Scientists have brewed an ancient Chinese beer – a sweet, fruity concoction – using a 5,000-year-old recipe discovered by them, in a bid to understand the evolution of alcohol.

Researchers discovered the ancient recipe by studying the residue on the inner walls of pottery vessels found in an excavated site in northeast China.

The research provides the earliest evidence of beer production in China so far.

"Archaeology is not just about reading books and analysing artifacts," said Li Liu, a professor in Chinese archaeology at Stanford University in the US.

"Trying to imitate ancient behaviour and make things with the ancient method helps students really put themselves into the past and understand why people did what they did," said Liu.

The ancient Chinese made beer mainly with cereal grains, including millet and barley, as well as with Job's tears, a type of grass in Asia, researchers said. Traces of yam and lily root parts also appeared in the concoction.

Liu said she was particularly surprised to find barley which is used to make beer today in the recipe because the earliest evidence to date of barley seeds in China dates to 4,000 years ago.

This suggests why barley, which was first domesticated in western Asia, spread to China.

"Our results suggest the purpose of barley's introduction in China could have been related to making alcohol rather than as a staple food," Liu said.

The ancient Chinese beer looked more like porridge and likely tasted sweeter and fruitier than the clear, bitter beers of today.

The ingredients used for fermentation were not filtered out, and straws were commonly used for drinking, Liu said.

Researchers tried to imitate the ancient Chinese beer using either wheat, millet or barley seeds.

They first covered their grain with water and let it sprout, in a process called malting. After the grain sprouted, they crushed the seeds and put them in water again.

The container with the mixture was then placed in the oven and heated to 65 degrees Celsius for an hour, in a process called mashing.

Afterward, researchers sealed the container with plastic and let it stand at room temperature for about a week to ferment.

For decades, archeologists have yearned to understand the origin of agriculture and what actions may have sparked humans to transition from hunting and gathering to settling and farming, a period historians call the Neolithic Revolution.

Studying the evolution of alcohol and food production provides a window into understanding ancient human behaviour, said Liu.

It can be difficult to figure out how the ancient people made alcohol and food from just examining artifacts because organic molecules easily break down with time. That is why experiential archaeology is so important, Liu said.