What is radiocarbon dating?

• A banyan tree in Bihar’s Munger, estimated to be around 700 years old, has been identified as the oldest accurately dated banyan tree, Ficus benghalensis, using radiocarbon dating.

• It is a method that relies exclusively on scientific evidence rather than historical records or local lore.

• Traditionally, estimating the age of banyan trees relied on folklore, local stories or historical records, which were often inaccurate. 

What is radiocarbon dating?

• Radiocarbon dating, or carbon-14 dating, is a scientific method that can accurately determine the age of organic materials as old as approximately 50,000 years. 

• Carbon is a fundamental component in all living materials. In nature there are two variants, or isotopes: carbon-12, which is stable, and carbon-14, which is radioactive. 

• Carbon-14 forms in the atmosphere when acted upon by cosmic radiation and then deteriorates. 

• When an organism dies and the supply of carbon from the atmosphere ceases, the content of carbon-14 declines through radioactive decay at a fixed rate.

• By measuring how much carbon-14 remains, scientists can estimate how long a particular organic object has been dead.

• In 1949 Willard Libby developed a method for applying this to determine the age of fossils and archeological relics.

• For his findings, Libby won the Nobel Prize in Chemistry in 1960.

• Libby was a professor of chemistry at the University of Chicago.

• Radiocarbon dating has been used for historical studies and atmospheric science, and triggered archaeology’s “radiocarbon revolution”.

How the team determined the age of banyan tree?

• Trina Bose from the Birbal Sahni Institute of Palaeosciences, Lucknow, an autonomous institute under the Department of Science and Technology (DST), was invited by the Bihar Forest Department to investigate and determine the age of the Munger banyan tree.

• Bose led a research team who collaboratively developed and applied an innovative methodology to establish the age of the tree.

• Field sampling and laboratory analyses revealed that the absence of distinct annual growth rings in most tropical broadleaf trees limited the application of conventional dendrochronological techniques, emphasising the need for alternative high-precision dating methods, including radiocarbon dating.

• They extracted alpha-cellulose, the most stable primary component of plant cell walls, from wood samples collected near the pith of a secondary trunk and an ancient primary branch. 

• The pith is particularly important because it represents the earliest wood formed during the juvenile stage of secondary growth. 

• The extracted cellulose samples were subjected to high-precision radiocarbon dating using Accelerator Mass Spectrometry (AMS), followed by calibration against the latest IntCal20 calibration curve and OxCal software, enabling the team to establish a robust, reliable estimate of the tree’s age.

• It established that the approximately 700-year-old tree is likely a surviving remnant of a natural forest that once existed in the region.

• The study refines radiocarbon dating approaches for tropical hardwoods by emphasizing precise pith targeting, a method rarely applied due to indistinct growth-ring boundaries.