To the mouse and any smaller animal [gravity] presents practically no dangers. You can drop a mouse down a thousand-yard mine shaft; and, on arriving at the bottom, it gets a slight shock and walks away, provided that the ground is fairly soft.
-J.B.S. Haldane, “On Being the Right Size”
J.B.S. Haldane was a British biologist, geneticist, and mathematician, and one of the most brilliant people to walk the planet. While the name may not sound familiar, you are surely aware of many of his discoveries, theories, and suppositions. He originated the “primordial soup” theory for the origins of life, first posited that sickle cell anemia provided protection against malaria, and laid the groundwork for in vitro fertilization, among numerous other accomplishments.
In 1926, he wrote a rollicking essay titled “On Being the Right Size”. In it, he discusses how the size a creature is dictates the form that it will take, articulating through plain language and humorous anecdotes what is also known as the square-cube law.
The square-cube law states that when an object undergoes a proportional increase in size, its new surface area is proportional to the square of the multiplier and its new volume is proportional to the cube of the multiplier. Or, put another way, when something increases in size the volume grows exponentially faster than the area.
In terms of supporting life, this provides advantages and disadvantages. The ability of bones to withstand stress depends in large part on the surface area of a cross-section of the bone. If you took a typical man and blew him up proportionally to 10 times his current size, the surface area of a cross-section of his bones would increase 100 times over, but his total mass would increase 1,000 times over.
This hypothetical giant man, then, would bear ten times as much weight on each bone. And since this represents the stress level around which human bones break, such a giant would literally break his own bones with every step.
As for the contest with the spider, the battle is indeed biased, but not the way the movie would have you believe. Certainly the spider has a wicked set of poison fangs and some advantage because it wears its skeleton on the outside, where it can function as armor. But our hero, because of his increased metabolic rate, will be bouncing around like a mouse on amphetamines.
-Michael C. LaBarbera
LaBarbera, a fellow biologist, expanded in many ways on Haldane’s thoughts with a decidedly more modern twist in his essay “The Biology of B-Movie Monsters”. A fun takedown in the biomechanical flaws of such classics as “King Kong” and “The Incredible Shrinking Man”, the essay further expounds on some principals of the square-cube law.
A man shrunk down to the size of an insect, he notes, would be able to lift 50 times his own body weight and leap down from any height without fear of injury. As a tradeoff, such a man would have to eat his own weight in food every day to maintain his core temperature; if he should fall asleep at night, he would surely starve to death.
The Biology of Football Players
While these essays are fun, what do they have to do with fantasy football? Just because the outer ranges of human anatomy fall within a much tighter window doesn’t mean the same principles and ratios do not apply.
Consider, for instance, the list of the tallest humans ever to live. Of the 16 people over 8’ tall for whom we have detailed enough records, 13 died at an average age of 37, while the three living members are 33, 33, and 28. (This sample also suffers from severe survivorship bias; doubtless there were others who could have potentially grown to 8 feet, but who died young to height-related health complications). Being overly short likewise carries with it numerous health complications.
Indeed, humans exist within a rather narrow range of sizes for good reason; deviation from that range takes a toll on the anatomy. In our athletic endeavors, therefore, we should only expect to see those deviations where they provide an advantage great enough to offset the costs.
Being tall is obviously advantageous for an NFL receiver, as the extra height enables him to go over the top of shorter defensive backs in contested catch situations. It is likewise advantageous for quarterbacks, where it enables them to see over the top of their blockers and release the ball above the reach of onrushing defenders.
At the same time, the NFL sees few exceptionally tall players at receiver, tight end, or quarterback. Scott Chandler’s 2379 career receiving yards rank 5th among players 6’7” or taller. Harold Carmichael is the only player in history to top 1,000 receiving yards at 6’8” or taller. (In fact, Carmichael has nearly three times as many receiving yards as every other 6’8” player combined; only 11 such players have even registered a reception.)
At quarterback, Brock Osweiler of the Denver Broncos just started his third career game, yet he already owns the all-time record for passing yards by a player 6’7” or taller. Not only that, but he has passed for more yards than every other 6’7” player combined. The aforementioned Harold Carmichael ranks 4th on that list with 45 passing yards, and is one of just three men standing 79” to throw a touchdown. (He joins Dan McGwire, noted draft bust best known as the brother of baseball’s Mark, as the only players standing 6’8” to attempt a pass.)
