Don't it Make My Brown Eyes Blue

We focus quite a bit on eye color. People find certain eye colors more attractive than others. Whether or not you can remember someone’s eye color is used as a gauge of how well you know them (much to the chagrin of men). In short, we have come to consider variation in eye color as an important part of who we are. Thus, it’s hard to imagine a time when everyone had the same color eyes: brown.

That’s the image a group of researchers from the University of Copenhagen are asking us to conjure up. They have recently reported finding a genetic mutation that occurred 6,000-10,000 years ago, which resulted in the first pair of blue eyes. The mutation, they assert, affected a gene called OCA2. This gene encodes for a protein involved in the production of melanin, a polymer responsible for the pigmentation of our skin, hair, and eyes. The mutation causes less melanin to be produced in the iris. This, according to the research group, is what caused eyes to become diluted from a universal brown, to blue.

How the heck could they know this, you might ask? The answer is by studying mitochondrial DNA (mtDNA). Every cell in our body contains DNA within its nucleus. This nuclear DNA is the type most of us are familiar with, and the type used for paternity testing, forensics, disease screening, etc. But mtDNA is a less publicized form of DNA that resides in the mitochondria, organelles outside the nucleus that provide energy for the cell (remember the “powerhouse of the cell” from grade school?). When two people procreate, their nuclear DNA is mixed, resulting in offspring that possess a combination of their genetic codes. The mtDNA from the father, however, never makes it into the egg with the sperm. It is left behind, and only the mother’s mtDNA is passed on. Thus, one’s mtDNA represents their pure line of maternal ancestry.

Geneticists can use mtDNA to obtain information about that ancestry back through many generations. To do this, they examine the mtDNA and compare it with samples from other individuals. They can then create a “family tree” of mtDNA. This was how scientists inferred the most recent common ancestor of humans was a woman from Africa (often referred to as “Mitochondrial Eve”).

The team from the University of Copenhagen studied the mtDNA of a group of 800 people from all over the world to estimate the time of the eye color mutation. A member of the team, Hans Eiberg, described the mutation as neither positive nor negative. This means it didn’t create a selective advantage or deficiency, but was simply the result of genetic shuffling. To me this can’t be said with conviction, however, as blue eyes may have possessed an advantage in sexual selection (meaning they were found attractive, leading to the trait being passed down more often through procreation). Or maybe I’m just inclined to think that way because I have blue eyes…

YOUR BRAIN, EXPLAINED

Sleep. Memory. Pleasure. Fear. Language. We experience these things every day, but how do our brains create them? Your Brain, Explained is a personal tour around your gray matter. Building on neuroscientist Marc Dingman’s popular YouTube series, 2-Minute Neuroscience, this is a friendly, engaging introduction to the human brain and its quirks using real-life examples and Dingman’s own, hand-drawn illustrations.

Reading like a collection of detective stories, Your Brain, Explained combines classic cases in the history of neurology with findings stemming from the latest techniques used to probe the brain’s secrets. - Stanley Finger, PhD, Professor Emeritus of Psychological & Brain Sciences, Washington University (St. Louis), author, Origins of Neuroscience
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An informative, accessible and engaging book for anyone who has even the slightest interest in how the brain works, but doesn’t know where to begin. - Dean Burnett, PhD, author, Happy Brain and Idiot Brain
...a highly readable and accessible introduction to the operation of the brain and current issues in neuroscience... a wonderful introduction to the field. - Frank Amthor, PhD, Professor of Psychology, The University of Alabama at Birmingham, author, Neuroscience for Dummies

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BIZARRE

This book shows a whole other side of how brains work by examining the most unusual behavior to emerge from the human brain. In it, you'll meet a woman who is afraid to take a shower because she fears her body will slip down the drain, a man who is convinced he is a cat, a woman who compulsively snacks on cigarette ashes, and many other unusual cases. As uncommon as they are, each of these cases has something important to teach us about everyday brain function.

Bizarre is a collection of stories of how the brain can create zombies, cult members, extra limbs, instant musicians, and overnight accents, to name a few of the mind-scratching cases. After reading this book, you will walk away with a greater appreciation for this bizarre organ. If you are a fan of Oliver Sacks' books, you're certain to be a fan of Dingman's Bizarre. - Allison M. Wilck, PhD, Researcher and Assistant Professor of Psychology, Eastern Mennonite University
Through case studies of both exceptional people as well as those with disorders, Bizarre takes us on a fascinating journey in which we learn more about what is going on in our skull. - William J. Ray, PhD, Emeritus Professor of Psychology, The Pennsylvania State University, author, Abnormal Psychology
A unique combination of storytelling and scientific explanation that appeals to the brain novice, the trained neuroscientist, and everyone in between. Dingman explores some of the most fascinating and mysterious expressions of human behavior in a style that is case study, dramatic novel, and introductory textbook all rolled into one. - Alison Kreisler, PhD, Neuroscience Instructor, California State University, San Marcos
Dingman brings the history of neuroscience back to life and weaves in contemporary ideas seamlessly. Readers will come along for the ride of a really interesting read and accidentally learn some neuroscience along the way. - Erin Kirschmann, PhD, Associate Professor of Psychology & Counseling, Immaculata University