Dart (1959)
Classification: Forelimb pre-emption (carrying models)
Mnemonic: "Freeing of the hands"
Specific Model: Weapon Wielding
Original Proponent(s): Dart 1959 ; Kortland (1980)    
Assessment Popularity Ranking: Carrying ranked 1st out of 9 broad categories (86% of texts) - 14% of texts reviewed mentioned this idea specifically.
Simple: #34 (=2) /42 (49%)
Detailed: #14  (=3) /42 (57%) 
Basic Summary: The idea that intra and/or inter specific violence lead to the adoption of bipedality through inceased weapon wielding.    
Discussion: It is possible that the ‘killer ape’ ideas of Dart (1959) and Ardrey (1961) resulted from reflections after the horrors of two world wars. Certainly they did leave an awesome legacy in Europe with tens of millions of deaths resulting directly from armed combat. Already, in his original paper describing the Taung Child in 1925, Dart alluded to his thinking behind the switch to bipedalism he found evidenced by the more anteriorly placed foramen magnum: “Bipedal animals, their hands were assuming a higher evolutionary role not only as delicate tactual examining organs which were adding copiously to the animal's knowledge of its physical environment, but also as instruments of the growing intelligence in carrying out more elaborate, purposeful and skilled movements and as organs of offence and defence” Dart (1925:197.) Later, he articulated this point more clearly: “The terrestrial human precursors, who adopted bipedal in preference to quadrupedal postural habits, were forced simultaneously to rely upon their hands instead of fangs for assault and repulse. The inevitable result of the absence of long tearing canines and shearing premolars (or the presence of stubbed canines and grinding premolars) in the advanced anthropoid is aggressive hands.” Dart (1949:1.)
 Strengths: • Using weapons often does require bipedal posture. “Jabbing with sticks or hurling stones would be most effective from a standing position” (Hewes 1961:694.)
• One of the key problems with adopting human-like bipedalism, particularly in open habitats, is that it would appear to put the individual under far greater vulnerability from predation. The strength of these kinds of bipedalism models is that they not only offer a very strong counter argument to that increased threat, they simultaneously suggest that carrying weapons itself would have favoured the adoption of bipedalism itself.
• One of the five key trends in the process of hominisation, as described by Lovejoy (1981) is dental reduction. Observers like Dart point out that the reduction in canine teeth, which appears to be an early feature hominins, is also suggestive that some alternative method of combat would have evolved to take its place .  
Weaknesses: • The archaeological evidence suggests that tool use, such as those that might have been used as weapons, came at much later stage (ca 2.6 Ma) of human evolution than the onset of bipedalism (at least 6mya). (Hewes 1961:695.) Although this does not disprove that the earliest bipeds were not using weapons that were not made of stone (e.g. clubs from branches or bones) it certainly is not an point in its favour.
• The argument that early bipedal hominins were effective hunters is questioned by Hewes on the basis that even ‘primitive’ hunter-gatherer societies today, equipped with much better weapons and with several million years of natural selection for better bipedalism behind them, still find it troublesome to hunt down big game. He summarises this: “A long preparatory phase is indicated, in which prehominid bipeds might have been meat and marrow eaters, but seldom actual hunters.” (Hewes 1961:695.)
• Weapon use could clearly have been very beneficial to early bipeds, but here is another example where cause and effect are difficult to discriminate between. It seems unlikely that danger from predators could have resulted in the adoption of a brand new form of locomotion to allow carrying weapons which would be very difficult to carry in early anatomical forms.  
1.1 Survival Value 7 (Good) Weapon wielding provides fairly positive argument for survival compared to other models. However, as it also suggests increased intra specific violence, the model was judged not as highly here as it possibly could have.    
1.2 Sexual Selection 7 (Good) There are also strong arguments that can be made here for female sexual selection so the model was judged 'good' here.    
1.3 Not Teleological 2 (Poor) As with the other weapon/tool ideas this model can be criticised for being somewhat teleological.    
2.1 Improved Food Acquisition 5 (Fair) This model was judged neutral in respect to this criterion.    
2.2 Accounts for Predation 9 (Good) This is perhaps the strongest model judged on this criterion.    
2.3 Why Apes are not Bipedal 4 (Fair) Dart originally proposed that it was the very harshness of the savannah that led to some hominins becoming "killer apes". However, purely savannah-based models of human evolution have been discredited lately so this model is judged slightly worse than neutral here.    
2.4 Extant Analogues 6 (Fair) As chimpanzees and gorillas have been observed using branches as "weapons" in threat displays sometimes switching to bipedalism whilst doing so, this model was rated better than neutral here.    
2.5 Applies to Both Sexes 2 (Poor) As most proponents of this model stress the role of males in inter and intra specific aggression it was judged poor by this criterion.    
3.1 Hominid Anomalies 4 (Fair) As Dart based his idea on the finding of the first australopithecine, the Taung Child (Dart, 1925) this model was rated higher than it would have been otherwise. australopithecine anatomy hasn't been used as an argument in favour of this idea other than to suggest that would have probably have needed weapons because they were very small.    
3.2 Fits Paleoecological Record 5 (Fair) This model was judged neutral by this criterion.    
3.3 Precursor to Strider and knuckle Walker 3 (Poor) The model does not propose any specific precursive form of locomotion.    
4.1 Extended Explanatory Power 5 (Fair) Although Dart originally suggested this idea in the context of a broad "killer ape" model, it has been largely discredited and so this model was judged neutral by this criterion.    
4.2 Complimentary 6 (Fair) This was complimentary to most other carrying models but contradictory to most involving climbing.    
4.3 Falsifiable or Testable 3 (Poor) The idea, when first proposed, was not portrayed in a scientifically rigorous way.    
References Ardrey R (1961): African Genesis. New York: Dell.
Dart, Raymond A (1925). Australopithecus africanus: The Ape-Man of South Africa. Nature Vol:145 Pages:195-199
Dart, Raymond A (1949). The Predatory Implemental Technique of Australopithecus. American Journal of Physical Anthropology Vol:7 Pages:1-38
Dart, Raymond A; Craig, Dennis (1959). Adventures with the Missing Link. The Institution Press (Philadelphia).
Hewes, Gordon W (1961). Food Transport and the Origin of Hominid Bipedalism. American Anthropologist Vol:63 Pages:687-710.
Lovejoy, C. Owen (1981). The Origin of Man. Science Vol:211 Pages:341-350.