Modern human expansion from (southern?) Africa: Origin, non-African ancestry, and linearity

Cenac, Zarus

doi:10.1101/2022.07.31.500977

Cited by 6 publications

(214 citation statements)

References 91 publications

(658 reference statements)

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“…Nevertheless, the sub-Saharan African analyses had few populations located near the origin (Cenac, 2022b), and the same can be said in the present study with populations globally (Table 1). And so, it is unclear what pattern is present across shorter distances from the origin of the expansion.…”

Section: Diversitysupporting

confidence: 86%

“…The area can be referred to as the expansion origin area, and the location from which the decline appears strongest can be called the peak point (Cenac, 2022b). The peak point can be found using a measure called the Bayesian information criterion (BIC)the lower the BIC, the better distance is at predicting diversity (Manica et al, 2007).…”

Section: Origin Areamentioning

confidence: 99%

“…Geographical distances in Cenac (2022aCenac ( , 2022b were made use of. Axes labels in figures follow Cenac (2022b) where appropriate. Peak point symbols are as in Cenac (2022b).…”

Section: Distances and Figuresmentioning

confidence: 99%

“…To see if there is any point in adjusting cranial size dimorphism for absolute latitude (in the context of expansion), previous research using linear models has compared BICs using African origins (the 99 from Betti et al, 2013), to see if any BICs found when adjusting cranial size dimorphism are notably lower (using the four-BIC condition) than the lowest BIC when dimorphism is not adjusted (Cenac, 2022b); the present study did the same, but with mitochondrial diversity in the place of cranial size dimorphism, and minimum temperature instead of absolute latitude. This was not only done amongst linear models but also amongst quadratic ones, and the aforementioned 26 non-African coordinate pairs were used too.…”

Section: Bayesian Information Criterion and The Origin Of Expansionmentioning

confidence: 99%

“…when it came to Y-chromosomal microsatellite heterozygosity (the area could very well be in Asia exclusively) (Cenac, 2022b).…”

mentioning

confidence: 99%

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Expansion of modern humans over the world: The origin when considering non-linearity

Cenac

2023

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Types of diversity have been known to decline linearly with the rise of geographical distance from Africa. Declines have helped to suggest the area in Africa which holds the origin for the global expansion of modern humans. Research has, at times, explored if there is a non-linear relationship between diversity and distance from Africa. A previous suggestion was that non-linearity could affect where the expansion appears to have originated. Linear analysis with Y-chromosomal microsatellite heterozygosity has been contrary to the expansion from Africa, instead indicating an origin involving Asia; could this be attributable to non-linearity? The present study looked into whether there are non-linear relationships between distance and diversities, and approximated where the expansion began. This study used diversities from previous research — genetic (autosomal, X-chromosomal, Y-chromosomal, and mitochondrial) and cranial shape. The Bayesian information criterion was the statistic for comparing linear and non-linear (quadratic) models to indicate if there is a non-linear relationship. This criterion was also used to estimate where the expansion launched from. Autosomal microsatellite heterozygosity favoured a non-linear relationship. This may be due to South American populations. Mitochondrial diversity suggested non-linearity too, but not when minimum temperature was controlled for. Whilst non-linear relationships indicated that the expansion had its start in Africa, for autosomal microsatellite heterozygosity, the area of origin appeared to be rather affected by the type of model (linear or non-linear). Other diversities (e.g., Y-chromosomal) supported linear relationships. Therefore, non-linearity does not seem to explain Y-chromosomal microsatellite heterozygosity being unexpressive of the global expansion.

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Section: Diversitysupporting

confidence: 86%

Section: Origin Areamentioning

confidence: 99%

“…Geographical distances in Cenac (2022aCenac ( , 2022b were made use of. Axes labels in figures follow Cenac (2022b) where appropriate. Peak point symbols are as in Cenac (2022b).…”

Section: Distances and Figuresmentioning

confidence: 99%

Section: Bayesian Information Criterion and The Origin Of Expansionmentioning

confidence: 99%

“…when it came to Y-chromosomal microsatellite heterozygosity (the area could very well be in Asia exclusively) (Cenac, 2022b).…”

mentioning

confidence: 99%

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Expansion of modern humans over the world: The origin when considering non-linearity

Cenac

2023

Preprint

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Y-chromosomal microsatellites and expansion from Africa

Cenac

2023

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Some diversities are thought to mark human expansion from Africa — they decline as distance from Africa accumulates, and suggest that the expansion originated from any of a range of locations which are only in Africa. Previously, a decline was found regarding Y-chromosomal microsatellite heterozygosity. However, this diversity has been noted to suggest a non-African starting point and, consequently, not appearing reflective of expansion from Africa. Declines have appeared in other variables derived through Y-chromosomal microsatellites, including effective population size, expansion time, and time to the most recent common ancestor. The present research inferred if these variables, and some Y-chromosomal diversities, indicate expansion from Africa; indicative variables could help with identifying which area of Africa the expansion started in. This research used variables derived previously from Y-chromosomal microsatellites for populations worldwide (effective population size, expansion time, and time to the most recent common ancestor) or only in Africa (haplotype and repeat unit diversities). Regarding populations worldwide, San were very high in each variable when considering distance from (southern) Africa. Without San, effective population size and time to the most recent common ancestor did not squarely indicate an African origin, and expansion time placed the origin wholly outside of Africa. When using San, each area was only in Africa. Amongst African populations, whilst both haplotype diversity and repeat unit diversity showed a geographical pattern of declining, only haplotype diversity suggested a completely African area of origin. Using Y-chromosomal haplotype diversity alongside some other genetic diversities, a southern African origin was broadly indicated.

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X-chromosomal diversity may reflect climate (when considering human expansion from Africa)

Cenac

2023

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A decreasing of diversity with increasing distance from Africa has been interpreted as a signal of modern humans having expanded (across the globe) from Africa. Research is consistent with a climatic signal being present in mitochondrial diversity, but not in other genetic diversities (e.g., X-chromosomal) or cranial diversity. Some of that research involved adjusting diversity for distance from Africa, and seeing whether this adjusted diversity is associated with climate. The choice of African location which the distance from Africa is measured from may affect whether adjusted diversity appears to be related to climate. To bypass this potential effect of location, some analyses in the present study featured only populations outside of Africa. Other analyses included African populations. The present study used diversities, distances, and minimum temperatures from beforehand. Autosomal, X-chromosomal, and cranial diversities were adjusted for distance from Africa. Y-chromosomal diversity was adjusted for distance from Asia because previous research suggested that Y-chromosomal microsatellite heterozygosity offers more support to expansion from Asia (than Africa). Whether populations were worldwide or only outside of Africa, adjusted X-chromosomal diversity increased with minimum temperature. Other adjusted diversities were not related to minimum temperature. Perhaps previous research found no indication of a climatic signal in X-chromosomal diversity because of two populations, one of which likely had an atypical adjusted diversity for their minimum temperature. These populations may have led to heteroscedasticity and the climatic signal being obscured.

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Modern human expansion from (southern?) Africa: Origin, non-African ancestry, and linearity

Cited by 6 publications

References 91 publications

Expansion of modern humans over the world: The origin when considering non-linearity

Expansion of modern humans over the world: The origin when considering non-linearity

Y-chromosomal microsatellites and expansion from Africa

X-chromosomal diversity may reflect climate (when considering human expansion from Africa)

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