Stable isotopes in fossil hominin tooth enamel suggest a fundamental dietary shift in the Pliocene.
Lee-Thorp JA, Sponheimer M, Passey BH, de Ruiter DJ, Cerling TE. Stable isotopes in fossil hominin tooth enamel suggest a fundamental dietary shift in the Pliocene. Philos Trans R Soc Lond B Biol Sci. 2010 Oct 27; 365(1556):3389-96.