One of the great things about blogging on Tumblr is the built-in “Ask” box function that lets other users submit questions or comments and allows the author to publish responses or reply in private. It really puts the “community” in “Most of the time the community asks me ridiculous things, but about ten percent of the questions are worth answering.”
Recently I spent a whole week answering some of the hundreds of questions I’ve gotten. Here’s one I saved for Scientopia:
Scientists use lots of methods to date things. Paleontologists calculate the decay of radioactive isotopes to help place fossils onto the geologic timeline. Climate scientists study the composition of atmospheric gases in ice cores drilled from deep beneath the polar regions. Ecologists count rings in felled trees, and geologists probe through layers of rock to construct timelines of early Earth. But how do you date a modern Homo sapiens?
One easy way is to discern the last organized dance craze that they remember. Still stuck on “the twist”? Congratulations on figuring out the internet! (How does this look on Internet Explorer 5?) Maybe you’re more of an “Electric Slide” era person. You’re probably worried about maturing that 401(k). “Boot Scootin’ Boogie” or “Macarena” make us yearn for the simplicity of the Clinton years, while the “Cupid Shuffle” brings us into the modern, rules-be-damned era of “Is grandma really doing that?”
If you know the next one, you’re officially pretty hip. A reader asked:
What’s the scientific explanation behind the “Dougie”?
Good question. Some quick background on the “Dougie”: In the final years of the 20th century, the primary habitat of Third Coast rap was centered around the Texas Gulf coast, featuring artists like UGK and Fat Pat. After near-extinction at the hands of predatory New Orleans and Atlanta hip-hop populations in the early 2000s, the surviving subspecies were forced to retreat to habitats like Dallas. In 2007, a local rapper by the name of Lil Wil memetically recombined the influence of beatboxer Doug E. Fresh with some regional sway dance moves to create the Dougie. A single occurrence of genetic flow in the form of a Texas Southern student visiting home introduced the Dougie to Inglewood, CA’s Cali Swag District. Possessing high fitness and with minimal competition for resources, “Teach Me How To Dougie” has quickly dominated the hip-hop ecosystem.
The Guardian laid out the Dougie in four parts, in about the squarest form imaginable. Let’s use that breakdown to consider the science behind the dance.
1. Bend your legs slightly at the knees, and bounce lightly from one leg to the other.
To bounce like this, you need bipedalism, and to be bipedal you need strong knees. The development of “habitual bipedalism”, the tendency of a species to walk almost exclusively on two limbs, occurred in hominins at least 3 million years ago. We know in part this thanks to the famous Lucy fossil, an Australopithecus afarensis specimen found in 1974 in eastern Africa. Although species like chimpanzees can attain bipedalism over short distances, as could earlier human ancestors, Lucy’s knee and lower leg bones show broad, enlarged joints that could support weight on two legs over long distances. Human knees also angle inward slightly compared to the hip joint, giving us greater balance and the ability to attain a certain degree of “swagger”.
2. Lean casually with your shoulders, put your arms out in front, and swing them gently from side to side, twisting your elbows like you're turning a steering wheel.
Likewise, to swing and twist your arms, you need a very particular kind of shoulder construction. The evolution of the human shoulder and arm joints were arguably as critical to our advancement as bipedalism. Our shoulder joint is capable of an amazing range of motions, from delicately painting the overhead frescoes of the Sistine Chapel to creating the enormous torque required to hurl a 100-mph fastball. If you look at the shoulder joint in early primates, it points nearly straight up, perfect for hanging in trees and using the arm as a mode of arboreal transportation.
As our ancestors left the trees, the joint moved outward from the rib cage and rotated forward over time. This allowed us to carry our arms out in front of our bodies and apply added dexterity to creating tools. That’s where it gets really interesting. Our shoulder joint’s range of motion became a nearly full circle, followed by a locking elbow and a whip-like wrist. These let us not only preserve detailed movements in our hands (more to come on that later), but also develop a powerful appendage for throwing. As recently as 500,000 years ago, our outboard, front-facing shoulder led to the invention of deadly tools like the spear and atlatl, the latter of which can hurl deadly darts the length of a football field.
3. Run your hands briskly through your hair, one after the other.
It’s no secret that dancing, in human culture and in the animal kingdom, is often a prologue to mating activity. As part of the difficult process of picking a potential mate, females often assess the vigor and biological fitness of a male by observing courtship displays. Likewise, in species like emperor penguins, there is a mutual courtship full of intricate and repetitive choreography such as bobbing the head and craning necks into an embrace of familiarity. It’s not a huge jump to believe that in humans' intricate coordinated dances, drawing attention to groomed hair or confident display of one’s “swagger” could be part of a similar ritual.
4. Apply your own variations. Lil' Wil, for instance, often crimps the shoulders of his shirts.
While evolution alone does not provide very compelling reasoning behind the wearing of shirts, it says a lot about our ability to crimp the shoulders (often seen in the “Dirt Off Ya _____” variation). Herein lies the marvel of the human thumb. One theory places the beginnings of the opposable primate thumb even earlier than bipedalism and the forward rotation of our shoulder joint, while other theories place the development of the human hand occurring after the advent of basic tools and upright gait.
It’s interesting that the formation of the modern hand, a form delicate enough to master neurosurgery and powerful enough to cling to ragged cliffs in the face of death, could have been a driving force behind our descent from the trees. Combined with a brain that could master the building of intricate tools and a body that could carry those tools over long distances, the development of a precision gripping appendage would have been an immense advantage in finding and killing food over the brute force techniques of other human ancestors. Just try picking a berry or removing the honey from a beehive with your foot. The thumb expanded the productivity of hominins more powerfully than perhaps any other development save the brain.
So there you have it. There are some that think our tendency to dance in ritualistic formations to songs like “Teach Me How To Dougie” put us closer to sheep than apes on the evolutionary ladder. But without this particular course human evolution, we wouldn’t have the music or the ability to dance to it. Of course, maybe the fact that some of us couldn’t do the Dougie if the species depended on it shows that human evolution moves forever on, and without a little swag you’ll get left behind.