Los tonos de los ojos marrones y lo que los hace únicos

Brown eyes are the oldest eye color on Earth, and seven or eight out of every ten people alive today have them. Almost everyone was taught that brown is just brown. Not honey, not copper, not amber, just one plain shade. The truth is a whole spectrum, from pale gold to almost black, and every shade has its own biology and its own story. In this video we go through eight types of brown eyes and see what makes each one different. Honey. Cognac. Chestnut. Russet. Chocolate. Black-brown. Hazel. Amber. The difference is not a different color. It is the same pigment in different amounts. Less melanin, more scattered light. More melanin, a deeper shade. And a second pigment, the same one behind red hair, that adds copper and gold. Why are brown eyes everywhere? Melanin in the iris works like thick curtains on a window, absorbing most of the light before it goes deeper into the eye, the same way dark skin protects the body under the equatorial sun. In two thousand eight, Danish geneticist Hans Eiberg traced blue eyes to a single mutation that appeared roughly six to ten thousand years ago, and before that nearly every human had brown eyes. The copper glow in cognac and russet eyes comes from pheomelanin, the pigment linked to the MC1R gene behind red hair and freckles. And in two thousand thirteen, Karel Kleisner and his team at Charles University in Prague found that brown-eyed faces were rated as more trustworthy, until they swapped the eye color on the photos and discovered it was really about the shape of the face. We close with amber, the rarest shade of the brown spectrum. It is the eye color of wolves, eagles and owls, and it can skip a whole generation in a family before it appears again in a grandchild. What type of brown eyes do you have? What color are your parents' eyes? And was anyone in your family born with eyes that changed color in their first years of life? Tell us in the comments. We read every one. DISCLAIMER: This video is for educational and entertainment purposes only and is not medical advice. If you notice a sudden change in the color of one eye, or any change in your vision, please see an ophthalmologist or another qualified doctor. The figures in this video come from population studies and describe tendencies across large groups, not any single person. Neither your eye color nor your surname can tell you anything definite about your own genes. For serious ancestry research, consult a professional genealogist or a genetic counselor. Subscribe for more science explained simply. Stay curious. #ADN #ojosmarrones #ojoscafés #colordeojos #genética #ciencia #datoscuriosos