Return of the Language Evolution Tree

April 20, 2011 in Irreverant and Irrelevant

A while ago, some collegues and I noticed that two prominent books on Language Evolution -Christiansen & Kirby’s Language Evolution and Fitch’s Evolution of Language – both included a picture of an acacia tree in the sunset on their covers.  On closer analysis, it turned out that they were the same tree:

Thus began the Acacia Tree Hypothesis of Language Evolution.

Following this up, I was thinking about Dediu & Ladd’s discovery that linguistic tone is has certain genetic correlates. Here’s the map of languages with linguistic tone:

However, I suspected the devious influence of acacia trees and so I found some information on their geographic distribution:

As I suspected, countries in which the acacia tree Acacia nilotica grows are significantly more likely to have tonal languages:

Tone No Tone
Acacia Trees 163 117
No Acacia Trees 104 237

(Chi-squared with Yates’ continuity correction = 47.1, df = 1, p < 0.0001, data from Crop Protection Consortium and the World Atlas of Language Structures).

The plot thickens …

 

Dediu, D., & Ladd, D. R. (2007). Linguistic tone is related to the population frequency of the adaptive haplogroups of two brain size genes, Microcephalin and ASPM. Proceedings of the National Academy of Sciences, 104, 10944–10949.

Fitch, W. T. 2010 The evolution of language. Cambridge, UK: Cambridge University Press.

Christiansen, M. and Kirby, S. (2003). Language Evolution. Oxford University Press.

 

Update:

I’ve added the images David mentioned to the post:

Also, The Babel’s Dawn blog banner

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The Return of the Phoneme Inventories

April 19, 2011 in Linguistics, Science

Right, I already referred to Atkinson’s paper in a previous post, and much of the work he’s presented is essentially part of a potential PhD project I’m hoping to do. Much of this stems back to last summer, where I mentioned how the phoneme inventory size correlates with certain demographic features, such as population size and population density. Using the the UPSID data I generated a generalised additive model to demonstrate how area and population size interact in determining the phoneme inventory size:

Interestingly, Atkinson seems to derive much of his thinking, at least in his choice of demographic variables, from work into the transmission of cultural artefacts (see here and here). For me, there are clear uses for these demographic models in testing hypotheses for linguistic transmission and change, as I see language as a cultural product. It appears Atkinson reached the same conclusion. Where we depart, however, is in our overall explanations of the data. My major problem with the claim is theoretical: he hasn’t ruled out other historical-evolutionary explanations for these patterns.

Before we get into the bulk of my criticism, I’ll provide a very brief overview of the paper.

Read the rest of this entry →

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Cultural Transmission observed in Whales

April 15, 2011 in Science, Science News

A new paper in Current Biology, published today has revealed that the songs of Humpbacked Whales are passed through the ocean by mechanisms of cultural transmission.

Cultural transmission is defined as the social learning of information or behaviours either over generations or via peers. It has been seen to occur in primates, cetaceans and birds.

Cultural transmission over generations, i.e. parent passing socially learnt traits to their offspring, is known as vertical transmission and cultural transmission via peers, unrelated individuals from within generations, is known as horizontal transmission. In humans, languages and memes are transmitted, learned and (in a lot of cases) evolved in this manner.

Male humpback whales have a repetitive and evolving ‘song’ which acts as a vocal sexual display. This song is highly repetitive and is used, by mechanisms of social sorting and attraction, to allow for sexual selection within the whale population. All males within a population are known to conform to the current version of the display (song type), and similarities have been seen to exist among the songs of populations within an ocean basin.

The study being discussed presents very strong evidence for patterns of horizontal transmission, whereby song types spread unidirectionally and rapidly in the pacific ocean eastward through populations in the western and central South Pacific. The study was done over an 11-year period. This is the first documentation of a repeated, dynamic cultural evolution occurring across multiple populations at such a large geographic scale and across such a large time scale.

The patterns of cultural transmission seen in these whales songs are analogous to the same mechanisms we see in humans given that the songs are subject to mistakes and changes which are replicated. This causes the same mechanisms we see in the cultural transmission of language. The authors note that the level and rate of change seen in the whales is unparalleled in any other nonhuman animal and involves culturally driven change at a vast scale.

