Zinc isotope ratios in fossil enamel from Tam Hay Marklot cave indicate that omnivorous fossil taxa exhibit the greatest intraspecific variability in δ66Zn values (mean range: 0.30‰), which reflects dietary flexibility between plant and animal resources and enables the identification of mixed-feeding behavior in fossil taxa.

When animals eat plants, their bodies absorb zinc that has more of a heavier isotope, making their teeth record a higher value. When animals eat meat, they get zinc that has less of that heavy isotope, making their teeth record a lower value. Animals that eat both plants and meat end up with teeth that show a wide range of values because their diet switches between these two sources. This variation gets locked into their tooth enamel as it forms, and stays there for millions of years, letting scientists tell if an ancient animal ate both plants and animals.