23 January 2020
DNA shows origins of mummified birds
Published online 13 November 2019
Ancient Egyptians may not have bred the sacred ibises they sacrificed to Thoth.
Kilometres of Egyptian catacombs are filled floor to ceiling with millions of jars containing mummified sacred ibises (Threskiornis aethiopicus). An unprecedented analysis of their mitochondrial DNA reveals that the birds were probably tamed over short periods rather than bred over generations.
Sacred ibises, which disappeared from Egypt by 1850, represent the most numerous type of mummy, more common than cats, dogs, other animals and humans. Pilgrims offered them to Thoth, the Egyptian god of wisdom, writing, and time, who was represented with an ibis-shaped head. However, scientists have debated how ancient Egyptians obtained such an impressive number of sacrificial birds. Ibis farms are described in a few hieroglyphics and writings, but the animals could have been reared over generations or sourced from the wild and tamed seasonally.
An international team, led by researchers from Griffith University in Australia, recovered 2,500-year-old DNA from ibis tissues extracted from six Egyptian burial sites. They were able to obtain complete mitochondrial genomes, called mitogenomes, from 14 ibises: the first achievement of this kind for Egypt’s non-human mummies.
“I was impressed that the team managed to recover full mitogenomes from the mummies and I think this bodes well for studies of mummified remains from Egypt,” says archaeologist, Hannes Schroeder of the University of Copenhagen, Denmark, who was not involved in the study.
The researchers looked for signs of inbreeding and compared these mitogenomes with those of 26 modern ibises from across Africa. “It had been assumed, based on the huge number of mummies, that these birds were farmed, hence the prediction was to find genetic similarities among birds from the same catacomb. However, the results were surprising: the mitogenomes of these mummies were as diverse from each other as those of modern ibises,” says molecular biologist, Sally Wasef, of Griffith University. “Our results suggest that the ibises were fed, rather than bred, specifically to be sacrificed.”
Molecular geneticist, Yehia Zakaria Gad, of the National Research Center, in Egypt, also not involved in the study, says that each site was represented by a limited number of birds, and that a more comprehensive study with a larger sample size, would be needed to “totally refute the long-term centralised farming theory.”.
The authors are planning to continue the analysis and extend it to nuclear DNA, which is less abundant than mitochondrial DNA but could offer more genetic information and evolutionary clues about this significant bird.
Wasef, S. et al. Mitogenomic diversity in Sacred Ibis mummies sheds light on early Egyptian practices. PLoS ONE 14(11), e0223964 (2019).