Human eye with its weird blind spot at #14
Detecting light is useful
To aim leaves at the sun,
To orient when swimming,
To find, or hide, or run.
Sight drove the Cambrian explosion
Half a billion years ago,
A race of “see” with “be seen”
To tell a friend from foe.
From cells just photosensitive,
Many eyes were built.
Your eye is backwards, upside down,
But right-side out for squids.
A fruit fly has a compound eye,
A hundred little circuits.
A mollusk has a hundred eyes
To search the ocean currents.
The eye evolved before the brain,
For what’s a brain good for
Without a lot of inputs
To process in its core?
So you can think because you see
Reflections, motions, trends,
The beauty of our sunlit world
Through iris, nerve, and lens.
There’s grandeur in this view of life,
From so simple a beginning,
Endless forms most beautiful,
Life’s web continues spinning.
Recent reports on the Chitons sea mollusk with hundreds of eyes embedded in its shell got me thinking about the evolution of the eye – or, rather, eyes. That led me to a favorite quote from Charles Darwin, from the conclusion of On the Origin of Species (1859):
There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.
There are lots of articles on evolution of the eye. For example, here and here.
Kate's Science - Real and Fantastic 
Neat. Evolution works in many different ways. We think of it mostly in terms of species competition, but the concept includes random variation, selection advantage and applies to such diverse operations as cellular competition in tissues, and even ideas, or memes. We use it in oncology to give normal cells an advantage to outgrow the cancer cells.
LikeLiked by 1 person
Neat concept – I guess in some ways a single human body is a jungle all its own. And we want those cancer cells to be an endangered species!
LikeLike