BIPEDALISM MODEL EVALUATOR		Home
Classification: Efficiency Mnemonic: Endurance Running
Specific Model:	Endurance Running
Original Proponent(s):	Carrier (1984), Bramble & Lieberman (2004),
Basic Summary:	Locomotor efficiency through endurance running led to greater bipedalism in early hominins. Overlaps considerably with the terrestrial hunting through endurance running model.
Assessment:	Popularity Ranking of classification: The broad Locomotor Efficiency category was ranked 3 out of 9 with 58% texts referring to suh ideas. 6% of texts referred to the Endurance Running model specifically. Simple Evaluation: #16 (=2) / 41 (57%) Detailed Evaluation: #21 (=3) / 41 (55%)
Discussion:	In two recent papers Brambble, Lieberman and others have added weight to Carrier's Endurance Running" ideas of the 1980s. It overlaps with that model greatly, of course, but is included here seperately under the category of "energy efficiency" whereas Carrier's version stressed the mode of locomotion more in the sense of hunting and carrying. Bramble and Lieberman's papers stress anatomical features of humans in terms of explaining endurance running, notably the size of the gluteus maximus muscle which has little role in walkig but is very important in running.
Strengths:	Bramble & Lieberman make a good case that the peculiar size and anatomy of the gluteus maximus of Homo sapiens might be explained by an adaptation to endurance running.
Weaknesses:	Endurance Running is clearly a post hoc modern human phenomenon. It is not so clear that it could argued to have driven that bipedality in the first place.
Evaluation:
1.1 Survival Value	4 (Fair) Assuming that ER running was as advantageous as the author ascribes, this would suggest quite strong selection for traits allowing long distance running. However, it is not clear that this selection would also translate into obligate terrestrial bipedalism – i.e. walking
1.2 Sexual Selection	5 (Fair) This model was judged neutral by this criterion.
1.3 Not Teleological	1 (Poor) This is, perhaps, where the model is at its weakest. The main evidence for Endurance Running is from modern humans. It is falling into the teleological trap to suggest that this ability, relying on traits that are clearly now fully evolved, could have actually driven the evolution of those traits.
2.1 Improved Food Acquisition	5 (Fair) This model was judged neutral on this criterion.
2.2 Accounts for Predation	2 (Poor) Bramble and Liebermean do not address the issue of pradtor vulnerability at all.
2.3 Why Apes are not Bipedal	5 (Fair) If one assumes, as do many of these models, that the main causal event in the Pan-Homo divergence was a switch in habitat, with hominids moving into more arid, open habitats and other great apes staying in more densely forests ones, then this model holds quite well. However much of the evidence of the paleohabitats of the early hominins seems to contradict this view.
2.4 Extant Analogues	1 (Poor) Very few mammals, and none among the primates, are known to use ER as a method for hunting.
2.5 Applies to Both Sexes	5 (Fair) Although Endurance Running is clearly possible for either gender, it was judged slightly lower than neutral because prgenant feamles and mothers with young infants are unlikely to have precticed it.
3.1 Hominid Anomalies	8 (Good) One of the strengths of Bramble and Lieberman's paper is their careful anatomical analysis of the postcranial anatomy of extant apes and how they compare with humans and hominins.
3.2 Fits Paleoecological Record	5 (Fair) As with Carrier's ER model it must be remembered that early bipeds appear to have lived in generally wet and wooded habitats ones where endurance running was not very plausible.
3.3 Precursor to Strider and knuckle Walker	7 (Good) Running clearly overlaps significantly with human-like bipedalism so this model was judged good here.
4.1 Extended Explanatory Power	7 (Good) This model may also explain the relative hairlessness of humans compared to other primates.
4.2 Complimentary	5 (Fair) This model was judged complimentary to the Carrier "ER Model". However because the Bramble and Lieberman variant does not have a specific food procurement or carrying component it was judged less compatible with other models.
4.3 Falsifiable or Testable	6 (Fair) Bramble and Lieberman do present a series of hypotheses in a scientific way although, as they admit, they are not open to much testability
References	Bramble, D R; Lieberman, D E (2004). Endurance running and the evolution of Homo. Nature Vol:432 Pages:345-352. Carrier, D R (1984). The energetic paradox of human running and hominid evolution. Current Anthropology Vol:25 Pages:483-494 Lieberman, D E; Raichlan, D A; Pontzer, H; Bramble, D R; Cutright-Smith, E (2006). The human gluteus maximus and its role in running. Journal of Experimental Biology Vol:209 Pages:2143-2155