I think for various reasons the gene for penis size is located on the X chromosome, and follows the X chromosome inheritance patter, i.e., the son's penis size is dependent on the mother's X, coming from her paternal or maternal line. Because if it were the other way around, that penis size is dependent on the father's gene, the Y , then penis size would be always increasing, to a homogenous size. Because females, in choosing a mate would more often than not select the male with the larger penis, ensuring that her sons would also have large genitals. But given that penis size has a Bell curve distribution, and that penis size has remained stable over evolution, it must be "hidden" on the X.
What are the opinions of the forum ?