Global human genomes reveal rich genetic diversity shaped by complex evolutionary history
Study will help identify the susceptibility of different populations to disease
A new study has provided the most comprehensive analysis of human genetic diversity to date, after the sequencing of 929 human genomes by scientists at the Wellcome Sanger Institute, the University of Cambridge and their collaborators. The study uncovers a large amount of previously undescribed genetic variation and provides new insights into our evolutionary past, highlighting the complexity of the process through which our ancestors diversified, migrated and mixed throughout the world.
The resource, published in Science, is the most detailed representation of the genetic diversity of worldwide populations to date. It is freely available to all researchers to study human genetic diversity, including studies of genetic susceptibility to disease in different parts of the world.
The consensus view* of human history tells us that the ancestors of present-day humans diverged from the ancestors of extinct Neanderthal and Denisovan groups around 500,000-700,000 years ago, before the emergence of ‘modern’ humans in Africa in the last few hundred thousand years.
Around 50,000-70,000 years ago, some humans expanded out of Africa and soon after mixed with archaic Eurasian groups. After that, populations grew rapidly, with extensive migration and mixture as many groups transitioned from hunter-gatherers to food producers over the last 10,000 years.
This study is the first to apply the latest high-quality sequencing technology to such a large and diverse set of humans, covering 929 genomes from 54 geographically, linguistically and culturally diverse populations from across the globe. The sequencing and analysis of these genomes, which are part of the Human Genome Diversity Project (HGDP)-CEPH panel**, now provides unprecedented detail of our genetic history.
The team found millions of previously unknown DNA variations that are exclusive to one continental or major geographical region. Though most of these were rare, they included common variations in certain African and Oceanian populations that had not been identified by previous studies.
Variations such as these may influence the susceptibility of different populations to disease. However, medical genetics studies have so far predominantly been conducted in populations of European ancestry, meaning that any medical implications that these variants might have are not known. Identifying these novel variants represents a first step towards fully expanding the study of genomics to underrepresented populations.
However, no single DNA variation was found to be present in 100 per cent of genomes from any major geographical region while being absent from all other regions. This finding underlines that the majority of common genetic variation is found across the globe.
“The detail provided by this study allows us to look deeper into human history, particularly inside Africa where less is currently known about the timescale of human evolution. We find that the ancestors of present-day populations diversified through a gradual and complex process mostly during the last 250,000 years, with large amounts of gene flow between these early lineages. But we also see evidence that small parts of human ancestries trace back to groups that diversified much earlier than this.”
Dr Anders Bergström, of the Francis Crick Institute and an alumnus of the Wellcome Sanger Institute
“The Human Genome Diversity Project resource has facilitated many new discoveries about human history in the past two decades. It is exciting to see that with the latest genomic sequencing technology, these genomes will continue to help us understand our species and how we have evolved.”
Hélène Blanché, Head of the Biological Resource Centre at the Centre d’Etude du Polymorphisme Humain (CEPH) in Paris, France
The study also provides evidence that the Neanderthal ancestry of modern humans can be explained by just one major ‘mixing event’, most likely involving several Neanderthal individuals coming into contact with modern humans shortly after the latter had expanded out of Africa. In contrast, several different sets of DNA segments inherited from Denisovans were identified in people from Oceania and East Asia, suggesting at least two distinct mixing events.
The discovery of small amounts of Neanderthal DNA in west African people, most likely reflecting later genetic backflow into Africa from Eurasia, further highlights how human genetic history is characterised by multiple layers of complexity. Until recently, it was thought that only people outside sub-Saharan Africa had Neanderthal DNA.
“Though this resource is just the beginning of many avenues of research, already we can glimpse several tantalising insights into human history. It will be particularly important for better understanding human evolution in Africa, as well as facilitating medical research for the full diversity of human ancestries.”
Dr Chris Tyler-Smith, recently retired from the Wellcome Sanger Institute
* For a summary of the current consensus on human evolution, see Nielsen et al. (2017). Tracing the peopling of the world through genomics. Nature. https://www.ncbi.nlm.nih.gov/pubmed/28102248
**The Human Genome Diversity Project (HGDP)-CEPH panel is a collection of cell lines from diverse human populations for use in human genetic history and medical research. The DNA is available to the scientific community involved in population genetic studies. Cell lines and DNA are held at the Centre d’Etude du Polymorphisme Humain (CEPH) in Paris. http://www.cephb.fr/en/hgdp_panel.php#presentation
Anders Bergström, Shane McCarthy and Ruoyun Hui et al. (2020). Insights into human genetic variation and population history from 929 diverse genomes. Science. DOI: https://doi.org/10.1126/science.aay5012
This study was funded by Wellcome and the Francis Crick Institute.
The Francis Crick Institute is a biomedical discovery institute dedicated to understanding the fundamental biology underlying health and disease. Its work is helping to understand why disease develops and to translate discoveries into new ways to prevent, diagnose and treat illnesses such as cancer, heart disease, stroke, infections, and neurodegenerative diseases.
An independent organisation, its founding partners are the Medical Research Council (MRC), Cancer Research UK, Wellcome, UCL (University College London), Imperial College London and King’s College London.
The Crick was formed in 2015, and in 2016 it moved into a brand new state-of-the-art building in central London which brings together 1500 scientists and support staff working collaboratively across disciplines, making it the biggest biomedical research facility under a single roof in Europe. https://crick.ac.uk/
The mission of the University of Cambridge is to contribute to society through the pursuit of education, learning and research at the highest international levels of excellence. To date, 107 affiliates of the University have won the Nobel Prize. Founded in 1209, the University comprises 31 autonomous Colleges, which admit undergraduates and provide small-group tuition, and 150 departments, faculties and institutions. Cambridge is a global university. Its 19,000 student body includes 3,700 international students from 120 countries. Cambridge researchers collaborate with colleagues worldwide, and the University has established larger-scale partnerships in Asia, Africa and America. The University sits at the heart of the ‘Cambridge cluster’, which employs 60,000 people and has in excess of £12 billion in turnover generated annually by the 4,700 knowledge-intensive firms in and around the city. The city publishes 341 patents per 100,000 residents. www.cam.ac.uk
The Wellcome Sanger Institute is a world leading genomics research centre. We undertake large-scale research that forms the foundations of knowledge in biology and medicine. We are open and collaborative; our data, results, tools and technologies are shared across the globe to advance science. Our ambition is vast – we take on projects that are not possible anywhere else. We use the power of genome sequencing to understand and harness the information in DNA. Funded by Wellcome, we have the freedom and support to push the boundaries of genomics. Our findings are used to improve health and to understand life on Earth. Find out more at www.sanger.ac.uk or follow us on Twitter, Facebook, LinkedIn and on our Blog
Wellcome exists to improve health by helping great ideas to thrive. We support researchers, we take on big health challenges, we campaign for better science, and we help everyone get involved with science and health research. We are a politically and financially independent foundation. https://wellcome.org/
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