Reading 426 African genomes found more than 3 million variants science had never seen
An H3Africa study sequenced 426 people from 50 ethnolinguistic groups and uncovered more than 3 million previously undescribed genetic variants. It is a plain measure of how much of Africa's diversity global databases had missed.
Key points
- The study sequenced the whole genomes of 426 individuals from 50 ethnolinguistic groups.
- It uncovered more than 3 million previously undescribed variants.
- Most of the new variants were found among people from groups that had never been sampled before.
- It also found 62 loci under strong selection, mainly in genes for viral immunity, DNA repair and metabolism.
What happened
Africa is where modern humans began, and African genomes carry more genetic variation than those of any other continent. Yet for years, most large genome databases were built mainly from people outside Africa, so a large share of African variation simply was not in the record that medical research relies on.
The Human Heredity and Health in Africa consortium - H3Africa - set out to close part of that gap. Its 2020 Nature study read the full genomes of people from groups across the continent, including some that had never been included in a study like this before.
Claim by claim
Why this label: From the abstract of the Nature paper itself.
On the ladder: a claim earns Verified from primary evidence, or from two independent sources that do not copy each other.
Why this label: Nature's abstract adds that most of these were found among individuals from newly sampled ethnolinguistic groups.
On the ladder: a claim earns Verified from primary evidence, or from two independent sources that do not copy each other.
Why this label: The opening statement of the Nature paper's abstract, and the reason the authors give for surveying African diversity more deeply.
On the ladder: a claim earns Verified from primary evidence, or from two independent sources that do not copy each other.
Why this label: As reported in the Nature abstract; H3Africa's own summary describes the same finding as evidence of selection in and around 62 genes.
On the ladder: a claim earns Verified from primary evidence, or from two independent sources that do not copy each other.
Why this label: Reported in both the Nature abstract and H3Africa's summary of the paper.
On the ladder: a claim earns Verified from primary evidence, or from two independent sources that do not copy each other.
What we know / what we don't know yet
What we know
- Sequencing even a few hundred people from unsampled groups reveals millions of variants missing from global databases.
- Disease and gene flow have strongly shaped variation across African populations.
- The authors themselves say far more African genomes, from more populations, are still needed.
What we don't know yet
- What most of the newly found variants actually do - finding a variant is not the same as understanding it.
- How quickly this wider data will change everyday medical care for African patients.
Why it matters
If the reference books of human genetics leave out most African variation, then tests, risk scores and medicines built from those books can work less well for African patients. Studies like this one are how that record gets corrected - by African-led research, on African populations.
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