The evolution of hand: how we became warriors and boxers

evolution of box

It is well known that the anatomy of hand had a great impact on the human evolution, by allowing the creation and usage of complicated tools. For a long time it has been considered that the human hand, in its actual form, has been a result of creation and usage of different tools; as the renowned quotation of Friedrich Engels says: “labour created man himself”.

However, new research offers a new conceptual explanation for the evolution of the hand – the human hand has evolved as an adaptation at the necessity of being used as a weapon. The individuals who used the fists during a fight had higher chances for victory and survival (the impact of a hit with the fist is from 1.7 to 3 times higher than that with a palm); as a consequence, the genes that are responsible for the ability to form a fist have been transmitted to other generations [Morgan, Carrier, 2013].

It follows that natural selection has biased the individuals who used the fist in a fight, and, as the time passed, the anatomy of the hand has also changed, as to facilitate the forming of a fist; the hand has become shorted and the thumb longer. A comparative anatomical analysis (see the image below) illustrates in a convincing way how the form of the hand has evolved, alongside with the hominids species.
hand evolution

The hand of a chimpanzee and that of a man, in a comparative perspective; the human hand (to the right) is more adapted to the fist formation, due to its shorter palm and longer thumb, which fixates the fingers in a fist.
Author: Morgan, Carrier, 2013.
Source: http://www.sciencedaily.com/releases/2012/12/121219223158.htm

Thus, an important component of our anatomy, the hand, has been formed as an answer to the necessity to fight. And the gestures made with closed fists were and are seen as gestures of anger and threatening.

It is interesting that, in 2014, the same team of scientists has come with a new study that was to complement the preceding one, in which they argued that the hominids’ faces have also evolved, to be able to withstand the hits applied with fists. From australopithecines onward, hominids’ face bones and mandible have become wider and thicker, due to the selection the males had to face in tough fighting, where they would get fist hits in their faces. According to the authors, it is more likely that the adaptation for hits in their faces, rather than that for chewing grass, have modeled the shape of hominids skulls [Carrier, Morgan, 2014].

It is true that the last supposition of the American scientists has raised many critical commentaries in which they were accused of an erroneous interpretation of facts [1]. Therefore, it is too early to draw clear conclusions as regarding the relationship between the evolution of the skull and aggressiveness.

At the same time, other scientists have hypothesized that the tougher zygomatic bone and larger cheeks, characteristic for some men, would correlate with a higher degree of their aggressiveness and makes them more resistant to direct hits; for, if they are to be involved in more violent acts, they should have thicker bones that would protect them from traumas [Lefevre et al., 2014].

Let us turn also to statistics; if we are to examine the traumas that the victims of violent attacks nowadays gain, we shall see that the proportion of damage of the face is very big [Walker, 1997]. During a study on 539 English adults that have fallen victims, it has been noted that facial traumas represent circa 83% of all the fractures, 66% of all wounds and 53% of all hematomas identified on the victims’ bodies [Shepherd et al., 1990]. Notably, women’s faces have proven to be much more vulnerable, their facial bones being fractured at least twice more often as a result of attacks [Walker, 2001, p. 582].

This statistical data reveals the fact that face is a favorite target during interpersonal conflicts; it may be that, under the influence of contact sports, hits in the face or the nose represent a cultural acquisition [ibid., p. 583], but we cannot exclude the hypothesis which says that it has always been this way and the facial skeleton has been subject to some specific natural selection, in order to be able to withstand physical impact during skirmishes.

Coming back to the evolution of hand, a study published in 2013 brings extra light on the way the human hand could have evolved by being linked with aggressiveness. Thanks to the discovery of an archaic metacarpal bone, a bone that is important for the hand’s anatomy, the anthropologists have deducted that the hominids hand has showed significant changes 0.8 – 1.8 million years ago. Homo erectus specimens, who lived cca. 1.4 mln. years ago, already had a hand that was very alike the one modern humans have.

