Another bountiful acorn crop, on schedule

We've been raking a lot of leaves these past several weeks, which we do every year here in rural central PA.  But we've also, again, been raking a whole lot of acorns, which is not something we do every year. I blogged about this a few times in the midst of the last bountiful acorn year, five years ago, wondering why some years there are more acorns than others. It seems appropriate to rerun these posts.


The Mystery of the Acorn Bonanza

Penn State is situated in the middle of what used to be vast hardwood forest.  Some areas of the county have been more completely deforested than others, and we happen to live in an area in which the developers retained as many oaks as they could when they put up houses in the 1970s.  One consequence of this is that we spend many hours raking leaves this time of year.

Photo: A Buchanan

Many many leaves, and this year, many many acorns.  Masses of them.  It's a good year for acorns.  I wanted to know why.

Taking Holly's message on the 'scientific method' to heart, I wondered, could I apply the scientific method to this question?  Well, unfortunately no, not without having collected data on possibly relevant variables last year as trees were making their acorns -- or even two years ago, since the acorn production of some oak species is a two year affair.  And that would have required knowing the relevant variables.

So I did the next best thing.  I googled 'variation acorn production', thinking someone must have applied the scientific method to this question and done the requisite hypothesis testing.

Photo: A Buchanan

Which of course they have.  It turns out that people look at this from various angles, though.  Some are thinking of the downstream effects, so advise hunters on how to maximize acorn production, because acorns are a staple food for deer.  Others are thinking about sustainable forests, and about how to keep deer from eating the acorns that they hope will go on to produce new trees.

Even so, this approach was not nearly as productive as I'd hoped.  In fact, I kept coming up with a similar theme:

The number of seeds produced by a population of woody plants can vary markedly from year to year. Unfortunately, knowledge of the patterns and causes of crop-size variation is limited....

and

However, little is known about the proximate factors that control the yearly variation in acorn production in oak species...

and

Most acorn production studies note wide and consistent differences in acorn productivity among individuals, but none clearly demonstrate determinants of productivity. 

Hm.  Well, this site looked more promising -- a list of actual variables!

  A number of factors affect acorn production in oaks.  

∙masting cycles	∙acorn predators
∙oak species	∙tree age and diameter
∙weather	∙tree dominance
∙genetics

When combined, these factors make acorn production highly variable from year to year, between the different oak species, between trees of the same species, and from one property to another.  

And further,

[Production is high] once every two to five years.  Acorn production during an abundant crop year may be 80 percent higher than in a low production year; the difference to deer can be hundreds of pounds of acorns per acre.  Although the exact mechanisms that control masting are not fully understood, biologists believe that oak species, weather, and genetics are important factors that determine how often oaks produce abundant crops.      

If we knew what masting was, this might be helpful, but probably not to answer my question -- there's that 'not fully understood' thing again.  And really, only 'weather' is a variable in this equation, as the species and genes of a tree don't change season by season, so this isn't really very helpful after all.

This was interesting:

LONG-TERM PATTERNS OF ACORN PRODUCTION FOR FIVE OAK SPECIES IN XERIC FLORIDA UPLANDS

We examined long-term patterns of acorn crop sizes for five species of shrubby oaks in three xeric upland vegetative associations of south-central peninsular Florida for evidence of regular fruiting cycles and in relation to winter temperature and precipitation. 

And potentially rewarding -- by looking at different species in a single area they were able to control for variation in all the possibly relevant factors.  What did they find?  "[E]vidence that annual acorn production is affected by the interactions of precipitation, which is highly variable seasonally and annually in peninsular Florida, with endogenous reproductive patterns." Oh, so it's rainfall.

Except that, as it turns out, a number of people have studied variation in acorn production in five local species in different areas.  There's a report of a study in California and one in Appalachia, and even one in Japan in which sea breeze was a factor, none definitively confirming the rainfall explanation.

In frustration, I emailed a local forestry agent.  I haven't heard back.  It's possible he's out counting acorns.

Ok, so I accept that there's no simple answer to this simple question.  The serious upshot of this little exploration is that here, too, complexity reigns.  Despite the list I cite above, who can really say what all the relevant variables are, not to mention measure them at the right time or place?  Oak flowers are wind-pollinated -- maybe acorn production depends greatly on wind catching the pollen at just the right time.  Which would be essentially unmeasurable.  And, perhaps variation in rainfall is a significant factor, but where and when?  The roots of mature oak trees run wide and deep, and when are which roots feeding which flowers?  And so on.

And how does one construct believable evolutionary (that is, adaptive Darwinian) scenarios for this?  There's no acorn gene!  (But, of course, it has been tried.)

And think how utterly confusing this must be for any squirrel who's just trying to use his experience to get ahead, to put away a good cache of meals, and wonders if he's going nuts because he's losing his memory.

