Fifer (1987)
Classification: Forelimb pre-emption (carrying models)
Mnemonic: "Freeing of the hands"
Specific Model: Weapon Throwing
Original Proponent(s): Fifer 1987; Dunsworth et al 2003    
Assessment: Popularity Ranking: 1st out of 9 categories (86% of texts)
Simple: #28 (=2) /42 (54%)
Detailed: #12 /42 (59%)
Basic Summary: Throwing of objects (especially missiles as weapons) was they key driver of hominin bipedality.    
Discussion: Throwing was promoted by Fifer (1987) and then more recently by Dunsworth et al (2003) as a mechanism for increased upright posture and hence a preadaptation for bipedalism. Throwing weapons to ward of predators and competing scavengers is perhaps the most commonly envisaged means for this to have worked but in its more recent form it was also promoted as a low-cost means of punishing non-cooperating members of a group and thus providing an aid to them cooperating in large groups of unrelated people.
Dunsworth et al (2003) looked at various features of throwing and found African ape biomechanics could have been preadaptive for throwing from a bipedal stance. The idea is perhaps weakest in that it really only provides a means for bipedal posture rather than locomotion and that it is rather teleological as apes have been observed throwing even whilst sat down.
 Strengths:/td> Provides a means for upright posture to have been used in open habitats. Later proponents have made reasonable anatomical arguments for throwing being compatible with early bipedal posture. Provides a good argument against predation and to ward off competition whilst scavenging.    
Weaknesses: Does not suggest a means for a bipedal mode of locomotion to have emerged.    
1.1 Survival Value 6 (Fair) Noting that throwing weapons to ward off predators and competition for scavenged food is covered later, it is difficult to see how throwing would help survival otherwise.    
1.2 Sexual Selection 6 (Fair) Although throwing ability is a reasonable mechanism for sexual selection it was only rated 6/9 here.    
1.3 Not Teleological 3 (Poor) Although chimpanzees have been observed throwing objects, they have rarely been observed standing up to do so. Throwing whilst standing, therefore, seems more likely to be a consequence of our bipedalissm than a cause of it.    
2.1 Improved Food Acquisition 6 (Fair) This model was judged neutral on this criterion although throwing could conceivably have helped ward off competitors for scavenged food.    
2.2 Accounts for Predation 8 (Good) Weapon throwing provides one of the best arguments against predation.    
2.3 Why Apes are not Bipedal 4 (Fair) As extant chimps also have been known to throw objects without standing the model was rated lower than neutral for this criterion.    
2.4 Extant Analogues 6 (Fair)  As extant chimps have been observed throwing objects the model was rated above neutral for thiss criterion.    
2.5 Applies to Both Sexes 6 (Fair)  As most models of human evolution based on scavenging models tend to make a distinction between male and female roles and because throwing weapons at predators and/or competition for scavenged food is often seen as a male activity, this model was judged perhaps lower than it might on this criterion.    
3.1 Hominid Anomalies 7 (Good) The recent paper by Dunsworth et al (2003) made a good argument that anatomical traits of early hominins are compatible with the weapon throwing hypothesis.    
3.2 Fits Paleoecological Record 5 (Fair) The model was judged neutral on this criterion.    
3.3 Precursor to Strider and knuckle Walker 2 (Poor) As this model really only promotes bipedal posture and not locomotion, it was judged poor by this criterion.    
4.1 Extended Explanatory Power 4 (Fair) This model was rated slightly lower than neutral on this criterion.    
4.2 Complimentary 6 (Fair) As with most models of forelimb pre-emption, this was judged to be complimentary to most others of its type apart from female driven infant carrying, for which it was rated only compatible. It was rated incompatible with most climbing models. It was also rated complimentary to many behavioural models, particularly those invoking threat displays.    
4.3 Falsifiable or Testable 6 (Fair) Dunsworth et al (2003) did address this model in a fairly scientific and rigourous way.    
References Fifer, F C (1987). The adoption of bipedalism by the hominids: a new hypothesis. Human Evolution Vol:2 Pages:135-147
Dunsworth, Holly; Challis, John H; Walker, Alan (2003). Throwing and bipedalism: a new look at an old idea. In: Franzen, Jens Lorenz; Kohler, Meike; Moya-Sola, Salvador (eds.), (2003). Walking Upright: Results of the 13th International Senckenberg Conference at the Werner Reimers Foundation, Bad Homberg v. d. H., and the Senckenberg Research Institution, Frankfurt