CSA), of the bone it was attached to. Since we have measures of bone CA for both La Ferrassie 2 and a representative group of average (non-bodybuilding) modern males, all I had to do was calculate the ratio between the two and multiply it by the average, non-bodybuilding male’s biceps CSA (1.8 inches square).
That, however, was where the first surprise hit me.
Despite the fact that modern males have 50 percent more upper body muscle than modern females, La Ferrassie 2 had bigger biceps than any average man alive today. The CA of her upper arm bone, or humerus, was 0.34 square inches, compared to our puny 0.3 square inches. Her biceps CSA was therefore probably around 2 inches square, around 16 percent larger than our 1.8 square inches. Multiplied by 62 pounds, that gave La Ferrassie 2 a hypothetical biceps force of around 124 pounds. Now, while this was enough to slam the average male pub challenger (with 112 pounds) to the table, it was a long way short of Voyevoda’s 220 pounds. I had not yet, however, corrected for the effect of training—one couldn’t be so unchivalrous, after all, as to let La Ferrassie 2 wrestle without a prolonged weight-training program to mirror Voyevoda’s. Several studies of elite female bodybuilders have shown that women’s muscles can grow, or hypertrophize, by approximately 31 percent in response to prolonged strength training. An increase of this size would bring La Ferrassie 2’s biceps CSA up to 2.6 inches square and her force output to around 162 pounds. Impressive as this is, it’s still just 75 percent of Voyevoda’s biceps output. At this point, it seemed, the Russian champion would have been counting his prize money and basking in the gratitude of vindicated modern males everywhere.
Except that La Ferrassie 2 had a nasty little surprise in store—two in fact. One was a trick of leverage and the other a quirk of Neandertal muscle anatomy. Put together they would have left Voyevoda regretting he’d ever been so stupid as to take her on.
It is widely acknowledged, among arm-wrestling champions, that a short forearm is a serious advantage. This is because the forearm is a third-class lever. Levers generally increase the amount of work that can be done as they grow longer, but third-class levers don’t—they decrease it. This is called the lever’s “mechanical disadvantage,” and its number rises as the lever lengthens. A short forearm, therefore, means a lower mechanical disadvantage. (The Neandertals had such short wrists because of another thermoregulatory principle, Allen’s law, which states that organisms living in cold environments will have dramatically shortened arms and legs, again to reduce heat loss.) My calculations show that Voyevoda’s forearm would probably have a mechanical disadvantage of 6.145, while La Ferrassie 2’s would be lower—around 5. If you divide each contestant’s absolute force by their mechanical disadvantage, it turns out that the amount of power La Ferrassie 2 delivered at her hand (the end of the forearm lever) would be just short of Voyevoda’s—roughly 33 pounds compared to 36.
By now the sweat beading the burly Russian’s forehead would no doubt be as much from relief at his close escape as from effort. But La Ferrassie 2 had a final, cruel anatomical trick to play. In Neandertal forearms, both male and female, the point where the biceps muscle was attached was located much further around on the radius bone than in modern humans, making Neandertals immensely strong in supination, or rotating the wrist counterclockwise, since full biceps contraction could be maintained through the whole movement. They likewise possessed much more highly developed muscles attaching to the other forearm bone, the ulna, giving them great strength, too, in clockwise rotation or pronation. These two features would have made La Ferrassie 2 an unbeatable dominatrix at two winning techniques in arm wrestling: the hook, where the wrist is supinated to get inside the opponent’s arm, and the top roll, where the wrist is pronated to get over the opponent’s wrists and bend his fingers back.
Once La Ferrassie 2 got her 10 percent bigger brain around those little numbers, Voyevoda’s pathetic 7 percent advantage would disappear in the snap of an upper-arm bone (fractured humeri are surprisingly common among arm wrestlers; see below). Of course, the beaten Russian could always cry foul, adding the title of “sorest loser” to the bulging trophy case of modern male failures. But the prospect of La Ferrassie 1—a fully grown male Neandertal bulging with 50 percent more upper body muscle than La Ferrassie 2—wading in to restore her honor, would probably dissuade him.
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It’s all fun and games until someone loses an arm
Though popular, arm wrestling can be dangerous. One study from the Department of Orthopedic Surgery at the Keio University Medical School in Tokyo, for example, reported forty cases of broken arms from arm wrestling over a period of twenty years.6 The injuries were invariably the same: a spiral fracture from twisting of the humerus (the upper-arm bone).
Surprisingly, the majority of injuries occurred in men who fought weaker or evenly matched opponents, rather than stronger ones. Alcohol, predictably, was a factor, but so was inexperience: 60 percent of victims had never arm wrestled before the bout (usually against a friend) in which they were injured.
