Described herein are methods and techniques for determining one or more characteristics of a hydrocarbon source. The method comprises obtaining a hydrocarbon fluid sample, determining at least one measured clumped isotope signature or measured position specific isotope signature for at least one hydrocarbon species of interest in the hydrocarbon fluid sample, determining at least one expected clumped isotope signature or expected position specific isotope signature for the hydrocarbon species of interest, comparing the measured clumped isotope signature or measured position specific isotope signature with the expected clumped isotope signature or expected position specific isotope signature, and determining at least one characteristic of the source of the hydrocarbon sample based on the comparison.