HENRY the Human Evolution News Relay

5Aug/08Off

Y-chromosomal evidence of a pastoralist migration through Tanzania to southern Africa

Henn et al. in P.N.A.S. present Y-chromosomal evidence of a pastoralist migration through Tanzania to southern Africa (doi):

Although geneticists have extensively debated the mode by which agriculture diffused from the Near East to Europe, they have not directly examined similar agropastoral diffusions in Africa. It is unclear, for example, whether early instances of sheep, cows, pottery, and other traits of the pastoralist package were transmitted to southern Africa by demic or cultural diffusion.

Here, we report a newly discovered Y-chromosome-specific polymorphism that defines haplogroup E3b1f-M293. This polymorphism reveals the monophyletic relationship of the majority of haplotypes of a previously paraphyletic clade, E3b1-M35*, that is widespread in Africa and southern Europe.

To elucidate the history of the E3b1f haplogroup, we analyzed this haplogroup in 13 populations from southern and eastern Africa. The geographic distribution of the E3b1f haplogroup, in association with the microsatellite diversity estimates for populations, is consistent with an expansion through Tanzania to southern-central Africa.

The data suggest this dispersal was independent of the migration of Bantu-speaking peoples along a similar route. Instead, the phylogeography and microsatellite diversity of the E3b1f lineage correlate with the arrival of the pastoralist economy in southern Africa. Our Y-chromosomal evidence supports a demic diffusion model of pastoralism from eastern to southern Africa ~2,000 years ago.

10Jan/08Off

Genome-wide Analysis Indicates More Asian than Melanesian Ancestry of Polynesians

The latest issue of the American Journal of Human Genetics has a new paper on Polynesian ancestry by Manfred Kayser and Mark Stoneking's lab(s):

Analyses of mitochondrial DNA (mtDNA) and nonrecombining Y chromosome (NRY) variation in the same populations are sometimes concordant but sometimes discordant. Perhaps the most dramatic example known of the latter concerns Polynesians, in which about 94% of Polynesian mtDNAs are of East Asian origin, while about 66% of Polynesian Y chromosomes are of Melanesian origin.
Here we analyze on a genome-wide scale, to our knowledge for the first time, the origins of the autosomal gene pool of Polynesians by screening 377 autosomal short tandem repeat (STR) loci in 47 Pacific Islanders and compare the results with those obtained from 44 Chinese and 24 individuals from Papua New Guinea.
Our data indicate that on average about 79% of the Polynesian autosomal gene pool is of East Asian origin and 21% is of Melanesian origin. The genetic data thus suggest a dual origin of Polynesians with a high East Asian but also considerable Melanesian component, reflecting sex-biased admixture in Polynesian history in agreement with the Slow Boat model.
More generally, these results also demonstrate that conclusions based solely on uniparental markers, which are frequently used in population history studies, may not accurately reflect the history of the autosomal gene pool of a population.

Abstract: Genome-wide Analysis Indicates More Asian than Melanesian Ancestry of Polynesians (doi:10.1016/j.ajhg.2007.09.010)

28Nov/07Off

Viking surnames and genetics

One of the most important questions in evolutionary biology today is how closely are genes and cultures linked. A new study in the latest issue of Molecular Biology and Evolution compares genetics and a heritable cultural marker: surnames. Just like Y chomosomes, surnames are (or were) paternally inherited, and should be strong markers of father-son descent patterns.

In particular, the authors were interested in the surnames left behind after the Viking raids and subsequent settlement of England around 1200 years ago. This ~200 year influx had a major influence on English history and culture (e.g. Danelaw). This is also demonstrated by the prevalence of Scandinavian placenames in the region (such as names ending in -thorpe or -by).

To do this, the authors compiled a list of 236 surnames from multiple sources including a 1545 survey of all the households during the reign of Henry VIII court proceedings records dating from 1353, and ale-house licensing records from 1572 (Aside: the fact that these records were considered so important to be kept for hundreds of years tells you a lot about the English!).

Then, the authors sampled Y chromosome data from individuals in two regions (West Lancashire and Wirral). Using the surnames, they could then divide this sample into two. People with surnames NOT present in the historical data were placed in a group called "modern", whilst people with surnames - such as Brown - found in the records dating back 500 years were grouped as a "medieval" sample.

Their results show a strong difference between the "modern" and "medieval" samples. The "medieval" samples had much higher genetic diversity, which suggests that the "modern" families had undergone some level of homogenisation, possibly due to immigration from populations with low genetic diversity. Unsurprisingly, the "medieval" samples also showed a higher proportion of haplotypes with a Scandinavian origin.

Open Access PDF: Excavating Past Population Structures by Surname-based Sampling: the Genetic Legacy of the Vikings in Northwest England.

The abstract:

The genetic structures of past human populations are obscured by recent migrations and expansions, and can been observed only indirectly by inference from modern samples. However, the unique link between a heritable cultural marker, the patrilineal surname, and a genetic marker, the Y chromosome, provides a means to target sets of modern individuals that might resemble populations at the time of surname establishment. As a test case, we studied samples from the Wirral peninsula and West Lancashire, in northwest England. Place names and archaeology show clear evidence of a past Viking presence, but heavy immigration and population growth since the Industrial Revolution are likely to have weakened the genetic signal of a thousand-year-old Scandinavian contribution. Samples ascertained on the basis of two generations of residence were compared with independent samples based on known ancestry in the region, plus the possession of a surname known from historical records to have been present there in medieval times. The Y-chromosomal haplotypes of these two sets of samples are significantly different, and in admixture analyses the surname-ascertained samples show markedly greater Scandinavian ancestry proportions, supporting the idea that northwest England was once heavily populated by Scandinavian settlers. The method of historical surname-based ascertainment promises to allow investigation of the influence of migration and drift over the last few centuries in changing the population structure of Britain, and will have general utility in other regions where surnames are patrilineal and suitable historical records survive.

   
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