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July
The Evolution of Love How did we evolve the most
loving brains?
How did we evolve the most loving brain on the
planet? Humans are the most sociable species on
earth - for better and for worse.
On the one hand, we have the greatest capacities
for empathy, communication, friendship, romance,
complex social structures, and altruism. On the
other, we have the greatest capacities for shaming,
emotional cruelty, sadism, envy, jealousy,
discrimination and other forms of dehumanization,
and wholesale slaughter of our fellow humans.
In other words, to paraphrase a Native American
teaching, a wolf of love and a wolf of hate live in
the heart of every person.
Many factors shape each of these two wolves,
including biological evolution, culture, economics,
and personal history. Here, I'd like to comment on
key elements of the neural substrate of bonding and
love; in next week's blog, I'll write about the
evolution of aggression and hate; then, in the next
several posts, we'll explore the crucial skill of
empathy, perhaps the premier way to feed the wolf
of love.
These are complex subjects, so I hope you'll
forgive some simplifications. Here we go.
Evolution
The growing length of childhood coevolved with
the enlarging of the brain - which has tripled in
size over the last 2.5 million years, since the
time of the first tool-making hominids - and with
the development of complex bonding, which includes
friendship, romantic love, parent-child attachment,
and loyalty to a group.
As the brain grew bigger, childhood needed to be
longer since there was so much to learn. To keep a
vulnerable child alive for many years, we evolved
strong bonds between parents and children, between
mates, within extended family groups, and within
bands as a whole - all in order to sustain "the
village it takes to raise a child." Bands with
better teamwork outcompeted other bands for scarce
resources; since breeding occurred primarily within
bands, genes for bonding, cooperation, and altruism
proliferated within the human genome.
Numerous physical, social, and psychological
factors promote bonding. Let's focus on physical
factors, and then drill down further to examine two
chemicals inside your brain: dopamine and oxytocin.
Both are neurotransmitters, and oxytocin also
functions as a hormone when it acts outside the
nervous system.
(By the way, dopamine and oxytocin, like many
other biochemical factors, are present in other
mammals, too, but as with most things human, their
effects are much more nuanced and elaborated with
us.)
Dopamine
It's an error to reduce love to chemicals, since
so many other factors are at work in the brain and
mind as well, so let's hold this material in
perspective.
That said, it appears that when people are in
love, among other neurological activities, two
parts of their brain really get activated. They are
called the caudate nucleus and the tegmentum. The
caudate is a reward center of the brain, and the
tegmentum is a region of the brain stem that sends
dopamine to it; dopamine tracks how rewarding
something is.
In effect, being in love rewards the pleasure
centers in your brain, which then crave whatever it
was that was so rewarding - in other words, your
beloved. Those reward centers are the same ones
that light up when people win the lottery. Or use
cocaine.
And being rejected in love activates a part of
the brain called the insula, which is the same
region that lights up when we are in physical
pain.
So we are doubly motivated to hold fast to the
object of our love: feel the pleasure, and avoid
the pain.
Interestingly, when people are in lust, rather
than in love, different systems of the brain get
activated, notably the hypothalamus and the
amygdala.
The hypothalamus regulates drives like hunger
and thirst. Interestingly, the word in the early
records of the teachings of the Buddha that is
translated in English as the "desire" or
"attachment" or "clinging" that is the root of
suffering has the fundamental meaning of "thirst,"
so it's pretty likely that the hypothalamus is
involved in much of the clinging that leads to
suffering.
The amygdala handles emotional reactivity, and
both it and the hypothalamus are involved in
arousal of the organism and readiness for action.
(While these systems are centrally involved in
fight-or-flight responses to stress, they also get
engaged in energizing activities that feel
emotionally positive like cheering on your favorite
team - or fantasizing about your sweetheart.)
These neural components may shed some light on
the subjective experience of being in love, which
commonly feels softer, more "Aaaaahh, how sweet!"
rather than the "Rawwrh, gotta have it!" intensity
of lust.
That said, dopamine - increased in love -
triggers testosterone production, which is a major
factor in the sex drive of both men and women.