They also state that:

Investigating the underlying mechanisms of song evolution may yield powerful insights into the transmission of cultural traits and the evolution of culture and plasticity in sexually selected traits.

They also observed that at least one of the song types was transmitted between two different ocean basins, the Indian and South Pacific Ocean. It’s amazing to think how far a single song type can be horizontally transmitted.

Humpback whale song is unique among the animal kingdom due to the conformity to the current norm. This is coupled with high plasticity in the trait (ability to change their song based on whatever the new ‘norm’ is). Why both plasticity and conformity might be selected, how these interact with sexual selection, and how cultural evolution influences both are intriguing questions in need of consideration.

References

Garland, E. C.; Goldizen, A. W.; Rekdahl, M. L.; Constantine, R.; Garrigue, C.; Hauser, N.; Poole, M. M.; Robbins, J.; Noad, M. J. (2011) Dynamic Horizontal Cultural Transmission of Humpback Whale Song at the Ocean Basin Scale. Current biology : CB doi:10.1016/j.cub.2011.03.019

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Phonemic Diversity Supports a Serial Founder Effect Model of Language Expansion from Africa

April 15, 2011 in Genetics, Linguistics, Science

Just read about an article on phoneme diversity via GNXP and Babel’s Dawn. Hopefully I’ll share some of my thoughts on the paper this weekend as it clearly ties in with work I’m currently doing (see here and here). Below is the abstract:

Human genetic and phenotypic diversity declines with distance from Africa, as predicted by a serial founder effect in which successive population bottlenecks during range expansion progressively reduce diversity, underpinning support for an African origin of modern humans. Recent work suggests that a similar founder effect may operate on human culture and language. here I show that the number of phonemes used in a global sample of 504 languages is also clinal and fits a serial founder-effect model of expansion from an inferred origin in Africa. This result, which is no explained by more recent demographic history, local language diversity, or statistical non-independence within language families, points to parallel mechanisms shaping genetic and linguistic diversity and supports an African origin of modern human languages.

Reference: Atkinson, Q.D (2011). Phonemic Diversity Supports a Serial Founder Effect Model of Language Expansion from Africa. Science 332, 346. DOI: 10.1126/science.1199295.

Update: I’ve given a lengthier response here.

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The Parental Antagonism Theory of Language Evolution

April 14, 2011 in Abstracts

Human Biology are publishing a special issue on “Integrating genetic and Cultural Evolutionary Approaches to Language” this month! Abstracts for all of the papers can be found here.

William Brown‘s paper has been published on his blog ahead of the boat today. The Abstract is below and there is a link to the paper at the bottom.

Language—as with most communication systems—likely evolved by means of natural selection. Accounts for the natural selection of language can usually be divided into two scenarios, either of which used in isolation of the other are insufficient to explain the phenomena: (1) there are group benefits from communicating, and (2) there are individual benefits from being a better communicator. In contrast, this paper argues that language emerged during a coevolutionary struggle between parental genomes via genomic imprinting, which is differential gene expression depending on parental origin of the genetic element. It is hypothesized that relatedness asymmetries differentially selected for patrigene-caused language phenotypes (e.g., signals of need) to extract resources from mother early in child development and matrigene-caused language phenotypes (e.g.,  socially transmitted norms) to influence degree of cooperativeness  among kin later in development. Unlike previous theories for language evolution, parental antagonism theory generates testable predictions at the proximate (e.g., neurocognitive areas important for social transmission and language capacities), ontogenetic (e.g., the function of language at different points of development), ultimate (e.g., inclusive fitness), and phylogenetic levels (e.g., the spread of maternally derived brain components in mammals, particularly in the hominin lineage), thus making human capacities for culture more tractable than previously thought.

Brown, W.M. (2011). The parental antagonism theory of language evolution: Preliminary evidence for the proposal. Human Biology, 83 (2)

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Evolved structure of language shows lineage-specific trends in word-order universals

April 13, 2011 in Abstracts, Linguistics, Science

Via Simon Greenhill:

Dunn M, Greenhill SJ, Levinson SC, & Gray RD (2011). Evolved structure of language shows lineage-specific trends in word-order universals. Nature.