Doctors concluded that the injuries came from inexperienced wrestlers trying to push their hand, arm, and shoulder in the same direction—a natural, throwing motion. The drawback is that this simply added to the torque, or twist, that the opponent was putting on their upper arms. This overloaded their rotator muscles, prompting a sudden switch from concentric contraction (in which muscle fibers shorten to provide resistance) to eccentric contraction (where they elongate and add to the opposing force).
This phenomenon probably explained why the “Arm Spirit” arm wrestling arcade game had to be withdrawn in Japan after three players broke their arms on it. The bone-breaking game should have been a pushover—contestants progressively wrestled a French maid, a drunken martial arts master, and a chihuahua!
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In any case, Voyevoda’s performance in this interspecies grudge match might actually have been even worse. These calculations all assumed that the individual muscles of ancient hominins were exactly the same strength, pound for pound, as those of modern humans. There is considerable evidence, however, that they may have been much, much stronger. Most of it comes from anatomical studies of our very close relative, the chimpanzee. The two species of chimpanzee—Pan tr
oglodytes, the common chimp, and Pan paniscus, the bonobo or pygmy chimp—are not our immediate ancestors, but they are direct descendants of whoever was. It is highly probable, therefore, that early human males at the time of our separation from chimps (about 5.5 million years ago) were exactly as strong as male chimpanzees are today.
So how strong is that?
Exceptionally strong, as it happens. Scientists who work with chimps often remark on the animals’ phenomenal physical strength. Jane Goodall, for example, told a Canadian TV host that she frequently saw chimps manipulate branches six times heavier than a man could. Given the savage attack suffered by the unfortunate Charla Nash, a Connecticut woman whose face and hands were almost ripped off by her friend’s pet chimpanzee, Travis, in early 2009, this seems more than plausible. Much scientific data also testifies to chimps’ incredible strength. A study of bonobos, the smallest chimpanzees, found they could jump, from a standing start, almost three times the height an average man could, and almost twice as high as any elite high-jump competitor despite the fact that their leg-muscle mass is just one-third that of humans.7
Why are chimps so phenomenally strong? Muscle bulk does seem to be part of the answer. Despite the fact that chimps’ overall muscle mass is lower, the level of it relative to their reduced body size is quite high. One study of dead chimps from English zoos found that every one of their muscle groups (except the quadriceps) was significantly larger than those of humans when scaled for limb length; their biceps were almost twice as large. But sheer muscle bulk can’t be the whole answer. For, as a fascinating 1926 experiment showed, common chimpanzees, even female ones, really are over four times as strong as human males, weight-for-weight.
There is a delicious irony about John Bauman’s early twentieth-century chimp strength tests at Muhlenberg College, a small Pennsylvanian university. The researcher tested his three chimps using a dynamometer: a lever connected to a two-thousand-pound-capacity steel loop spring and a dial to register the maximum pulling force. The machine had been provided by the Narragansett Machine Company to Muhlenberg (a Lutheran college) for the purposes of anthropometry—recording the physical strength of male students—a craze that swept American universities in the late nineteenth century as part of the “muscular Christianity” movement. Instead of aiding the development of the perfectly masculine Christian man, however, Muhlenberg’s machine would, in Bauman’s hands, prove just how feeble that man really was.
Bauman used the dynamometer to test the pulling power of three “anthropoid apes…of suitably vicious disposition” against that of five “husky farm lads” attending the college. To his astonishment, the chimps dramatically out-pulled the men, without really trying.8 Suzette, a female circus chimp who’d been donated to the New York Zoological Park on account of her “increasing treacherousness and meanness,” made a random pull of 1,258 pounds—four times the college students’ average. (Interestingly, the only student who, at 127 pounds, weighed less than Suzette, pulled the highest human total: 460 pounds.) Bauman’s male chimp, Boma, made a single-hand pull of 847 pounds, again over four times the strength of the male students’ single-hand pulls. Bauman drew two conclusions from these results. First, that the individual fibers in chimp muscle must be roughly four times the strength of human fibers. (In fact, later research has shown that chimp muscle fibers are not individually stronger than ours; instead they are recruited en masse in one explosive contraction, in contrast to our more staggered firing. It is this that gives chimps their super strength.) Second, that this strength must be genetic and inherent, rather than conditioned. Bauman pointed out that his farm lads were fresh from a season of strenuous farm labor, while the chimps had been idling their years away in tiny cages.9
Here Bauman had stumbled onto a theory that would later become important in evolutionary explanations of human origins: that Homo sapiens is simply a kind of degenerate ape. Several lines of evidence support this idea. Some of the genetic mutations that differentiate us from the chimp and our common ancestor seem to involve a simple loss of function—put simply, our version just doesn’t work anymore. Then there are our visible differences in body form, or phenotype. Though we have roughly as many hair follicles as chimps, our hairs (except on our heads) are pathetic remnants by comparison. Our kids grow more slowly than chimp children do: so slowly, in fact, that the chimpanzees adult humans most resemble are the juveniles, leading some anthropologists to label us “neotenous” organisms—ones that become adult in their juvenile stage. We are, effectively, a bald chimp that never grows up. A bald, weak, chimp, according to Bauman.
