Evolutionary tidbits

To reiterate my understanding of the biological roots of our humanity, I see human empathy as something special and it laid the foundation for symbolization and that enables us to think and talk about everything and nothing and to create it if it is not already there in reality.  Through our empathy we humans are keenly aware of another’s mind, that they have subjective considerations, and how we can interact with each other mindfully.  Symbols carry this social effort forward with scope and power.

This empathic capability is centered in the right hemisphere that processes kinesic communication and maintains Empathy Central in the temporal-parietal junction where knowledge about our relationships contributes to what the academics call ToM (theory of mind).  Anyway, my thought is that this keen sensitivity to others’ minds became integrated with our mirroring capabilities, so that certain actions could be replicated readily upon observing them in another.  This replication of mirrored actions comprises the invariant forms of social communication, and when our mirroring system came to include vocal signals, so that we could hear a conspecific vocalize/verbalize and reproduce that sound and not just the objectively observable motoric behaviors, e.g., lifting a cup to drink.  This is the functional significance of the arcuate fasciculus on both the right and left sides, but especially on the left, where the af enables the repetition of what we just heard another say (see my post of 4/24/2014 on the arcuate fasciculus and mirroring).  Putting together, i.e., integrating, the awareness of another’s mind and the knowledge produced by the mirrored invariant behaviors led to symbolization, at first linguistic and then artistic (ask me to explain that sometime).  Symbols, if you remember, have a deep structure (what resides in our minds subjectively) and a surface structure (what we use to formulate and then communicate those subjective musings), and voila! language, art and the cultural wealth of our kind.

That said, I have been reading Georg Striedter’s Principles of Brain Evolutionand find a couple of evolutionary tidbits that help to carry my speculative imaginings forward (and I find nothing so far contrary to this path). Consider that human eyes are almond shaped and that our irises are surrounded by white sclera while the eyes of other primates are round and the irises surrounded by dark sclera (though the sclera hidden within the eye socket is white.  Striedter interprets this to show that we humans monitor each other’s gaze and so gather more information about the other’s subjective musings; further that our eyes’ structure facilitates this with its almond shape and white sclera shows that such kinesic communication is important evolutionarily. I see this as an example of our keen awareness of the other’s mind.

Think of some examples of this.  Parents follow the gaze of pre-verbal infants and move to facilitate their exploratory activity.  As Michael Tomasello explains, joint action is a critical advance in our social coordination and eye gaze is an important means by which we cooperate, e.g., one holds something still while another performs a more intricate action such as a nurse clamping a wound while another stitches it up, or one hunter with a bow shifting gaze to match another’s and finding prey.  Finally in this regard, in my early career I learned about the challenge of hearing impaired children (and adults) who must watch the other’s hands to communicate about a task that needs to be seen to be learned. Eye gaze is important in juggling these gaze shifts and we humans have extra talent for this.

Father child

joint gaze and joint action

Streidter also discusses the size of our brains in absolute terms, compared to our body mass, relative to other animals, the amount of cortex relative to the medulla, etc.  He points out that large brains are ‘expensive’, e.g., they require high protein diets, they pose problems for live births due to mismatch between skull size and birth canal, and they pose challenges to communication between neural areas.  This last comes about because areas farther away take longer to communicate with each other and that poses a problem for timing.  Much of our neural processing depends upon the simultaneity or temporal match of parallel processes.  Our brains have evolved with some work-arounds such as long, thicker nerve tracts that nerve impulses travel along faster than thin fibers.  Our brains have many more modules and these connect especially to those nearby with some longer fasciculi, e.g., the arcuate fasciculus, the superior longitudinal fasciculus, the claustrum and the corpus callosum, bearing the burden of longer range communication.

Sobo_1909_670_-_Uncinate_fasciculus

The arcuate fasciculus is part of the superior longitudinal fasciculus. Thicker axons help nerve impulses travel long distances faster.