Some colleagues and I have a new paper out in Nature showing that the evolved structure of language shows lineage-specific trends in word-order universals. I’ve written an overview/FAQ on this paper here, and there’s a nice review of it here and here.

The Abstract:

Languages vary widely but not without limit. The central goal of linguistics is to describe the diversity of human languages and explain the constraints on that diversity. Generative linguists following Chomsky have claimed that linguistic diversity must be constrained by innate parameters that are set as a child learns a language. In contrast, other linguists following Greenberg have claimed that there are statistical tendencies for co-occurrence of traits reflecting universal systems biases, rather than absolute constraints or parametric variation. Here we use computational phylogenetic methods to address the nature of constraints on linguistic diversity in an evolutionary framework. First, contrary to the generative account of parameter setting, we show that the evolution of only a few word-order features of languages are strongly correlated. Second, contrary to the Greenbergian generalizations, we show that most observed functional dependencies between traits are lineage-specific rather than universal tendencies. These findings support the view that—at least with respect to word order—cultural evolution is the primary factor that determines linguistic structure, with the current state of a linguistic system shaping and constraining future states.

 

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Origins of Culture

April 13, 2011 in Uncategorized

NPR hosts a fascinating debate on the connections between science and art and the origins of culture.  The guests include the utterly bizarre mix of novelist Cormac McCarthy (The Road, No Country for old Men), filmmaker Werner Herzog (The cave of forgotten dreams, Grizzly Man),  and physicist Lawrence Krauss (The physics of Star Trek).  Artificial Intelligence, Neanderthal culture and our place in the universe.  And a buffalo humping a woman.

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How old am I?

April 9, 2011 in Uncategorized

It’s my birthday!  But how old am I?  Well, that’s not such a straightforward question.  Even a seemingly well-defined concept such as age can be affected by cultural factors

First, my age in years is a bit of an estimate of the actual amount of time I’ve been alive, due to leap-years etc.  Second, a year is a culturally determined (although not all that arbitrary) amount of time.  But these are petty squabbles.

There are bigger differences.  For instance, there are cultural differences when it comes to the recall of birth dates.  And I’m not talking about saying you’re 24 when you’re 68.  Matched comparisons of age reporting in death certificates and census data found minimal differences for white Americans (Hill et al., 2000) but nearly half were inconsistent for African-Americans (Hill et al., 1997). These may be due to economic differences.

Furthermore, the definition of age can vary cross-culturally.  Knodel & Chyovan (1991) surveyed women between the ages of 15 and 49 in Thailand.  As well as finding that up to 20% reported an age that was more than one year different to their actual age, they surmised that most calculated their age as difference between the present year and the year of their birth, disregarding whether their birthday had passed.

 

So in some parts of the world I’ve been 26 for four months now, or was it 25?

 

Hill, M., Preston, S., Elo, I., & Rosenwaike, I. (1997). Age-Linked Institutions and Age Reporting among Older African Americans Social Forces, 75 (3) DOI: 10.2307/2580528

Hill, M., Preston, S., & Rosenwaike, I. (2000). Age Reporting among White Americans Aged 85+: Results of a Record Linkage Study Demography, 37 (2) DOI: 10.2307/2648119

Knodel J, & Chayovan N (1991). Age and birth date reporting in Thailand. Asian and Pacific population forum / East-West Population Institute, East-West Center, 5 (2-3) PMID: 12343437

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Colour terms and national flags

April 8, 2011 in Uncategorized

I’m currently writing an article on the relationship between language and social features of the speakers who use it. As studies such as Lupyan & Dale (2010) have discovered, language structure is partially determined by social structure.  However, it’s also probable that many social features of a community are determined by its language.

