|MadSci Network: Genetics|
Hi, I have asked a doctor about this. If you are actually talking about a person having a third breast then this is EXTREMELY unusual. But if you are talking about a person having a second SET of nipples then this is not uncommon. When you compare humans to other mammals - such as dogs, cats, pigs - you will notice that most mammals have a row of nipples extending from the top of the chest to the pelvis, each nipple occurs as a pair with another nipple that is equally distant from the top of the chest. In humans and other hominids - such as apes - this is not the case. But the ability to have multiple sets of nipples is still coded in the genes. For some reason humans and apes do not form multiple pairs of nipples - likely this is because humans and other hominids have small litters and so do not need more than one set of nipples to meet the needs of the offspring for milk. But if humans have a mutation in the gene that causes them to only have one set of nipples then then they can have multiple sets of nipples. Usually only one set actually develops into breasts, and often the second set of nipples is not noticed - ie extremely poorly developped. David Beck
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