Tracing Vegetation Changes through Carbon Isotopes

Implication for ecosystems and human evolution

•C3 and C4 plants have photosynthetic pathways that fractionate stable carbon isotopes to different degrees •d values between -36.5‰(VPDB) and -22‰ for C3

•d values between -15‰ and -11‰ for C4

•~14‰ enrichment factor in large mammals compared to their diet

[Cerling et al., 1997]

Extant d13C values for herbivore tooth enamel

[Levin et al., 2008]

d13C values in ‰ of tooth enamel for fossil herbivores from:A. As Duma MemberB. Segala Noumou MemberC. Gona Western Margin SouthD. Adu-Asa Formation

Gray bars represent d13C values for averages expected of strict C3 diet from closed-canopy, C3 from forest/bushland, and C4 grassland.

[Levin et al., 2008]

• These fossil herbivore teeth were found in situ with Ardipithecus kadabba and Ardipithecus ramidus.

• Most similar to isotopic values from extant herbivores living in bushland and grassland

What type of environment did early man evolve in?

Ardipithecus ramidus