But one interesting thing caught our eye here as we ventured away from our usual comfort level, scientific literature-wise.  Ecological studies, by their very nature, are less prone to reductive thinking than what we're used to.  "When combined, these factors make acorn production highly variable from year to year." By and large, these studies accept that the cause of variation in crop production is the result of interactions among various factors.

If only this were so readily accepted in genetics and anthropology.



This year's acorn crop, continued

I did hear back from the forester on the question of why so many acorns this year.  He says that oaks are generally sporadic fruit producers, with really good crops every 4 to 7 years.  There are several reasons for this, one being the weather and the other an ecological adaptation.

A late spring frost is hard on oak flowers, and will lead to a low yield, he says.  And, insects play a role.  There are on the order of 30 different species of acorn weevils "that can destroy up to 90% of any given year's production either while it is on the tree developing or after they fall in the autumn."  The cyclic nature of fruit production helps keep the insect population down.

And, he says that there are advantages to sporadic fruit production.  It keeps predator populations down, which increases the chances that some acorns from a given tree will survive and grow.  If not, my informant says, the tree would always be having to produce more and more fruit to stay ahead of the rodents.  Similarly, the fluctuation keeps weevil populations down, and thus acorn destruction down.  Good for the tree, not so good for the predators. 

Source

Both explanations sound plausible.  However, regular MT readers won't be surprised if we are a bit reluctant to accept the adaptive explanation right off the shelf. First, an oak tree is lucky if even a few of the acorns it produces in any given year makes its perilous way to treehood.  Even in a bad year, oaks way overproduce acorns relative to what will take root, or replacement needs and so on.

However, sporadic fruit production in response to the vagaries of climate or other means of destruction of flowers or developing acorns is completely in keeping with the adaptability or facultativeness that is a core evolutionary principle.  Oak trees need to be able to adapt to change, and good and bad fruit production years is one way they do so.  It's easier to suggest but a lot more difficult to conceive how a tree 'knows' (genetically evolves) to adjust for variable predator loads in the hypothesized way, when climate itself is unpredictable.

Two-eyed cyclops -- the plasticity of the brain

The brain is a remarkable thing.  Part of what's so remarkable about it is how it responds to and molds itself around experience.  Alfred Wallace exempted humans from the march of evolution because we are able to do so many things that can't be attributed to natural selection: calculus, the invention of televisions and robots, smell tar and Twinkies, none of which are abilities that we specifically can thank natural selection for since they are all recent.  We can do them because of our brain's adaptability, its ability to make sense of input it clearly isn't hardwired to understand.

Toy tin robot in the show. Boston MA United States. Picture taken by Jonathan McIntosh, 2003; Wikimedia

I remember lying in bed when I was a child, before I was even in kindergarten, closing one eye and then the other and noticing that I could clearly see the books on the bookshelf across the room with one eye but the same books were a blurry mass with the other.  This was just a fact of life, of idle interest to my 4-year old self but nothing more, and I don't think I ever thought to mention it to anyone. I was fine; I could read up close, I could see in the distance, just not with both eyes at once, so it didn't occur to me that anything was weird or wrong about that.  A routine eye exam at school found me out and I finally got glasses to correct this thing that wasn't really a problem.

As I've gotten older, my vision has gotten worse, each eye in its own way.  My eyes are equidistant from 20:20 in opposite directions, one myopic, the other hyperopic; I can still see without glasses, though not perfectly. And still, without my glasses, it's one eye working at a time.

Vision pathway; Weiss and Buchanan, The Mermaid's Tale, 2009

But think about what that means.  Without my glasses, light is pouring into both eyes, hitting my retina at essentially the focally right place in one eye, but all wrong in the other.  The curious thing, to me, is that my brain long ago learned not to pay attention to the blurry input, to only interpret the light waves hitting my retina in the 'right' place. How did it know which was right?

And at some point, in managing input anywhere along the continuum from my eyes to the furthest point I can see, my brain switches from paying attention to my right eye to paying attention to my left.  All the light waves are getting passed along in the same way to both eyes and on to my visual cortex -- I know this because if I close the 'good' eye, of course I'm seeing something, it's just blurry -- but at the very final step in the vision pathway, when my visual cortex is coordinating all the input into a single image, my brain dumps the blurry images and retains the clear.

But it's even more impressive, I think -- with my glasses on, my brain allows input from both eyes to make its way to the final image.  It's switching from monocular to binocular vision all the time.  Again, how does it know to do that?

My eyes as a metaphor for life
The plasticity of the brain isn't confined to the vision pathway, of course.  Plasticity defines the brain -- it's why we can meet new people, learn things, have new experiences, create memories, and then make sense of it all as we go.  Not only are we constantly making new synapses between neurons, we are still making new neurons well into old age, which is what makes our brains able to successfully make sense of all the information with which we're bombarded all the time.  Adaptability, or facultativeness, is so fundamental to evolutionary success that we think of it as a basic principle of life (see chapter 3, The Mermaid's Tale).

