Evolution of Language tested with genetic analysis
Human Migration, National Geographic
Evolutionary Babel was in southern Africa
“Where did humanity utter its first words? A new linguistic analysis attempts to rewrite the story of Babel by borrowing from the methods of genetic analysis – and finds that modern language originated in sub-Saharan Africa and spread across the world with migrating human populations.
Quentin Atkinson of the University of Auckland in New Zealand designed a computer program to analyse the diversity of 504 languages. Specifically, the program focused on phonemes – the sounds that make up words, like “c”, “a”, and “tch” in the word “catch”.
Earlier research has shown that the more people speak a language, the higher its phonemic diversity. Large populations tend to draw on a more varied jumble of consonants, vowels and tones than smaller .
Africa turned out to have the greatest phonemic diversity – it is the only place in the world where languages incorporate clicks of the tongue into their vocabularies, for instance – while South America and Oceania have the smallest. Remarkably, this echoes genetic analyses showing that African populations have higher genetic diversity than European, Asian and American populations.
This is generally attributed to the “serial founder” effect: it’s thought that humans first lived in a large and genetically diverse population in Africa, from which smaller groups broke off and migrated to what is now Europe. Because each break-off group carried only a subset of the genetic diversity of its parent group, this migration was, in effect, written in the migrants’ genes.
Dr. Mark Pagel sees language as central to human expansion across the globe.
“Language was our secret weapon, and as soon we got language we became a really dangerous species,” he said.
— Nicholas Wade, Phonetic Clues Hint Language Is Africa-Born, NYT, Apr 14, 2011.
Atkinson argues that the process was mirrored in languages: as smaller populations broke off and spread across the world, human language lost some of its phonemic diversity, and sounds that humans first spoke in the African Babel were left behind.
To test this, Atkinson compared the phoneme content of languages around the world and used this analysis to determine the most likely origin of all language. He found that sub-Saharan Africa was a far better fit for the origin of modern language than any other location. (…)
“It’s a compelling idea,” says Sohini Ramachandran of Brown University in Providence, Rhode Island, who studies population genetics and human evolution. “Language is such an adaptive thing that it makes sense to have a single origin before the diaspora out of Africa. It’s also a nice confirmation of what we have seen in earlier genetic studies. The processes that shaped genetic variation of humans may also have shaped cultural traits.”
Out of Africa (Map source: The Mother of All Languages, WSJ.com, Apr 15, 2011)
Language universality idea tested with biology method
(The study challenges the idea that the “language centres” of our brains are the sole driver of language)
“A long-standing idea that human languages share universal features that are dictated by human brain structure has been cast into doubt.
A study reported in Nature has borrowed methods from evolutionary biology to trace the development of grammar in several language families.
The results suggest that features shared across language families evolved independently in each lineage.
The authors say cultural evolution, not the brain, drives language development.
At the heart of both studies is a method based on what are known as phylogenetic studies.
Lead author Michael Dunn, an evolutionary linguist at the Max Planck Institute for Psycholinguistics in the Netherlands, said the approach is akin to the study of pea plants by Gregor Mendel, which ultimately led to the idea of heritability of traits. (…)
“He inferred the existence of some kind of information transfer just from knowing family trees and observing variation, and that’s exactly the same thing we’re doing.”
Modern phylogenetics studies look at variations in animals that are known to be related, and from those can work out when specific structures evolved.
For their studies, the team studied the characteristics of word order in four language families: Indo-European, Uto-Aztec, Bantu and Austronesian.
They considered whether what we call prepositions occur before or after a noun (“in the boat” versus “the boat in”) and how the word order of subject and object work out in either case (“I put the dog in the boat” versus “I the dog put the canoe in”).
The method starts by making use of well-established linguistic data on words and grammar within these language families, and building “family trees” of those languages.
“Once we have those trees we look at distribution of these different word order features over the descendant languages, and build evolutionary models for what’s most likely to produce the diversity that we observe in the world,” Dr Dunn said.
The models revealed that while different language structures in the family tree could be seen to evolve along the branches, just how and when they evolved depended on which branch they were on.
“We show that each of these language families evolves according to its own set of rules, not according to a universal set of rules,” Dr Dunn explained.
“That is inconsistent with the dominant ‘universality theories’ of grammar; it suggests rather that language is part of not a specialised module distinct from the rest of cognition, but more part of broad human cognitive skills.”
The paper asserts instead that “cultural evolution is the primary factor that determines linguistic structure, with the current state of a linguistic system shaping and constraining future states”.
However, co-author and evolutionary biologist Russell Gray of the University of Auckland stressed that the team was not pitting biology against culture in a mutually exclusive way.
“We’re not saying that biology is irrelevant - of course it’s not,” Professor Gray told BBC News.
“But the clumsy argument about an innate structure of the human mind imposing these kind of ‘universals’ that we’ve seen in cognitive science for such a long time just isn’t tenable.”
Steven Pinker, a cognitive scientist at Harvard University, called the work “an important and welcome study”.
However, Professor Pinker told BBC News that the finer details of the method need bearing out in order to more fully support their hypothesis that cultural boundaries drive the development of language more than biological limitations do.
“The [authors] suggest that the human mind has a tendency to generalise orderings across phrases of different types, which would not occur if the mind generated every phrase type with a unique and isolated rule.
