Index to Creationist Claims,  edited by Mark Isaak,    Copyright © 2007

Previous Claim: CB921   |   List of Claims   |   Next Claim: CB921.2

---

Claim CB921.1:

Source:

Response:

1. Half an eye is useful for vision. Many organisms have eyes that lack some features of human eyes. Examples include the following:
   • Dinoflagellates are single cells, but they have eyespots that allow them to orient toward light sources (Kreimer 1999).
   • Starfish and flatworms have eyecups; clustering light-sensitive cells in a depression allows animals to more accurately detect the direction from which the light is coming from.
   • Most mammals have only two kinds of color photoreceptors, allowing less color discrimination than most humans have. Some deep-sea fish can see only black and white.
   
   Visual prosthetics (bionic eyes) with as few as 16 pixels are found to be very useful by people who had become blind (Wickelgren 2006, Fildes 2007).
   
   
2. Humans themselves have far from perfect vision:
   
   
   • Humans see in only three colors. Some fish see five. (A very few women are tetrachromats; they have four types of color receptors; Zorpette 2000.)
   • Humans cannot see into the ultraviolet, like bees.
   • Humans cannot see infrared, like pit vipers and some fish.
   • Humans cannot easily detect the polarization of light, like ants and bees.
   • Humans can see only in front of themselves. Many other animals have far greater fields of view; examples are sandpipers and dragonflies.
   • Human vision is poor in the dark; the vision of owls is 50 to 100 times more sensitive in darkness. Some deep-sea shrimp can detect light hundreds of times fainter still (Zimmer 1996).
   • The range of distances on which one may focus is measured in diopters. A human's range is about fourteen diopters as children, dropping to about one diopter in old age. Some diving birds have a fifty-diopter range.
   • The resolution of human vision is not as good as that of hawks. A hawk's vision is about 20/5; they can see an object from about four times the distance of a human with 20/20 vision.
   • Humans have a blind spot caused by the wiring of their retinas; octopuses do not.
   • The Four-eyed Fish (Anableps microlepis) has eyes divided in half horizontally, each eye with two separate optical systems for seeing in and out of the water simultaneously. Whirligig beetles (family Gyrinidae) also have divided compound eyes, so one pair of eyes sees underwater and a separate pair sees above.
   • The vision of most humans is poor underwater. The penguin has a flat cornea, allowing it to see clearly underwater. Interestingly, the Moken (sea gypsies) from Southeast Asia have better underwater vision than other people (Gislén et al. 2003).
   • Humans close their eyes to blink, unlike some snakes.
   • Chameleons and seahorses can move each eye independent of the other.
   
   If you want to know what use is half an eye, ask yourself how you survive with much less than half of what eyes are capable of.

Links:

References: