LXVII: A Little Extra

Evolution is a beautiful thing. Over the millennia, it has allowed each unique species to change itself to best be suited for survival in its environment. Every creature alive today exists because it was descended from the very best evolved members of its species.

However, sometimes species need to change faster than evolution can keep up, and they end up with a little bit extra. These useless yet harmless leftover bits that evolution hasn’t gotten rid of yet are known as “vestigial structures”. Whales, for example, have tiny little foot bones inside those big old flippers. Very cute.

Human vestigial structures are distinctly less cute, unfortunately. You’re probably familiar with the appendix, a useless little bit of large intestine that can get inflamed and burst with astonishing ease, flooding the body with dangerous and even deadly toxins. Once upon a time this often-removed tissue was an independent organ, crucial to the digestive process, but modern humans no longer need it, as so it has gradually shrunk and ceased to function over generations.

Another often-removed human vestigial structure is the wisdom teeth. These third molars erupt quite late relative to the other teeth, appear in early adulthood. In an age before dental hygiene, it was important to grow some new molars as the other ones rotted out, but modern grooming practices have led humans to keep most or all of their teeth throughout their lives, meaning that wisdom teeth are often crowded out of the gums and prone to impaction and infection if not removed. Evolution works hard to clear out these now-harmful structures — many members of my family only have two wisdom teeth, and there are some familial lines among indigenous Mexicans documented as having no wisdom teeth at all.

Humans also evolved form creatures with tails, and our coccyx (the five fused vertebrae at the base of the spine) are a vestigial remnant of our long-lost tails. Our ears too possess multiple vestigial structures; about 10% of the population has a small point called the Darwin’s tubercle which is a remnant of our pointed primate ears, which once resembled those of a macaque. Our ears are also attached to several weak muscles, which were once strong enough to tilt and rotate our ears like horses do, but now are only strong enough to make a very underwhelming party trick. Even our highly advanced and delicate eyes have extra parts. The plica semilunaris, the goopy pink bit in the corner of the eye, is all that’s left of a long-lost third eyelid which protected our eyes from dust and debris without compromising our vision millennia ago. Our ability to curl our toes is leftover from our once-prehensile chimp-like feet. Some vestigial structures are present in only small portions of the human population, like the %5.6 of humans who have a supernumerary  nipple.

Evolution is pretty darn good at what it does, but sometimes it just can’t keep up. Humans are full of little extra bits that our species has long outgrown but evolution just hasn’t gotten on to removing yet. There’s some suspicion that one day our sense of smell will become obsolete since we no longer need to track prey or check wild plants for safety and freshness. Some humans like myself already display a congenitally diminished sense of smell. Either way, humans will keep on evolving, keep on moving forward and evolving to fit our new environment as it changes around us.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s