What are armpits for? | Greg Foot | Ask Head Squeeze

This week on #AskHeadSqueeze Thursdays, Greg Foot answers a question from Kevin Sheppard on our Head Squeezers Google+ community. What are armpits for, and why are they hairy? Interested in how the smell of your sweat could help you score? Watch away.....

00:43 Why do we have hairy pits?

There's a few theories here. One idea is that your hairy armpits stop your lymph nodes from overheating.

Foot Note 1: A moat around castle walls: The role of axillary and facial hair in lymph node protection from mutagenic factors. KomarovaS. Medical Hypotheses, Vol67, Issue 4 (2006), Pg 698-701



Another is that the hairs actually reduce friction when you walk. But the third theory is the one Greg's keen to talk about -- that hairy armpits are all about sweating and releasing sex pheromones.

01.08: Where does the sweaty smell come from?

Before Greg goes Sherlock, he has to explain where your smell comes from.

Foot Note 2: Microbiological and biochemical origins of human axillary odour.

James AG, Austin CG, Cox DS, Taylor D, Calvert R. FEMS Microbiol Ecol. 2013 Mar;83(3): 527-40.



02:01 What does your sweat say about you?

Sometimes your smell can say a whole lot about you, your status, your gender, and your reproductive state - especially if you are a Hyena.

Foot Note 3: Animal behaviour meets microbial ecology

Archie E, Theis K. Animal Behaviour, Vol 82, Issue 3, 2011, Pg 425--436



Even in humans, the underarm smell could have a role in attracting a partner.

Foot Note 4: MHC-correlated mate choice in humans: a review.

Havlicek J, Roberts SC. Psychoneuroendocrinology. 2009 May;34(4):497-512.



03:00 What is the Major Histocompatibility Complex?

The MHC is a bunch of genes that are important and are linked to not only your smell but your immune system. Experiments have shown that some women found a man's smell more attractive if his MHC was different from their own. It's thought that this is because their children will have a stronger immune system if they get two different sets of these genes.

Foot Note 5: MHC-Dependent Mate Preferences in Humans

Wedekind C, Seebeck T, Bettens F, and Paepke A. Proc. R. Soc. Lond. B 22 June 1995 vol. 260 no. 1359 245-249



04:01 How are steroids linked to your smell?

Androstadienone is a by product of testosterone, and researchers have found that women exposed to it at a speed dating event were more likely to rate men as attractive.

Footnote 6: Evidence that androstadienone, a putative human chemosignal, modulates women's attributions of men's attractiveness.

Saxton T, Lyndon A, Little A, Roberts C. Hormones and behavior 2008; 54(5): 597-601



04:44 Who has the smelliest armpits?

This is the battle of the sexes -- who is smellier, men or women? Well, the research was done by the Monell Chemical Senses Center, and they found...it was men. Sorry guys. And, bonus fact , women apparently prefer the "odor signatures" from men who are on a non-meat diet.

Foot Note 7: The effect of meat consumption on body odor attractiveness.

Havlicek J, Lenochova P. Chem Senses. 2006 Oct;31(8):747-52. Epub 2006 Aug 4.



Do you smell? James May can't help, but he can tell you how deodorant works.

And if you're still feeling hopped up on animal magnetism, Greg Foot answers more mammalian questions in Can Animals Taste.