[skysearcher (OP)]

As plant life prefers 12C, significantly greater than 13C and 14C, as it is not as heavy, wouldn't this contaminate herbivores' carbon 14 decay to 12C half-life dating computations? Is the presence of 12C by diet/absorption considered in carbon dating?

[evan_au]

Plants absorb carbon dioxide from the atmosphere this year (plus some carbon from the soil that has built up over several years).
- Many herbivores live less than 5 years (elephants being a notable exception), and their carbon is being continually recycled and refreshed from their food throughout their lifetime, so reporting the age at death by carbon dating would be fairly accurate.
- I guess researchers could report on whether the sample was taken from a juvenile or adult, if you needed a bit more clarity
 .
PS: when they report Carbon-14 dates, they do it as years BP (Before Present), where "Present" is defined as 1950.
- So misreading the Present as 2020 would introduce an error of 70 years

See: https://en.wikipedia.org/wiki/Radiocarbon_dating

[Bored chemist]

Do vegetarians contain more carbon-12?
Not much more.
Carnivores eat vegetables and they also eat meat. But the meat they ate was typically a vegetarian.

And all of us, regardless of diet are continuously ingesting and excreting carbon.
So we are fairly close to equilibrium with the air around us.

What sort of plants we (or our food) eat makes more difference.
http://luna.cas.usf.edu/~rtykot/PR39%20-%20Enrico%20Fermi%20isotopes.pdf