Learn something new every Friday. Join 2,000+ nerds and satisfy your curiosity one question at a time with topics including science, technology, history, and more.
Why do men have nipples if they can't breastfeed?
|
β Why do men have nipples if they can't breastfeed?β
|
In short, nipples start forming in human embryos before sex-specific genes are activated. After that point, females will develop female traits, while males will develop male traits. Both sexes keep breast tissue and nipples thanks to this early milk ridge formation.
Now we know how nipples develop in male humans. But why hasn't evolution removed them if they seemingly serve no purpose?
Theory #1: There's no harm in males keeping their nipples.
Some argue that male nipples remain not because they have an evolutionary advantage, but simply because they have no evolutionary disadvantage. When a trait is useful in one sex, as nipples are for nursing in females, and harmless in the other sex, there's no benefit in removing them.
Nipples aren't even the only part of male anatomy that develops by default in the embryo before sex differences kick in. The prostate contains a tiny, nonfunctional structure called the prostatic utricle. It is a remnant of embryonic MΓΌllerian ducts, which develop into the uterus and fallopian tubes in females.
Theory #2: Nipples contribute to the desire to reproduce in males.
It's also possible that nipples do serve an evolutionary advantage in male humans. Nipples contain a dense network of nerves, making them a highly stimulatory organ. Some researchers think their role in sexual pleasure helps boost the desire to reproduce.
Theory #3: Nipples allow for the possibility of male lactation.
While exceedingly rare, some male mammals are capable of lactation. The dayak fruit bat, a very rare bat species found in southeast Asia, can produce milk in both male and female bats. The exact evolutionary advantage is unclear, but dad bat may take the pressure off of mom bat from feeding the baby bat all the time.
Interestingly, human males are technically capable of lactation if there is a medication or medical condition that triggers an increase of the hormone prolactin. In these rare cases, males can produce milk. So, while far fetched, it's possible nipples haven't disappeared in males because it leaves the door open for male lactation.
π§ Bonus brain points
Can you be born with extra nipples?
Yes, around one in 20 people have what's called supernumerary nipples. These extra nipples are leftovers from mammary crest development, rarely functional, and often appear to look like nothing more than a small mole.
|
--- Thanks for reading this week's newsletter! If you have any thoughts, questions, or favorite GIFs, my inbox is always open. Just hit reply to send me a note! :) All my best, |
βSources for this week's newsletterβ
|
π Wikipedia article of the week
βPublic Universal Friendβ
"The Public Universal Friend (born Jemima Wilkinson; November 29, 1752 β July 1, 1819) was an American preacher born in Cumberland, Rhode Island, to Quaker parents. After suffering a severe illness in 1776, the Friend claimed to have died and been reanimated as a genderless evangelist named the Public Universal Friend, and afterward shunned both birth name and all pronouns. In androgynous clothes, the Friend preached throughout the northeastern United States, attracting many followers who became the Society of Universal Friends."
π Catch up on other curious questions
- βWhy does plastic turn yellow?ββ
- βWhy do we have emotions?ββ
- βWhy does a tire company rate restaurants?ββ
P.S. π€ Do you have a question for the newsletter? Click here to submit your question (or reply to this email!)
|
π‘ Today You Should Know
Learn something new every Friday. Join 2,000+ nerds and satisfy your curiosity one question at a time with topics including science, technology, history, and more.
Why do we say "achoo" when we sneeze? This question came from a reader submission (thanks Duncan!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question π The short answer "Achoo" mimics the sound of the sneeze itself, shaped by how we breathe and move our mouth. But not everyone says "achoo" since different languages have their own versions, and making a sound at all is a cultural habit, not a biological need. π The long answer We've all...
What happens to the temperature of the atmosphere the higher you go? This question came from a reader submission (thanks Omar!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question π The short answer The higher you go in the atmosphere, the temperature either rises or falls depending on the layer. These changes are caused by how different parts of the atmosphere absorb energy from the Sun and how air pressure affects heat. π The long...
Do sports teams that train in high altitudes have a home advantage? This question came from a reader submission (thanks Jacqui!). Has a curious question stumped you lately? Feel free to submit your own question here: Submit your question π The short answer There is strong statistical evidence that high-altitude teams have a home advantage, largely because visiting players experience reduced oxygen intake and quicker fatigue at elevation. π The long answer It's high time we level up our...