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2016-06-16 03:12:52   •   ID: 1373

Symmetry and Human Evolution

Figure 1
Figure 1 shows a highly symmetric handaxe from the Algerian Sahara and Figure 2 a similar example from St Meme (Charente; France) This Handaxes may be 300-500 k.a. old. The Third example comes from the MTA in France.

Exhibiting external bilateral symmetry about a vertical midline, the animal and human body consists of two enantiomorphs — the right and left sides.

The overwhelming preponderance of bilateral symmetry in animals suggests that it provides an evolutionary advantage.

A large body of experimental evidence supports the hypothesis that many species of animals including all primates prefer symmetry.

For example, Rensch et al. demonstrated that monkeys, raccoons, and birds prefer symmetry to asymmetry and irregularity. Humans, including infants, find the symmetrical faces and bodies more beautiful, than asymmetrical ones.

There is also a significant degree of cross-cultural agreement between tests of ratings of facial attractiveness conducted in populations of different genetic backgrounds.

Figure 2
From an evolutionary perspective many important environmental elements are symmetrical and sensitivity to symmetry may have evolved because it is important for discriminating living organisms from inanimate objects.

Thus, symmetry preferences may arise as a by-product of the need to recognize objects irrespective of their position and orientation in the visual field.

Many Authors from a variety of disciplines argue that symmetrical tools function more efficiently than asymmetrical ones. Experimental data did not really substantiate this assumption.

Since the Acheulian - symmetry of form is frequently over-determined in relation to functional necessities. This means that bifacial artifacts often appear to be more symmetrical than is strictly necessary for the purposes of efficient mechanical design.

This observation may indicate that symmetry may have constituted an instrument for the generalization and abstraction of a perceptual imperative into the world of artificial objects. In this sense handaxes may be an early example, how people modified and manipulated their environment.

Gowlett found, that averaged sized handaxes from many Acheulean sites exhibit a Breadth/Length Ratio (B/L) approxi­mated closely to Golden Section (expressed as 0.61: 1, or inversely as around 1:1.64), showing that 1 my ago, people had already a sense for “proportions”.

Derek Hodgson described neurobiological pathways and networks that are involved in the perception on symmetry.

More interesting, areas of the brain that were associated with symmetric perception also overlap with areas implied in aesthetic judgment. Therefore, the production of symmetric handaxes seems to be related to first manifestations of an aesthetic sense.

Material from modern excavations Gesher Benot Ya´aqov) shows a high level of sophistication and symmetry in biface -manufacture approximately at 800 k.a. BP. Naama Goren-Inbar, regarding the operational sequence at this site showed that:

Figure 3
“The diverse methods of production observed on the site clearly demonstrate flexibility in decision-making as well as creativity in order to achieve the desired goal. In contrast to the view of the lithic reduction sequence as “repetition and rhythm”, the evaluation processes of each individual blow and the flexibility shown in selecting a particular method out of a varied repertoire, tailored to the specific circumstances at hand, are clearly indicative of advanced cognitive abilities” (Phil. Trans. R. Soc. B 2011 -see external link).

Iovita et al. recently evaluated the symmetry of bifaces at some of the oldest European Acheulean sites (la Noira: 700 and 500 k.a., and Boxgrove (500 k.a.). They found that symmetry was an important concept of the makers of these handaxes and concluded “that it is likely that, by the time the Acheulian arrived in Europe, its makers were, from a cognitive and motor-control point of view, already capable of producing the symmetric variant of this technology".