your FACE

 

The human mind is prone to identifying recognizable shapes in whatever we are looking at. I’m always reminded of this when I watch those ghost shows and they show the picture someone took of a mirror in which there is supposedly the face of a man who killed himself in the house and continues to haunt it. They will draw a little red circle around the figure and zoom in on it. “Can you see the apparition?” the host will ask.

“NO,” I reply sassily through a mouthful of barbeque chips from my couch. I see a blob of discoloration in the photo in which there are two darker areas that could be mistaken for eyes, in the very loosest sense. A human face I see not. But I remind myself it is only natural to recognize the familiar. And the arrangement of eyes, a mouth, and a nose on a head on top of a body is certainly familiar. We see it all throughout Animalia. Have you ever stopped to think why it is that so many animals are built so similarly? There has to be a reason…

Eyes and a mouth on a head, followed by the rest of the body containing vital organs, off of which there may or may not be limbs. Fish, mammals, reptiles, amphibians, and birds share this blueprint. They are all distinct and sometimes dramatically different lineages, making this similarity worth investigating. As with many evolutionary inquiries, let’s start where they all originate…. a common ancestor.

Way back when the ocean was still the simmering pot of animal origins, sponges emerged as the first critters. They did not really have any body plan- they are haphazard and could grow to be really any shape.

Sponges have no body symmetry (Wikicommons)

Next came jellies- which certainly have a body plan. They have radial symmetry- meaning that they are organized in a circle.

Jellies have radial body symmetry (Wikicommons)

The next step up in body planning came bilateral symmetry. And what a coincidence, the rest of the animal kingdom should be dubbed Bilateria. Here is where we start seeing critters like early worms… which were unique in that they were the first to have “ends”- a front end and a back end with which to process food unidirectionally.

Imagine you are an early worm, really more like a living tube, swimming around. You don’t have eyes or any other sensory mechanisms but the most very basic sense of touch. This makes you an easy target, as well as an inefficient hunter. So let’s add some sensory organs. You name the place that they would be most beneficial…

Did you say head? If yes, you would be right. The most advantageous sensory placement would be at your front end so that you can tell what you’re headed towards, or into, before the rest of your body proceeds and is eaten or injured. Here, I flashback to how many times I’ve swum into the end of the pool because my primary sense, sight, was compromised by my overwhelming fear to open my eyes underwater…

The accumulation of sensory perception on an organism’s “front end” is one of the most profound evolutionary steps taken in the path to modern-day vertebrates (fish, amphibians, reptiles, birds, and mammals). It is called cephalization, which is Latin for “head development." Cephalization continued over the next couple hundred million years making increasingly complex animals that all share the same basic blueprint.

Where an animal has the most sensory perception would be an ideal spot for a feeding structure, oh say, like jaws. So, jaws were the next step. Well in that case, teeth would make it easier to capture prey, so teeth emerged. This produced an increased ability to hunt, which necessitated more mobility and agility. Enter rudimentary limbs. Then when life began to emerge from the water, air-breathing became necessary. So nasal openings (nares) appeared near the other respiratory structure- the mouth- so they could both stick out of the water at the same time. We’re getting pretty darn close to the thing we might refer to as a face…

When you’re brushing your teeth tonight and looking in the mirror, look at your face. I mean, really look at it. We’ve come a long way since being worms.

This faced worm is SO. WRONG. (co.marion.or.us)