There are a few theories on how the universe, the earth and life itself came about. There is evolution:
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes that are passed on from parent to offspring during reproduction. Different characteristics tend to exist within any given population as a result of mutations, genetic recombination and other sources of genetic variation. Evolution occurs when evolutionary processes such as natural selection (including sexual selection) and genetic drift act on these variations, resulting in certain characteristics becoming more common or rare within a population.
[Source: Wikipedia: Evolution].
There is also Creationism:
A doctrine or theory holding that matter, the various forms of life, and the world were created by God out of nothing and usually in the way described in Genesis.
I think that there are other beliefs as well, but right now, I don’t remember what they are, and I am discussing these two at the moment. I will discuss both, but will have to do a few posts in Parts. In this post, we will look at a part of the human body and see if there is evidence of evolution or design and creation in it.
The following is copied out from a book By Design written by Dr. Jonathan Sarfati. It is discussing the eye.
One of the most important senses is sight: it is our main means of sensing objects at a distance and quickly analyzing a wide area of our surroundings. The organ of sight is of course the eye, and this has long been popular as a design argument. This chapter shows how eyes both parallel our own optical instruments, and surpass them. New discoveries of the information processing in the eye itself, before the brain even receives the image, add to the complexity. Also, there are a number of very different ways that organisms form images of their surroundings. Finally, evolutionary scenarios are addressed.
EYES AND CAMERAS
William Paley, in his classic Natural Theology, compared the eye to obviously designed instruments such as the telescope and camera. Their function is to produce an image, where every point has a one-to-one correspondence with a point on the object. If one point on the object links to more than one point on the image, the image is blurred.
In a camera, there is an aperture to admit light, an iris diaphragm that can change the size of the hole to control the amount of light entering, a lens to focus the light, and the film to capture the image. Similarly, our eye has a pupil to admit light, an iris to enlarge or contract the pupil to control the amount of light, a lens to focus the light on the retina, which is full of photoelectric cells that convert the image to electrical signals. The lenses are somewhat different; the camera focuses (varies the focal length) by moving the rigid lens, while our lens has a fixed position and its shape is changed to vary the focal length.
A simpler design is the pinhole camera. This achieves the one-to-one correspondence simply because the hole is tiny enough so that light from a point on the object is in a straight line only to one point on the screen. This phenomenon has been known since ancient times – Aristotle (384 – 322 BC) and Euclid (fl. 300 BC) wrote about the sharper images seen through naturally occurring tiny holes, such as the slits in wicker baskets.
However, because the tiny hole cuts out so much light, the pinhole camera requires bright light. Enlarging the hole to admit more light blurs the image, by allowing light from one point to travel to more than one point on the screen. Hence the camera and eye combine variable opening with a variable lens.
However, as will be seen, the eye has very many complex features that leave the camera far behind. After all, the eye must also be able to repair itself and be connected to an information processing system. Also, the living world reveals many ingenious solutions both to the problem of forming a clear image, and processing the information.
The next section will cover some of the design features of the individual components of the eye; followed by some case studies of design in nature; and concludes with analysis of evolutionary scenarios.
THE EYE’S COMPONENTS
Cornea: amazing transparency
Essential for the eye to work is the transparent window. Not surprisingly, this is easy to overlook, since we take it so much for granted. However, it is not so easy to make something highly transparent from biological materials. It is especially important, because the cornea also provides about 2/3 of the focusing, while the lens provides only 1/3, but this is variable while the cornea is fixed.
The cornea is of a unique tissue type: it has no blood supply, so nutrients are supplied by the tears. It obtains its oxygen by direct contact with the air – this is why contact lenses should be permeable to oxygen. It has one of the highest nerve densities of any tissue in the body, hence its great sensitivity to touch.
The best explanation for the cornea’s transparency is diffraction theory, which shows that light is not scattered if the refractive index doesn’t vary over distances more than half the wavelength of light. This in turn requires a certain very finely organized structure of the corneal fibres, which in turn requires complicated chemical pumps to make sure there is exactly the right water content. This ceases at death; hence the eyes then become cloudy.
Interrupting the quote with a quick thought: is that possible by evolution, happening over millions of years? Or does this suggest that it was all made at the same time through creation? Now, back to the book:
Many evolutionary accounts, starting with Darwin, basically commence by saying, ‘Assume a light-sensitive cell’. However, Behe has shown that even a ‘simple’ light-sensitive spot requires a dazzling array of biochemicals in the right place and time to function. He states that each of its ‘cells makes the complexity of a motorcycle or television set look paltry in comparison’. His following description, although written for a semi-popular audience, describes a small part of the eye’s complexity:
‘When light first strikes the retina a photon interacts with a molecule called 11-cis-retinal, which rearranges within picoseconds to trans-retinal. (A picosecond [10−12 sec] is about the time it takes light to travel the breadth of a single human hair.) The change in the shape of the retinal molecule forces a change in the shape of the protein, rhodopsin, to which the retinal is tightly bound. The protein’s metamorphosis alters its behaviour. Now called metarhodopsin II, the protein sticks to another protein, called transducin. Before bumping into metarhodopsin II, transducin had tightly bound a small molecule called GDP. But when transducin interacts with metarhodopsin II, the GDP falls off, and a molecule called GTP binds to transducin. (GTP is closely related to, but different from, GDP.)
