I remember wondering about eyes when I was a university student. I understood the idea of evolution, and accepted that it was the best explanation for how life appeared and spread across the Earth. But I couldn’t imagine how eyes could have evolved. If each evolutionary change was a small step, how could something as complex as an eye appear? How useful is half an eye, or a quarter of an eye?
Luckily, there are scientists who study these things. There are stages in the development of eyes, from more simple to more complex and effective (and sometimes back again, such as creatures that start to live underground). We can feel sunlight on our skin. Perhaps the eye started with a patch of skin that was just a little bit more sensitive at finding the sunlight.
I heard about some new research about the evolution of eyes this week. Scientists have found an ancient life form, which lived before the evolution of fish. It had a worm-like body and one simple eye in the top of its head to help it detect sunlight. The scientists believe that later animals such as fish evolved from these creatures. So if you travel back far enough into our evolutionary past, there was a time when we were born with one eye, not two.
The story also made me think of the English expression, “I have eyes in the back of my head.”
Parents often say this to their naughty children. It means, “I can see you, even when you think that you are out of my line of sight.”
“Stop reading manga when you are supposed to be doing your homework! I have eyes in the back of my head.”
