Talking to the animals

An Introduction to Language (by Victoria Fromkin and Robert Rodman, Third Edition, 1974) defines language as "rule-governed arbitrary symbolic communication."

The "rule-governed" and "arbitrary" parts might seem contradictory, but they're not.  That language has rules is self-evident whether you are a prescriptivist (someone who believes there are correct and incorrect ways to use language) or a descriptivist (someone who believes that as long as communication is occurring, it's language; so the primary role of the linguist is not to enforce rules but to document them).  Being that my master's degree is in historical linguistics, I'm strongly of a descriptivist bent; if I thought there were an inflexible lexicon and set of grammatical rules that never ever changed, I'd kind of be out of a job.

The arbitrary part is less obvious.  It has to do with the sound-to-meaning correspondence.  Dog in English is inu in Japanese, chien in French, kare in Hausa, and hundur in Icelandic; none of those words are, in fact, especially doggy in nature.  Other than a handful of onomatopoeic words like bang, oink, meow, and hiccup, the connection between a word and its meaning is essentially accidental.

Curiously, humans are the only species on Earth that we are certain have true language, by the Fromkin and Rodman definition.  There's long been a suspicion that dolphin and whale vocalizations might be language, but as of this writing, that remains conjecture.  Recently, there have been some interesting studies of other primates indicating that certain features of language might exist outside of Homo sapiens -- a paper out of the University of Warwick last week suggests that orangutan vocalizations might exhibit recursion, the nesting structure you see in the children's rhyme "This is the House That Jack Built."  The researchers found that the sounds orangutans make are grouped into clusters, and those clusters put together in at least two additional tiers of structure, hinting that their vocalizations might have a much richer information-carrying capacity than we'd thought.

Another recent study, this one out of the University of Vienna, found that chimps might use drumming as a means of long-distance communication -- that the spacing of beats when they drum on tree roots varies but is non-random.  Like the recursion found in orangutans, the fact that the rhythm of drumming in chimps isn't just random noise opens up the possibility that it might be meaningful.  The researchers found that different chimps have different rhythmic styles, and that groups also developed their own unique patterns of drumming -- suggestive that drumming in chimps could be a cultural phenomenon.

How we developed language, and (likely) no other extant species did, is still open to question.  There are some interesting genetic pieces to the puzzle; the forkhead box protein 2 (FOX-P2) gene seems to be an important one, as the human variant of FOX-P2 isn't found in any known living species other than ourselves, and mutations in that sequence result in significant problems with learning and utilizing language.  (Genetic studies of Neanderthal remains found that Neanderthals had an identical FOX-P2 gene to that of modern humans; obviously we can't be sure that they had language, but it seems likely.)

[Image licensed under the Creative Commons Emw, Protein FOX-P2 PDB 2a07, CC BY-SA 3.0]

Actually, it was genetics that got me thinking about this topic today; yet another study, this one out of Rockefeller University and Cold Springs Harbor Laboratory, did a gene insertion on mice, replacing the murine version of the NOVA-1 gene with the human variant.  The human NOVA-1 has only a single base pair substitution as compared with that of other mammals, but -- like FOX-P2, damage to this gene is known to impair language learning and production.

And when you replace a mouse embryo's NOVA-1 gene with a human's, the resulting adult mouse is capable of making strikingly more complex vocalizations than your ordinary mouse can do.

"When adult male mice were genetically altered with the human NOVA-1 variant, their squeaks during courtship didn't become higher pitched like the pups," said Robert Darnell, who was lead author on the paper.  "Instead, their vocalizations included more complex syllables.  They 'talked' differently to the female mice.  One can imagine how such changes in vocalization could have a profound impact on evolution....  NOVA-1 encodes a protein that can cut out and rearrange sections of messenger RNA when it binds to neurons.  This changes how brain cells synthesize proteins, probably creating molecular diversity in the central nervous system...  The 'humanized' mice with the NOVA-1 variant had molecular changes in the RNA splicing seen in brain cells, especially in regions associated with vocal behavior."

So we're one step closer to figuring out a uniquely human phenomenon.  That communication in the animal world exists on a spectrum of complexity is certain, but by the Fromkin/Rodman definition, we're kind of it for true language, as far as we know.  How we gained that ability is still not entirely clear, but its advantages are obvious -- and it may be that mutations in two regulatory genes are what kickstarted a capacity for chatter that in large part is responsible for our dominance of the entire biosphere.

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The arms of the ancestors

My maternal grandmother was born Flora Meyer-Lévy, in the little town of Chackbay, Louisiana, in 1893.  I never knew her -- she died fourteen years before I was born, at the young age of 53 -- but I have photographs of her that show a striking woman with auburn hair and a serious expression (consistent with my mom's description of her mother as being a no-nonsense type).

Flora's grandfather, Solomon Meyer-Lévy, was an Ashkenazi Jew, born in the village of Dauendorf, in Alsace.  He emigrated to the United States in the 1850s, only to get caught up in the Civil War -- he fought for a time on the Confederate side, and after the war came home and gave a go at raising horses.  He never made much of a success of it.  One of his grandchildren told me, somewhat euphemistically, that "he made bad deals while drunk."  Solomon, like his granddaughter, died young, at the age of 44.  His widow -- a French Creole woman named Florida Perilloux -- outlived him by over forty years.  She never remarried, and lived most of that time in poverty, converting their home into an inn just to make ends meet.

When I had my DNA tested a couple of years ago, I was fascinated to find that it detected my Ashkenazi great-great grandfather's contribution to my genetic makeup.  I am, the test said, about six percent Ashkenazi -- just about spot-on for having one Jewish ancestor four generations back.  I was surprised that my Jewish heritage was so clear; I didn't realize that Ashkenazi DNA is that distinct.