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Homo pugilistus
Paleoanthropologists have long wondered how our earliest ancestors defended themselves on the harsh African savannah, home to such nasty predators as leopards, hyenas, and lions. Early humans lost their large canines as soon as they left the trees, and effective spears didn’t become available for 2 million years. So how did they fend off ravening carnivores?
Remarkably, they might have punched them senseless.
We humans are natural-born boxers. Like our chimp cousins, we were originally brachiating (or branch-swinging) apes, with shoulder joints adapted to an almost 360-degree range of motion. When we shifted to bipedalism, however, this meant we also suddenly acquired the ability to throw vicious jabs, hooks, and sweeping haymakers.
Chimps still use these to devastating effect today. Anthropologist Richard Wrangham describes witnessing a male chimp, Hugo, punch out a male baboon, Stumptail, that had canines as long as a lion’s:
As Hugo approached, Stumptail reared [and] bared his fangs…but before he could close to biting range, Hugo swung his arm in a wide arc and punched Stumptail in the belly. Stumptail crumpled…looking sick. Moving like a prizefighter, Hugo quickly landed a second punch…snapping the baboon’s head backwards. That was it. Stumptail retreated…and Hugo, taking his place among the delicious palm fruits, ate for a peaceful half-hour.10
So much for Stumptail, but could our tiny ancestors (they averaged between 3 and 4 feet tall) really have punched out leopards and hyenas? Well, maybe. Consider, for example, the Homo sapiens boxer, Rocky Marciano. Engineers tested Marciano’s punch in the 1950s, reporting that it generated enough force to lift an 1,100-pound weight 12 inches off the ground, break facial bones, and smash its victim into instant unconsciousness. Now consider the fact that our earliest ancestors were probably, like their chimp brothers, about four times as strong as Marciano. Put this way, a punch from early Homo pugilistus could have knocked any 110-pound spotted hyena out of the ring…and then some.
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But why should such degeneration have proven so successful, evolutionarily speaking? Surely natural selection should have weeded out ninety-eight-pound weaklings like us long ago? Evidence from a 2004 study on another human muscle, the jaw, may tell us why it didn’t. That study, by the Pennsylvania School of Medicine Muscle Institute, found that the fast-twitch fibers in human jaw muscles are now just one-eighth the size of their chimp counterparts, thanks to a mutation in the genes encoding for the myosin protein that provides muscle-fiber bulk. It’s the same condition that expresses itself in bodily muscles as Inclusion Body Myopathy-3 (IBM3), a wasting disease, and means our jaws generate just a fraction of the bite force that chimp jaws do. But this loss of function may, paradoxically, have been indispensable to the enlargement of our brains. It may have reduced the need for a thick, low braincase with a heavy, bony crest—such as chimps have, to which their powerful jaw muscles attach—thereby freeing the skull up for the first round of hominin brain expansion, which in fact took place shortly after this jaw weakening mutation appeared around 2.4 million years ago. It’s possible our loss of general body strength carried similar benefits, such as trading off strength in our muscles for fine motor control—useful for such things as making tools and throwing stones and spears.11
It’s hard to see, though, what benefits came with our next trophy in the masculine Hall of Shame, for, a
s it turns out, we’re not only weaker than just about any male human who ever walked the earth, we’re also slower.
The evidence this time is written into the earth itself. In 2003 archaeologists from Bond University discovered a series of human footprint trackways preserved in a fossilized claypan lake bed in the Willandra Lakes region of New South Wales, Australia. The twenty-three trackways date back twenty thousand years and feature almost seven hundred individual footprints. The most interesting are those of six adult men, probably hunters, who seem to have been running to outflank a prey animal. An analysis of the men’s speed (calculated from their stride length) shows that all were running fast, but that the outside individual, the 6'5" “T8,” was achieving incredible speeds. The record of his athleticism, written into the dried hardpan of an Ice Age Australian lake bed, raises serious doubts that any modern sprinter can honorably claim the title “Fastest Man on Earth.”
Take Usain Bolt, currently the world’s fastest man. Bolt set the 100-meter world record of 9.69 seconds at the Beijing Olympics in 2008. His top speed, measured at peak acceleration near the 60-to 70-meter mark, is approximately 27 miles per hour. He achieved it by running at maximum effort on a prepared track with the aid of spiked shoes and strict training backed by decades of scientific research into how to crank the maximum speed from the human body. He is also an elite competitor selected from a pool of many millions of men alive today, and has the lure of glory and a lucrative career to drive him.