Now here is another interesting tidbit.  Our corpus callosum is relatively smaller than those in other primate species, i.e., our cerebral hemispheres are less connected than might be expected.  Streidter says the data show that the human brain is more asymmetrical than other species’ brains; this works because our two hemispheres specialize in different functions (yes, even as they perform much of the same functions, one leads, and while brain damage when young can be compensated for, damage when older is less so because the specialization has become at least partially irreversible). Again this difference in connectivity is relative; I have posted here before that studies of our connectomes show females generally have more bilateral connections, i.e., they make more use of their corpus callosum, while males have more connections within each hemisphere than between.

corpuscallosum

corpus callosum with part of right hemisphere cut away

Now this bit of information speaks to two issues.  First is that females and males (please remember that I use the terms in a relative manner and appreciate all manner of androgeny in our variations) approach interactions differently.  This is especially noticeable in preschoolers where girls are both more verbal and tuned into relationships and boys are somewhat less verbal and their attunement to others is, shall we say, less robust.  Actually, talking with my 30 something daughter and others, this difference may even be accentuated in mature humans (maturity, again, is a relative term, guys).  In any event, the functioning of the connectome when emphasizing social and linguistic information together would use the corpus callosum more fully and that would correlate with a female sort of pattern.

The second issue here goes back to my thesis that symbolization arose from, first, the integration between the keen empathic apprehension of another’s subjectivity and the invariant behavioral forms that operate in mirroring, and then, second, once the connections are formed, their separation into the surface and deep structures of our symbols.  Human brains are more asymmetrical and this I associate with the differentiation of function between Empathy Central on the right side and linguistic functions on the left, e.g., one side is pragmatic and the other syntactic/semantic.

The last tidbit comes from Streidter’s analysis of the human brain’s enlarged lateral prefrontal cortex (adjacent to motor and premotor areas) primarily on the left side.  This relatively species-specific area serves, Streidter hypothesizes, our abilities to use our hands and words in very flexible, facile, novel and unconventional ways.  We are able to do things hitherto unseen, un-imitated and even unimagined until we do them.  This includes our words as well as our hands.  This highlights one of the great paradoxical strengths of our language. We use words, conventional symbols with socially established meanings, to say many things that have never been said before, i.e., they are novel and unconventional.  We do this day in and day out in small and large ways for mundane and profound topics.  Back in the day Noam Chomsky focused on this generative capacity to demonstrate the theoretical poverty of behaviorism, and we are still learning about this today.

Lobes_of_the_brain

lateral prefrontal is in lower blue area towards the front

So a long post.  Funny how tidbits expand when I am (you are too hopefully) having fun and learning about our humanity, eh?  Travel on.

a cultural tidbit

I have been thinking of culture again for some reason probably having to do with reading about neuroanthropology and their emphasis on how our brains do culture, and thinking more about Bourdieu’s habitus as the cultural way of doing things and how that does not seem to capture the knowledge structures that also contribute to culture, e.g., our values.  Along with this I continue to ponder with reverence Monod’s analysis of religion, science and values and his exhortation that an ethic of knowledge will lead to a knowledge of ethics.  And being a modern American I frequently worry about the media term, ‘culture wars’, as I resist the notion that people with conflicting values necessarily must clash and war over them and search for other metaphors to capture this phenomena.

I recently read a Vanity Fair article about Emmanuel Macron, the president of France, who advocates for acculturation as a way of assimilating the dispossessed, including immigrants, into mainstream society.  That is an interesting contrast with some in this country (and others) who assume that others must adopt on the own and immediately the general culture and its values to some specific degree or else be rejected as outsiders and alien.  Macron wants to help those who do not already participate in the majority’s cultural tradition to appreciate what he considers to be a friendly French culture and to incorporate new aspects from the cultures these ‘others’ bring with them. Sounds so very civilized, even normal, including the criticism that Macron is focusing on the cultural facet enjoyed by the more highly educated, even Parisian as some gasp, and that his effort to assimilate some cultural bits from others amounts to appropriation by the dominant majority (elite).  While I still think his effort to be inclusive is laudable, this notion of ‘high’ culture is what stimulated Dorothy Parker to pun, “You can lead a horticulture [whore to culture] but you can’t make her think”.  I think my country is now demonstrating that being an advanced nation with great material culture, even an educational system once held in high esteem, is no guarantee of intelligence, especially of a critical sort.