Today, I wondered whether the number of basic colour terms a language has is reflected in the number of colours on its country’s flag. The idea being that a country’s flag contains colours that are important to its society, and therefore a country with more social tools for discussing colour (colour words) will be more likely to put more colours on its flag. It was a long shot, but here’s what I found:

The World Atlas of Language Structures has data on the number of basic colours in many languages (Kay & Maffi, 2008). Wikipedia has a list of country flags by the number of colours in them.  Languages with large populations (like English, Spanish etc.) were excluded.  It’s known that the number of basic colour terms correlates with latitude, so a partial correlation was carried out.  There was a small but significant relationship between the number of colour terms in a langauge and the number of colours on the flag where that language is spoken (r = 0.15, τ = 254, p=0.01, partial correlation, 2-tailed using Kendall’s tau).

Here’s the flag of Belize, where Garífuna is spoken (9-10 colours in the language, 12 colours on the flag):

Here is the flag of Nigeria where Ejagham is spoken (3-4 colours in the langauge, 2 colours on the flag):

Interestingly, the languages with the highest number of colours in their language and flag come from Central America while the majority of the languages with the lowest number of colours in their language and flag come from Africa.  Maybe there’s some cultural influence on neighbouring flags.

Update:

Here’s a boxplot, which makes more sense:

Also, I re-ran the analysis taking into account distance from the equator, speaker population and some properties of the nearest neighbour of each language (number of colours on flag and number of basic colours in langauge).  A multiple regression showed that the number of basic colours in a language is still a significant predictor of the number of colours in its national flag (r = 0.12, F(106,16)=1.8577, p= 0.03).  This analysis was done by removing languages with populations more than 2 standard deviations from the mean (9 languages out of 140).  The relationship is still significant with the whole dataset.

There are still problems with this analysis, of course.  For example, many of the languages in the data are minority languages which may have little impact on the national identity of a country.  Furthermore, the statistics may be compromised by multiple comparisons, since there may be a single flag for more than one language.  Also, a proper measure of the influence of surrounding languages would be better.  The nearest neighbour was supposed to be an approximation, but could be improved.

Lupyan G, & Dale R (2010). Language structure is partly determined by social structure. PloS one, 5 (1) PMID: 20098492

Kay, Paul & Maffi, Luisa. (2008). Number of Basic Colour Categories.In: Haspelmath, Martin & Dryer, Matthew S. & Gil, David & Comrie, Bernard (eds.) The World Atlas of Language Structures Online. Munich: Max Planck Digital Library, chapter 133.

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The path to empathy

April 7, 2011 in Evolution, Science, Science News

Published online at Plos one yesterday a study done at the Yerkes National Primate Research Center by Campbell and de Waal (2011) has found a link between social groups and empathy in chimpanzees as demonstrated by involuntary yawning responses.

The study is based on the psychological concept of ingroups and outgroups. In humans ingroups are those we see as similar to ourselves and outgroups are those we perceive as different.

Biases involved in ingroup-outgroup discrimination in know to even extend to involuntary responses which includes empathy for pain. This has never been tested in other animals though.

Contagious yawning is thought to be linked with empathy. The study used this assumption to test if chimpanzees’ ingroup-outgroup biases would effect how contagious a yawn can be. In other words if contagious yawning is linking to empathy and empathy is linked to ingroup-outgroup biases within chimpanzees then the chimpanzees should yawn more in response to watching ingroup members yawn than outgroup.

The study used 23 chimpanzees from two separate groups and they were made to watch videos of familiar and unfamiliar individuals yawning. Videos of the same chimps not yawning were also used for control. The chimpanzees yawned more when watching the familiar yawns than the familiar control or the unfamiliar yawns, demonstrating an ingroup-outgroup bias in contagious yawning.

The authors have suggested that these result may be more magnified in chimpanzees than it is in humans as chimpanzees live in much smaller communities than humans and are generally very hostile to those outside of their small social group. Ingroup-outgroup biases are therefore probably much more absolute in chimpanzees.

This study adds empirical evidence to suggest that contagious yawning is subject to empathy. This may have further implications for studying the evolutionary foundations of empathy which obviously has implications for things like theory of mind which is pretty high up on the list for preadaptations for language.

References

Campbell MW, de Waal FBM (2011) Ingroup-Outgroup Bias in Contagious Yawning by Chimpanzees Supports Link to Empathy. PLoS ONE 6(4): e18283. doi:10.1371/journal.pone.0018283

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