Mate selection

September 22, 2011 at 6:51 pm

“As we act out the complex rituals of courtship, many of them inscribed deep in our brain, scent-based cues help us zero in on optimal partners—the ones most likely to stay faithful to us and to create healthy children with us.” (“Scents and Sensibility,” Psychology Today)

You already know that I love new baby smells and believe that our sense of smell plays an important role in the bonding process.  Since making this discovery a couple of years ago, I have thought off and on about the subject as news stories or ideas have come up on my radar.  Then, a couple of days ago, I had an experience that brought smell and bonding onto my radar again.


As my husband was saying good-bye to all of us to leave for work, he came over to hug and kiss me like he always does.  It was an ordinary hug, no different from every other hug on every other morning.  But this time I noticed something I had never paid attention to before. When we hugged each other, both of us, simultaneously (instinctively?), drew in a long breath through our noses, smelling each other deeply. As I watched this exchange, almost as an outside observer, I was absolutely fascinated.  When he came home from work, later in the day, it happened again… hug… deep breath in through our noses.  Maybe we’re not so different from our dog-friends after all? I’m becoming more convinced than ever that our sense of smell plays a far more important role in our relationships than we realize.

I was telling my husband about this observation last night.  He had never noticed our smell-hugs before either.  And then I was telling him about the blogpost I was planning to write.  During our conversation, I told him, “I used to think that the most important factors in choosing a mate were spiritual and emotional, but I don’t anymore.”  Yes, they are important, but I would now say that physical chemistry comes first, at least if you’re planning on reproducing (and giving those children stronger/healthier immune systems) and remaining faithful to each other forever.  Here’s why…

Major Histocompatibility Complex

We humans have these things called major histocompatibility complex (MHC) genes which play a part in immune responses.  Research suggests that having wide variation in MHC genes may lead to higher reproductive success (fewer miscarriages, more live babies with better immune systems and fewer autoimmune problems).  We also seem to be able to sniff out mates with whom we would have the most reproductive success.  And women seem to be more attuned to these genetic nuances of smell than men are.

Potential mates with dissimilar MHC genes will smell more pleasant to us, studies suggest.  And once we have chosen a mate, those with dissimilar MHC odors will keep us more consistently sexually interested.  We are less likely to remain faithful to mates withsimilar MHC genes, especially during the fertile parts of our menstrual cycles. Our bodies and hormones want us to have reproductive success and genetic variation, so they will attract us to those with whom we are most likely to find those things, whether we think we should be attracted to those people or not! (See here and here and here.)

AsPsychology Today explains:

Couples experiencing difficulty conceiving a child—even after several attempts at tubal embryo transfer—share significantly more of their MHC than do couples who conceive more easily. These couples’ grief is not caused by either partner’s infertility, but to an unfortunate combination of otherwise viable genes. (Source)

It’s to our advantage as far as fertility, faithfulness, and future healthy children to rely on our body’s wisdom and instinctual attractions.

Birth Control Pills

The catch is that these effects appear to be reversed when a woman is taking birth control pills.  So, rather than being physically attracted to mates with ideal MHC for reproductive and marital success, she will be attracted to mates whose genes are similar to her own.  Researcher Stewart Craig Roberts explains: “Not only could MHC-similarity in couples lead to fertility problems, but it could ultimately lead to the breakdown of relationships when women stop using the contraceptive pill, as odor perception plays a significant role in maintaining attraction to partners” (source).  I’d say this probably isn’t going to affect every woman in the same way, and it’s probably true that many women have had wonderful, successful relationships despite taking oral contraceptives.  But it’s still something to be aware of.

Mate Selection Tips

Most of my readers have already chosen a mate and started families, so this information may not be very useful to us ourselves, but it can benefit our children and future posterity.  We can teach them the importance of doing the following things as they select a potential mate:

1) Avoid hormonal contraceptives, when possible.

2) Seek out opportunities to work up a sweat together.  You know… like hiking, raking someone’s yard, helping build a school for disadvantaged children, stuff like that. Pay attention to his body odor. Do you like the way he smells?

3) Pay attention to your gut response to this person when you’re mid-cycle and likely fertile.  If you find your eyes wandering, take that as a red flag.  If you feel more attracted than ever, take that as a good sign for a healthy and productive long-term relationship.

4) Let your hormones and body draw you in the right direction, but be sure that the other important components of a healthy relationship are present as well: spiritual compatibility, emotional safety, and intellectual suitability.  Far too many women, I believe, become physically bonded and attached (which can be a very deep and lasting attachment) to men who may be reproductively suitable for them, but who lack the other important relationship factors.  This can lead to heartache down the road.

5) Be careful when choosing dating partners online.  I believe online dating can be a wonderful way to find a soul-mate.  But I think it’s possible to become emotionally, spiritually, and intellectually bonded to someone on a deep level who is not necessarily our ideal mate reproductively.  This can be tricky.  So I’d suggest doing your best to stay detached until you can sniff out those suitors (if you want to have a family and long-term relationship).

Psychology Today offers more excellent genetically-compatible mate-selection tips here.

My husband smells good to me.  He always does.  Even after coming in sweaty from a long run, and even after sitting in that sweat all day (if he hasn’t had time to shower).  And I know what stinky boys smell like.  I grew up with six brothers.  The past few weeks, I’m pretty sure my body has been revving-up to ovulate.  All the signs are there.  One of them being that suddenly my husband looks and smells more delicious than ever. I take that as a sign that I managed to select a mate with ideal MHC variability. Good to know.

I’ll definitely be teaching all of these things to my children, especially my daughters.

Stay tuned for my next post in which I will share some more cool stuff I’ve learned about our sense of smell as it applies to relationships and bonding.