I also think that this notion of culture is like icing on a cake, lovely icing sometimes, not too sweet, but it is the cake underneath that is the basis of culture. This is why Bourdieu’s idea of the habitus is so apt, i.e., the habitual way a cultural group does things.  This applies to such things as eye contact, e.g., what is respectful between children and adults or younger adults with their elders, physical distance when conversing, e.g., Americans stand a couple of feet way, many Europeans move closer, emotional expression, e.g., boys don’t cry, some Asian societies maintain impassive expressions, how children are disciplined, etc, etc., etc.  Bourdieu did much cultural research into how marriages are arranged and determined to be good for both families in some Arab societies.  Look at how different cultures manage what are acceptable roles for females or the role of fighting between young males or more generally what is respectable or orthodox.

I read in The Encultured Brain, a primer for neuroanthropology, that some less modern cultures regard knowledge of healing practices as secret and that if shared outside the healer-patient relationship, the knowledge becomes useless, i.e., the practice consisting of magical chants will not be effective. Contrast this with western medicine where healing knowledge is publicly disbursed and evaluated so it may be made more effective.

Then I also read there:  “Long term neurological and perceptual adaptation to the tasks we set ourselves is a form of enculturation”.  In a chapter about how equilibrium varies among cultures Greg Downey focuses on his training in capoeira, an Afro-Brazilian form of martial arts, where it seems you spend some time upside down or sideways and must keep you eyes on your opponent, thus you cannot use vision to maintain balance but must train your body to rely on body awareness and vestibular feedback.   Acknowledging that maintaining one’s equilibrium is not really a conscious task, i.e., the more you have to focus on balance, the less you can focus on otherwise, he maintains that equilibrium is a learned skill and that makes it a cultural one (I am not sure about that).  He cites research showing that toddlers just learning to walk use vision more to right themselves; older kids rely more on vestibular sensing; again this seems biological more than cultural.

He also mentions that many Japanese walk using more of a lower leg focus, e.g., knee to foot, while many Westerners organize their gait from their hips and so take longer strides.  I found this interesting for a couple of reasons.  I spent my teenage years in Japan and remember that many used a more shuffling sort of gait, i.e., short steps, coming down less severely on the heel, almost stepping flat-footed but not quite.  This was more prominent with elders and with women and I attributed this to the constraints of their clothing and their wooden sandals that have two vertical strips of wood underneath the flat bed rather than a raised heel, instep, etc. like our shoes do.  (These sandals seemed especially apt on rainy days.)  Any way, another cultural feature is that they never wear shoes in the house, only slippers.

Another reason is that with two joint replacements and a bit of age on me I find walking in the dark more difficult, harder to maintain my balance without visual input.  And our farm here in a high mountain valley has no level or even ground anywhere except garden patches, so I find that a knee to foot gait with shorter steps and less emphasis on heel-toe ala Japanese is quite adaptive to maintaining balance on this terrain.  Now here is my question:  What is the distinction among cultural phenomena, adaptive skills given age, terrain, etc., and training specific abilities to a higher level?

Culture is an amorphous concept with many levels, from the high culture historical identity, the arts, key values, and form of governance down to more basic levels in roles ascribed to females, males, etc., and body language and social mores.  A martial art such as capoeira is certainly cultural, so I guess the subsidiary training for proficiency is also cultural, but I also wonder if skill development should really be termed cultural.  Sure play and sports contribute to culture because they are social forms (mental, behavioral, cognitive) that are shared amongst members of the group. A kid on the playground practicing dribbling with either hand and between the legs or a farmhand working to pick faster with both hands while still handling the fruit carefully do not, to my thinking, share cultural forms as much as they concentrate on one’s individual ability.  True that ability is for cultural practice but that seems to me a social frame or role. Otherwise I think everything we do might be called cultural when I think everything we do is biological and culture should be reserved for the social constructs governing our participation in group interactions, i.e., habitus, or this is how we do things and how you perform some of those things is your own making special your performance.

