The ancient Egyptians left us with plenty of head scratching. How did they actually build the pyramids? Where is Queen Nefertiti buried? What’s inside that mysterious void in the Great Pyramid of Giza?

Then there are the deeper cuts. For example: Where did Egypt get the millions — yes, millions — of African sacred ibises that they mummified as offerings to the god Thoth?

Experts have put forth a number of explanations, including large-scale ibis breeding farms. DNA analysis from a study published Wednesday in the journal PLOS One undercuts that hypothesis, and may help archaeologists get closer to solving the riddle.

The study’s authors also managed to obtain full mitochondrial genomes from more than a dozen mummified ibises, further proving “the feasibility of Egyptian mummies for ancient DNA studies,” said Albert Zink, head of the Institute for Mummy Studies at Eurac Research in Bolzano, Italy, who was not involved in the study.