The most serious and important question in the world

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The purpose of the belly button: you press it and turn invisible.

 

Big up to Roald Dahl, one of the best writers in history.

 

I believe the inward or outward bellybutton is hereditary. Runs in the family. I don't have a link but do recall reading somewhere that it is hereditary.

As to the male nipples I have no idea.

 

http://en.wikipedia.org/wiki/Nipples#Nipples_on_male_mammals

Starting at conception and lasting until about 14 weeks, all mammalian fetuses look the same, regardless of sex. After 14 weeks, genetically-male fetuses begin producing male hormones such as testosterone. As "female" is the "developmental default" for mammals, by 14 weeks, the nipples have already formed.


Most of the time, males' nipples don't change much past this point. However, some males develop a condition known as Gynecomastia, in which the fatty tissue around the nipple develops into something similar to a female breast. This may happen whenever the testosterone level drops because of medications (like those that treat prostate cancer) and by natural hormonal changes caused by aging, obesity, or puberty.

 

That first link said that it had to do with the abdominal muscle structure... which is probably hereditary.

 

Lol...spoken like a true computer geek.

More questions...why do we have an appendix if it doesn't get used? If we evolved from primates, why do we have a lot of hair on the tops of our head, armpits and pubic area, but not a lot everywhere else (unless you're Ron Jeremy )?

 

I am Ron Jeremy and I resent that comment.

 

we have hair in places we still need to keep warm. the head has lots of blood flowing through, if we were naked and bald we would lose lots of heat through it. seeing as humans already spend more than 60% of our energy at maintaining our body temperature, we cant afford to lose any.

same thing with the groin and upper legs - very important blood vessels there. thats why groin stab injuries are often fatal, as seen in the movie hannibal.

your wrists and hands probably arent hairy because hair might interfere in their use I'm guessing.

 

It's a homologus structure which has become a vestigial organ in humans and provides evidence of a common ancestor and evolution.

Yay, I remembered something from HSC Biology.

 

Uhhhh....what?

Try that again in English please...

 

Hehehe now I get to sound smart!

Basically a homologous structure is something that shares common structures, like the pentadactyl limb of vertebrates.
http://www.zoology.ubc.ca/~bio336/Bio336/Lectures/Lecture5/pentadactyl.jpg

(edit: Found that picture on the net haha)

Thus similar structures like these (and the appendix) point to a common ancestor.

Vestigial organs are homologous strucures no longer or not being used as it is in most other animals i.e the human appendix. The prescence of this vestigial organ points to evolution and a common ancestor.

Hope that helped, seeing as usually I'm bad at explaining things~ ^^'' Also hope I didn't get anything wrong, or offend people since its about evolution -but that's what I learnt.

 

"Female" is the default sex. There are rare cases when people born with XY chromosones (i.e. male) don't kick-start into changing to "Male" and therefore default as "female". (Thinking about it, isn't there an episode of "House" which covered this?)

 

Oh yeah, the episode in season 2 about the model who is actually a guy right? That was wierd. O.o

 

Navels - answered to my satisfaction.
(and I always wanted to be a Naval Architect and sit around all day designing belly buttons! )

Male nipples - same.

Hair on head - yep, heat conservation; if the brain gets too cold, EVERYTHING shuts down, quite apart from wasting heat going out through the bare scalp.

Hair in 'recessed joints' like armpits and groin - not only for 'armour' and heat conservation (brachial artery in arm, femoral artery in leg) but also as...well, KINDA solid lubrication to prevent skin chafing as it rubs together - individual hairs acting like rollers or 'linear bearings'

And hair not on other parts of body like palms, points of elbows, etc - simple friction, resulting in evolutionary improvement; these are parts of the body constantly in contact with other objects (hands and feet, and even knees and elbows for 'all fours' etc).

As for you less 'hirsute' people (yes, I make Ron look shaven ) a) you technically DO have tiny, colourless hairs on your arms, face, back, etc - look REALLY, really closely - and b) those areas got hair 'phased back' when we started to wear clothes, covering those areas and removing the need for heavier, insulating hair.

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Now for my 'most important question': Did Adam & Eve have navels?

 

Not sure about the House episode, but that there are genetic males who develop as females is true. The problem is that these people lack a testosterone receptor. So when the fetus starts producing testosterone, there's no receptor to detect it, and the fetus continue developing as female.

Functionally, these people continue developing as females after they are born, and even as adults, they look like normal females. However, they are sterile. Even though they have all the female parts, and are capable of having sex, their genetic code lacks the information for the proper functioning of these parts. It's kind of like they have all the hardware, but lack the software.

 

Reduced thickness of bodyhair?

Aquatic ape! Aquatic ape! Aquatic ape!

I saw plenty of those when I was in Sydney.

Men having nipples? For breast-feeding, of course!