This is a guest blog post by Vallmer Jordan, a graduate student in Dr. Mark Batzer's lab at LSU.
Vallmer came to LSU to study and research in the area of biological sciences after receiving his undergraduate degree in psychology from Morehouse College. His research interests include comparative genomics, human population genetics and bioinformatics. He has examined the phylogenetic relationship between Saimiri, Cebus and Aotus monkeys using squirrel monkey-specific Alu elements. So when we helped host a King Kong science movie night the CxC Science Studio last month, Vallmer was eager to answer the question: Could King Kong really exist?!
Since his cinematic debut in 1933, King Kong has captivated audiences as a larger-than-life mythical beast. Whether we root for or against Kong, his massive size is captivating. Despite his brutish exterior, he is often portrayed as compassionate. Without the use of words, directors have relied on the language of facial cues to allow Kong to express human-like emotions. In part, our affection for this fictional ape may be due to our evolutionary connection to the primate family.
But it is difficult to watch the latest edition of the Kong narrative without pondering the question: Could King Kong really exist? Before we investigate this possibility, we first must answer another question. How big are we talking? The largest primate that ever lived, aptly named Gigantopithicus, inhabited the forests of what is now known as China nearly 100,000 years ago. Standing roughly 10 feet tall and weighing over 1,000 pounds, this primate would have been more than qualified to play the role of Bigfoot. However, even at this size, Gigantopithicus is no match for King Kong.
Kong’s original creator, Merian C. Cooper, envisioned Kong standing 50 feet tall, but his animator Willis O’Brien scaled Kong between 18 and 24 feet tall. At this size, Kong would have been neither the tallest nor the heaviest land mammal during the Pleistocene epoch (roughly 2.5 million to 11 thousand years ago). During this era, the earth was inhabited by 20-ton mammoths, 20-foot long rhinoceros, and rodents as large as a modern day hippopotamus.
Over the past several decades, King Kong has grown immensely. In the 2017 film, Kong: Skull Island, Kong stands roughly 100 feet tall, weighing over 1,400 tons! At this size, he would easily be the largest animal that ever lived, either on land or in the sea. It is unlikely that this Kong could ever exist or have existed. Why? Because he would find it nearly impossible to move. Not only would the ground crumble under his weight, his bones would as well.
When you attempt to scale up an object, mass and material strength do not increase proportionally. As we increase height, the change in mass equals the change in height cubed (to the power of three, or "^3"). Thus, if we doubled the height of a gorilla, its mass would increase by a factor of 8 (2^3 = 8). However, the animal’s support strength relies on the cross sectional area of its supporting limbs. This cross sectional area equals the height squared. Thus, if we doubled the height of a gorilla, the cross sectional area would increase by a factor of 4 (2^2 = 4). Ultimately, a gorilla “doubled in height” would be eight times as heavy as normal gorilla, but only four times as strong. Proportionately, it would have only half the strength to support its own body weight.
Since Kong is 20 times the height of a normal gorilla, he would be 8,000 times as heavy (20^3), yet have only 400 times the strength (20^2). In the end, he would have 1/20th the proportional strength or a normal gorilla to support himself. So if Kong were to exist, he would require a bone structure very different from that of any living primate. This is likely the reason the heaviest animal that ever lived, the blue whale, evolved in an aquatic environment. Although the blue whale weighs more than 200 tons, water’s buoyancy reduces the amount of pressure placed on its skeleton.
Aside from the laws of physics, what other factors influence size selection in animals? If giant mammals were commonplace thousands of years ago, why did so many of them go extinct?
It seems intuitive that size would provide an animal with an advantage. However, it appears that in many cases the bad outweighs the good. By evaluating the mass extinction of many large mammalian species at the end of the Pleistocene, scientists have suggested that smaller mammals are often more adaptable to environmental changes. During this period, harsh environmental conditions inhibited the growth of numerous plant species. Many smaller mammals successfully adapted by eating different plant species, whereas many larger mammals were unable to make this transition while meeting the taxing demands of their necessary daily caloric intake. Larger mammals also reproduce at a much slower rate. Longer gestation time combined with a later age of sexual maturity makes it difficult for larger species to persist during periods when a substantial portion of their population suddenly dies off.
The relatively inability to adapt to environmental changes has proven deadly for many giant mammalian species. So with regards to natural selection, the ability to snatch helicopters out of midair offers less utility than the ability to persist despite changes to one’s natural environment.
However when it comes to the big screen, Kong is King.
Interested in primate biology and genetics? Check out Batzer lab research studies here, and consider a visit to LSU's Museum of Natural Science!