‘GTP-transducin-metarhodopsin II now binds to a protein called phosphodiesterase, located in the inner membrane of the cell. When attached to metarhodopsin II and its entourage, the phosphodiesterase acquires the chemical ability to ‘cut’ a molecule called cGMP (a chemical relative of both GDP and GTP). Initially there are a lot of cGMP molecules in the cell, but the phosphodiesterase lowers its concentration, just as a pulled plug lowers the water level in a bathtub.’
The retina is a very thin layer composed of the photosensitive cells described above. It has a number of features that eclipse man-made devices, such as the photoelectric sensors used in digital cameras.
Super sensitivity and dynamic range
The retina can detect a single photon of light, so it’s impossible to improve on this sensitivity! More than that, the eye works marvellously in a wide variety of light intensities, i.e. from hardly any light to very bright light. In technical terms, it has a dynamic range of 10 billion (1010) to one; that is, it will still work well in an intensity of 10 billion photons. Modern photographic film has a dynamic range of only 1,000 to one.
Even specialist equipment hasn’t anywhere near the dynamic range of the eye, and I have considerable experience in state-of-the-art supersensitive photomultipliers. My Ph.D. thesis and published papers in secular journals largely involve a technique called Raman spectroscopy, which analyses extremely weak scattering at a slightly different frequency from that of the incident laser radiation. The major equipment hazard from Raman spectroscopists is scanning at the incident frequency – the still weak Rayleigh scattering at the same frequency would destroy the photomultiplier (the newer ones have an automatic shut-off). I managed to safely scan the Rayleigh line (for calibration) only by using filters to reduce the intensity of light entering the photomultiplier by a factor of 107 to 108 . But having to take such extreme precautions made me envious and admiring of the way the eye is so brilliantly designed to cope with a far wider range of intensities.
So how does it work? When you emerge from a darkened room out into bright sunlight, muscles in your iris automatically shrink the pupil, cutting down the amount of light entering the eye. There is also a blink reflex.
But the biochemists Craig Montell and Seung-Jae Lee have discovered that there is also biochemical machinery involved, not just the large-scale motion of the iris and eyelids. They examined fruit fly eyes, which have similar proteins and light detector cells to ours. These cells have the light-detecting proteins in one end of the cell. But another protein, called arrestin, is moved around in the cell in response to light, it is shuttled so that it can bind and ‘calm’ the light-detecting protein.
The arrestin doesn’t just drift into place. Rather, it is moved quickly by a motor protein, myosin, along ‘train tracks’ of the cell’s internal skeleton. The myosin and arrestin are ‘glued’ together with sticky fats called phosphoinositides.
Dr Montell explains, ‘For the cell to properly adapt to bright light, arrestin needs to move. If it doesn’t, the cell remains as sensitive to light as it was when it was dark.
And this latest research shows the intricate machinery behind the eye’s dynamic range – a motor, glue, ‘calmer’ and internal ‘train tracks’. All these features would need to be present and coordinated; otherwise, the eye would be blinded by bright light. Thus mutations and natural selection could not build this system up step-by-step, since each step by itself has no advantage over the previous step, until all is complete.
Another amazing design feature of the retina is the signal processing that occurs even before the information is transmitted to the brain. This occurs in the retinal layers between the ganglion cells and the photoreceptors. For example, a process called edge extraction enhances the recognition of edges of objects. John Stevens, an associate professor of physiology and biomedical engineering, pointed out that it would take ‘a minimum of a hundred years of Cray [supercomputer] time to simulate what takes place in your eye many times each second.’ And the retina’s analog computing needs far less power than the digital supercomputers and is elegant in its simplicity. Once again, the eye outstrips any human technology, this time in another area.
Indeed, research into the retina shows that the 12 different types of ganglion cells send 12 different ‘movies’, i.e. distinct representations of a visual scene, to the brain for final interpretation. One movie is mainly a line drawing of the edges of the objects, and others deal only in motion in a specific direction, and still others transmit information about shadows and highlights. How the brain intergrates these movies into the final picture is still a subject of intense investigation. Understanding this would help researchers trying to design artificial light sensors to help the blind to see.
Okay, so I would do more, but it becoming long. I am thinking of doing more on the eye in another post soon. I hope you found this interesting and intriguing as much as I did. Until next time.