Brown hares and chickens were considered gods when they first arrived in Britain during the Iron Age, research suggests.
Instead of being seen as food, the creatures were associated with deities, and buried with care and intact.
Archaeological evidence shows no signs of butchery on bones examined, and the ongoing research suggests the two animals were not imported for people to eat.
Work by experts from the Universities of Exeter, Leicester and Oxford is revealing when brown hares, rabbits and chickens were introduced to Britain, and how they became incorporated into modern Easter traditions.
The team previously analysed the earliest rabbit bone to be found in the country, which dates to the first or second century AD.
New radiocarbon dates for bones found on sites in Hampshire and Hertfordshire suggests brown hares and chickens were introduced to Britain even earlier, arriving simultaneously in the Iron Age, between the fifth and the third century BC.
Researchers say the discovery of buried skeletons fits historical evidence that neither animal was eaten until the Roman period, which began hundreds of years later.
Professor Naomi Sykes, from the University of Exeter – who is leading the research, said: “Easter is an important British festival, yet none of its iconic elements are native to Britain.
“The idea that chickens and hares initially had religious associations is not surprising as cross-cultural studies have shown that exotic things and animals are often given supernatural status.
“Historical accounts have suggested chickens and hares were too special to be eaten and were instead associated with deities – chickens with an Iron Age god akin to Roman Mercury, and hares with an unknown female hare goddess.
“The religious association of hares and chickens endured throughout the Roman period.”
She added that archaeological evidence shows that as their populations increased, they were increasingly eaten, and hares were even farmed as livestock.
The animals’ remains were then disposed of as food waste, rather than being buried as individuals.
During the Roman period, both species were farmed and eaten, and rabbits were also introduced, researchers say.
But in AD 410, the Roman Empire withdrew from Britain causing economic collapse.
Rabbits became locally extinct, while populations of chickens and brown hares crashed, and due to their scarcity they once again regained their special status.
After the Romans had left Britain, people stopped hunting hares and this may explain why archaeologists have found few remains of the animal until the medieval period.
But chicken populations increased.
Experts say this is likely because in the sixth century Saint Benedict forbade the consumption of meat from four-legged animals during fasting periods such as Lent.
His rules were widely adopted in the 10th and 11th centuries, increasing the popularity of chickens and eggs as fast-day foods.
Historical and archaeological evidence show rabbits were reintroduced to Britain as an elite food during the 13th century AD.
According to experts, they were increasingly common in the 19th-century landscape, likely contributing to their replacement of the hare as the Easter Bunny when the festival’s traditions were reinvigorated during the Victorian period.