The Eyes Have It! Evolution’s Witness: How Eyes Evolved

Posted September 30th, 2011 at 10:49 pm (UTC-4)



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…

Audio clip: Adobe Flash Player (version 9 or above) is required to play this audio clip. Download the latest version here. You also need to have JavaScript enabled in your browser.

Other stories we cover on the “Science World” radio program this week include:

Rick Pantaleo
Rick Pantaleo maintains the Science World blog and writes stories for VOA’s web and radio on a variety of science, technology and health topics. He also occasionally appears on various VOA programs to talk about the latest scientific news. Rick joined VOA in 1992 after a 20 year career in commercial broadcasting.

6 responses to “The Eyes Have It! Evolution’s Witness: How Eyes Evolved”

  1. Scott says:

    This perhaps is the poorest attempt for the evolution community. How it somehow did this and that. Somehow? When you finally get to the top of the hill of knowledge, you will find that the theologians have been waiting many years for you to catch up. Amazed that some scientists get paid to do the cutting edge fantasy science fiction you do. I guess it’s a living but not one that will not bring you the inner joy of acknowledging the Occam’s Razor approach to science.

    “Pluralitas non est ponenda sine neccesitate”
    “Frustra fit per plura quod potest fieri per pauciora”
    “Entia non sunt multiplicanda praeter necessitatem”

  2. Jason says:

    This article is a classic example of how Evolution has become a religion or dogma for atheists. The title of this article, like much of Evolution “Science” is completely deceptive. There is nothing in this article to support or witness evolution. It only talks about current eye forms and how they work. I am amazed at how much deception there is by the scientific community about the problems with the Theory of Evolution yet at the same time, thanks to the education system, most non-scientific people think it is the Law of Evolution. Unfortunately science has been seriously degraded by what has become a religious dogma.

  3. Sahil Maqsudy says:

    If there is no evolution there will not be a witness. Not a damn evolution occured for mankind, we are what we were( if you think thats not true prove it). There is EVOLUTION SCIENCE but we cant understand it; The information on the top cannot proof anything about the EYE EVOLUTION;

  4. Mark J says:

    It’s complete nonsense article without any actual proof. Modern science is full of cut & paste.

  5. Elisak Finch says:

    We are the raze of God,we came from human raze.Elisa Finch

  6. Jim says:

    The problem of how eyes developed is a major impasse to the Darwinian theory of evolution by natural selection. We humans can make many entirely useless experimental models when designing a new device, but this is not possible for natural selection, for each step must confer some advantage upon its owner, to be selected and transmitted through the generations. But what use is a half-made lens? What use is a lens giving an image, if there is no nervous system to interpret the information? How could a visual nervous system come about before there was an eye to give it information? In evolution there can be no master plan, no looking ahead to form structures which, though useless now, will come to have importance when other structures are sufficiently developed. Something had to plan all this in advance.