In the song "Woodstock" by Joni Mitchell, she refers to humans as "billion year old carbon." While the line may sound poetic, it does not accurately represent the age of carbon atoms in our bodies.
Carbon is one of the fundamental building blocks of life, and it cycles through various processes on Earth. The carbon atoms in our bodies, as well as in all living organisms, are constantly being exchanged with the carbon reservoirs in the environment through processes like respiration, photosynthesis, and decomposition.
The carbon atoms in our bodies are not billions of years old. Instead, they are part of a carbon cycle that includes both relatively recent carbon from the atmosphere, which is incorporated into plants through photosynthesis, and carbon from other sources such as food we consume. The carbon atoms in our bodies are continuously replenished throughout our lives.
While the line from Joni Mitchell's song may have metaphorical or symbolic meaning, it does not accurately reflect the scientific understanding of the age of carbon atoms in living organisms.