Around 1638 BC, a foreign dynasty ruled in Egypt for the first time. They were called the Hyksos, which means “rulers of a foreign land.” The Hyksos stayed in power for nearly a hundred years, lasting until 1530 BC. Most archaeologists speculate that the Hyksos were foreigners, coming from the Near East to invade and conquer Egypt.

But a new theory suggests that, while the Hyksos were of Near Eastern origin, they weren’t foreign invaders. Instead, the Hyksos rose to power from within, researchers argue in a PLOS ONE paper published July 15. The results “challenge the classic narrative of the Hyksos as an invading force,” they write.

Most of our understanding of the rise and fall of the Hyksos Dynasty is based on the testimony of one person: Manetho, an Egyptian priest who lived 1,200 years after the Hyksos Dynasty ended. He recounts the Hyksos invading from the northeast, taking over part of northern Egypt. Manetho’s words survived in the work of later historians like Flavius Josephus, a Roman historian writing in the first century AD. But Manetho’s account was the only source of information about the Hyksos Dynasty. Other accounts about the Hyksos rulers because of the censorship and propaganda that ancient Egyptian rulers used to stay in power.

Then in 1996, archaeologists unearthed the Hyksos capital city at a site north of modern-day Cairo, Egypt. The city was founded in the 12th dynasty and quickly grew to become a large harbor city home to Egyptians and foreigners from all over the region. When the Hyksos rose to power, they made the city their capital and renamed it Avaris. The city was abandoned in 1550 BC, just before the fall of the Hyksos Dynasty.

When the researchers excavated the site, they found several skeletons buried in a cemetery. They also excavated ceramics, weapons, personal decorations, and remnants of buildings. However, the artifacts didn’t have the typical features of Egyptian artifacts from the same time period. The burial customs and architecture found in the city were also distinctly non-Egyptian.

The discovery provided Egyptologists with lots of insights into who the Hyksos were and where they came from – and it cast doubt on Manetho’s account. The people living in the Hyksos capital city of Avaris appeared to be non-Egyptians, many of them of Near East descent. But the artifacts and human remains found at the site still didn’t prove whether or not the Hyksos rulers invaded Egypt or not. Now, the first research using chemical analysis suggests that the rulers of the Hyksos Dynasty were foreigners living in Egypt who rose to power, not invaders.

An international team of scientists extracted molars or other teeth from 75 of the skeletal remains found in the Hyksos capital city. About half of the bodies were from the Hyksos Dynasty and the other half dated to some time before that period. There were slightly more female bodies than male ones.

By analyzing the chemical variants of the element strontium in the teeth, the scientists were able to determine whether the person was from Egypt or another region. The amount of strontium in the bones and teeth directly correlates with the geology of where that person lived. Strontium in the soil is taken up by plants, and when humans or other animals ingest strontium when they eat those plants. The body then incorporates some of that strontium into the bones and the enamel of the teeth. So, looking at the strontium in human remains can tell archaeologists where that person likely lived.

In this study, researchers used strontium levels found in ancient animal bones from Egypt as a baseline. Human remains with strontium levels similar to those in animal bones from the region were considered ‘locals’. The team found that most of the skeletons dating to before the Hyksos Dynasty were immigrants from several regions, whereas the skeletons from the Hyksos Dynasty were Egyptian ‘locals’. This indicated that the ancestors of the Hyksos likely immigrated to Egypt long before 1638 BC, and – generations later – their descendants became the Hyksos rulers. Females also tended to be immigrants, not males. The researchers would have expected more of the skeletons to belong to non-local males if a predominantly male group of foreigners had invaded.

To the team, the strontium evidence suggests that the Hyksos weren’t invaders like Manetho claimed. Rather, the Hyksos were a group of Egyptian-born descendants of immigrants that rose to power in Egypt. And, though the Hyksos only stayed in power for 100 years, they clearly made an impact in Egypt and the world beyond.