And yes, there's a larger point here.  The idea that some of us evolved 'for' sprinting, ping-pong, money-lending, economic prowess, or the ability to do well in 20th century school systems is based on, we think, a superficial understanding of evolution, and the way the brain works.  But it's an appealing one, one that too many scientists and journalists still believe.

Ideology assumes, science asks.

Yes, species are adaptable, but there are limits

For a species, habitats are successful in the long term when they sustain seasonal balancing between food sources and prey.  Flowers that insects feed on have to be in bloom when the insects that feed on and pollinate them have hatched and are looking for food, insects that a given species of bird feed on have to have hatched when that bird has arrived back from its winter or summer migrations, and so on.  So, climate change has the potential to disrupt complex habitats if migration times change, flowering times change, the timing of thaws and hibernations change, food species can't survive the changes, etc., all of which are occurring at the present time. It is likely that some of this has always been taking place, but generally at not nearly the rapid pace we see today.

So a paper in last week's Science is of interest.  In "Population Growth in a Wild Bird Is Buffered Against Phenological Mismatch," Reed et al. describe the effect of recent climate change on the cycling of a European songbird, the great tit, and its food sources.  In theory, gradual environmental change is less of a threat than rapid change because directional selection would favor organisms with extreme trait values that allow them to best adapt to the change, and because that change would be gradual enough that useful variation would be present and the selective intensity would not simply make the species extinct.

When this is the case, the average organism would do less well in the new environment than a subset of organisms with more extreme but adaptive trait values.  If environmental change is rapid, however, there may not be enough genetic variation in a population to allow it to adapt and keep pace with the changes.  And so the population is expected to experience reduced fitness, or a 'demographic cost' as the speed of change increases. If too severe, extinction is the ultimate price.

The Reed et al. study was a test of whether disruptions in the phenology, or seasonal timing, of predator and prey interactions affected the demography of the predator population.  If food is no longer available in abundance at the right time due to climate changes, is there a measurable effect of natural selection on traits that affect phenology in, in this instance, the tit?

We studied great tits (Parus major) in the Netherlands in relation to the phenology of their caterpillar food supply. This part of Western Europe has experienced substantial spring warming in recent decades related to global climate change. Great tits rely on caterpillars to feed their chicks and strive to match their breeding time with the pronounced seasonal peak in caterpillar biomass, which enhances offspring survival. Previous studies illustrated how climate change has produced a steadily increasing mismatch between great tit and caterpillar phenology in our study area, because the caterpillar food peak has advanced in response to rising spring temperatures at more than twice the rate of great tit laying dates. When temperatures during the period after great tits have laid their eggs (late spring) are high, the mismatch is larger (by 2.96 ± 0.43 days per 1°C increase, F1,36 = 47.40, P < 0.001), because caterpillars develop faster under warmer conditions and hence the food peak is early relative to the great tit nestling phase. The greater this mismatch, the stronger is directional selection for earlier laying dates (linear regression slope = –0.007 ± 0.003, F1,36 = 5.066, P = 0.031).

That is, the hypothesis is that great tits that lay their eggs early enough to take advantage of the peak supply of caterpillars to feed this chicks will produce more surviving offspring than those who continue to lay eggs at the later date.  And, this would be an 'extreme' trait, so presumably the great tit population would decline in years when the peak caterpillar supply was later than usual.  And, keep in mind that if we are considering this as an evolutionary effect, the variation must have a genetic basis.

But, the researchers don't find this.  Nor do they find an association between population growth and directional selection; phenological mismatch in this instance doesn't affect fitness (the genetically based reproductive success).  They controlled for the effects of variation in winter food supply (beech nuts), but found that it had no effect on fitness either.

Population growth as a function of (A) annual population mismatch
and (B) annual standardized selection gradient.  Source: Thomas et al.,
Science 26 April 2013 Vol. 340 no. 6131 pp. 488-491

Why is fitness not affected by this predator/prey timing mismatch?  The authors suggest two reasons.  One, the timing of egg laying is never optimal for all females relative to the peak supply of caterpillars because the peak supply window is always narrower than the variation in timing of egg laying.  So, fitness is never optimal for the entire population.

And second, reduced survival of hatchlings due to scare food supply is offset by improved survival of fledglings because there's less competition due to lower population size.  The survival of young birds is highly correlated with population density.

Again, we would note that even if there were  a difference in fitness, it would have no evolutionary relevance unless it were due to specific genetic variation.  This is easy to forget, even if an effect were found. 

In our book, The Mermaid's Tale, after which we named this blog, we suggested a set of general fundamental principles of life that 150 years of observation since Darwin have made apparent.  (We've blogged about these principles before, including here.)  We referred to one such principle as 'facultativeness', or the ability to adapt, which we have suggested must have been one of the earliest traits to evolve given that it is so ubiquitous.  Another word we've used to describe this is 'slop', or imprecision -- as opposed to the exquisitely finely-tuned adaptation that many people think of when they think of the effects of natural selection.

