Mummies from ancient Egypt have revealed another secret — some of them share very little of the sub-Saharan African ancestry that dominates the genetic heritage of modern Egyptians.

Key points: Genetic analysis done on 93 mummies that lived in an important centre in ancient Egypt

Genetic analysis done on 93 mummies that lived in an important centre in ancient Egypt Ancient genome from this area contains almost no sub-Saharan DNA that dominates the genetic profile of modern Egyptians

Ancient genome from this area contains almost no sub-Saharan DNA that dominates the genetic profile of modern Egyptians It more closely resembles the genetic heritage of people from the Near East and Levant

The discovery, published today in Nature Communications, suggests the African heritage evident in modern Egyptian populations may have been the result of the slave trade down the Nile in the past 1,500 years.

Researchers used modern genetic analysis techniques to study the genomes of 93 mummies that lived between 1300 BC — the late New Kingdom Period — and around 30 BC during the time of the Romans.

The mummies were buried at Abusir el-Meleq, which was an important religious and trading centre.

Map of Egypt showing the site of Aubusir-el Meleq (inset) and modern Egyptian samples (orange circles) ( Supplied: Krause et al, Nature Communications )

"One of the questions that motivated us for our study is trying to find out when Egypt was conquered by the Greeks or Alexander the Great or by the Nubians or by the Romans, and did that actually have an impact on the population?" said archaeogeneticist Professor Johannes Krause, from the Max Planck Institute for the Science of Human History in Germany.

It's a question that is difficult to answer using artefacts and historical records, so Professor Krause and his colleagues decided to look in preserved genetic material.

They took samples of biological material from the bones and teeth of the mummies, and extracted the DNA using sequencing techniques that also allow them to verify the genetic material was indeed ancient, and not the result of modern contamination.

They then compared the genomes of these ancient Egyptians with data from the genome of modern Egyptians.

Their results were the opposite of what they were expecting to find, Professor Krause said.

"Instead of finding that ancient Egyptians were more African, we actually found them to be almost zero or much less sub-Saharan African than the population that live in Egypt today," he said

"They have these closest genetic links to the fertile crescent and the eastern populations of what's now Israel, but if they came from there or if they just evolved with gene flow all the time in this region, we cannot really say."

They also saw a clear genetic continuity right across the 1300-year time period of the studied mummies, despite the fact that over that time course Egypt was invaded by the Greeks, the Romans and Nubians.

"We don't really see that there is a lot of genetic turnover when all those foreign invaders came, so they don't seem to have an impact on the normal population of Egypt," Professor Krause said.

"It turns around some of the assumptions that people had on Egyptians' history."

Sarcophagus of a young girl known as Tadja from Abusir el-Meleq ( Supplied: bpk/Aegyptisches Museum und Papyrussammlung, SMB/Sandra Steiss - kontakt@bpk-bildagentur.de )

And yet, at some point in the past 1,500 years, there has been a major addition of sub-Saharan genetic material — largely West-African Yoruba — into Egypt's population.

Unfortunately, there isn't much archaeological information from Egypt that covers this medieval period, Professor Strause said.

"In fact, we have sometimes better historical records from the Roman or the ancient Egyptian time than we have from the medieval time in Egypt," he said.

But there is evidence of an active slave trade that reached its peak in the 19th century, and which was responsible for the transportation of millions of slaves from sub-Saharan Africa to Northern Africa and Egypt.

Modern techniques key to unravelling the past

Even though some of the earliest work on ancient DNA was done using Egyptian mummies, Professor Krause said this is first time their genetic material has been analysed using such modern techniques.

Previous attempts to do this sort of research were thwarted by contaminated samples, and the difficulties in extracting viable DNA from soft tissue such as muscles.

"What we show in our paper is that soft tissue is extremely bad, so you should not look at soft tissue, you should actually look at bones and teeth; they are much better preserved in ancient mummies," he said.

As the genetic material comes from just one site in Middle Egypt, the researchers said the study may not be representative for all of ancient Egyptians.

But it paves the way for genetic analysis of more and older mummies, which will hopefully shed more light on their origins, said Professor Krause.