Anthropologists believe that the process of morphological change of the hand is a direct consequence of the need for stone processing for the creation of tools and primitive weapons. The process of stone processing has stimulated and conditioned the accelerated evolution of the hand; the hominids and groups who processed small and rigid object quicker and more efficiently were advantaged [Ward et al., 2013].

In other words, the hominids that, due to some mutations, had the manual ability to manufacture stone axes and arrowheads, were more combative and advantaged during the fighting for existence; accordingly, the natural selection has biased the multiplication at the level of the population of the genes that showed modifications at the hand’s level, and more exactly in enhancing the abilities of manufacturing of tools. This way, the hand has evolved during hundreds of thousands of years by getting perfectly adapted for the manufacturing of arms and hunting tools, and, after a while, of household items. Ultimately, these abilities have led to the apparition of human civilization.

But the saga of hand evolution doesn’t stop here. The anatomy of the shoulder has also played esential role in hunting success, therefore in survival and aggresiveness. Humans are great stone throwers. In fact, we are the best in the world at this chapter. For instance, a baseball player can throw a ball with great speed an amazing accuracy. Chimpanzees are incredibly strong and athletic, yet adult male chimps can only throw about 20 miles per hour — one-third the speed of a 12-year-old little league pitcher.

Our ability of throwing stones with speed and accuracy is due to some changes in the anatomy of the humerus and that of the clavicle, bones that appears circa 2 million years ago in Homo erectus and have developed in their successors. Thanks to these modifications, we can bend our hands way back, we can spin it freely, and the energy that is necessary for the throw is mostly offered by other muscles of our bodies. The hominids slender waist dynamics also takes part at this process [Roach et al., 2013; Roach, Richmond, 2014].

It is also in the period of the development of shoulder’s anatomy that the adaptation for running has appeared. The impact of these transformations on the evolutional success of hominids was huge – they allowed them to throw blunt objects, stones and spears, in order to chase and kill animals easier. And predators started to avoid the groups of hominids, because they were afraid to get remotely hit and wounded.

Finally, there is a hypothesis, although speculative in some ways, which says that the native ability of some people to manipulate objects with their left hand would also be an adaptation for fighting. It is known that very many athletes (from the field of box, fencing, tenis etc.) are left-handed; their percentage in sport is higher than the general population average.

evolution of fighting

The scientists believe that the transfer of abilities on the left hand is too costly in the evolutionary plan, because it implies both a restructuration, even if it’s minimal, of the nerve connections, and a vulnerability of the immune system. A question arises: which are the advantages of this polymorphism, i.e. the transfer of abilities on the left hand, from an evolutionary point of view? What advantages did left-handed people have, so that, despite some evolutionary costs, they have passed the test of natural selection and have ensured the spreading of their genes?

Some scientists consider that the advantage was in the enhanced combative abilities during hands fight, when the blows applied with the left hand, by being non-standard, surprised the enemy and brought victory in the fight [Raymond et al., 1996; Grouios et al.; 2000, Faurie, Raymond, 2005, apud Goetz, 2010, p. 16; Dochtermann et al., 2014].

Consequently, some million years ago, the first species of hominids already had an anatomic gear and a neuronal system that allowed them to manufacture hunting weapons, to kill animals, to kill their tribal neighbors and to transform the aggression into warfare. And once the first projectiles were manufactured and thrown with skill, the process of social evolution has shown a highly accelerated pace.

Some authors have proposed the thesis of “remote death”, through which they support the idea that the invention of spears and arrows have crucially contributed to the consolidation and development of the human groups. Stone weapons, and especially projectiles, have transformed fights into real wars and, from that moment, in order to survive, human groups had to focus on cohesion and numerical growth. This way the foundation of societies and civilization were laid [Bingham, Souza, 2009; Blitz, Porth, 2013].