If height is advantageous at these positions, why do we see so few exceptionally tall players? Because the height reaches a point where it ceases providing advantages. Once a receiver is tall enough to reach over every defensive back in the league, additional inches provide only an extra burden for him to carry. Likewise, a hypothetical 10’ tall quarterback would have no advantage whatsoever over a hypothetical 8’ tall quarterback; both would stand head and shoulders over the traffic in the middle of the field, meaning the taller player would bring extra injury risk with no additional benefit to offset.
Biomechanics in Motion
All of this suggests that, for every possible function on the field, there is indeed a “perfect” size. Heavier players generate more force, but trade off an ability to quickly change directions. Taller players present a bigger target, but also place more stress on their frames during play, (and present a bigger target to defenders). Lanky players are great at reaching around defenders to make tackles, but poor at running through traffic at the line of scrimmage. Tall running backs are easier for the defense to pick out on misdirection plays.
This idea that there is a size and shape best suited to every task is why we see players falling into certain “prototypes”, (illustrated beautifully as the darker red patches in this handy visualization of player size over time). Indeed, there’s often pushback against the idea that there’s a “perfect” size for NFL players, but it is hard to argue with the biomechanics, and even harder to argue with the way that NFL players have naturally sorted themselves based on size and shape.
So what does this mean? Am I finally admitting that bigger receivers are better? Not quite. Careful readers might note that I have repeatedly said there is an ideal size for every “task” or “function”, and not for every “position”.
Nowhere on the field is this distinction more evident than at wide receiver. While height is a benefit on the outside where receivers are frequently tasked with out-leaping and out-muscling defenders for 50/50 balls, there's a reason slot receivers typically resemble the shorter Wes Welker; success between the numbers requires a more compact frame to enable the sudden change-of-direction required to flash open quickly.
Even on the outside, we see receivers succeed in different manners. Steve Smith and Santana Moss each topped 10,000 career receiving yards at 5’10” or shorter, not by out-leaping the competition, but by outrunning it. Antonio Brown and Marvin Harrison were two of the most prolific outside receivers in recent memory despite standing 6’0” or shorter because of the precision and suddenness with which they were able to run their routes, (aided, undoubtedly, by their shorter limbs).
Anquan Boldin, Terrell Owens, and Demaryius Thomas were bulkier receivers, but they used that bulk not to outmuscle defenders at the catch point, but to outmuscle defenders after the catch, dominating the field with the ball in their hands. Jimmy Graham, Antonio Gates, and Mike Evans aren’t as deadly after the catch, but their size allows them to easily box out defenders on shots down the field.
Even players who succeed in similar areas can do so in radically different ways. Of the top 30 players by receiving yards since 2008, only six averaged more than 15 yards per reception, and only two averaged more than 16— DeSean Jackson, with 7578 yards at 17.62 yards per reception, and Vincent Jackson, with 7767 yards at 17.15 yards per reception.
Both Jacksons are three-time pro bowlers who have been among the most deadly deep threats in the NFL on two different teams. But Vincent’s hulking 6’5” and 241 pound frame makes him one of the largest receivers in the NFL, while DeSean’s diminutive 5’10”, 178-pound frame makes him one of the smallest. Likewise, Vincent Jackson’s 4.46 40-yard dash time is blazing for a man of his size, but DeSean Jackson’s 4.35 is blazing for a man of any size.
DeSean Jackson and Vincent Jackson succeed in different ways, and it’s fair to say that each is sized perfectly for what he does. Making DeSean four inches taller would be unlikely to make him a better receiver. Likewise, making Vincent four inches shorter would likely render him much less effective.
The "Right" Size
While wide receiver is the most diverse position, plenty of others with different roles exhibit a similar range. Jordan Reed at 6’3”, 236 pounds does not succeed in the same way as Greg Olsen at 6’6”, 254 pounds, but both still succeed. Warrick Dunn at 5’9”, 180 pounds looked nothing like Jerome Bettis at 5’11”, 252 pounds, but both topped 15,000 career yards from scrimmage at nominally the same position.
At the end of the day, preoccupation with a player’s size and athletic ability is perfectly justified. All life is going to trend towards a size perfectly suited to the tasks it performs. It is merely important to remember that the tasks involved in professional football cover a broad spectrum that allows for players ranging from 5’9”, 174-pound Tavon Austin to 6’7”, 260-pound Jimmy Graham. To answer whether a player is built to win, we must first ask "win where?"
“Being the right size”, in the end, is hardly “one size fits all”.
