According to an old proverb, the eyes are the windows of the soul. They’re also one of the most important accomplishments of evolution, nature’s perfect camera providing us with a vivid visual sense of the world around us.
However, did you ever wonder how the eye came to be? What caused the eye to be formed to begin with? How did it evolve and develop to fit the specific needs for all current and past species on Earth?
Thanks to the curiosity of an ophthalmology professor at the University of California, Davis, we can read all about it in a new book called “Evolution’s Witness: How Eyes Evolved”.
Dr. Ivan Schwab wanted to find out how animals were able to see. As he got further into his research, he realized he also wanted to learn about the origins of the eye itself and how it developed through years of evolution.
So how did it begin? What was the stimulating factor that set off what would become the eye? Dr. Schwab simply points to the sun and the energy its produces.
“The eye didn’t start as an eye as we know it, for sight,” he says.
Indeed, what would become the eye first started as the means for transferring the sun’s energy into energy for the cells.
“This was done by a variety of molecules… the best one is related to Vitamin A, the same vitamin you get from carrots or mangoes,” according to Dr. Schwab. “That particular chemical will transform the light rays of the sun into energy for the cell so that it can perform its internal mechanics.”
When the first eye, as we know it, appeared is kind of a guessing game, says Dr. Schwab, since the eye doesn’t fossilize most of the time due to its soft parts. The eye gradually evolved into an organ capable of seeing light and dark and perhaps some form.
Dr. Schwab imagines that the first real eye saw very poorly, registering blurry images and used, perhaps, to find where to capture energy or locate enemies.
Once eyes appeared, they evolved in different ways, developing into at least 10 to 12 varied forms. Each species’ eyes are developed into one that fits its specific niche.
One example is the the marine crustacean, the stomatopods, or mantis shrimp. Dr. Schwab says, since this creature tends to live near coral reefs, it has eyes with more color receptors than we have. As a result, they can see more colors than we can – 16 pigments compared to the three pigments humans can detect.
The human eye is referred to as camera-style eye since its mechanics resemble those of a film-loaded camera.
Dr. Schwab describes them as a sphere with a front element called the cornea. Another element is the lens, which does the focusing. The back of the eye, or retina, creates the visual image that is delivered to the brain.
Another type of eye style is the telescopic eye.
As an example, Dr. Schwab cites the “jumping spider.” Jumping spiders have excellent vision, with one of the highest acuities among invertebrates. Its eyes are small and compact, utilizing telephoto-type optics to maximize its vision.
Since this spider can’t move its eyes externally, like we can, it must do so internally.
“It’s like a raster scan on your TV,” says Dr. Schwab. “It lays out a line of dots, another line, another line, until it’s formed a whole image, but, of course, it does so rapidly.”
Dr. Schwab says that, although eyes will continue to evolve, the eyes of many species are already at a mature level so they’re not going to evolve much further in terms of the optics themselves. So where our eyes or vision will improve, speculates Dr. Schwab, is probably in the interpretation of the visual signals the eye produces.
Dr. Schwab, joins us this weekend on the “Science World” radio program to talk about his new book, the eye’s first appearance and its subsequent evolution and development.
>>>> Listen to the interview here…
Other stories we cover on the “Science World” radio program this week include:
- Warning sounded on dangers of arsenic in India’s groundwater
- Study: Female coffee drinkers are less depressed
- China launches first module of future space station
- South Korean weather forecasters tell you when you’ll catch a cold
- Reducing an invasive species while fighting hunger at the same time
- Whew! NASA finds fewer ‘planet-buster’ asteroids than predicted