Timing of egg laying in the great tit, however it is determined, is clearly imprecise, and there's still variation in the trait.  And, importantly, that imprecision is tolerated.  It has not been drummed out of the population by natural selection, balancing or not.  And that's a good thing for great tits, given that their food supply varies.

It might be tempting to interpret these results as meaning that climate change isn't going to be a problem because organisms will just adapt.  And yes, organisms are adaptable -- within limits. Including the great tit.  But many species have already gone extinct, and many more will do so.  The Reed paper documents the response to a 3 degree temperature change.  As with the proverbial frog in a pot of water set to boil, there's no reason to think these results are generalizable to the greater changes to come.

If evolution has led to, or tolerated, facultativeness, there is still the question as to how it is maintained.  We don't suggest that there is a gene 'for' such a trait.  Instead, genetic mechanisms have evolved the ability to react to environmental conditions, rather than requiring very precise environments.  The result is that organisms can survive and reproduce in a range of circumstances.  This should not be a surprise to anyone, but may seem so if your view of evolution is that natural selection fine-tunes every species for  highly specific, restricted circumstances.  There's a word for species that were so programmed:  extinct.

Burrowing into the unending nature vs nurture debate

Behavior modules
Two interesting stories about behavior this week.  You've probably read about the mouse that builds its nest in a stereotypical way.  The Nature paper (Weber, Peterson, and Hoekstra) describing this was reported in The New York Times, as a story about how genes control complex behavior. 

The research was motivated by the question of how genetics influences the evolution of complex behaviors, but the researchers also wonder whether the environment influences variation in heritable behavior, and whether many or few genetic changes affect behavioral evolution.

The authors describe the burrow built by oldfield mice as having a long entrance and escape tunnels, and they say that the length is consistent wherever these mice build them, although tunnel depth depends on the soil in which they build.




Deer mice make a smaller, simpler burrow, and when the two species are interbred in the lab, the offspring reproduce the more complex burrow of the oldfield mouse, though with varying length.  First generation backcross mice (offspring of the interbreeding then bred with the parental strain) build burrows of varying length, and not all built escape tunnels, which suggests to the researchers that these behaviors are separately determined. 

The researchers then looked for genetic loci that might be influencing these behaviors and found three different loci that seem to contribute to tunnel length, and another that influences the building of escape tunnels.  As explained in the NYT:

All complicated behaviors are affected by many things, Dr. Hoekstra said, so these regions of DNA do not determine tunnel architecture and length by themselves. But tunnel length is about 30 percent inherited, she said, and the three locations account for about half of that variation. The rest is determined by many tiny genetic effects. As for the one location that affected whether or not mice dug an escape tunnel, if a short-burrow mouse had the long-burrow DNA region, it was 40 percent more likely to dig a complete escape tunnel. 

Well, if tunnel length is about 30 percent inherited (and there is variation in tunnel length; average length is 181 cm, with a standard deviation of ± 53), and the three locations account for about half of that variation, or perhaps 15% of the variation in tunnel-building, then the rest of the causation is not due to a few major genes.  Though, if it's 70% non-genetic, then one wonders how the environment specifies that a tunnel will have an escape hatch.

The authors conclude that "discrete genetic modules" control complex behaviors and that, "Together, these results suggest that complex behaviours—in this case, a classic ‘extended phenotype'—can evolve through multiple genetic changes each affecting distinct behaviour modules."  One could challenge this rather strong genetic-determinism view.  But how genes (much less environments) determine this type of thing is interesting and challenging to think about.

Overcoming behavior modules

Manduca sexta, or Hawkmoth;
Wikimedia Commons

The second story this week is from a paper in Science reporting that while the hawkmoth seems to innately prefer the nectar of night-blooming flowers, it can learn to collect nectar from other sources.  These moths seem to innately prefer flowers that give off a specific class of aromatic compounds, or at least the aromatics of their preferred flowers are processed similarly by the moth's olfactory response.

But the researchers wondered whether olfactory response necessarily reflects the moth's preference.  To test this, they exposed naive moths to paper flowers scented with different classes of compounds from those they generally prefer.  The moths were then observed to visit flowers emitting these scents at similar frequencies to those they innately prefer.  The authors conclude that "olfactory conditioning provided moths with flexibility in their foraging behavior but did not extinguish their innate preferences for scents from the moth-pollinated flowers." They suggest that "olfactory conditioning may operate in an olfactory "channel" separate from, but parallel to, that involved in the innate responses."  Modularity again. 

So much for exquisitely fine-tuned co-evolution of flower and pollinator. 