Apparently, the Ashkenazi have retained their genetic signature because of two factors -- being reproductively isolated and having experienced repeated bottlenecks.  The former, of course, is due to the taboo (on both sides) against Jews marrying non-Jews.  (My great-great grandparents are an interesting counterexample; he was a devout Jew, she was a devout Catholic, and neither one ever changed their religion.  They apparently lived together completely amicably despite their religious differences.  All seven of their children were raised Jewish -- and every single one converted to Catholicism to marry.  Evidently such tolerance was not the rule in nineteenth century Louisiana.)

The latter -- a genetic bottleneck -- refers to the situation when a population has its numbers reduced drastically, and the resurgent population all descends from the small group of survivors.  The bottlenecks in the European Jewish population, of course, were due largely to the repeated pogroms (massacres) that at times looked like eradicating the Jews from Europe entirely.  In fact, this is why the topic comes up today; a paper in Science that came out this week about a genetic investigation of the remains in a Jewish cemetery in Erfurt, Germany.  Many of the dead there were victims of a pogrom in March of 1349, and their teeth -- which contain intact DNA -- confirmed that the Ashkenazi were even then a genetically distinct population, descended from a small group of people who came originally from the Middle East or the Caucasus, and settled in central Europe some time around the year 1000 C.E.

Interestingly, the DNA from Erfurt was strikingly similar to DNA from a twelfth-century Jewish cemetery in Norwich, England, the subject of a paper only four months ago.  The geographical distance, apparently, was not enough to erase the distinct Ashkenazi signature.  "Whether they’re from Israel or New York, the Ashkenazi population today is homogenous genetically," said Hebrew University geneticist Shai Carmi.

Which explains how the DNA test was able to pick up my own ancestry.

It's fascinating to me that, on that one line at least, my family tree can trace its origins to a little group of migrants from the Near East who made their way to what is now eastern France, survived repeated attempts to eradicate them, and eventually produced a branch that went to Louisiana, ultimately leading to me here in upstate New York.  I can only hope I've inherited some of the dogged tenacity these people obviously had.

It's interesting, too, to look at the stern visage of the grandmother I never met, and to know a little more about her heritage.  Even though she, like all the generations before her, now rests in the arms of the ancestors, her genetic legacy lives on in me and her other descendants -- a handful of the "countless stars in the sky" that represent the lineage of Abraham.

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Switching on humanity

Humans, chimps, and bonobos share a little over 99% of their DNA.

That remaining just-under-one-percent accounts for every physical difference between you and our nearest ape relatives.  It's natural enough to be surprised by this; we look and act pretty different from them most of the time.  (Although if you've read Desmond Morris's classic study The Naked Ape, you'll find there's a lot more overlap between humans and apes behaviorally than you might have realized.)

[Image licensed under the Creative Commons Greg Hume, Bonobo-04, CC BY-SA 3.0]

Part of that sense of differentness is from the cultural context most of us grew up in -- that "human" and "animal" are two separate categories.  In a lot of places that comes from religion, specifically the idea that the Creator fashioned humans separately from the rest of the species on Earth, and that separation persists in our worldviews even for many of us who no longer believe in a supreme deity.  The truth is we're just another branch of Kingdom Animalia, Phylum Chordata, Class Mammalia, Order Primata, albeit a good bit more intelligent and technologically capable than most of the other branches.

It's that last bit that has captured the curiosity of evolutionary geneticists for decades.  The similarities between ourselves and apes are obvious; but where did the differences come from?  How could less than one percent of our DNA be responsible for all the things that do set us apart -- our larger brains, capacity for language, upright posture, and so on?

Just last week, a paper in the journal Cell, written by a team out of Duke University, may have provided us with some answers.

The researchers found that the most striking differences between the genomes of humans and those of chimps and bonobos lay in a set of switches they dubbed Human Ancestor Quickly-Evolved Regions (HAQERs -- pronounced, as you might have guessed, like "hackers").  HAQERs are genetic regulatory switches, that control when and how long other genes are active.  The HAQER sequences the team discovered seem to mostly affect two sets of developmental genes -- the ones that influence brain complexity and the ones involved in the production of the gastrointestinal tract.

"We see lots of regulatory elements that are turning on in these tissues," said Craig Lowe, who co-authored the paper, in an interview with Science Daily.  "These are the tissues where humans are refining which genes are expressed and at what level...  Today, our brains are larger than other apes, and our guts are shorter.  People have hypothesized that those two are even linked, because they are two really expensive metabolic tissues to have around.  I think what we're seeing is that there wasn't really one mutation that gave you a large brain and one mutation that really struck the gut, it was probably many of these small changes over time."

What's most interesting of all is that the HAQER sequences provide another example of how evolution is so frequently a trade-off.  Consider, for example, our upright posture; our vertebral column evolved in animals that walked on all fours, and when we switched to being bipedal it gave us the advantage of freeing up our hands and being able to see farther, but it bequeathed a legacy of lower back problems most other mammals never have to worry about.  Here, the HAQERs that seem to be responsible for our larger and more complex brains also correlate to a variety of disorder susceptibilities.  Particular variants of HAQER sequences are associated with a higher risk of hypertension, neuroblastoma, depression, bipolar disorder, and schizophrenia.

It's just the way genetic change works.  Sometimes you can't improve one thing without screwing something else up.  And if, on balance, the change improves survival and reproductive likelihood, it's still selected for despite the disadvantages.

So we seem to finally be making some inroads into the question of why such a tiny slice of our genome creates all the differences between ourselves and our nearest relatives.  It's worth a reminder, though, that we aren't substantially different than the other species we share the planet it.  It reminds me of the famous quote from Chief Seattle: "We did not weave the web of life, we are merely one strand in it.  Whatever we do to the web, we do to ourselves."

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