Stanislas Dehaene's and Laurent Cohen's (2007) Cultural Recycling of Cortical Maps has an interesting argument about how the ability to read might have developed by taking over visual circuits specialized for biologically more relevant tasks, and how this may constrain different writing systems:

According to the neuronal recycling hypothesis, cortical biases constraint visual word recognition to a specific anatomical site, but they may even have exerted a powerful constraint, during the evolution of writing systems, on the very form that these systems take, thus reducing the span of cross-cultural variations. Consistent with this view, Changizi and collaborators have recently demonstrated two remarkable cross-cultural universals in the visual properties of writing systems (Changizi and Shimojo, 2005; Changizi et al., 2006). First, in all alphabets, letters are consistently composed of an average of about three strokes per character (Changizi and Shimojo, 2005). This number may be tentatively related to the visual system’s hierarchical organization, where increases in the complexity of the neurons’ preferred features are accompanied by a 2- to 3-fold increase in receptive field size (Rolls, 2000). Inferotemporal neurons are thought to gain their sensitivity to complex shapes by pooling over neurons coding for simpler shapes at the immediately earlier level (Brincat and Connor, 2004; Serre et al., 2007). Assuming that this pooling occurs within a radius of about three receptive fields, elementary letter shape would only be recognized as combinations of about three simpler strokes, thus accounting for Changizi’s ‘‘magic number’’ (Changizi and Shimojo, 2005). This account might be extended to other levels of the word recognition system (Dehaene, 2007a; Dehaene et al., 2005). Upstream of the single-letter level, the elementary strokes used in the world’s writing systems may themselves be composed of approximately three line segments. Downstream of it, it may be suggested that writing makes frequent use of combinations of two to four letters as morphemes (prefixes, suffixes, or word roots). Chinese characters also typically combine two to four functional subelements (Ding et al., 2004). These predictions, however, still await quantitative confirmation.

A second cross-cultural universal is that, in all writing systems, topological intersections of contours (e.g., T, Y, L, D) recur with a universal frequency distribution (Changizi et al., 2006). Remarkably, these intersections are not typically observed in random images, but occur with the same frequency in natural images (Changizi et al., 2006). Many of these intersections signal ‘‘nonaccidental properties’’ that denote important and invariant connection and occlusion relations (Biederman, 1987) and are already encoded in monkey infero-temporal cortex (Kayaert et al., 2005). Thus, the suggestion is that, while the occipitotemporal cortex could not evolve for reading, the shapes used by our writing systems were submitted to a cultural evolution for faster learnability by matching the elementary intersections already used in any primate visual system for object and scene recognition.

This is relevant for discussions about superintelligent AI in that it helps reinforce the case that there are cognitive constraints in our brains that are hard (if not impossible) to overcome, and that a mind which could custom-tailor new cognitive modules for specific skills, unburdened by the need to recycle previously-evolved neural circuitry, could become qualitatively better at them than humans are.