Complicated issues here and I must say these are my first thoughts upon reading in The Encultured Brain.  One sign of a good book is what thoughts it provokes and I am enjoying reading it.  Think about this a little bit before traveling on.

Partial review: The Encultured Brain

Sometimes quantitative assessments lead to important ideas.  I have been enjoying later chapters in my new book, The Encultured Brain: an introduction to neuroanthropology, edited by Daniel Lende and Greg Downey.  Their early chapters giving synopses of later chapters to introduce the rest of the book seemed more a marketing ploy for yet another new academic discipline (worthy, yes, but do we really need a new term for every time we do cross discipline thinking?)  Their chapter on “Evolution and the Brain” was, however, magnificent, and later chapters by others have so far been very interesting.  So consider this list of findings from their brain evolution chapter.

  • The biomass of humans is 8 times that of all the wild terrestrial vertebrates, i.e., we are successful replicants. (Also I remember von Neumann’s estimate that each human body has about a tablespoonful of genetic material in all its cells that control the soma).
  • The genus Homo appeared around 2,000,000 years ago with a sudden increase in brain volume that then slowly increased until 500,000 years ago when another surge in brain size appeared.
  • Human encephalization (the concentration of nervous tissue in a brain, i.e., head) is 5-7 times what would be predicted based on a mammal of our size.
  • As the neocortex evolved to dominate lower brain structures, specialized cortical fields developed that facilitated complex processing and inter-connectedness throughout the brain. Early mammals have 15-20 cortical fields; humans have maybe 150.
  • Larger areas both evolved later and mature more slowly.
  • Our brains have continued a mammalian and primate trend in lateralizing so much that some scientist refers to us as the “lop-sided ape”. (In addition, remember that males and females have relatively different patterns in our connectome with males showing more connections within hemispheres and females more connections between hemispheres).
  • Birds, fish and reptile brains grow throughout their life spans (neurogenesis or generating new neurons) but mammalian brains finish up neurogenesis relatively early.
  • Our brains triple in volume after birth while other primate brains only double.
  • Finally our post partum brain growth comes despite pervasive neural pruning in the first years of life; the estimates are that the adult brain has only 20-80% (quite a range, I know, but you get the idea) the number of neurons present at the peak early in life. Neurons survive because they become integrated into functional circuits; if they stay isolated, they die off.

 

All of these are pretty amazing and all support the idea that our brains are shaped, as Gerald Edelman maintained, first by genetic information and then in very large and important ways by experience.

White_Matter_Connections_Obtained_with_MRI_Tractography

Our connectome with many systems lit

Now Lende and Downey quote two well known neuroscientists (Cosmides and Tooby) that “our modern skulls house a Stone Age mind,” and I have no qualms about that because I think a Stone Age mind was actually a pretty good one (some politicians today cannot manage even that level of intelligence).  They also point to the remarkable and wonderful development of our social capabilities and find that we are drawn to social interaction for “intrinsic emotional rewards” and not just self-interest for our genes’ continuation.  And they recognize that the true power of human intellect, while derived from our rather different brains, is really due to the “synergy of many brains.”

Neuroanthropologists, as best I can see with my limited exposure, treat culture as part of our extended phenotype, i.e., culture is not an acquired overlay but is rather an integral component of the human Umvelt.  It is a direct outgrowth of our biological roots of empathy and symbolization (though I do not see anything here about art).  More to say later but I need to get to my farm work. Oh, one more recommendation for this book—the lists of references yield a lot of gems.  Travel on.