“The tendency may be partial, and it may be elaborated in different ways in differently language families, but it needs an explanation in terms of the working of the mind of language speakers.”
— Jason Palmer, Science and technology reporter, Language universality idea tested with biology method, BBC News, 14 April 2011.
Evolution of Language Takes Unexpected Turn
“The findings “do not support simple ideas of the mind as a computer, with a language processor plugged in. They support much-more complex ideas of how language arises.” (…)
One school of thought, pioneered by linguist Noam Chomsky, holds that language is a product of dedicated mechanisms in the human brain. These can be imagined as a series of switches, each corresponding to particular forms of grammar and syntax and structure.
Such a system would account for why, of the nearly infinite number of languages that are possible — imagine, for instance, a language in which verb conjugation changes randomly; it is possible — relatively few actually exist. Our brains have adapted to contain a limited, universal set of switches.
A limited set of linguistic universals is exactly what was described by the late, great comparative linguist Joseph Greenberg, who empirically tabulated features common to language. He made no claims as to neurological origin, but the essential claim overlapped with Chomsky’s: Language has universals.
If you speak a subject-verb-object language, one in which “I kick the ball,” then you likely use prepositions — “over the fence.” If you speak a subject-object-verb language, one in which “I the ball kicked,” then you almost certainly use postpositions — “the fence over.” And so on.
“What both these views predict is that languages should evolve according to the same set of rules,” said Dunn. “No matter what the language, no matter what the family, if there are two features of language that are somehow linked together structurally, they should be linked together the same way in all languages.”
That’s what Dunn, along with University of Auckland (New Zealand) computational linguist Russell Gray, set out to test.
Unlike earlier linguists, however, Dunn and Gray had access to powerful computational tools that, when set to work on sets of data, calculate the most likely relationships between the data. Such tools are well known in evolutionary biology, where they’re used to create trees of descent from genetic readings, but they can be applied to most anything that changes over time, including language.
In the new study, Dunn and Gray’s team created evolutionary trees for eight word-order features in humanity’s best-described language groups — Austronesian, Indo-European, Bantu and Uto-Aztecan. Together they contain more than one-third of humanity’s 7,000 languages, and span thousands of years. If there are universal trends, say Dunn and Gray, they should be visible, with each language family evolving along similar lines.
That’s not what they found.
“Each language family is evolving according to its own set of rules. Some were similar, but none were the same,” said Dunn. “There is much more diversity, in terms of evolutionary processes, than anybody ever expected.”
In one representative example of divergence (diagram above), both Austronesian and Indo-European languages that linked prepositions and object-verb structures (“over the fence, ball kicked) tended to evolve preposition and verb-object structures (“over the fence, kicked ball.”) That’s exactly what universalism would predict.
But when Austronesian and Indo-European languages both started from postposition, verb-object arrangements (“the fence over, kicked ball”), they ended up in different places. Austronesian tended towards preposition, verb-object (“over the fence, kicked ball”) but Indo-European tended towards postposition, object-verb (“the fence over, ball kicked.”)
Such differences might be eye-glazing to people unaccustomed to diagramming sentences, but the upshot is that the two language families took opposite trajectories. Many other comparisons followed suit. “The things specific to language families trumped any kind of universals we could look for,” said Dunn.
“We see that there isn’t any sort of rigid” progression of changes, said University of Reading (England) evolutionary linguist Mark Pagel, who wasn’t involved in the study. “There seems to be quite a lot of fluidity. That leads me to believe this isn’t something where you’re throwing a lot of parameter switches.”
Instead of a simple set of brain switches steering language evolution, cultural circumstance played a role. Changes were the product of chance, or perhaps fulfilled as-yet-unknown needs. For whatever reason, “the fence over, ball kicked” might have been especially useful to Indo-European speakers, but not Austronesians.
There is, however, still room for universals, said Pagel. After all, even if culture and circumstance shapes language evolution, it’s still working with a limited set of possibilities. Of the six possible combinations of subject, verb and object, for example, just two — “I kicked the ball” and “I the ball kicked” — are found in more than 90 percent of all languages, with Yoda-style “Kicked I the ball” exceedingly rare. People do seem to prefer some structures.
“What languages have in common is to be found at a much deeper level. They must emerge from more-general cognitive capacities,” said Dunn.
What those capacities may be is a new frontier for investigation. As for Dunn, his team next plans to conduct similar analyses on other features of language, searching for further evolutionary differences or those deeper levels of universality.”
“This can be applied to every level of language structure,” he said.
☞ Andis Kaulins, Principles of Historical Language Reconstruction, AABECIS, Feb 24, 2010.
☞ Researchers Synthesize Evolution of Language
☞ Evolution of Language Parallels Evolution of Species
☞ Gut Bacteria, Language Analysis Solve Pacific Migration Mystery
☞ Cultural Evolution Could Be Studied in Google Books Database
☞ Human-Chimp Gene Comparison Hints at Roots of Language
☞ Mark Changizi on how we read
☞ Mark Changizi, The Topography Of Language, Science 2.0, Sep 17, 2009.
☞ A brief history of writing
☞ Evolved structure of language shows lineage-specific trends in word-order universals, Word-Order Research, Basic Vocabulary Database
☞ The Tree of Life: Tangled Roots and Sexy Shoots. Tracing the genetic pathway from the first Eukaryotes to Homo sapiens.
☞ The Genographic Project ☞ A Landmark Study of the Human Journey