Analysis of zinc isotopes in fossilized teeth from ancient mammals in Laos reveals a predictable pattern: meat-eating animals have lower zinc isotope values than plant-eating animals, with herbivores...
Mechanism
Synthesis from 1 study
Plants soak up more of the heavier zinc from the ground, so plant-eaters end up with more of it in their teeth. Meat-eaters get zinc from plant-eaters, but that zinc has already lost some of the heavy stuff during digestion, so their teeth have less. This difference gets frozen into teeth as they...
Most probable mechanism
Plants take up more of the heavier zinc isotope from the soil, so animals that eat only plants end up with higher levels of this heavier zinc in their teeth. Animals that eat other animals get zinc that has already been lightened by the animals they consumed, so their teeth have less of the heavy zinc. This difference gets locked into tooth enamel as it forms and stays unchanged for tens of thousands of years, even in hot, wet environments where other body parts decay.
Plants absorb zinc from soil with a preference for heavier isotopes during root uptake, resulting in higher concentrations of the heavier zinc isotope in leaves and above-ground tissues.
Herbivores consume plant material rich in the heavier zinc isotope, and during metabolic processing, minimal isotopic shift occurs, allowing the high isotopic signature to be incorporated into developing tooth enamel.
Carnivores consume muscle tissue from herbivores, which has been depleted in the heavier zinc isotope due to preferential excretion or retention of lighter isotopes during metabolic turnover in prey animals.
Zinc is incorporated into the mineral structure of tooth enamel during formation, and once mineralized, the isotopic composition is chemically stable and resistant to postmortem alteration, even under tropical conditions.
Evidence from Studies
Supporting (1)
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Zinc isotopes in Late Pleistocene fossil teeth from a Southeast Asian cave setting preserve paleodietary information
Contradicting (0)
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