From Mongol warriors to Silk Road traders: Interactive map reveals how fallen European empires have left their lasting stamp on the world's gene-pools

Map shows the mixing of genes of 95 different populations across Europe, Africa, Asia and South America

It reveals colonialism, the Arab slave trade and European traders on the Silk Road mixing with people in China



Scientists pinpointed time when mixing took place by looking areas of DNA that exchanged genetic information

To use the map, double click on the location you want to view. You can then use the scroll bar to zoom in and out

Blue circles indicate the local populations. Orange shows the population that this group may have mixed with




DNA footprints left in the wake of ancient warriors can unravel long-held secrets about a country’s past.

Now, for the first time, scientists have mapped the DNA of 95 different populations to see if they can paint a clearer picture of major historical events.

This incredible interactive map looks at the mixing of genes in major populations in Europe, Africa, Asia and South America spanning over the last four millennia.



INTERACTIVE MAP: Double click on the location you want to view. You can then use the scroll bar on the left to zoom in

HOW TO USE THE INTERACTIVE MAP

Double click on the location you want to view. You can then use the scroll bar on the left hand side to zoom into the map. Blue circles indicate the local populations. Orange shows the population that this group may have mixed with.

The size of each circle represents the sample size used by the scientists. Grey circles, indicate that there was no admixture with populations, as is the case with England.

The map reveals the genetic impact of European colonialism, the Arab slave trade, the Mongol Empire and European traders near the Silk Road mixing with people in China.

‘We made some very surprising discoveries,’ Dr Garrett Hellenthal of the University College London Genetics Institute told MailOnline.

‘For instance, the Kalash group are an isolated population in Pakistan. They are believed to be descendants of Alexander the Great's invading army, and our map doesn’t dispute that fact.'

Many of the map’s genetic observations match historical events, and provide evidence of previously unrecorded genetic mixing.

The group with the longest time since admixture is the Kalash from Pakistan. They have an ancient inferred event prior to 206BCE, involving mixing between a more European and West Asian group, and a more Central/South Asian group

Many Kalash people (left) believe they are descended from the army of Alexander the Great (right). The date shown in the interactive map does not rule this out but the date range also allows for many other possibilities

WHAT THE RESULTS TELL US

Most human populations are a product of mixture of genetically distinct groups that intermixed within the last 4,000 years.

Mixture events are often localised in time and space: neighbouring populations can sometimes have distinct ancestry and history, especially for recent events.

Many mixture events involve source populations from very distant locations separated by thousands of miles.

For example, the DNA of the Tu people in modern China suggests that in around 1200CE, Europeans similar to modern Greeks mixed with an otherwise Chinese-like population.

Plausibly, said the researchers, the source of this European-like DNA might be merchants travelling the nearby Silk Road.

The powerful technique, dubbed 'Globetrotter', also provides insight into past events such as the genetic legacy of the Mongol Empire.

Historical records suggest that the Hazara people of Pakistan are partially descended from Mongol warriors, and this study found clear evidence of Mongol DNA entering the population during the period of the Mongol Empire.

Six other populations, from as far west as Turkey, showed similar evidence of genetic mixing with Mongols around the same time.

'What amazes me most is simply how well our technique works,' said Dr Hellenthal.

The Pima people are a group of Indigenous Americans living in an area consisting of what is now central and southern Arizona. Their genetic data reveals their ancestors came from far and wide with significant local populations with Maya heritage

This map of England was based on genetic data from 6 individuals. It shows that much of the admixture was with local populations in Wales, Ireland and Scotland. A tiny per cent of DNA was found to come from Palestine, but the researchers have described this as 'noise' and not reflective of the general population

MAJOR HISTORICAL EVENTS

An event which is easy to identify signal is the Mongol expansion. Seven populations in the sample are involved in the event. A second is the Arab slave trade, with DNA contributions from sub-Saharan Africa. people from around the Mediterranean, the Arabian Sea and the Persian gulf. The Mongol expansion seems, according to both history and genetics, to have been a particularly abrupt transfer of people and DNA across Asia.

DNA of the Tu people in modern China suggests that in around 1200CE, Europeans similar to modern Greeks mixed with an otherwise Chinese-like population.

Plausibly, the researchers say, the source of this European-like DNA might be merchants travelling the nearby Silk Road.



'Although individual mutations carry only weak signals about where a person is from, by adding information across the whole genome we can reconstruct these mixing events.



‘Sometimes individuals sampled from nearby regions can have surprisingly different sources of mixing.’

‘For example, we identify distinct events happening at different times among groups sampled within Pakistan, with some inheriting DNA from sub-Saharan Africa, perhaps related to the Arab Slave Trade, others from East Asia, and yet another from ancient Europe.

‘Nearly all our populations show mixing events, so they are very common throughout recent history and often involve people migrating over large distances.'

The team at UCL and Oxford University used genome data for all 1490 individuals to identify 'chunks' of DNA that were shared between individuals from different populations.



They were able to pinpoint time frame when genetic mixing took place using genetic recombination – the biological process in which two DNA molecules exchange genetic information.



Populations sharing more ancestry share more chunks, and individual chunks give clues about the underlying ancestry along chromosomes.

'Each population has a particular genetic “palette”’, said Dr Daniel Falush of the Max Planck Institute for Evolutionary Anthropology in Leipzig, co-senior author of the study.

'If you were to paint the genomes of people in modern-day Maya, for example, you would use a mixed palette with colours from Spanish-like, West African and Native American DNA.’

This mix dates back to around 1670CE, consistent with historical accounts describing Spanish and West African people entering the Americas around that time.

The Mongol expansion seems, according to both history and genetics, to have been a particularly abrupt transfer of people and DNA across Asia Researchers identified distinct events happening at different times among groups sampled within Pakistan (pictured), with some inheriting DNA from sub-Saharan Africa

KALASH PEOPLE MAY BE RELATED TO ALEXANDER THE GREAT

The group with the longest time since admixture is the Kalash from Pakistan. They have an ancient inferred event prior to 206BCE, involving mixing between a more European and West Asian group, and a more Central/South Asian group. Some Kalash believe they are descended from the army of Alexander the Great.

The date shown in the interactive map does not rule this out but the date range also allows for many other possibilities.

Though we can't directly sample DNA from the groups that mixed in the past, we can capture much of the DNA of these original groups as persisting, within a mixed palette of modern-day groups,’ said Dr Falush. ‘This is a very exciting development.'

As well as providing fresh insights into historical events, the new research might have implications for how DNA impacts health and disease in different populations.

'Understanding well the genetic similarities and differences between human populations is key for public health,' said Dr Simon Myers.

Some populations are more at risk of certain diseases than others, and how well certain drugs work is also known to vary significantly.

Rare genetic mutations are particularly likely to show strong differences between populations, and understanding their role in human health is an area of intense current research efforts.

The researchers hope that in the future they can include even more detailed sequencing, to spot these rare mutations and better understand their global spread.

‘This really is a fascinating insight,’ said Dr Hellenthal. ‘Imagine just how much more can be found out with even more detailed sequencing.’