Genetic Stratigraphy of Key Demographic Events in Arabia

The issue of admixture in human populations is normally addressed by genome-wide (GW) studies, and several approaches have been developed to date admixture events [1,2,3,4,5]. Admixed populations bear chromosomes with segments of DNA from all contributing source groups, the size of which decreases over successive generations until recombination renders them undetectably short. Several algorithms attempt to date admixture events by inferring the size of the nuclear ancestry segments, and these can work well when dating recent episodes in human history, such as the sub-Saharan African input into the New World [6], but they fail to detect several known episodes that took place at earlier times, such as the African input into Iberia [1] and genetic exchanges across the Red Sea [7]. Simulations with the suite of methods available at the ADMIXTOOLS package indicated that these methods could detect admixture events as early as 500 generation ago, but real data did not allow the tracing of such old events [8]. A recent improved algorithm, called GLOBETROTTER, has been used to tackle the detection of the co-occurrence of several mixture events by decomposing each chromosome into a series of haplotypic chunks and then analysing each chunk independently [3], but the problem of detecting ancient events remains. Its application to the systematic screening of worldwide admixture events was able to reveal around 100 events, but all occurring over only the past 4,000 years [3

Population Structure of African Populations Inferred from Alu Insertions.

The population genetic study was carried out on 188 unrelated individuals from 5 populations of the Sahel. Relationships of nomadic Fulani to sedentary populations of different linguistic backgrounds and geographic origins were inferred from 16 polymorphic Alu insertions. Bayesian clustering approaches could be applied due to biallelic multilocus nature of the data. Fulani were shown to be divergent from neighbouring sedentary populations (Kassena and Mossi) and similar to Somali of East Africa. In context of already published genetic data, these results could be interpreted as Saharan origin of Fulani diaspora that was caused by Sahara drying out around 6 000 BP. After this initial migration of nomads to West Africa, a primarily female gene flow (integration of females) must have influenced the Fulani population. In contrast to Fulani, Songhai have shown a signal of recent admixture in concordance with historical and linguistic assumptions. KEY WORDS Alu insertions, Fulani, population genetics, Sahe

2000 years of parallel societies in Stone Age Central Europe

Debate on the ancestry of Europeans centers on the interplay between Mesolithic foragers and Neolithic farmers. Foragers are generally believed to have disappeared shortly after the arrival of agriculture. To investigate the relation between foragers and farmers, we examined Mesolithic and Neolithic samples from the Blatterhohle site. Mesolithic mitochondrial DNA sequences were typical of European foragers, whereas the Neolithic sample included additional lineages that are associated with early farmers. However, isotope analyses separate the Neolithic sample into two groups: one with an agriculturalist diet and one with a forager and freshwater fish diet, the latter carrying mitochondrial DNA sequences typical of Mesolithic hunter-gatherers. This indicates that the descendants of Mesolithic people maintained a foraging lifestyle in Central Europe for more than 2000 years after the arrival of farming societies

Founder analysis results on JT lineages.

<p>Probabilistic distribution of founder clusters across migration times, with time scanned at 200 year intervals from 0–60 ka, using <i>f1</i> (blue line) and <i>f2</i> criteria (red line), when considering putative migrations from the Near East, Iran and Pakistan to Arabia for (A) whole-mtDNA genomes or (C) HVS-I for haplogroups J and T; and probabilistic proportion of founder clusters considering different migration events, using <i>f1</i> (blue bar) and <i>f2</i> criteria (red bar), when considering putative migrations from the Near East, Iran and Pakistan to Arabia for (B) whole-mtDNA genomes or (D) HVS-I for haplogroups J and T.</p

Matrices of <i>F</i>_<i>ST</i> distances.

<p>Matrices of <i>F</i>_<i>ST</i> values between ADMIXTURE components (A) and Arabian and Near Eastern populations (B).</p

ADMIXTURE results.

<p>Population structure inferred by ADMIXTURE analysis. Each individual is represented by a vertical (100%) stacked column of genetic components proportions shown in colour for K = 6.</p

Estimates of admixture proportions (%) and date of admixture (in generations) calculated in ROLLOFF when using western (Yoruba) and eastern (Maasai) African and Italians + Spanish as ancestral populations.

<p>N/A—not assigned.</p><p>* By eliminating one individual with a high level of African ancestry.</p><p>Estimates of admixture proportions (%) and date of admixture (in generations) calculated in ROLLOFF when using western (Yoruba) and eastern (Maasai) African and Italians + Spanish as ancestral populations.</p

PCA results.

<p>Scatter plot of individuals, showing the first two principal components. Each symbol corresponds to one individual and the colour indicates the region of origin.</p

Founder analysis results.

<p>Probabilistic distribution of founder clusters across migration times, with time scanned at 200 year intervals from 0–60 ka, using <i>f1</i> (blue line) and <i>f2</i> criteria (red line), when considering putative migrations: (A) from the Near East, Iran and Pakistan to Arabia; (C) from Africa into Arabia plus the Near East and Iran; (E) Arabia plus the Near East and Iran into eastern Africa; (G) Arabia plus the Near East and Iran into North Africa; and probabilistic proportion of founder clusters considering different migration events, using <i>f1</i> (blue bar) and <i>f2</i> criteria (red bar), when considering putative migrations: (B) from the Near East, Iran and Pakistan to Arabia; (D) from African into Arabia plus the Near East and Iran; (F) Arabia plus the Near East and Iran into eastern Africa; (H) Arabia plus the Near East and Iran into North Africa.</p