modern variation and evolutionary change in the hominin eye orbit

models fall short of explaining why myopia is so common, and consistently found tocorrelate with variables like ancestry, sex, intelligence, and socioeconomic status. Twocommonly cited explanations for this type of refractive error are the biological theory andthe use-abuse or near-work model (Angle & Wissman, 1980; Cordain et al. 2002; Miller,2000; Quinn et al. 1999; Saw et al. 2002).The near-work hypothesis ascribes myopia progression to the permanentmalformation of the eyeball caused by muscles tensing during regular use throughout anindividual’s lifetime. Evidence to support this hypothesis generally comes from thehigher rate of myopia among more intelligent people and those in higher socioeconomicclasses. In this model it is presumed that intelligence is the result of reading throughoutlife, and that this act causes the muscles to tighten and distort the eyeball, however it hasyet to be shown how convergence and eye strain can permanently alter the shape of ahuman eyeball (Angle & Wissmann, 1980).Another problem with this model relates to the ambiguous relationship betweencorrelation and causality in observational studies, and with reference to the near-workhypothesis it cannot be known whether reading produces myopia over time as assumedby the near-work camp, or rather if myopes read more because of an overall greater thirstfor knowledge associated with a pre-existing higher level of intelligence (Mak et al.2005; Miller, 2000; Saw et al. 2004; WGMPP, 1989).A final objection to the use-abuse/near-work model is that it doesn’t account forwhy some individuals, who do as much or more reading as other members of the samegroup, do not develop myopia. If near-work were a primary contributor to thedevelopment of near-sightedness, then any highly literate population should be affected25