Washington: Researchers have discovered the first evidence of milk consumption by humans preserved in a mineralised form of dental plaque from ancient times.
Using the latest mass spectrometry-based techniques for ancient protein sequencing, researchers detected a milk protein, beta-lactoglobulin (which they had previously reported from a modern dental plaque sample) in ancient remains.
"It seemed too good to be true; beta-lactoglobulin is the dominant whey protein - the one used by bodybuilders to build muscle mass - and therefore the ideal marker for milk consumption," lead author Jessica Hendy, from the University of York's BioArCh research facility, said.
"We kept finding sequences of beta-lactoglobulin and at first we thought it could be modern contamination. But we repeated the analysis several times, at three different laboratories in three different countries, each time finding the same results," said Hendy.
The study has far-reaching implications for understanding the relationship between human diet and evolution.
"Dairy products are a very recent, post-Neolithic dietary innovation, and most of the world's population is unable to digest lactose, often developing the symptoms of lactose intolerance," lead author Dr Christina Warinner, from the Department of Anthropology, University of Oklahoma, said.
The new research provides direct protein evidence that cattle, sheep, and goat whey has been consumed by human populations for at least 5,000 years.
This corroborates previous isotopic evidence for milk fats identified on pottery and cooking utensils in early farming communities.
"The discovery of milk proteins in human dental calculus will allow scientists to unite these lines of evidence and compare the genetic traits and cultural behaviours of specific individuals who lived thousands of years ago," said Warinner.
The team found direct evidence of milk consumption preserved in human dental plaque from the Bronze Age to the present day.
"Most of the molecular evidence for milk consumption has previously come from residues on ceramics. While pot residues can tell you that people are using dairy products, it can't tell you which individuals in the group are actually consuming the milk," Dr Camilla Speller, from York's BioArCh research facility, said.
"This study is very exciting, because for the first time, we can link milk consumption to specific skeletons, and figure out who has access to this important nutritional resource," said Speller.
The research was published in the journal Scientific Reports.