Biology subjects

Hammaren, R.

Publications and source records attributed to Hammaren, R..

4 recordsLinked to original sources

bioRxiv2024

Wide-scale Geographical Analysis of Genetic Ancestry in the South African Coloured Population

The South African Coloured (SAC) population, a prominent admixed population in South Africa, reflects centuries of migration, admixture, and historical segregation. Descendants of local Khoe-San and Bantu-speaking populations, European settlers, and enslaved individuals from Africa and Asia, SAC individuals embody diverse ancestries. This study investigates the genetic makeup of SAC individuals, utilizing autosomal genotypes, mitochondrial DNA and Y-chromosome data. We analyze new genotype data for 125 SAC individuals from seven locations. Our analysis, based on a dataset comprising 356 SAC individuals from 22 geographic locations, revealed significant regional variations in ancestry. Khoe-San ancestry predominates in 14 locations, highlighting its lasting influence. Inland regions exhibit higher proportions of Khoe-San ancestry, eastern regions show more Bantu-speaker/West African ancestry, and western/coastal areas, particularly around Cape Town, display increased Asian ancestry. These patterns reflect historical migrations and settlement patterns. Additionally, sex-biased admixture ratios show male-biased admixture from East Africans and Europeans, and female-biased admixture from Khoe-San populations, which is supported by mitochondrial and Y-chromosome data. This research underscores the importance of studying the SAC population to understand South Africas historical migrations, providing insights into the complex genetic heritage of South Africans.

evolutionary biology↗

bioRxiv2023

The genetic legacy of the expansion of Bantu-speaking peoples in Africa

With the largest genomic dataset to date of Bantu-speaking populations, including newly generated data of modern-day and ancient DNA from previously unsampled regions in Africa, we shed fresh light on the expansion of peoples speaking Bantu languages that started [~]4000 years ago in western Africa. We have genotyped 1,740 participants, including 1,487 Bantu speakers from 143 populations across 14 African countries, and generated whole-genome sequences from 12 Late Iron Age individuals. Our results show that Bantu speakers received significant gene-flow from local groups in regions they expanded into. We show for the first time that genetic diversity amongst Bantu-speaking populations declines with distance from western Africa, with current-day Zambia and the DRC as possible crossroads of interaction. Using spatially explicit methods and correlating genetic, linguistic and geographical data, we provide cross-disciplinary support for a serial founder migration model. Finally, we discuss the utility of our dataset as an exhaustive modern-day African comparative dataset for ancient DNA studies. These new findings and data will be important to a wide range of disciplines from science and humanities as well as to the medical sector studying human genetic variation and health in African and African-descendant populations. One-sentence summaryA comprehensive genetic analysis of the expansion of people speaking Bantu languages reveals a complex history of serial founder events, variable levels of contact with local groups, and spread-over-spread events.

evolutionary biology↗

bioRxiv2022

Eurasian back-migrations into Northeast Africa was a complex and multifaceted process

Recent studies have identified Northeast Africa as an important area for human movements during the Holocene. Eurasian populations have moved back into Northeastern Africa and contributed to the genetic composition of its people. By gathering the largest reference dataset to date of Northeast, North, and East African as well as Middle Eastern populations, we give new depth to our knowledge of Northeast African demographic history. By employing local ancestry methods, we isolated the Non-African parts of modern-day Northeast African genomes and identified the best putative source populations. Egyptians and Sudanese Copts bore most similarities to Levantine populations whilst other populations in the region generally had predominantly genetic contributions from Arabian peninsula rather than Levantine populations for their Non-African genetic component. We also date admixture events and investigated which factors influenced the date of admixture and find that major linguistic families were associated with the date of Eurasian admixture. Taken as a whole we detect complex patterns of admixture and diverse origins of Eurasian admixture in Northeast African populations of today.

evolutionary biology↗

bioRxiv2019

Patterns of African and Asian admixture in the Afrikaner population of South Africa

The Afrikaner population of South Africa are the descendants of European colonists who started to colonize the Cape of Good Hope in the 1600s. In the early days of the colony, mixed unions between European males and non-European females gave rise to admixed children who later became incorporated into either the Afrikaner or the "Coloured" populations of South Africa. Ancestry, social class, culture, sex ratio and geographic structure affected admixture patterns and caused different ancestry and admixture patterns in Afrikaner and Coloured populations. The Afrikaner population has a predominant European composition, whereas the Coloured population has more diverse ancestries. Genealogical records estimated the non-European contributions into the Afrikaners to 5.5%-7.2%. To investigate the genetic ancestry of the Afrikaner population today (11-13 generations after initial colonization) we genotyped ~5 million genome-wide markers in 77 Afrikaner individuals and compared their genotypes to populations across the world to determine parental source populations and admixture proportions. We found that the majority of Afrikaner ancestry (average 95.3%) came from European populations (specifically northwestern European populations), but that almost all Afrikaners had admixture from non-Europeans. The non-European admixture originated mostly from people who were brought to South Africa as slaves and, to a lesser extent, from local Khoe-San groups. Furthermore, despite a potentially small founding population, there is no sign of a recent bottleneck in the Afrikaner compared to other European populations. Admixture among diverse groups during early colonial times might have counterbalanced the effects of a founding population with a small census size. SIGNIFICANCE STATEMENTAfrikaners are a southern African ethnic group primarily descended from colonial settlers (population ~2.8-3.5 million). Genome-wide studies might offer interesting insights into their ancestry, not the least due to South Africas history of segregationist laws known as "apartheid", resulting in an expectation of low levels of admixture with other groups. Originating from a small founder population, their genetic diversity is also interesting. In our genome-wide study of 77 Afrikaners we found their majority ancestry (average 95.3%) came from Europeans, but almost all Afrikaners had admixture from non-Europeans (Africans and Asians). Despite their small founding population, we found no signs of decreased genetic diversity. Admixture among diverse groups during colonial times might have counterbalanced effects of a small founding population.

evolutionary biology↗