Human inventors often turn to nature for inspiration, like in designing the wings of a plane.

But how come there are no wheels or motors in nature? Animals have electricity, so they could have a bone-based propeller with magnetic material that they rotate, right?

Perhaps the problem is that the wheel would have to be an independent, freely moving component, which would be too hard to service. Even if the organism could lick the propeller, the propeller would have to be a full-blown independent organism in order to do something with the nutrients.

Which leads me to the idea that nature isn't that modular. You can't pull out a liver and replace with another one without destroying the organism. Machines, you can power down, replace a part, and it's good to go.

What if life on other planets looks 90% like life on Earth?

1. Life starts a blob.
2. The blob develops motor skills.
3. Motor skills lead to advantages in an elongated form.
4. Consuming food happens at the point of first contact: the head.
5. Excrement naturally flows out the back, creating a digestive tract.
6. More sensors are needed at the place of first contact: the head.
7. Eyes evolve at the head to give foresight.
8. Stereoscopic vision becomes more useful, especially to predators.
9. Size matters and we see larger blobs.
10. Larger blobs require hardened internal support structures, or skeletons.
11. The organism evolves a bilateral symmetry around an up-down plane, since turning left and right are the same.
12. If the organism is in water, we'd see fins.

For a couple minutes, I stared at a bird flapping its tail feathers back and forth like it was struggling to scratch an itch. I then slipped into a vicarious state, where I was the bird with the same struggle. And then I felt a tingling at the base of my spine, like I was struggling to contract a muscle that I didn't know I had. The feeling reminded me of when I first learned to wiggle my ears, and how I used all my concentration to get a muscle to flex for its first time.

And then I wondered if I was tapping into some leftover nerve endings connected to my vestigial ape tailbone. I even had a few brief moments where I felt what I imagined amputees felt, that I was manipulating a phantom limb.