In view of these discoveries and findings, we understand that the above-mentioned affirmation of Friedrich Engels that “labour created man himself” needs to be reconsidered. Today, the most suitable affirmation would be that both the work and the aggression or fighting has created the man by modeling his brain and hand. We evolved by fighting.

© Dorian Furtună, ethologist

Sources:

1. Our Skulls Didn’t Evolve to be Punched // by Brian Switek. National Geographic. June 10, 2014 / http://phenomena.nationalgeographic.com/2014/06/10/our-skulls-didnt-evolve-to-be-punched/#.U5d2UHkR_0Q.twitter

• Bingham P.M., Souza J. Death from a Distance and the Birth of a Humane Universe: Human Evolution, Behavior, History, and Your Future. BookSurge Publishing. November 17, 2009. 714 p.
• Blitz J.H., Porth E.S. Social Complexity and the Bow in the Eastern Woodlands // Evolutionary Anthropology: Issues, News, and Reviews. Vol. 22, Issue 3. May/June 2013. P. 89-95.
• Carrier D.R., Morgan M.H. Protective buttressing of the hominin face // Biological Reviews. Article first published online: 9 Jun 2014. DOI: 10.1111/brv.12112
• Dochtermann N.A., Gienger C.M., Zappettini S. Born to win? Maybe, but perhaps only against inferior competition // Animal Behaviour. Vol. 96. October 2014. P. e1–e3.
• Faurie C., Raymond M. Handedness, homicide and negative frequency-dependent selection // Proceedings of the Royal Society B. Vol. 272. 2005. P. 25-28.
• Goetz A.T. The evolutionary psychology of violence // Psicothema. Vol. 22(1). 2010 Feb. P. 15-21.
• Grouios G., Tsorbatzoudis H., Alexandris K., Barkoukis V. Do left-handed competitors have an innate superiority in sports? // Perception and Motor Skills. Vol. 90. 2000. P. 1273-1282.
• Lefevre C.E., Etchells P.J., Howell E.C., Clark A.P., Penton-Voak I.S. Facial width-to-height ratio predicts self-reported dominance and aggression in males and females, but a measure of masculinity does not // Biology Letters. Vol.10, Issue 10. October 2014. DOI: 10.1098/rsbl.2014.0729
• Morgan M.H., Carrier D.R. Protective buttressing of the human fist and the evolution of hominin hands // The Journal of Experimental Biology. Vol. 216, no. 2. January 2013. P. 236-244.
• Raymond M., Pontier D., Dufour A.-B, Moller A.P. Frequency-dependent maintenance of left handedness in humans // Proceedings of the Royal Society B. Vol. 263. 1996. P. 1627-1633.
• Roach N.T., Richmond B.G. Clavicle length, throwing performance and the reconstruction of the Homo erectus shoulder // Journal of Human Evolution. Available online 4 November 2014.
• Roach N.T., Venkadesan M., Rainbow M.J., Lieberman D.E. Elastic energy storage in the shoulder and the evolution of high-speed throwing in Homo // Nature. Vol. 498(7455). 27 June 2013. P. 483-486. doi:10.1038/nature12267
• Shepherd J.P, Shapl M., Pearce N.X., Scully C. Pattern, severity, and aetiology of injuries in victims of assault // J. R. Soc. Med. Vol. 83. 1990. 161-162.
• Walker P.L. A Bioarchaeological Perspective on the History of Violence // Annual Review of Anthropology. Vol. 30. 2001. P. 573-596.
• Walker P.L. Wife beating, boxing, and broken noses: skeletal evidence for the cultural patterning of interpersonal violence. See Martin & Frayer. 1997. P. 145-175.
• Ward C.V., Tocheri M.W., Plavcan J.M., Brown F.H., Manthi F.K. Earliest evidence of distinctive modern human-like hand morphology from West Turkana, Kenya // The 82nd Annual Meeting of the American Association of Physical Anthropologists. 2013.

Comments

comments