Scientists have unveiled the largest human family tree ever created, a shared ancestry that is woven out of more than 3,600 individual genome sequences that date back more than 100,000 years, providing an unprecedented glimpse into the deep past and complex present of our species.
The immense family tree was stitched together from existing datasets and contains modern genetic information from around the world as well as samples from extinct human relatives such as Neanderthals and Denisovans. Scientists led by Anthony Wilder Wohns, who conducted the research while earning a PhD at the University of Oxford’s Big Data Institute, were able to confirm major events in human history from this integrated framework, such our species’ migration out of Africa, while also encountering surprises about past populations that will require more research to understand.
The outcome is a “unified genealogy of modern and ancient humans” that demonstrates the power of computational methods “to recover relationships between individuals and populations as well as to identify descendants of ancient samples,” according to a study published on Thursday in Science. Though this particular study is focused on humans, the team noted that the same approach could be used for almost any other species.
“The unified genealogy presented in this work represents a foundation for building a comprehensive understanding of human genomic diversity, including both modern and ancient samples, which enables applications ranging from improving genome interpretation to deciphering our earliest roots,” said Wohns and his colleagues in the study.
A genome is a blueprint for how to make an organism, and every human carries a unique version of it in our cells. These genetic units contain a massive amount of heterogeneous information that is often generated by different techniques, which has long posed a computational obstacle for scientists hoping to combine various datasets.
One of the innovations of study is a new algorithm that can more efficiently collate all this information into a single genealogy or tree sequence. By revealing relationships between individuals and populations of humans that stretch back deep into our prehistory, the approach mapped out 231 million ancestral lineages of our human family over time, as shown in the below video.
The findings confirmed the timing of many migrations that are known from archaeological evidence, but there were a few unexpected implications in the data as well. For instance, the new family tree hints that humans first arrived in North America 56,000 years ago, much earlier than is currently estimated, and points to human migration to Papua New Guinea a full 100,000 years before the earliest documented evidence of habitation in that region. These tantalizing results do not necessarily mean that those migration timelines should be pushed back, but they do offer a compelling avenue of research going forward.
To that end, the team hopes to continue adding branches to this unprecedented family tree. While this initial version of the project contains genetic information from several thousand individuals, the researchers said this method could potentially accommodate millions of genomes in future iterations, providing an ever-evolving portrait of our vast human family.
“Although much work is still required to build the genealogy of everyone, the methods presented here provide a solution to this fundamental task,” the researchers concluded in the study.