Glass half full/half empty
There's something for everyone here. The mouse researchers conclude that behavior is modular and evolves by the mixing and matching of genetic modules. Maybe, but there's plenty of non-heritable influence on mouse burrowing behavior as well, if tunnel length is only "about 30 percent inherited."

Modularity is a fundamental principle of life, and the idea that behavior, as well as morphological traits, can be modular is certainly a possibility -- every 4th grade class has its clown and its bully and its teacher's pet, after all.  But this doesn't mean that it must be genetically determined.  It could be, but the evidence isn't yet there. Maybe the non-mapped variation has to do with general cognitive function and how an animal scopes out its environment and decides what would be a good strategy for living in it.

We are all ultimately reducible to genes, in the sense that they are the basis of who and what we are.  But, as the hawkmoth study shows, the fact that even a lowly moth can easily overcome "innate" behavior with a whiff of something it wasn't born to crave is yet further evidence that organisms are inherently adaptable, a fundamental principle of life.  Given that environments can change quickly and unpredictably, that's a good thing. 

The microbiome: competition or cooperation, adaptation or adaptability?

We're just now getting around to blogging about a Perspectives piece in the Oct 12 Science called "Animal Behavior and the Microbiome" by Vanessa Ezenwa et al. It's an overview of current thinking about the role microorganisms play in animal behavior.  The Human Microbiome Project documenting the extent of such organisms in humans, and the essential role these guys play in human health and disease, has found that the genes in the trillions of microorganisms with which we share our bodies outnumber ours by 100 to 1.

Since at least some of these are necessary for life, one offshoot of learning about this is to ask what 'the' human genome really is.  Most bacteria we know of, like the ones in our gut, have to do with rather prosaic, if vital, physiology such as digestion.  These are interesting and important, but they don't involve more sensitive issues such as our personal identity -- our behavior.  The role of microbes in animal behavior is just beginning to be understood, and it may be more profound than had been thought. 

Kudzu bug; Wikipedia

For example, as described in the paper, "the Kudzu bug (Megacopta cribraria), an agricultural pest, is born without any symbionts (species with which both have a mutually necessary affiliation for survival). After birth it acquires a specific symbiont from bacterial capsules left by its mother. If these capsules are removed, the bugs show dramatic wandering behaviors, presumably to search for symbiont capsules left with nearby eggs."

Or, bumble bees acquire gut microbiota either through contact with nest mates or by feeding on feces containing the microbiota required by the gut. Bees without these microbiota were more susceptible to a bumble bee parasite, Crithidia bombi. Fruit flies that share the same diet-acquired microbiota are much more likely to mate with each other than with those that don't.  And then there's the zombie ant, infected by killer fungi, and the rats -- and cat ladies -- infected by Toxoplasma gondii, both of which we described here.  The examples go on and on.

But what does the recognition that we don't go through life alone mean for the usual understanding of social context, ecosystems and the evolution of behavior?  It's tempting to suggest that these are examples of exquisitely fine-tuned co-evolution, and the usual darwinian interpretation would be that every organism is out for itself, selfishly hijacking another's gut, brain, feces, nasal passages, skin, eyes, now manipulating their behavior -- any and everything -- to make a living.  And needing to out-compete all the other microbes fighting for the same territory.  But don't get too greedy or you'll kill your host and then you're in trouble too.  (Reminiscent of how humans feel about climate change -- we have to save the planet so we can continue to exploit it ourselves.) 

But this is rather a stretch, really, and depends on fitting the facts to a preconceived view of the purpose of organismal interactions (apply our take on why people believe microbes will be found on Mars here).  And that preconceived view is that life is all about selfishness, exploitation and competition.

But there's an alternative view, and that is that what this represents is cooperation, one of the fundamental principles of life that we've often written about here and in our book MT.  It's a principle that requires abandoning the long-held belief in the primacy of "survival of the fittest" because that very rarely happens.  A better description would be "failure of the frail" -- it's only the weakest organisms that can't reproduce; most everyone else does just fine.  Plus, much of survival depends to a large degree on luck and has nothing to do with genes or competition or your ability to outwit your neighbor.

So, this Russian doll kind of life-within-life-within-life that's being catalogued is an ongoing documentation of the centrality of cooperation in life.  There's surely some adaptation going on -- the bumble bee is better off without Crithidia bombi than with, but 10-20% of worker bees in hives in the field have been shown to be infected and bees have carried on; it's only now that they're bombarded with infection with multiple parasites and more that it's a problem.  But the bee did not evolve to be infected with gut microbiota to fight off C. bombi, the bee evolved with the ability to host gut microbiota and to fight off the parasite, however that happens. 

Further, some infection was survivable, and the parasite didn't need the bumble bee because it's an equal opportunity infector, infecting other insects.  This brings up another fundamental principle of life, and that's adaptability.  Because it's ubiquitous, we believe adaptability is a characteristic of life that was present very early in evolution. So, humans can't live without a gut full of microbiota, but the species that we host are widely variable, they change when we're ill or pregnant, we can kill them off in great numbers with antibiotics, can add more with probiotics or natural exposures, and we're fine.  The same has to be true for other organisms.

