Ancient goat DNA offers insight into genetic legacy of agriculture

New research on DNA from one of the earliest goat herds has shed light on how farming has shaped the genetic makeup of modern livestock.

The findings were assimilated from DNA taken from the remains of 32 goats that died 10,000 years ago in the Zagros mountains, in what is now western Iran.

Archaeological evidence has previously pointed to the Zagros Mountains of western Iran as providing the earliest evidence of goat management by humans meaning the animals could provide clues to how early agricultural practices shaped the evolution of these animals.

The bone remains at the Ganj Dareh site indicate deliberate slaughtering of male goats once they were fully grown suggesting that they were farmed.

However, in contrast, the female goats were allowed to reach older ages, meaning early goat-keepers maximised the number of breeding female animals, similar to herders in the area today.

Legacy on modern goat DNA

Genetic analyses allowed the researchers to determine that the ancient goats fell at the very base of the domestic goat lineage, suggesting that they were closely related to the animals first recruited during domestication.

A surprising find, however, was the discovery of a small number of goats’ genomes appeared more like their wild relatives – strongly suggesting that early goat herders continued to hunt goats from wild herds while also farming them.

The close relationship between these early herders and goats can also be seen in the very foundations of the settlement, with several bricks bearing the imprint of cloven goat hooves.

The international project included researchers from:

  • The Smithsonian Institution;
  • The University of Copenhagen;
  • France’s National Centre of Scientific research and National Museum of Natural History;
  • The National Museum of Iran;
  • Trinity College Dublin.

Dr. Kevin G. Daly, research fellow in Trinity’s School of Genetics and Microbiology and first author of the paper, said: “Our study shows how archaeology and genetics can address highly important questions by building off ideas and results from both fields.

“Our genetic results point to the Zagros region as being a major source of ancestry of domestic goats and that herded, morphologically wild goats were genetically on the path to domestication by about 10,200 years ago.”

Dan Bradley, professor of population genetics, at Trinity, said: “This first livestock keeping shaped the goats’ genomes. There were signs of reduced Y chromosome diversity – fewer males were allowed to breed, leading to an increased tendency of relatives mating. Surprisingly, the Zagros goat appeared to not have undergone a population bottleneck often associated with and lacked strong signals of selection found in later domestic goats.

“Ancient DNA continues to allow us to plumb the depths of ancient prehistory and examine the origins of the world’s first livestock herds. Over 10,000 years ago, early animal farmers were practising husbandry with a genetic legacy that continues today.”

This research was funded by the European Research Council (project AncestralWeave) and has just been published in the Proceedings of the National Academy of Sciences of the United States of America journal.