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How To Use DNA To Create Largest Family Tree of Humanity

By combining old and new data on the human genome together, researchers have put together a huge family tree that traces the history of humanity over time.

If they told us that we are all related, perhaps we would not be too surprised. But if they showed us how we are related and the relationships with our ancestors , well, maybe things would change. Until now it seemed an impossible mission, yet there are those who have tried to rebuild the various family relationships . And he succeeded, achieving what is presented today as the largest family tree of humanity ever made. The authors of the enterprise are researchers scattered between Boston, Oxford and Vienna. How did they do it? Thanks to the huge amount of genetic data available thanks to DNA sequencing, both modern and past populations.

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Rebuild kinship ties, thanks to DNA

Putting the family back together was no easy walk. The main reason is that the “photographs” – the various genomes – are quite different from each other, for the techniques used, accuracy, coverage, accessibility. And they represent a huge amount of data. For this the team of Anthony Wilder Wohns of the Big Data Institute of the University of Oxford, now at the Broad Institute of the Massachusetts Institute of Technology (MIT) and Harvard, head of the work just published in Science , has resorted to a special analysis technique of genomes.

“We have developed a method that combines information from ancient and modern genomes to understand how they relate to their common ancestors,” Whons himself tells Wired . The method in question is in fact a particular type of genomic analysis that aims to identify the emergence of a specific allele (one of the possible alternative versions of a gene, linked to a chromosome position), through a technique known as ancestral recombination graph. (ancestral recombination chart), up to go back in time, to when it appeared, they explain from Oxford.

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To do this, the researchers combined data from approximately 6,500 genomes , from over 200 human populations, of high and low quality. “This is a fairly innovative approach – continues Wohns – because until now the researchers had not developed a method to combine genomic sequences from many different databases or had not developed algorithms to manage data of this magnitude. Our method has met these challenges by easily combining data from multiple sources and hosting hundreds of thousands, and potentially millions of genomic sequences . “

One big family tree

The result, continues the expert, is surprising: in this way it was possible to reconstruct both the genomes of our ancestors and the temporal and spatial coordinates in which they lived: “This allows us to reveal important characteristics of human evolutionary history” . In this way, the researchers were able for example to see the migration events known as out of Africa – when the first hominids left the continent – confirming the existence of ancestors far back in time in these areas.

This is also demonstrated by the following video, which shows the age and origin of our ancestors , up to two million years ago, where each point represents a different lineage , colored according to the different regions of its descendants. If the offspring is mixed, the color of the dots will also appear mixed (as colors) as a result, the authors explain.

Another way of representing the results of the largest human family tree ever made is the following, in which the different lines show a relationship of descent, the thicker the more the relationships are marked, colored according to the period from which the ancestor (and also in this case it is possible to observe the migration events from the African continent, through the blue lines).

largest human family tree
largest human family tree

 

Image: Reproduced, with permission, from Wohns et al., A unified genealogy of modern and ancient genomes. Science (2022). PHOTO: REPRODUCED, WITH PERMISSION, FROM WOHNS ET AL., A UNIFIED GENEALOGY OF MODERN AND ANCIENT GENOMES. SCIENCE (2022). 

The exercise of reconstructing the family genealogical tree has no meaning only in the anthropological field. “In addition to studying human evolutionary history, much of the research that is done in biology requires knowing how populations of individuals change over time and space – resumes Wohns – We can therefore do it by recreating these genetic genealogies, whether it is domestic animals, endangered species or vectors of human disease. Another possible line of research is to use genealogy to better understand the basis of human diseases, for example to trace the origin and spread of genetic variants associated with diseases ”.

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