So, in short, we fall in love, and among other
neural circuits and psychological complexities, the
same reward chemicals involved in drug addiction
lead us to crave our beloved and want sex with him
or her. Sorry to be mechanistic here, but you get
the idea.
The intended result, in the evolutionary
playbook, is, of course, babies.
Then what?!
Oxytocin
Oxytocin promotes bonding between mothers and
children, and between mates, so they work together
to keep those kids alive.
For example, in women, oxytocin triggers the
let-down reflex in nursing, and is involved in that
blissful, oceanic feeling of peace and comfort and
love experienced by many women while
breastfeeding.
It also seems to be part of the female response
to stress (more than in men - since women have much
more oxytocin than men do), in part by encouraging
what Shelley Taylor at UCLA has termed
"tend-and-befriend" behaviors in women when they
are stressed.
(Of course, men, too, will often reach out to
others and be friendly during tough times, whether
it's crunch quarter at the office, or somewhere in
a dusty war - another example of how there are many
pathways in the brain to important functional
results.)
The experiential qualities of oxytocin are
pleasurable feelings of relaxation and rightness,
so it is an internal reward for all bonding
behaviors - not just with mates.
Oxytocin encourages sociability; for example,
when oxytocin capabilities are knocked out in
laboratory mice, their relationships with other
mice are very disturbed.
And oxytocin dampens the stress response of the
sympathetic nervous system and the
hypothalamus-pituitary-adrenal axis - besides
having functional benefits, this is another pathway
for rewarding, and thus encouraging, bonding
behaviors.
What triggers this warm and fuzzy and
let's-get-together-now chemical?
Oxytocin is released in both women and men:
• When nipples are stimulated (such as
through nursing)
• During orgasm, promoting the afterglow of
warm affection (and a tendency, sometimes annoying
in a partner, to fall asleep!)
• During extended, physical, especially
"skin-to-skin" contact (e.g., cuddling children,
long hugs with friends, teens forming packs on the
couch, lovers caressing after sex)
• When moving together harmoniously, like
dancing
• When there are warm feelings of rapport
or love; a strong sense of compassion and kindness
probably entails releases of oxytocin, though I
haven't seen a study on that specific subject (a
great Ph.D. dissertation for someone).
• Probably during devotional experiences,
such as in prayer, or while with certain kinds of
spiritual teachers
Probably, oxytocin can also be released just by
imagining - the more vividly, the better - the
activities just mentioned, particularly when
combined with warm feelings.
* * *
Of course, dopamine and oxytocin are just two of
the many factors at work in our relationships. For
example, philosophical values or ideals of
universal compassion, such as in the major
religions of the world, can also influence a
person's behavior greatly, with or without any
measurable surges of dopamine or oxytocin.
Nonetheless, appreciating the biochemical
factors at work on Valentine's Day, or at any time
we experience bonding or love, can help a person
not get quite so swept away by the ups and downs of
relationships.
©2010, Rick
Hanson
* * *
As they say in Tibet, if you take care of the
minutes,
the years will take care of themselves.
Rick Hanson
is a neuropsychologist and author of
Buddha's
Brain: The practical neuroscience of
happiness, love
& wisdom with
Rick Mendius and Mother Nurture: A Mother's
Guide to Health in Body, Mind, and Intimate
Relationships. A summa cum laude graduate of
UCLA who received his doctorate from the Wright
Institute in Berkeley, CA, he founded the
Wellspring Institute for Neuroscience and
Contemplative Wisdom, edits the Wise Brain
Bulletin, and writes a blog for PsychologyToday.com
as well as a weekly newsletter called Just One
Thing; his articles have also appeared in Tricycle
Magazine, Insight Journal, Inquiring Mind, and
Buddhist Geeks on-line magazine. He teaches
regularly at universities and meditation centers in
Europe, Australia, and North America, and has audio
programs with Sounds True. Rick began meditating in
1974 and has practiced in several traditions; he
was a board member at Spirit Rock Meditation Center
for nine years and is a graduate of its Community
Dharma Leaders program. He leads a regular
meditation gathering in San Rafael, CA. Currently a
Trustee of Saybrook University, he was also
President of the Board of FamilyWorks, a non-profit
agency. He and his wife have two adult children.
www.RickHanson.net
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