Unfortunately Mr. Minshall your argument fails to recognize multifactorial traits, traits which result from combinations of genes. Not every human trait is dictated by a single gene. Your argument also fails to recognize that genetics is a science of probabilities rather than absolutes. There isn't a little sign that pops up and says "blue eyes" or "black skin" but rather a series a genetic patterns common to a preponderance of people with a common trait. So even though a preponderance of left handed people have a similar genetic pattern there are also a few right handed people with the same genetic patterns. In gender and sexuality the preponderance of people with genetic pattern "XX" are female and the preponderance of people with the genetic pattern "XY" are males ... except with every group in a probability there are exceptions. There also permutations such as people with the genetic pattern "XXY", "XYY" and others. The only thing absolute about genetics is there are no absolutes!