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Spatial Structure of Evolutionary Models of Dialects in Contact.

Murawaki Y - PLoS ONE (2015)

Bottom Line: We found that a group of dialects can be considered tree-like even if it has not evolved in a temporally tree-like manner but has a temporally invariant, spatially tree-like structure.In addition, the simulation experiments appear to reproduce unnatural results observed in reconstructed trees for real data.These results motivate further investigation into the spatial structure of the evolutionary history of dialect lexicons as well as other cultural characteristics.

View Article: PubMed Central - PubMed

Affiliation: Department of Advanced Information Technology, Graduate School of Information Science and Electrical Engineering, Kyushu University, Fukuoka, Japan.

ABSTRACT
Phylogenetic models, originally developed to demonstrate evolutionary biology, have been applied to a wide range of cultural data including natural language lexicons, manuscripts, folktales, material cultures, and religions. A fundamental question regarding the application of phylogenetic inference is whether trees are an appropriate approximation of cultural evolutionary history. Their validity in cultural applications has been scrutinized, particularly with respect to the lexicons of dialects in contact. Phylogenetic models organize evolutionary data into a series of branching events through time. However, branching events are typically not included in dialectological studies to interpret the distributions of lexical terms. Instead, dialectologists have offered spatial interpretations to represent lexical data. For example, new lexical items that emerge in a politico-cultural center are likely to spread to peripheries, but not vice versa. To explore the question of the tree model's validity, we present a simple simulation model in which dialects form a spatial network and share lexical items through contact rather than through common ancestors. We input several network topologies to the model to generate synthetic data. We then analyze the synthesized data using conventional phylogenetic techniques. We found that a group of dialects can be considered tree-like even if it has not evolved in a temporally tree-like manner but has a temporally invariant, spatially tree-like structure. In addition, the simulation experiments appear to reproduce unnatural results observed in reconstructed trees for real data. These results motivate further investigation into the spatial structure of the evolutionary history of dialect lexicons as well as other cultural characteristics.

No MeSH data available.


Survival times for words in Star.Survival time is defined as the number of steps between birth and death. The words used in the initial and final states were excluded.
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pone.0134335.g010: Survival times for words in Star.Survival time is defined as the number of steps between birth and death. The words used in the initial and final states were excluded.

Mentions: There are several matters to address in the current simulation model. Fig 10 depicts the distribution of survival times in Star. We see that a large number of short-lived words are required to allow some words to survive over long periods of time. This is because new words are often quickly replaced by existing words surviving in neighboring nodes. In the current simulation model, new words are less likely to enter nodes with larger populations. Since the probability distribution is constructed using an exponential function, larger nodes have more skewed distributions. New words generally have smaller scores and thus have much lower probabilities. However, once new words are accepted in a large node, they are likely to spread to surrounding nodes. On the one hand, this phenomenon seems to be supported by the astonishingly diversified dialects of Ryukyuan, which have been spoken by a hundreds of small, isolated populations [49]. On the other hand, despite its small population, Icelandic is known as a very conservative language [50]. Thus, more evidence is required to support or refute our assumptions.


Spatial Structure of Evolutionary Models of Dialects in Contact.

Murawaki Y - PLoS ONE (2015)

Survival times for words in Star.Survival time is defined as the number of steps between birth and death. The words used in the initial and final states were excluded.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4519344&req=5

pone.0134335.g010: Survival times for words in Star.Survival time is defined as the number of steps between birth and death. The words used in the initial and final states were excluded.
Mentions: There are several matters to address in the current simulation model. Fig 10 depicts the distribution of survival times in Star. We see that a large number of short-lived words are required to allow some words to survive over long periods of time. This is because new words are often quickly replaced by existing words surviving in neighboring nodes. In the current simulation model, new words are less likely to enter nodes with larger populations. Since the probability distribution is constructed using an exponential function, larger nodes have more skewed distributions. New words generally have smaller scores and thus have much lower probabilities. However, once new words are accepted in a large node, they are likely to spread to surrounding nodes. On the one hand, this phenomenon seems to be supported by the astonishingly diversified dialects of Ryukyuan, which have been spoken by a hundreds of small, isolated populations [49]. On the other hand, despite its small population, Icelandic is known as a very conservative language [50]. Thus, more evidence is required to support or refute our assumptions.

Bottom Line: We found that a group of dialects can be considered tree-like even if it has not evolved in a temporally tree-like manner but has a temporally invariant, spatially tree-like structure.In addition, the simulation experiments appear to reproduce unnatural results observed in reconstructed trees for real data.These results motivate further investigation into the spatial structure of the evolutionary history of dialect lexicons as well as other cultural characteristics.

View Article: PubMed Central - PubMed

Affiliation: Department of Advanced Information Technology, Graduate School of Information Science and Electrical Engineering, Kyushu University, Fukuoka, Japan.

ABSTRACT
Phylogenetic models, originally developed to demonstrate evolutionary biology, have been applied to a wide range of cultural data including natural language lexicons, manuscripts, folktales, material cultures, and religions. A fundamental question regarding the application of phylogenetic inference is whether trees are an appropriate approximation of cultural evolutionary history. Their validity in cultural applications has been scrutinized, particularly with respect to the lexicons of dialects in contact. Phylogenetic models organize evolutionary data into a series of branching events through time. However, branching events are typically not included in dialectological studies to interpret the distributions of lexical terms. Instead, dialectologists have offered spatial interpretations to represent lexical data. For example, new lexical items that emerge in a politico-cultural center are likely to spread to peripheries, but not vice versa. To explore the question of the tree model's validity, we present a simple simulation model in which dialects form a spatial network and share lexical items through contact rather than through common ancestors. We input several network topologies to the model to generate synthetic data. We then analyze the synthesized data using conventional phylogenetic techniques. We found that a group of dialects can be considered tree-like even if it has not evolved in a temporally tree-like manner but has a temporally invariant, spatially tree-like structure. In addition, the simulation experiments appear to reproduce unnatural results observed in reconstructed trees for real data. These results motivate further investigation into the spatial structure of the evolutionary history of dialect lexicons as well as other cultural characteristics.

No MeSH data available.