Researchers identify fist fighting as the key to the evolution of the human hand’s unique proportions

(This article first appeared at www.science20.com on 15 Jan 2013)

A recent article titled ‘Protective buttressing of the human fist and the evolution of human hands’ rests on the assumption that human evolution has been characterised by competition for mates, however despite modern human’s propensity for violence and competition, it is an assumption that should not be taken for granted.

A recent study by Michael H. Morgan and David R. Carrier titled ‘Protective buttressing of the human fist and the evolution of human hands’ makes clear that the human hand has unique proportions that allow it to be used effectively as a fist. They suggest this is no accident – rather that the fist evolved to help males compete for mating opportunities. However the premise of a competitive past should not be accepted without questioning.

E.O. Wilson certainly thinks violence is in our blood – or rather genes - saying in his latest 2012 book The Social Conquest of Earth, that “wars and genocide have been universal and eternal, respecting no particular time or culture”. Indeed, even before Darwin’s idea of natural selection was re-named by Herbert Spencer ‘survival of the fittest’, the idea that our nature was a reflection of ‘nature red in tooth and claw’ was widely held.

Theories that rely on violence as a potent force in hominid evolution suggest that it is a continuation from an earlier primate state. Raymond Dart was the first to propose such a link, when in the 1950s he put forward his killer ape theory. In it he argued for the “predatory transition from ape to man”. Later the anthropologist Robert Ardrey wrote that “man has emerged from the anthropoid background for one reason only: because he was a killer.”

Recently, the primatologist Richard W. Wrangham put forward the ‘chimpanzee violence hypothesis’, which says that “selection has favoured a tendency among adult males to assess the costs and benefits of violence, and to attack rivals when the probable net benefits are sufficiently high.” Wrangham asserts that this instinct is behind human’s history of warfare.

So it is understandable that Morgan and Carrier accept a violent evolutionary heritage as a foundation from which to hypothesise as to why the human hand has developed the proportions it has. “Great apes” says Carrier, “are a relatively aggressive group with lots of fighting and violence, and that includes us”. However Carrier also made the interesting admission that not all primates are violent, adding the important caveat, “with the notable exception of bonobos”.

There are scientists that do not assume that human evolutionary history is a violent one. I.J.N. Thorpe for example, suggests that the archeological record does not support the idea of a continuation of violence from an earlier, violent primate state. Similarly, both the anthropologist Richard Leakey, and the primatologist Robert W. Sussman, suggest that violence is a relatively recent development in human history.

In particular, the biologist Jeremy Griffith says that bonobos – Carrier’s ‘exception’ – represent a living model of human’s ancestors Australopithecus. Griffith accounts for human’s current propensity for violence, saying it is not a continuation of primate violence, but rather, that it is psychologically derived – the result of a clash between an emerging consciousness and a pre-established instinctive orientation. Prior to 2 million years ago, Griffith says that our ancestors were still led by cooperative instincts, as bonobos currently are today; and further he gives a credible explanation for bonobos’ current cooperative state and humans’ cooperative past – a process derived from nurturing that he calls ‘love indoctrination’.

The case for bonobos representing a model of human evolution is a solid one. Not only does the bonobo share (along with the common chimpanzee) more human DNA than any other primate (approximately 98%), but compared with common chimps, and indeed all other primates, they appear to be most advanced in developing the particular traits that define humans.

For example, bonobos are more bipedal than any other primate; they are more neotonous than common chimpanzees (humans have been described as “the neotonous clan of apes”); and while intelligence tests are hard to calibrate, it appears that of all the non-human primates, bonobos have a unique aptitude for language and conceptual thinking. Incidentally, unlike other theories such as Brian Hare’s self-domestication hypothesis, Griffith’s theory does account for all these aspects.

The problem that this presents for the ‘fist as weapon hypothesis’ is that bonobos have no use for a fist in winning mating opportunities. As reported by Furuichi, and later Hohmann and Fruth, male bonobos do not physically contest for mating opportunities. Instead, as reported for example in a 2011 article by Martin Surbeck, published in the Proceedings of the Royal Society, bonobo males’ mating success is largely influenced by the support of their mothers.

In summary, should bonobos better represent human’s ancestors than other, more violent species of primates, and indeed, violent competition does not characterize human evolution, the main plank supporting Morgan and Carrier’s hypothesis is removed. This would result in not only their theory missing the mark, but so too, many other theories that rely on violent competition to account for human evolution.

This Blog Post was written by Damon on March 18, 2013