One can say that what's here has to work, or at least to have worked successfully enough in the past to be here today.  But that's only a part of the biology, and there has been a tendency to focus more on how that evolved via competition, than on the interactions themselves.  How cooperation works is turning out to be an elegant but complex business.  Even if Darwinian explanations are 100% correct -- and there are reasons to temper such a view -- understanding how such things work today is in itself a challenge, and a very interesting one at that.  Though, perhaps our very interest in it is because of some microbe in our brains, that makes us sympathetic to the lives of microbes...

Brains are like jelly....and they're fluid, too.

Intelligence is malleable?
Two pieces in the April 22 New York Times Sunday Magazine suggest that the idea that intelligence is fixed at birth has been greatly exaggerated.  We can get smarter if we work at it.  According to one piece, we have to exercise our fluid intelligence, and in the other, we have to exercise our bodies.

Fluid intelligence lifting weights
In 2008, two psychologists, Susanne Jaeggi and Martin Buschkuehl, published a paper in which they reported that young adults who play a challenging game requiring concentration can improve their "fluid intelligence", which the NYT article defines as "the capacity to solve novel problems, to learn, to reason, to see connections and to get to the bottom of things."

Psychologists have long regarded intelligence as coming in two flavors: crystallized intelligence, the treasure trove of stored-up information and how-to knowledge (the sort of thing tested on “Jeopardy!” or put to use when you ride a bicycle); and fluid intelligence. Crystallized intelligence grows as you age; fluid intelligence has long been known to peak in early adulthood, around college age, and then to decline gradually. And unlike physical conditioning, which can transform 98-pound weaklings into hunks, fluid intelligence has always been considered impervious to training.

The inflexibility of fluid intelligence has been the explanation for why we can't do better on I.Q. tests over our lifetimes.  Though, the pesky little problem of the Flynn effect, the sustained increase in I.Q. scores over decades in much of the world, has been a thorn in the side of those who hold that I.Q. is fixed.  And, even if people have never actually settled on what intelligence actually is, the idea that at least we know it's fixed, and that most studies show a considerable amount of heritability, has lead many to believe there must basically be due to the genotypes we're each born with.

Raven Matrix component of IQ test: fill in the blank square
Wikimedia Commons

So, if Jaeggi and Buschkuehl are correct that fluid intelligence can be improved with practice, a result they continue to demonstrate, this is a challenge to the idea that we're blessed or cursed with innate intelligence.  The idea is that intelligence must be similar to other highly heritable traits, like height, which is also susceptible to environmental effects -- even if within each individual's genetic or other constraints.

Mice lifting weights
The second intelligence story in the Sunday magazine comes at the issue from a different angle.  Mice given the chance to exercise get smarter.  Researchers determined this by giving them before and after cognitive tests, as well as before and after assessments of the structure of their brains.  And, as it happens, people who exercise get smarter, too.  Or at least their brains don't shrink nearly as much as they age as do the brains of sedentary people.

For more than a decade, neuroscientists and physiologists have been gathering evidence of the beneficial relationship between exercise and brainpower. But the newest findings make it clear that this isn’t just a relationship; it is the relationship. Using sophisticated technologies to examine the workings of individual neurons — and the makeup of brain matter itself — scientists in just the past few months have discovered that exercise appears to build a brain that resists physical shrinkage and enhance cognitive flexibility. Exercise, the latest neuroscience suggests, does more to bolster thinking than thinking does.

So, forget personalized genomic medicine, to get smart, just bike (or run) to work, thinking about something profound all the way.

Can this really be true?
Of course, Jaeggi and Buschkuehl have their critics.  Some simply don't believe that fluid intelligence is mutable, and studies continue to confirm this view. But J and B aren't the only psychologists who are beginning to find mutability and as a result, other psychologists are starting to believe their work. But, it's an interesting thing when expert assessment of scientific results depends on belief.  And the word is laced throughout the NYT piece.

Indeed, you're more likely to buy their work if you're not predisposed to think that I.Q. is genetically determined.  Well, and if you think I.Q. is real, measurable, not culturally determined and so on.  And where you come down on these issues seems to be correlated with your politics, at least to some extent.  Rather like where you come down on climate change, or evolution, or the genetics of how people vote.

But let's step away from the politics for the moment, and think about what our particular view of evolution might have to offer here.  Specifically, the idea that seems fairly obvious, that evolution has been consistently good at producing adaptability.  Over and over and over again, so much so that it seems to us to be a fundamental principle of life, organisms have been imbued with the ability to detect, evaluate, and adapt to changing circumstances.  So, to us, it's no surprise that our brains, too, can respond to changing circumstances, can respond to environmental challenges by, say, building new neuronal synapses.  It would be more surprising if it couldn't.  And changes in the brain can involve non-cognitive as well as cognitive intelligence -- that is, it need not involve consciousness as it often does in humans and presumably other animals.

