She's probably lactating.

“…You don’t want to mess with mama grizzlies.” – Sarah Palin, May 2010, in reference to novice female political candidates.

Yes, “mama grizzly” Sarah Palin is right, you don’t want to mess with a mother bear, in particular when her cubs are involved. Turns out, you don’t want to mess with mama humans, either, especially the lactating kind.

In a fitting follow-up to my bumpy nipples post, I’ve come across new research that shows for the first time that human mothers, just like other nonhuman mammal mothers, display heightened aggressiveness for the duration of lactation. As an extra bonus to the enhanced protection of their young, the aggression of breastfeeding moms also relieves stress.

Because there’s nothing like the will to kill for the sake of your offspring to really help you unwind.

The concept of aggressively protective mother animals in nature is nothing new. However, UCLA scientists are now the first to actually do a behavioral experiment to prove this phenomenon occurs in human mothers, and that it is directly linked to lactation, as it is in nonhuman mammals.

The subjects in this study were divided in to three groups: breast-feeding women, formula-feeding women, and nulliparous women (women who had never given birth). These women were individually introduced to female competitors who were actually just actors working for the study. The test subject women were told that they were going to play against their competitors in separate rooms in a reaction-time test, and that if they won, they could choose the volume and duration of the buzzer sound played for the loser. In reality, the test subject women were just playing against a pre-set computer program that measured how aggressive the mothers chose to be with the buzzer sound.

Even though the three groups of women studied reported themselves to be equally aggressive, they clearly weren’t, as the data show (note that women were assessed for aggression before and after feeding their babies, but no difference was observed relating to feeding time):

Get a load of those aggressive breast feeders! There isn’t even a significant difference between formula-feeding women and women who’ve never had babies.

Now, aggression definitely isn’t an inherently bad thing. When you have offspring carrying on your genetic information, it behooves you to be extra protective. Not only that, but while the breastfeeding mothers were letting out their aggression during the test, they had lower blood pressures than either of the other two groups of women. I imagine it’s also probably a good thing for mothers of young infants to keep their blood pressure down.

Interestingly, women with more committed romantic partners or with higher incomes showed less aggression. This probably makes sense, because having someone to help protect a child, or having a wealth of resources, could take the pressure off of a mother to be as aggressively protective.

In summary, maybe Sarah Palin didn’t need to use a metaphor about grizzlies at all – human mothers are a force to be reckoned with in their own right.

Stay nerdy And check out the new sidebar addition, “What I’ve Been Reading”! It’ll be updated periodically, and you can probably count on finding something kind of nerdy there.

Hahn-Holbrook J, Holt-Lunstad J, Holbrook C, Coyne SM, & Lawson ET (2011). Maternal defense: breast feeding increases aggression by reducing stress. Psychological science, 22 (10), 1288-95 PMID: 21873570

At times it seems there are no mistakes in biology….

The bumps on areolas are formally known as Montgomery’s glands, and they’ve long been known to increase in number during pregnancy and even secrete a liquid that’s been thought to keep the nipple lubricated against the friction of breastfeeding.  Now, scientists in France have discovered that compounds in these secretions stimulate newborn babies to breastfeed.

Just so we're all clear on what we're talking about here...

In a group of 121 breastfeeding women, most (96.7%) had areolar glands, with the average woman having about 10 of them per breast. So the authors divided these women up based on whether they had a higher or lower than average number of areolar glands, and assessed how long they took to start lactating after giving birth, as well as their babies’ birth weights and feeding habits in the first three days of life.

The simple conclusion is this: the more areolar glands, the better, for everyone. First-time mothers with a higher number of glands started lactating 10 hours earlier on average than mothers with scant glands. Babies of the more bumpy-breasted mothers ate more frequently and gained weight faster in their first three days. The smell of areolar gland secretions, even more so than the smell of breast milk itself, elicited head and mouth feeding movements (e.g. suckling and licking) in newborns.

So, basically…

Vast oversimplification of findings

This research is great because it teaches us something new about a body part and a process that are as old as mankind. Not only that, but if the compounds of interest in the areolar gland secretions can be isolated, they may be extremely helpful for mother-infant pairs with breastfeeding troubles.

So, ladies, be proud of your “nipple Braille”! Should you choose to become a mother, those lumps and bumps will most likely do a world of good in helping your baby answer one of life’s fundamental questions: “Got milk?”

Stay nerdy . And remember, if you like what you see, tell a friend (tell lots of friends!), and Like us on Facebook and Follow us on Twitter! Your support is greatly appreciated. And if you want to look cool while Trying Nerdy: our online store.

Doucet S, Soussignan R, Sagot P, & Schaal B (2011). An overlooked aspect of the human breast: Areolar glands in relation with breastfeeding pattern, neonatal weight gain, and the dynamics of lactation. Early human development PMID: 21852053

Doucet S, Soussignan R, Sagot P, & Schaal B (2009). The secretion of areolar (Montgomery’s) glands from lactating women elicits selective, unconditional responses in neonates. PloS one, 4 (10) PMID: 19851461