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SUMMARY:Revisting the Savanna Hypothesis - Prof Julia Lee-Thorp (Research 
 Laboratory for Archaeology and the History of Art\, University of Oxford)
DTSTART:20150121T163000Z
DTEND:20150121T173000Z
UID:TALK56943@talks.cam.ac.uk
CONTACT:Aurélien Mounier
DESCRIPTION:Understanding the environmental context in which early (and la
 ter) hominins lived remains a crucial issue in human origins research\, as
  not only does it provide the wherewithal and limits for life’s necessit
 ies\, but more broadly it helps to shape evolutionary pathways. The “Sav
 anna Hypothesis” grew out of observations that early hominins typically 
 dwelt in open and arid landscapes unlike those of their closest great ape 
 relatives who preferred moist forests. It emerged before we had developed 
 a fuller comprehension of the hominin phylogenetic record\, or its age\, a
 nd lacking in fuller records for associated faunal\, climate and environme
 ntal shifts. It has thus been repeatedly challenged\, to be followed by an
  alternative “Forest Origins Model”\, which now holds sway. The debate
  concerns both the nature and timing of the emergence of open environments
  in Africa as a broad influence\, and also early hominins’ habitat and f
 oraging preferences. New carbon isotope evidence for Miocene and Pliocene 
 fauna contributes to resolving the first issue. A more secure (although st
 ill patchy) understanding of vegetation cover has emerged showing that in 
 East Africa C4 grasses\, as typical\, essential components of savannas\, f
 irst appeared as significant elements of vegetation structure just before 
 9Ma. First equids\, and then elephantids and Gomphotheres\, quickly adapte
 d to the new resources\, while bovids\, suids\, and hippopotamids showed m
 ore gradual\, mixed adaptations. There are some hints\, from faunal and po
 ssibly from other isotopic sources\, for low frequency fluctuations in the
  proportions C4 vegetation from the Late Miocene onwards\, suggesting perh
 aps some expansion of C3-dominated vegetation in the earlier Pliocene\, an
 d a later expansion of C4 again by ca. 2 Ma. If that is the case it may he
 lp to explain the evidence for forest habitat associations in early Plioce
 ne sites and isotope data for the associated hominins. Published carbon is
 otope evidence for hominin diets suggests that hominins began to exploit C
 4 resources only after ca. 4Ma\, more than 5Ma after the emergence of C4 g
 rasses. These results are consistent with the woodland/forest model as the
 y suggest a preference for C3 resources in spite of the presence of open v
 egetation elements elsewhere on the landscape. However\, new carbon isotop
 e data for Sahalenthropus individuals from Chad\, Central Africa\, indicat
 e mixed diets that include highly variable C4 resources\, not dissimilar t
 o co-existing suids and bovids. Viewed from the longer perspective it woul
 d seem that neither model is a good fit\; unsurprisingly\, evolutionary tr
 ends are extremely complex and highly variable.  
LOCATION:Seminar Room\, Henry Wellcome Building\, Division of Biological A
 nthropology\, Fitzwilliam Street\, Cambridge\, CB2 3QG
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