Brains and central nervous systems are, after all, centers of evaluation.  Sensory inputs go there, and are sorted through and evaluated, and decisions made on how to respond to them.  The idea, no pun intended, is that the brain is not a pre-programmed, hard-wired automoton, but allows each unique moment to be sifted and judged, and even more, each moment can leave its mark.  Someone whose cognition is too rigid might be much more likely to be a former someone.

Brains have the texture of jello, but they're fluid as well -- food for thought at least.

That's disgusting! Make up your own Just-So story about the evolution of an emotion

The evolution of disgust
Everyone seems to be talking about disgust these days, from why it evolved to what parts of our brains light up when we feel it (it's the anterior insular cortex).  There was a story in the NYT about it on Tuesday ("Survival's Ick Factor"), and a review of a new book (one of many) about it in the Sunday NYT Book Review, a conference in Germany, and an issue of the Philosophical Transactions of the Royal Society devoted to the subject.  Darwin included disgust in his list of the 6 basic human emotions, and wrote of seeing it on the faces of his infant children. 

Indeed, it seems that disgust now explains many human characteristics from tribalism, to disease avoidance, to poison critter avoidance, and mate choice.  And, disgust gone haywire explains psychological pathologies from obsessive compulsive disorder to excessive anxiety.

A paper in Perspectives in Biology and Medicine in 2001 lists the basic disgust elicitors. 

We suggest that the objects or events which elicit disgust can be placed in the following five broad categories:

1. Bodily excretions and body parts

2. Decay and spoiled food

3. Particular living creatures

4. Certain categories of "other people"

5. Violations of morality or social norms

Bodily secretions are the most widely reported elicitors of the disgust emotion. Feces appear on all of the lists, while vomit, sweat, spittle, blood, pus, and sexual fluids appear frequently. Body parts, such as nail clippings, cut hair, intestines, and wounds, evoke disgust, as do dead bodies. Certain animals are repeatedly mentioned, in particular pigs, dogs, cats, fish, rats, snakes and worms, lice, cockroaches, maggots, and flies. Spoiled food, especially meat and fish, and other decaying substances, such as rubbish, are disgusting to many respondents. Certain categories of other people are also found disgusting, notably those who are perceived as being either in poor health, of lower social status, contaminated by contact with a disgusting substance, or immoral in their behavior.

And then there are sensory cues, smells, feel, sounds.  A number of writers explain that all these things are disgusting because they remind us of our animal -- unhealthy? -- origins.  Others say it evolved to defend body and soul from pollution (as apparently being reminded of our animal origins pollutes the soul).  

In their exploration of Darwinian medicine, Nesse and Williams (Evolution and Healing, 1995) suggest that an instinctive disgust may motivate the avoidance of feces, vomit, and people who may be contagious, and that disgust is one of the mechanisms crafted by natural selection to help us keep our distance from contagion. Pinker (How the mind works,1998) proposes that disgust is "intuitive microbiology," and that this explains our aversion to objects that have been in contact with disgusting substances: "Since germs are transmissible by contact, it is no surprise that something that touches a yucky substance is itself forever yucky." 

It's nice that this emotion is finally getting the attention that it clearly deserves.

But wait a second!
Except -- there had to be an except! -- except that a lot of this starts to sound suspiciously like just another elaborate evolutionary Just-So story.  New parents, nurses, physicians all quickly lose any disgust at bodily excretions, and one person's spoiled food is another's delicacy.  Just think of the rich array of foods that people on this planet eat.  Not to mention dogs, who'll eat just about anything.  Dogs share many of our emotions, and, if essentially all humans feel disgust, our sense of disgust had to have evolved earlier than we did, so shouldn't other lineages who share our disgust-feeling common ancestor, such as dogs, also share our supposedly instinctual disgust with eating, say, rotten meat, or vomit?

Dead Zambian shrew, not Holly's shrew

Which may explain why Holly reports holding up a dead shrew to her two dogs and finding that they wouldn't touch it.  She says her dogs would happily tear apart a dead squirrel, but not the shrew.  She thinks maybe it died of pesticide poisoning, though she couldn't smell anything.  Were they disgusted (by at least this one thing!), thus saving themselves from pesticide poisoning?  Or is it that they have learned to tear apart squirrels and not shrews?  Who knows?

But then, why is it disgusting to some people to eat insects, while others thrive on them (roasted, chocolate covered, etc.)?  Or why did Americans once disdain disgusting lobster....and now drop big bucks for a nice, juicy claw?  European Americans recoil at the thought of eating horse meat, while to many of their Old World brethren it's a delicacy. Or what about latakia pipe tobacco and lapsong suchong tea, 'cured' as one might say, over dung fires?  The list could go on and on and on, but what it means is that there's an obvious learned component.

