Can a linguistic serial founder effect originating in Africa explain the worldwide phonemic cline?

It has been proposed that a serial founder effect could have caused the present observed pattern of global phonemic diversity. Here we present a model that simulates the human range expansion out of Africa and the subsequent spatial linguistic dynamics until today. It does not assume copying errors, Darwinian competition, reduced contrastive possibilities or any other specific linguistic mechanism. We show that the decrease of linguistic diversity with distance (from the presumed origin of the expansion) arises under three assumptions, previously introduced by other authors: (i) an accumulation rate for phonemes; (ii) small phonemic inventories for the languages spoken before the out-of-Africa dispersal; (iii) an increase in the phonemic accumulation rate with the number of speakers per unit area. Numerical simulations show that the predictions of the model agree with the observed decrease of linguistic diversity with increasing distance from the most likely origin of the out-of-Africa dispersal. Thus, the proposal that a serial founder effect could have caused the present observed pattern of global phonemic diversity is viable, if three strong assumptions are satisfied.

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A serial founder effect model for human settlement out of Africa

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2008.0750 ◽

2008 ◽

Vol 276 (1655) ◽

pp. 291-300 ◽

Cited By ~ 64

Author(s):

Omkar Deshpande ◽

Serafim Batzoglou ◽

Marcus W Feldman ◽

L Luca Cavalli-Sforza

Keyword(s):

Genetic Diversity ◽

Founder Effect ◽

Published Data ◽

Geographical Patterns ◽

Effect Model ◽

Occupied Territories ◽

Out Of Africa ◽

Serial Founder Effect ◽

Parameter Values ◽

Linear Decay

The increasing abundance of human genetic data has shown that the geographical patterns of worldwide genetic diversity are best explained by human expansion out of Africa. This expansion is modelled well by prolonged migration from a single origin in Africa with multiple subsequent serial founding events. We discuss a new simulation model for the serial founder effect out of Africa and compare it with results from previous studies. Unlike previous models, we distinguish colonization events from the continued exchange of people between occupied territories as a result of mating. We conduct a search through parameter space to estimate the range of parameter values that best explain key statistics from published data on worldwide variation in microsatellites. The range of parameters we use is chosen to be compatible with an out-of-Africa migration at 50–60 Kyr ago and archaeo–ethno–demographic information. In addition to a colonization rate of 0.09–0.18, for an acceptable fit to the published microsatellite data, incorporation into existing models of exchange between neighbouring populations is essential, but at a very low rate. A linear decay of genetic diversity with geographical distance from the origin of expansion could apply to any species, especially if it moved recently into new geographical niches.

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Faculty Opinions recommendation of Support from the relationship of genetic and geographic distance in human populations for a serial founder effect originating in Africa.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1029413.343733 ◽

2005 ◽

Author(s):

Molly Przeworski

Keyword(s):

Founder Effect ◽

Geographic Distance ◽

Human Populations ◽

Serial Founder Effect ◽

Relationship Of ◽

The Relationship

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Cooperation mitigates diversity loss in a spatially expanding microbial population

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1910075116 ◽

2019 ◽

Vol 116 (47) ◽

pp. 23582-23587 ◽

Cited By ~ 10

Author(s):

Saurabh R. Gandhi ◽

Kirill S. Korolev ◽

Jeff Gore

Keyword(s):

Genetic Drift ◽

Founder Effect ◽

Microbial Population ◽

Growth Dynamics ◽

Low Density ◽

Drastic Reduction ◽

Diversity Loss ◽

Abrupt Changes ◽

Expanding Population ◽

Serial Founder Effect

The evolution and potentially even the survival of a spatially expanding population depends on its genetic diversity, which can decrease rapidly due to a serial founder effect. The strength of the founder effect is predicted to depend strongly on the details of the growth dynamics. Here, we probe this dependence experimentally using a single microbial species, Saccharomyces cerevisiae, expanding in multiple environments that induce varying levels of cooperativity during growth. We observe a drastic reduction in diversity during expansions when yeast grows noncooperatively on simple sugars, but almost no loss of diversity when cooperation is required to digest complex metabolites. These results are consistent with theoretical expectations: When cells grow independently from each other, the expansion proceeds as a pulled wave driven by growth at the low-density tip of the expansion front. Such populations lose diversity rapidly because of the strong genetic drift at the expansion edge. In contrast, diversity loss is substantially reduced in pushed waves that arise due to cooperative growth. In such expansions, the low-density tip of the front grows much more slowly and is often reseeded from the genetically diverse population core. Additionally, in both pulled and pushed expansions, we observe a few instances of abrupt changes in allele fractions due to rare fluctuations of the expansion front and show how to distinguish such rapid genetic drift from selective sweeps.

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Range expansion of Brewer's blackbird: phenetics of a new population

Canadian Journal of Zoology ◽

10.1139/z71-027 ◽

1971 ◽

Vol 49 (2) ◽

pp. 175-183 ◽

Cited By ~ 5

Author(s):

Dennis M. Power

Keyword(s):

United States ◽

Genetic Variability ◽

Range Expansion ◽

Founder Effect ◽

The United States ◽

Directional Selection ◽

Population Variability ◽

Two Samples ◽

Stable Part ◽

Made In

The Brewer's blackbird (Euphagus cyanocephalus) is rapidly expanding its range eastward across Ontario and parts of the United States. This study was to determine if phenetic changes have taken place during or immediately after expansion. A sample was collected in 1968 in the vicinity of McKerrow, Ontario, near the periphery of the zone of expansion and where breeding was first recorded in 1962. For comparison, a second collection was made in the stable part of the range near Winnipeg, Manitoba. Statistical comparisons for 37 skin and skeletal characters were made between the two samples for both sexes. Tests for differences in character means suggest that strong directional selection, different from that in the stable part of the range, is not operating in the newly occupied area. Likewise, differences in population variability seem slight and do not show alterations in genetic variability that would be expected during a Carsonian population flush or that would be expected because of a partial founder effect.

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