Dawkins (2005)
Classification: Behavioural models.
Mnemonic: Social Behaviour
Specific Model: Copied Gimmick Idea
Original Proponent(s): Dawkins (2005)    
Basic Summary: Bipedalism simply "caught on" as a behavioural meme (or fashion).    
Assessment: Popularity: Behavioural Models were ranked 4th (out of 9) most popular in the texts reviewed. One text referred to it explicitly.
Simple: #40  / 42 (35%)
Detailed: #40 / 42 (30%)
Discussion: Another idea, related to sexual selection, regarding bipedal origins which can also be broadly classified under the heading ‘social factors’ is that which suggests that bipedalism was practiced by some hominids for reasons that are not really important, but once it was observed, others copied it and consequently it ‘took off’ as a kind of fashion.

The chief proponent of this idea is Richard Dawkins who, in his rather famous work ‘The Selfish Gene’ proposed another level of natural selection on top of that taken for granted at the level of the gene – the ‘meme’, or memory selection unit. The meme concept has been embraced by many workers in anthropology and several books have been written based on them (e.g. Blackmore 2000,) although others have argued that they may have been taken too literally. However, as a concept they would appear to be quite useful in describing cultural artefacts that can get passed on from one person to another. Languages and many other cultural elements, not necessarily human, seem to fit into the model quite nicely and, according to Dawkins, behavioural changes might do also. Dawkins has applied his memetic notion to the problem of hominid bipedal origins and suggested that, perhaps, it could have just started, originally, as some kind of ‘fashion’.

He expounds this idea, perhaps better than elsewhere, in his popular book ‘The Ancestors Tale.’

Sexual selection, and its power to drive evolution in non-utilitarian arbitrary directions, is the first ingredient in my theory of the evolution of bipedality. The second is the tendency to imitate. The English language even has a verb, to ape, meaning to copy, although I am not sure how apt it is. Among all the apes, human are champion copyists, but chimpanzees do it too, and there is no reason to think the australopithecines did not. The third ingredient is the widespread habit among apes generally of rising onto the hind legs, including during sexual and aggressive displays.” Dawkins (2004:226)

He goes on to give examples of a chimpanzee called ‘Oliver’ which appeared to copy people in the way he moved and it is a well known phenomenon with other great apes too. Some orang utans at Perth Zoo appear to have a similar tendency.

Dawkins then continues… “Putting all these ingredients together, my suggestion for the origin of human bipedality is this. Our ancestors, like other apes, walked on all fours when not up in trees, but reared up on their hind legs from time to time, perhaps in something like a rain dance, or to pick fruits off low branches, or to move from one squat-feeding position to another, or to wade across rivers, or to show off their penises, or for any combination of reasons just as modern apes and monkeys do. Then – this is the crucial additional suggestion I’m making – something unusual happened in one of those ape species, the one from which we are descended. A fashion for walking bipedally arose, and it arose suddenly and capriciously as fashions do. It was a gimmick.” Dawkins (2004:227)

Dawkins’ idea is once some apes began to move like this, it was somehow perceived as a ‘cool’ thing to do, such that it attracted the opposite sex. Once it was perceived that the opposite sex found it attractive, it was reinforced as a valued behaviour and a positive feedback loop of behavioural reinforcement had begun. The argument follows that once this behaviour began to be practiced regularly, other benefits (e.g. carrying objects) became apparent to the group and so the behaviour became well established in the culture of the tribal group. Eventually, through natural selection, the anatomies of these hominids caught up with the behaviour and began to select for those traits that made it easier and more efficient to do. Dawkins suggests that most models of bipedalism are compatible and that his is compatible with, at least, Kingdon’s (Dawkins 2004:83.)
 Strengths: Memetic evolution has strong evidence in human cultures.    
Weaknesses: There is no adaptive advantage offered by this model and it's reliance on evidence from cultural phenomena of modern humans makes it appear somewhat telological.    
1.1 Survival Value 0 (Poor) No survival advantage is postulated for this model.    
1.2 Sexual Selection 8 (Good) Citing sexual selection as an evolutionary explanation for a phenomenon is somewhat controversial as, clearly, any ‘normal’ existing trait is likely to be something that a potential mate would seek. Distinguishing cause from effect is therefore difficult at best most likely to be achieved, when it comes to sexual selection, in features that are different between the sexes. In this regard bipedalism does not qualify, except in that it does preferentially enhance sexual displays of the male. The ‘fashion’ model, however does not even assume this and so any postulated selection coming from it must be seen as rather speculative.    
1.3 Not Teleological 6 (Fair) The strength of sexual selection models is that they provide a plausible positive feedback loop where ‘runaway sexual selection’ can result in rather odd effects. However, this model is based on cultural phenomenon (memes) that are best seen in modern humans and so thiss evaluation judged them only fair.    
2.1 Improved Food Acquisition 0 (Poor) No improved food acquisition is proposed for this model.    
2.2 Accounts for Predation 3 (Poor) The model, as articulated by Dawkins, does not address the question of predation at all and it is difficult to see how making one’s self appear more ‘cool’ to the opposite sex could not also have the unwelcome side effect of enhancing visibility to potential predators too.    
2.3 Why Apes are not Bipedal 5 (Fair) The model is quite speculative about the origins of this behaviour, suggesting that it was actually a fairly random process. In that sense it does explain the unique nature of bipedalism amongst the apes as it is less likely that two lineages would have undergone this evolutionary trend than just one    
2.4 Extant Analogues 4 (Fair) Apes, especially infants, are often observed engaging in playful “showing off” behaviour and they often do this bipedally. It therefore is concluded here that there is some evidence in extant apes for scenarios which might lead to this behaviour becoming a more ‘serious’ adult activity.    
2.5 Applies to Both Sexes 7 (Good) As Dawkins expresses this idea, it does apply to both sexes. However, as mentioned elsewhere, this bi-sexual application appears to reduce its sexual selective benefit.    
3.1 Hominid Anomalies 3 (Poor) Apes, especially infants, are often observed engaging in playful “showing off” behaviour and they often do this bipedally. It therefore is concluded here that there is some evidence in extant apes for scenarios which might lead to this behaviour becoming a more ‘serious’ adult activity.    
3.2 Fits Paleoecological Record 3 (Poor) There is no attempt by Dawkins to imply that the random commencement of this kind of behaviour was induced by any ecological shift.    
3.3 Precursor to Strider and knuckle Walker 3 (Poor) No precusive mode of locomotion is postulated.    
4.1 Extended Explanatory Power 2 (Poor) Dawkins makes no attempt to stretch the explanatory power of this model any further than explaining our bipedality.    
4.2 Complimentary 5 (Fair) This model was judged compatible with most models and complimentary to those promotiing sexual selection.    
4.3 Falsifiable or Testable 0 (Poor) No testable predictions about the hypothesis are articulated by Dawkins.    
References Blackmore, S. (1999) The meme machine. Oxford University Press.
Dawkins, Richard (2004). The Ancestor's Tales. Weidenfeld and Nicolson (London)