Scientists have created “the largest family tree in the world”, which brings together about 27 million people around the world – both living and dead.
A new genealogy network developed at Oxford University shows how people around the world are connected to each other in “unprecedented detail”.
Taking the form of a scientific method, research paper and video, it actually takes us back in time to show where and when human populations lived.
The earliest pre-Homo sapiens ancestors can be traced back in time to a geographic location that is in present-day Sudan, probably over a million years ago.
This image visualizes putative human ancestral bloodlines across time and space. Each lineage represents the relationship of ancestors and descendants in our “proposed genealogy of modern and ancient genomes.” The width of the line corresponds to how many times the relationship is observed, and the lines are colored depending on the estimated age of the ancestor.
WHAT IS A GENOME?
Your genome is the blueprint for building and maintaining you. It is written in a chemical code called DNA. All living things—plants, bacteria, viruses, and animals—have a genome.
Your genome is made up of 3.2 billion letters of your DNA. It contains about 20,000 genes.
Genes are the instructions for making the proteins our bodies are built from, from keratin in hair and nails to antibody proteins that fight infection.
Source: Genomics of England.
The project was published today in the journal Science by researchers at Oxford University’s Big Data Institute.
“Basically, we have built a huge family tree, a genealogy for all of humanity, which most closely models the history that gave rise to all the genetic variations that we find today in humans,” said study author and evolutionary geneticist Dr. Ian Wong.
“This genealogy allows us to see how each person’s genetic sequence is related to everyone else across all points of the genome.
“Although the focus of this study is on humans, this method is applicable to most living beings; from orangutans to bacteria. This can be especially useful in medical genetics to separate true links between genetic regions and diseases from false links arising from our shared hereditary history.”
The past two decades have seen remarkable advances in human genetics research, resulting in genomic data for hundreds of thousands of people, including thousands of prehistoric humans.
According to the team, this provides an opportunity to trace the origins of human genetic diversity to provide a complete map of how people around the world are connected to each other.
Two-dimensional histograms showing the geographic location of pedigrees at six points in time. 1,000 years ago is short for a thousand years ago.
Since individual regions of the genome are inherited from only one parent, mother or father, the origin of each point of the genome can be considered as a tree.
A set of trees, known as a “sequence tree” or “hereditary recombination graph”, links genetic regions through time to ancestors where genetic variation first appeared.
Until now, researchers have struggled to find a way to combine genome sequences from many different databases and develop algorithms to process data of this size.
However, the new method can easily combine data from multiple sources and scale to handle millions of genome sequences.
The study pooled data on modern and ancient human genomes from eight different databases and included a total of 3,609 individual genome sequences from 215 populations.
Ancient genomes included samples found around the world ranging in age from 1,000 to over 100,000 years.
“Essentially, we are reconstructing the genomes of our ancestors and using them to form a vast network of relationships,” said study lead author Dr. Anthony Wilder Wans, currently a postdoctoral fellow at the Broad Institute of the Massachusetts Institute of Technology and Harvard.
“Then we can estimate when and where these ancestors lived. The strength of our approach is that it makes very few assumptions about the source data and can also include both modern and ancient DNA samples.”
About 2000 years ago, people were widely settled throughout the world, with the exception of most of North America, Oceania and other places.
But over 300,000 years ago, humans were more concentrated in Africa, as the animation shows.
The algorithms predicted where common ancestors should be present in evolutionary trees in order to explain patterns of genetic variation. The resulting network contained nearly 27 million ancestors.
After adding location data to these genome samples, the authors used the network to estimate where the predicted common ancestors lived.
The results successfully reconstructed key events in the history of human evolution, including migration out of Africa.
The earliest ancestors the team identified were “highly likely” Homo erectus, an extinct species of archaic human that can be traced back in time to a geographic location that is in present-day Sudan.
Dr. Ian Wong and Dr. Wons said in a joint statement: “These ancestors lived up to and over a million years ago, which is much older than current estimates of the age of modern humans (250,000 to 300,000 years ago) – so not much. Our genomes were inherited from individuals that we would not recognize as modern humans, but who most likely lived in northeast Africa.
“It is very likely that these very ancient ancestors were Homo erectus, but we cannot be sure of their identity or location without extremely ancient DNA.
“One important takeaway from our work is that the people we often refer to as the ‘cradle of mankind’ themselves had ancestors in the distant past, whose descendants are still among us today.”
WHAT DO WE KNOW ABOUT HUMANITY’S JOURNEY FROM AFRICA?
The traditional “out of Africa” model suggests that modern humans evolved in Africa and then left in one wave about 60,000 years ago.
The model often claims that after modern humans left the continent, there was a brief period of interbreeding with Neanderthals.
This explains why people of European and Asian descent still have ancient human DNA today.
There are many theories as to what led to the death of the Neanderthals.
Experts have suggested that early humans may have brought with them tropical diseases from Africa that wiped out their ape-like cousins.
Others argue that the dramatic drop in temperature due to climate change wiped out the Neanderthals.
The prevailing theory is that early humans killed the Neanderthals as a result of competition for food and habitat.
How history is changing in the light of new research
Recent discoveries show that the “out of Africa” theory does not reveal the full history of our ancestors.
Instead, many small human movements out of Africa that began 120,000 years ago were followed by a major migration 60,000 years ago.
Most of our DNA is made up of this latter group, but earlier migrations, also known as “scattering”, are still evident.
This explains recent research into early human remains that have been found in the far corners of Asia that are over 60,000 years old.
For example, H. sapiens remains have been found at several sites in southern and central China that have been dated to between 70,000 and 120,000 years ago.
Other recent finds show that modern humans reached Southeast Asia and Australia before 60,000 years ago.
Based on these studies, people could not come in one wave from Africa around this time.
Instead, human origins suggest that modern humans evolved in many regions of the world.
The theory claims that groups of prehuman ancestors emerged from Africa and spread through parts of Europe and the Middle East.
From here, the species evolved into modern man in several places at once.
The argument is based on a new analysis of a 260,000-year-old skull found in Dali County in China’s Shaanxi province.
The skull suggests that early humans migrated to Asia, where they developed features of modern humans, and then returned to Africa.