Biology subjects

Soodyall, H.

Publications and source records attributed to Soodyall, H..

6 recordsLinked to original sources

bioRxiv2026

Rethinking human AMY1 copy number evolution in light of demographic history

Dietary change is often invoked as a major selective force in recent human evolution, with increased copy number of the salivary amylase gene (AMY1) widely cited as an adaptation to starch-rich agricultural diets. However, most evidence for this model comes from limited geographical sampling and analyses that do not fully account for shared ancestry. Here we combine newly generated droplet digital PCR estimates from 390 individuals representing 30 Sub-Saharan African populations with published copy number data from up to 1,307 individuals worldwide and re-evaluate AMY1 evolution using ancestry-aware and phylogenetically informed models. Across Africa, AMY1 copy number shows no consistent association with agriculture once population structure is accounted for. At a global scale, differences between agriculturalists and non-agriculturalists are substantially smaller than previously reported and are largely explained by shared ancestry rather than diet. Phylogenetic analyses further reveal baseline differences in AMY1 copy number between Sub-Saharan and non-Sub-Saharan populations, pointing to deep demographic processes shaping present-day variation. These results challenge the long-standing "agriculture hypothesis" and identify demographic history, rather than subsistence strategy, as the primary driver of AMY1 CN evolution worldwide.

evolutionary biology↗

bioRxiv2025

Revisiting the African mtDNA Landscape: A Continental Update from Complete Mitochondrial Genomes

AbstractAfrica harbors the richest diversity of mitochondrial DNA lineages, reflecting its central role in human evolutionary history. Early studies of mtDNA variation provided the first genetic evidence for the African origin of modern humans. With complete mitochondrial genome sequencing, we can now reconstruct maternal lineages with high resolution, yet large parts of the continent remain underrepresented. Using a newly developed long-range sequencing assay, we generated 1,288 complete mitochondrial genomes from 14 countries across sub-Saharan Africa, focusing on previously understudied regions. We combined these with over 3,600 publicly available African mitogenomes to produce a comprehensive dataset and updated overview of maternal genetic diversity across the continent. We contextualized this diversity with autosomal structure and information on major human expansions, integrating archaeological and linguistic evidence. Our analyses reveal a demographic expansion of Niger-Congo speakers around 17 thousand years ago (kya), followed by a second expansion associated with Bantuspeaking groups around 6 kya. We identify haplogroup L3e as a key marker of this early Bantu expansion, tracking its spread across sub-Saharan Africa. Distinct demographic signatures also emerge for different geographic sub-branches of Bantu speakers. These findings highlight the power of mitochondrial DNA to trace maternal ancestry and demographic history in Africa, while also acknowledging its limitations for phylogeographic reconstruction.

evolutionary biology↗

bioRxiv2024

Ancient tree-topologies and gene-flow processes among human lineages in Africa

The deep history of human evolution in Africa remains intensely debated, with increasingly complex models being proposed. To investigate this, we sequenced and analysed 73 novel high-quality whole genomes from 14 Central and Southern African populations with diverse cultural practices. Using extensive simulations and machine-learning Approximate Bayesian Computation (ABC), we jointly reconstructed their demographic history of divergences and migrations. We find extensive genome-wide diversity within and among populations, including substantial local genetic differentiation not fully explained by geography or cultural practices. These patterns highlight the importance of explicitly considering local genomic diversity when reconstructing human evolutionary history. We find that tree-like population histories with long periods of drift separated by short pulses of unidirectional gene-flow better explain the data than continuous gene-flow. Without invoking archaic admixture, our models accurately fit observed genomic variation and identify multiple episodes of gene-flow coinciding with major ecological and cultural changes in Sub-Saharan Africa.

genetics↗

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↗

bioRxiv2017

Ancient genomes from southern Africa pushes modern human divergence beyond 260,000 years ago

Southern Africa is consistently placed as one of the potential regions for the evolution of Homo sapiens. To examine the regions human prehistory prior to the arrival of migrants from East and West Africa or Eurasia in the last 1,700 years, we generated and analyzed genome sequence data from seven ancient individuals from KwaZulu-Natal, South Africa. Three Stone Age hunter-gatherers date to ~2,000 years ago, and we show that they were related to current-day southern San groups such as the Karretjie People. Four Iron Age farmers (300-500 years old) have genetic signatures similar to present day Bantu-speakers. The genome sequence (13x coverage) of a juvenile boy from Ballito Bay, who lived ~2,000 years ago, demonstrates that southern African Stone Age hunter-gatherers were not impacted by recent admixture; however, we estimate that all modern-day Khoekhoe and San groups have been influenced by 9-22% genetic admixture from East African/Eurasian pastoralist groups arriving >1,000 years ago, including the Ju| hoansi San, previously thought to have very low levels of admixture. Using traditional and new approaches, we estimate the population divergence time between the Ballito Bay boy and other groups to beyond 260,000 years ago. These estimates dramatically increases the deepest divergence amongst modern humans, coincide with the onset of the Middle Stone Age in sub-Saharan Africa, and coincide with anatomical developments of archaic humans into modern humans as represented in the local fossil record. Cumulatively, cross-disciplinary records increasingly point to southern Africa as a potential (not necessarily exclusive) hot spot for the evolution of our species.

evolutionary biology↗