After 20 years of trying to unravel the human genome, we now take a vital step further to unravel the origins of human genetic diversity and explain our genetic links and relationship.
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| Visualizing inferred human ancestral lineages over time and space. (Wohns et al., 2022) |
Researchers from the Big Data Institute at the University of Oxford have successfully compiled 3609 individual genomic sequences to create the largest human family tree up to date.
Published last February 25 in Science, this study compiled 3601 sequences from 215 populations, along with eight ancient human genome sequences (as roots) that includes Neanderthal and Denisovan genomes, and then branching out to 27 million ancestors and 231 million ancestral lineages.
“This genealogy allows us to see how every person’s genetic sequence relates to every other, along all the points of the genome,” said Dr. Yan Wong, an evolutionary geneticist and one of the principal authors.
With the pressing challenge to combine and to develop algorithms to process this big data, the researchers found this new method which can easily squeeze millions of genomic sequences from multiple sources, together with an algorithm that predicts the location of our ancestors in evolutionary trees to explain patterns of genetic variation.
Using a concept called Succinct Data Structure for their tree sequence method, this set of trees, also known as the ancestral recombination graph, reconstruct and link regions of the genome in the past with our ancestors to find primary genetic variations and subsequently, correlates between different tree branches for the data of this size to be easier to examine and interpret.
“The exact way it works is that we try and have a guess at what the genetic ancestors of different sets of people looked like in terms of their DNA sequence at different points in the past, and then once we’ve had a guess at what those genomic sequences look like, DNA sequences, then we can map the sequences that we know about today on to each of those ancient ancestors, and we do that in different places in the genome,” Wong explained.
After adding geographical locations on the sample genome, the researchers used the tree network to estimate where our ancestors might have lived and moved.
Lead author Dr. Anthony Wilder Wohns said: ‘One of the most interesting results that came of this work was insight into where and when human ancestors lived.’
This study made it apparent that human populations migrated out of Africa, and human genetic diversity is highest in Africa, among many key events in human evolutionary history, while also exploring complex interactions of populations, including Denisovans.
Researchers also plan to improve the network in the future, making it more comprehensive and accurate by continually adding new genomic data.
Dr Wong said: ‘This study is laying the groundwork for the next generation of DNA sequencing. As the quality of genome sequences from modern and ancient DNA samples improves, the tree will become even more accurate and we will eventually be able to generate a single, unified map that explains the descent of all the human genetic variation we see today.’
Dr Wohns added: ‘While humans are the focus of this study, the method is valid for most living things; from orangutans to bacteria. It could be particularly beneficial in medical genetics, in separating out true associations between genetic regions and diseases from spurious connections arising from our shared ancestral history.’
'This tell us a lot that the process by which our DNA was generated and if we know that, then we can start incorporating it into our understanding of what the DNA actually does. So, for example if you wanted to know why some people have some sort of medical conditions or more predisposed to heart attacks or for example more susceptible for coronavirus then there’s a huge amount of that is described by their ancestry because they’ve inherited their DNA from other people, but it also tells us about where people came from. It tells migration routes around the world, how big populations were in different places where whole segments of the human race essentially come from, and I think that’s interesting.'
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