If you have a big dick you might want to thank your mom.
Now, that might sound counter-intuitive, but in an odd twist of genetic fate our mother’s genes are mostly responsible for penis size. The trait for penis size is in fact hereditary, and although it happens to be somewhat of a joint effort, the majority of the traits live on the X chromosome.
Our father’s Y chromosome possesses the SRY gene that determines biological sex, as well as the growth of internal and external male genitalia. (Just for a refresher, women always give an X chromosome while men can give an X or Y chromosome. If your father passes down an X chromosome the offspring will be a girl, and if it’s a Y chromosome it will be a boy).
Now, how exactly do we know to thank our moms for this? Well for starters, genetic brothers can have vastly different penis sizes, and that means they must have gotten different X chromosomes from their mom (she has two). If size was wholly determined by your dad, brothers would have the same penis size since he only has one Y chromosome. However, not only is your mom’s genetics to thank for your endowment (or to blame for lack thereof), but her behavior during pregnancy has a pretty big impact too. Drinking, using drugs, or being exposed to chemicals can often decrease penis size in babies too (although at that point penis size may not be the most pressing genetic issue at hand). Nutrition is another important factor during early development. Studies have shown that babies who have been malnourished suffer, along with a slew of other health and developmental problems, smaller penises on average.
Although vital, genetics is just one, albeit large, piece of a larger puzzle that all comes together to lead to a final penis size. Things such as testosterone production (especially during adolescence), nutrition and exposure to chemicals during embryonic development can also play a major part. At the end of the day you really can’t do much to change your penis size (outside of losing weight around your upper pubic area) so it’s best to love yourself exactly how you are.