OXFORD, United Kingdom — The world’s biggest family tree linking around 27 million people has been created by scientists. The genetic model combines thousands of modern and prehistoric genomes, providing new insight into key events in human history.
The breakthrough is a major step towards mapping the entirety of human relationships, with a single lineage that traces the ancestry of all people on Earth. The family tree also has widespread implications for medical research, identifying genetic predictors of disease.
“We have basically built a huge family tree, a genealogy for all of humanity that models as exactly as we can the history that generated all the genetic variation we find in humans today. This genealogy allows us to see how every person’s genetic sequence relates to every other, along all the points of the genome,” says principal author Dr. Yan Wong in a university release.
The University of Oxford team combed through eight databases containing 3,609 different genome sequences from 215 populations. They included samples from across the world; some being over 100,000 years-old. The resulting network contained almost 27 million ancestors and 231 million ancestral lineages.
Tracing the origins of humanity
The tree reveals how people across the world are related in unprecedented detail. Individual regions of DNA are inherited from either the mother or father. Each point can be thought of as a tree.
A set — known as a “tree sequence” — links them to common ancestors where mutations first appeared. Computer algorithms explain the patterns, predicting when and where they lived. The study covers the migration out of Africa, interbreeding with Neanderthals, and the arrival of primitive humans in Asia and Oceania.
“Essentially, we are reconstructing the genomes of our ancestors and using them to form a vast network of relationships. We can then estimate when and where these ancestors lived. The power of our approach is that it makes very few assumptions about the underlying data and can also include both modern and ancient DNA samples,” says lead author Dr. Anthony Wilder Wohns.
‘The next generation of DNA sequencing’
The past two decades have generated genomes from hundreds of thousands of people. Many lived tens of thousands of years ago. Variable quality and limitations in analyses made painting an accurate picture impossible, until now. The revolutionary technique described in the journal Science allows for missing and erroneous data and uses fragmented ancient genomes.
“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 trees 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. Wong adds.
The genealogical map could easily accommodate millions more genomes as they become available.
“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,” Dr. Wohns concludes.
South West News Service writer Mark Waghorn contributed to this report.