As the semester is getting rolling, and I am teaching Mendelian genetics in two courses this week, I want to link again to the invaluable “Myths of Human Genetics” website, from John McDonald at the University of Delaware.
McDonald has collated a series of human traits that have been used, at one time or another, to teach Mendelian inheritance in humans. None of them are Mendelian traits in reality, and many of them are demonstrably non-genetic in their etiology.
Some traits, such as tongue rolling, were originally described as fitting a simple genetic model, but later research revealed them to be more complicated. Other traits were shown from the very beginning to not fit the simple genetic model, but somehow textbook authors decided to ignore this. A quick search in the standard reference on human genetics, Online Mendelian Inheritance in Man (OMIM), makes it clear that most of these traits do not fit the simple genetic model. It is an embarrassment to the field of biology education that textbooks and lab manuals continue to perpetuate these myths.
Tongue rolling, hitchhiker’s thumb, asparagus urine – they’re all there, along with many references and citations to studies that show what scientists actually know about their inheritance.
I’m introducing students to a few more anthroposcopic traits than usual this semester, and it’s interesting what they come in already “knowing” about the inheritance of various traits. Thanks, High School Biology!