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A common misconception is that Darwin suggested that something as complex as the eye could not have evolved through natural selection. While the misunderstanding often comes from an incomplete reading of his argument, we have long known that intermediate varieties of eyes (e.g., eyespots, cupped eyes, and complex camera-type eyes) exist in a variety of organisms. Eyes are so common that it was thought that they had evolved independently 40-60 times. More recent molecular work, however, has identified the role of Pax6 genes and their homologs in the formation of eyes during development. The basic information for eye formation appears to have been present in the common ancestor to all bilaterans, and perhaps may be more ancient than that. This interrupted case study examines the history of evidence for eye evolution from Darwin's initial postulates, through evidence of multiple intermediate forms, concluding in an examination of Pax6 homologs. The case is primarily for an introductory biology class but an additional section would be appropriate for upper-level evolution or developmental biology courses.

The eyes may be the windows to the soul, but they're also the keepers of all kinds of secrets-secrets our eye doctors are in on but we typically aren't. Those little tidbits of info our baby blues (or greens or browns) are hiding are actually chock-full of important details, not only about our eyes and vision, but about our overall health.

SciShow explains the genetics -- and physics -- behind why blue eyes are blue, and what the future may be for the trait. Spoiler alert: Blue eyes aren't really blue! SciShow explains!

Normally, male squirrel monkeys can't distinguish between red and green hues-they're what is called color-blind in humans. The South American Saimiri genus lacks a gene that allows color-sensitive cells in the eye, called cones, to differentiate red and green from gray. To these animals, other colors, such as blue, brown and orange, appear faded. But Sam was one of two males in the experimental group of a groundbreaking 2009 ophthalmological study conducted at the Washington National Primate Research Center in Seattle. Husband-and-wife vision researchers Jay and Maureen Neitz injected a viral vector behind the retinas, the part of the eye that responds to color, of Sam and his simian lab partner, Dalton. The virus contained the genetic code in human eyes for red pigment, giving the monkeys an extra class of cone photoreceptor.

When babies are born, their eyes and hair are one color, but change within the first few years of their life! Why do hair and eye colors change? Trace explains the process of inheriting certain traits from your parents, and discusses why the colors change!

This indicates that the mutation originated in just one person who became the ancestor of all subsequent people in the world with blue eyes, according to a study by Professor Hans Eiberg and colleagues at the University of Copenhagen.

A decade-old technique that allows researchers to control brain function in lab animals could partially restore sight to the blind. In a trial sponsored by RetroSense Therapeutics, a startup company in Ann Arbor, Michigan, doctors will inject a harmless virus loaded with DNA from photoreceptive algae into the eyes of 15 patients suffering from retinitis pigmentosa. The experimental procedure represents the first human test of optogenetics, which is a technique that genetically modifies neurons to make them responsive to light. Doctors from the Retina Foundation of the Southwest will perform the procedure, and attempt to transfer the job duties of photoreceptor cells to different cells in the eye to restore sight.

Off with their heads. Light-averse planarian flatworms, known for their incredible ability to regenerate lost body parts, shy away from light even after they have been decapitated. This suggests they have evolved a second way to respond to light that doesn't involve eyes. Planarian flatworms, which often live in dark, watery environments shielded from direct light, don't have complex eyes like we do. But many do have two lensless, primitive "eyespots" on their heads that can detect the intensity of light.

We see color because of specialized light-sensing cells in our eyes called cones. One type, L-cones, sees the reds of strawberries and fire trucks; M-cones detect green leaves, and S-cones let us know the sky is blue. But vision scientists have now discovered that not all cones sense color (see video).

4 min We tend to think of blindness as something you're born with, but with certain genetic diseases, it can actually develop when you're a kid, or even when you're an adult. But could blind eyes possibly regenerate? David Davila explains how the zebrafish's amazing regenerative retinas are causing scientists to investigate that very question.

Jackson would eventually be diagnosed with the rare genetic eye disease Autosomal Dominant Neovascular Inflammatory Vitreoretinopathy (ADNIV), which eventually causes blindness in those who carry the gene.

3 minute video Each father and mother pass down traits to their children, who inherit combinations of their dominant or recessive alleles. But how do we know so much about genetics today? Hortensia Jiménez Díaz explains how studying pea plants revealed why you may have blue eyes.

The next time you look in a mirror, think about this: In many ways you're more microbe than human. There are 10 times more cells from microorganisms like bacteria and fungi in and on our bodies than there are human cells. But these tiny compatriots are invisible to the naked eye. So we asked artist Ben Arthur to give us a guided tour of the rich universe of the human microbiome.

Researchers analysed the genomes of 51 individuals who lived between 45,000 years ago and 7,000 years ago. The results reveal details about the biology of these early inhabitants, such as skin and eye colour, and how different populations were related. It also shows that Neanderthal ancestry in Europeans has been shrinking over time, perhaps due to natural selection. The study in Nature journal shines a torchlight over some 40,000 years of prehistory, showing that ancient patterns of migration were just as complex as those in more recent times.

Even if you feel like you have a pretty good hold on what deoxyribonucleic acid is and how it works, you will still appreciate this video. It might not add greatly to your depth of understanding, but it will please your eyes, tickle your brain, and remind you about the many wonders of the double helix.

If you think of your dog as your "fur baby," science has your back. New research shows that when our canine pals stare into our eyes, they activate the same hormonal response that bonds us to human infants. The study-the first to show this hormonal bonding effect between humans and another species-may help explain how dogs became our companions thousands of years ago.

4:01 video Ever wonder what it looks like from a birds-eye-view? Hank explains they see more than you think!

Cells are everywhere. Even though most can't be seen with the naked eye, they make up every living thing. Your body alone contains trillions of cells. Students will be able to explain why cells are small and calculate a cell's surface area to volume ratio.

Fascinating narrative science that explores the next frontier in medicine and genetics through the very personal prism of the children and families gene therapy has touched. Eight-year-old Corey Haas was nearly blind from a hereditary disorder when his sight was restored through a delicate procedure that made medical history.  Like something from a science fiction novel, doctors carefully introduced viruses bearing healing genes into Corey's eyes-a few days later, Corey could see, his sight restored by gene therapy.

When you leave the house, does your dog or cat even remember you? Read More: A Rat's Tenacious Memory http://www.indiana.edu/~rcapub/v17n1/... "In the wild, rats scramble over the network of pathways they have created, combing their surroundings for food, water, mates, and shelter. Their movements may seem automatic to the untrained eye, simply a reflexive pattern. Decades ago, however, researchers established that rats know where they are going and remember where they have been."