DNA reveals clues to Egyptian ancestry

In 332 BCE Alexander the Great led his troops across the Nile and entered the ancient Egyptian capital of Memphis, ushering in a new period in history.

But did the incursion by the Macedonian general and his legions leave a genetic mark on the conquered population? The answer, it turns out, is a mildly surprising “no”.

A team led by Johannes Krause of the Max Planck Institute for the Science of Human History in Jena, Germany, sequenced mitochondrial DNA sourced from 90 mummies originally interred in the ancient settlement of Abusir el-Meleq on the Nile floodplain.

The mummies, now stored in two German museum collections, date from between 1400 BCE and 400 CE, providing a DNA palette that stretches from the time of the Eighteenth Dynasty ruler Amenhotep II through to the more recent periods marked by invasions and settlements by Greeks and Romans.

The sequenced DNA was compared to reference genomes obtained from modern Egyptian people.

The results, published in the journal Nature Communications, found that ancient Egyptians shared more DNA with Levant populations than their modern counterparts.

In contrast, today’s Egyptians share around eight per cent more DNA with sub-Saharan African people. Krause and his team speculate this could be due to the slave trade, which saw up to seven million sub-Saharan Africans brought into Egypt over a 1,250 year period, peaking in the nineteenth century.

Of Greek and Roman genetic influence, however, there was nary a trace. The result was in one way unexpected because there is ample archaeological and written evidence that Greek and Roman migrants settled in the area, and that Egyptian high society, at least to some extent, adopted and modified Greek and Roman language and customs.

Krause and his colleagues suggest the lack of genetic intermingling might be due to political imperatives.

“Under Ptolemaic and Roman rule, ethnic descent was crucial to belonging to an elite group and afforded a privileged position in society,” they write.

“Especially in the Roman Period there may have been significant legal and social incentives to marry within one’s ethnic group, as individuals with Roman citizenship had to marry other Roman citizens to pass on their citizenship. Such policies are likely to have affected the intermarriage of Romans and non-Romans to a degree.”

The researchers acknowledge that the geographically restricted area from which the mummies were sourced might have influenced the results. Abusir el-Meleq was long associated with religious piety and was a centre of devotion for the god Osiris. This may have affected population behaviours.

Similar studies from remains sourced from other parts of modern Egypt may tell a different story – but, Krause and his team recount, it is a story that until this piece of research was considered impossible to tell.

Traditionally, ancient Egyptian mummies have been regarded as poor and unreliable sources of genetic information. The combination of centuries of hot weather, rough and ready excavation techniques and even the embalming processes used in the first place have been shown to destroy and degrade genetic material.

The standard DNA extraction method used – direct polymerase chain reaction, or PCR – is also regarded as a potential source of contamination.

In this study, Krause and colleagues used a different method – high-throughput DNA sequencing – and then ran the results through several additional tests to ensure the material retrieved was truly of ancient origin.

The findings using the new sequencing method are considered robust, and open the door to similar studies across Egypt, potentially painting a significantly different picture of population movement and integration in classical history.

“Our results revise previous scepticism towards the DNA preservation in ancient Egyptian mummies due to climate conditions or mummification procedures,” the paper states.

“The methodology presented here opens up promising avenues for future genetic research and can greatly contribute towards a more accurate and refined understanding of Egypt’s population history.”