Hair and Flowers; Hands and Wings

Human hair is fascinating. At the base of a hair is a follicle—a little hole in your scalp or on your skin that’s perfect for planting a little bulb.

The bulb contains all the actively dividing cells. This is where new hair starts to grow. Inside the follicle, along with the bulb, you have a papilla—a cluster of blood vessels that supply nutrients and oxygen as the hair grows. There’s a gland that excretes oil to coat your hair, and another gland that helps it stand on its end from time to time.

The shaft is the part of the hair that grows out beyond your skin.

Likewise, if you want to plant a flower in your garden, you need to start by digging a little follicle—a hole in the ground that’s perfect for planting your little bulb.

The bulb of the flower contains all the actively dividing cells. Nutrients are supplied steadily from the bulb upward, as the flower begins to grow out of the ground. There are glands that protect the flower’s surface, and other glands that make the flower stand at attention (in the direction of light, for instance).

The shaft is the part of the flower that grows out beyond the ground.

What’s going on here? Is nature just lazy? Did hairs evolve from flowers?

This is called convergent evolution. When two unconnected species in nature solve a similar problem in a similar way, it’s often because there’s just no other way to solve the problem, or it’s just the most efficient way for a species to adapt.

A human version of this is when pyramids are built in Egypt and in Mesoamerica. Did ancient Egyptians cross the ocean to share their knowledge of geometry and architecture with the Olmecs, or is it more likely that stacking squares on top of one another is a very efficient way to build a tall structure?

The opposite effect can also happen in nature. Divergent evolution happens when one thing splits off into two things, and different species use those sexy new tools.

Take a look at your hand. See all those little bone segments?

Your forearm is made up of a radius and ulna, and they end at a set of carpal bones—your wrist—which connect to your metacarpals, which connect to your phalanges.

You can follow these bones by feeling where they are in your hand and wrist. Everywhere there’s a knuckle marks the beginning of a new bone.

Birds and bats have all of these bones, too. Over millions of years, they developed the ability to fly, leaving behind any potential for hands. Likewise, humans have developed the incredible ability to create tools, leaving behind any potential for wings.

Our hands evolved to be able to grab things and pick them up, and birds and bats evolved much longer finger-like bones that were no good for grabbing—but great for gliding and flying.

Flying is an interesting example of both convergent and divergent evolution. On one hand (pun intended!), forelimbs became sophisticated hands and wings, going off in two completely directions. At the same time, different species besides bats and birds solved the problem differently.

Birds and bats aren’t the only groups of animals to have solved the problem of flight. In fact, insects were flying hundreds of millions of years before bats or birds, or even flying dinosaurs.

Can you think of any examples of either convergent or divergent evolution today? Let’s keep this open to both the natural and human-made worlds.