When we consider the penis-related questions we hear most often, "Is penis size genetic?" falls somewhere between "Does size really matter?" and "Is girth more important than length?" (For the record: no, and that's a personal preference.)
Surprisingly — or maybe not — the topic of penis size has been researched extensively. I mean, scientists have even looked into the link between foot size and penis size. And according to the current evidence, genes do seem to play a role in the growth of one's member.
In a slightly unexpected revelation, it turns out that willies get most of their genetic material from the mother's side of the equation.
"This is an area that isn’t completely understood, but many genes involved in the growth of penis and limbs come from the X chromosome," Darius Paduch, director of sexual health and medicine at Weil Cornell, said in an interview with Mel Magazine. "Men have one X chromosome, and women have two. Since boys always inherit the X chromosome from the mother and the selection of that X chromosome is random, this can explain why one brother may have inherited genes for a large penis from one of the mother’s X chromosomes, but another brother inherited an average-size penis from the other."
That's not to say that the dad doesn't have any impact, Paduch added: "If a father has a bigger penis, the son’s will probably be similar in length."
Of course, there are other things besides mom and dad's genes that could affect the size of one's member. An animal study conducted by the U.K. Research and Innovation Medical Research Council found that if levels of hormones known as androgens are low as the fetus grows, penis length could be stunted. Other research has indicated that exposure to endocrine-disrupting toxins including phthalates may impact fetal penis development, possibly by messing with hormone balance in utero.
Ultimately, the size of a person's penis is largely out of their control. Of course, most members end up falling within the "average" range. But at the end of the day, size matters very little. The number of inches someone's packing says nothing about their sex drive, their fertility, or their ability to pleasure a partner, after all.