But, let's agree for the sake of argument that disgust as an emotional reaction in fact evolved as a specific trait.  And even that disgust might have its uses (though, too much of it can be a problem).  All this means is that, as other successful traits that have stood the test of evolutionary time, disgust itself is adaptable.  That is, yes, we may all feel disgust, but what disgusts us at any given time is culturally determined, not innate.  Otherwise, how could we learn that Twinkies were disgusting?  (Or not.  It turns out that if you search in Google Images for Twinkies, you'll find a photo of Twinkies Fondue; Twinkies, circus peanuts, caramel Ho-Hos, marshmallows, and candied orange slices on a skewer, waiting to be dipped into molten chocolate.  Or Scottish deep-fried Mars bars!  Who thinks these things up?)

Our better idea!
And any of us can think of alternative hypotheses as to what disgust is 'for'.  Here's ours -- how about that it's part of our repertoire of communication, rather than an innate ability to save ourselves from decaying meat?  Why would we need a facial expression that communicates disgust if the emotion itself were the survival tactic, alerting us not to eat that rotting wildebeest?  Surely we could teach our children that even bunny rabbits were disgusting, if we started them young enough.  So, in adaptive terms, it's communicating that we're disgusted that's important, not what we're disgusted by.  Why?  Because it elicits caretaking, a survival tactic if there ever was one. And of course survival is very directly tied to evolutionary fitness.

But all this hoopla about disgust is a bit disgusting itself.  Are we really desperate to have specialties so that someone can be called by the NY Times "a pioneer of modern disgust research"? It's one thing to specialize, even to this extent, and perfectly legitimate to identify 'disgust' and try to understand its neurophysiology and physiological triggers -- if there really is an 'it'.  But it's quite another big step to attempt to Darwinize something so vague, and the fact that Darwin mentioned it doesn't change that.  Evolutionary scenarios are hard to pin down, even with well-defined traits.  The evidence by and large suggests that most of the human versions of this emotion, if it is a particular emotion, are learned and experiential and culture-specific -- adaptable. 

Obviously the inherent aspects, the 'adaptive' aspects of our disgusting behavior are unclear, hard to identify, harder to prove, and in any case it is not obvious that we have any such adaptations that were not in place eons before a human ever stepped on a wildebeest patty (barefoot--UGH!).

This year's acorn crop cont.

More on this year's magnificent crop of acorns.  I did hear back from the forester on the question of why so many acorns this year.  He says that oaks are generally sporadic fruit producers, with really good crops every 4 to 7 years.  There are several reasons for this, one being the weather and the other an ecological adaptation.

A late spring frost is hard on oak flowers, and will lead to a low yield, he says.  And, insects play a role.  There are on the order of 30 different species of acorn weevils "that can destroy up to 90% of any given year's production either while it is on the tree developing or after they fall in the autumn."  The cyclic nature of fruit production helps keep the insect population down.

And, he says that there are advantages to sporadic fruit production.  It keeps predator populations down, which increases the chances that some acorns from a given tree will survive and grow.  If not, my informant says, the tree would always be having to produce more and more fruit to stay ahead of the rodents.  Similarly, the fluctuation keeps weevil populations down, and thus acorn destruction down.  Good for the tree, not so good for the predators. 

Both explanations sound plausible.  However, regular MT readers won't be surprised if we are a bit reluctant to accept the adaptive explanation right off the shelf. First, an oak tree is lucky if even a few of the acorns it produces in any given year makes its perilous way to treehood.  Even in a bad year, oaks way overproduce acorns relative to what will take root, or replacement needs and so on.

However, sporadic fruit production in response to the vagaries of climate or other means of destruction of flowers or developing acorns is completely in keeping with the adaptability or facultativeness that is a core evolutionary principle.  Oak trees need to be able to adapt to change, and good and bad fruit production years is one way they do so.  It's easier to suggest but a lot more difficult to conceive how a tree 'knows' (genetically evolves) to adjust for variable predator loads in the hypothesized way, when climate itself is unpredictable.

Evolutionary psychology has had its day?

David Brooks had an interesting piece in the New York Times yesterday about evolutionary psychology. He says that evolutionary psychology has had a good run, but that it's time to recognize that organisms are much more adaptable than the field allows.

Adaptability is one of the basic principles of life that we propose in our book, but it has been out of favor in this era of genetic determinism. Genetic determinism has a long and sorry history as biological essentialism, a value-based view of what or who is good and what or who isn't, and what we really are like despite what we may think (and an assault on free will as well). It is part of a cycle in human thought....one that included decades of eugenics and Naziism as justifications for the worst possible actions by some against others.

It's interesting to see this conservative columnist taking up this cause.