modern variation and evolutionary change in the hominin eye orbit

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CHAPTER 1INTRODUCTION1.1 BackgroundThrough years of travel and research, Charles Darwin was able to provide a broadaccount of how species adapt and change over time. Despite this invaluable contribution,the technology of his time could not provide the tools necessary to answer questionsrelating to the mechanisms of inheritance or the way in which complex structures couldarise through the process of evolution. “To suppose that the eye with all its inimitablecontrivances for adjusting the focus to different distances, for admitting different amountsof light, and for the correction of spherical and chromatic aberration, could have beenformed by natural selection, seems, I freely confess, absurd in the highest degree”(Darwin, 1859 pg. 227).In the 150 years since this assertion, it has become much clearer how incrementalchanges result in highly complex systems such as the eye. This instrument for gatheringvisual information from the natural environment is so useful in fact that it is estimated tohave arisen independently 65 times throughout the long history of life (Salvini-Plawen &Mayr, 1961; Weiss, 2002). Even with the many stages of evolutionary development andmultitude of environments to which it has adapted, the general form of the eye acrossdifferent organisms is remarkably similar.1
Although there is a great deal of commonality in the structure of the eye amongmembers of the animal kingdom, research has shown that the appearance of the eye inhumans is relatively unique in comparison with even closely related non-human primates.This uniqueness is indicated by an exposed sclera that lacks any pigmentation, the mostexposed sclera relative to eye outline of any species, and an extraordinarily elongated eyeoutline in the horizontal direction (Kobayashi & Koshima, 2001).Kobayashi and Koshima (2001) suggest that the distinctiveness of the human eyeis the result of social factors, such as the need to recognize the direction of anindividual’s gaze. While this is important in humans and some non-human primates withsophisticated social systems, and particularly in the context of group hunting, otherfactors such as ecological and morphological constraints have been proposed to explainthe evolution of gaze perception and the unique eye of humans (Emery, 2000).Morphological changes primarily center around reduced facial projection and anoverall flattening of the face in hominoids, which has acted to reduce the cues availablefrom the snout and head as a whole, resulting in more reliance on the eyes to indicategaze direction (Emery, 2000). Among the hominoids, humans are characterized by agreater degree of facial reduction that has occurred in association with markedencephalization during hominin evolution. Increased cranial size in conjunction withreduced facial prognathism are important to consider in investigating the unique form ofthe human eye as a result of changing reliance on certain features to indicate gaze, butalso due to the position of the eye and orbit amid these coalescing neurocranial and lowerfacial features.2
Page 1: MODERN VARIATION AND EVOLUTIONARY C
Page 7 and 8: VITAJanuary 2, 1978……………
Page 9 and 10: TABLE OF CONTENTSPageAbstract .….
Page 11 and 12: 7. Summary and Conclusion………
Page 13 and 14: Table 3.13: Wilks' lambda and Chi-s
Page 15: Figure 5.4: Change in orbital bread
Page 19 and 20: extent that in modern humans it sit
Page 21 and 22: in the face and cranium” (Enlow &
Page 23 and 24: etween the neurocranium and face, u
Page 25 and 26: Schultz (1940) observes a negative
Page 27 and 28: sphenoid, and between 5 and 6 in th
Page 29 and 30: its relative position during forwar
Page 31 and 32: fact more variation exist between r
Page 33 and 34: plane is highly related to factors
Page 35 and 36: cranial and facial height occurs in
Page 37 and 38: assessed in relation to patterns of
Page 39 and 40: or throughout hominin evolution cou
Page 41 and 42: in roughly the same proportions (An
Page 43 and 44: association with juvenile-onset myo
Page 45 and 46: Craniofacial Variables Label Landma
Page 47 and 48: In this investigation the FH is not
Page 49 and 50: this study most research questions
Page 51 and 52: Craniofacial Variables Label ErrorC
Page 53 and 54: CHAPTER 3MODERN HUMAN VARIATION IN
Page 55 and 56: Sample Sample Size RepositoryAfrica
Page 57 and 58: change in orbital anatomy and will
Page 59 and 60: 3.3.1 Interorbital breadth and bior
Page 61 and 62: 3.3.2 Orbital height and orbital br
Page 63 and 64: Basion-Superior Orbit, Basion-Infer
Page 65 and 66: 98Vertical Angle of Orbital Margins
Page 67 and 68:
statistical tools. In the next sect
Page 69 and 70:
Correlation obbobhobdobvobfekbdkbbs
Page 71 and 72:
obbobhobdobvobfekbdkbbsobioFunction
Page 73 and 74:
variables in the first discriminant
Page 75 and 76:
distance matrix, which shows the Af
Page 77 and 78:
golxcbzybbbhbplufbnphnlhobbobhobdob
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non-orbital cranial and facial trai
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Function 242012AncestryAfricanAsian
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eadth (ekb), and basion-orbitale (b
Page 85 and 86:
CHAPTER 4EVOLUTIONARY CHANGE IN THE
Page 87 and 88:
This sample represents the most mor
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analysis. This was done to remove a
Page 91 and 92:
190Boxplot of Cranial Size vs Time1
Page 93 and 94:
flexed in association with neurocra
Page 95 and 96:
Variables N Coefficient t p R²1) B
Page 97 and 98:
Ross (1995) also finds a relationsh
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Figure 4.4: Image of Shandingdong (
Page 101 and 102:
CHAPTER 5EVOLUTIONARY CHANGE IN THE
Page 103 and 104:
ecause of a general reduction in cr
Page 105 and 106:
adequate space within the orbits fo
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Western European temporal groups sa
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Upper Paleolithic (Figure 5.4). The
Page 111 and 112:
Regardless of the relative contribu
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of facial projection vs. time indic
Page 115 and 116:
Boxplot of Cranial Index vs Time908
Page 117 and 118:
5.6 Results of regression analyses:
Page 119 and 120:
Although the direction and magnitud
Page 121 and 122:
Additionally, because the eyeball s
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corroborates the findings of other
Page 125 and 126:
Sample Sample Sizes Method DataFema
Page 127 and 128:
approximately 3.5 show little to no
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In females there is a clear differe
Page 131 and 132:
Boxplot of Orbital Vol vs Sex25.022
Page 133 and 134:
Ancestral Group N mean s.d. t pAfri
Page 135 and 136:
5.5Boxplot of Relative Eye Size vs
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away from emmetropia in individuals
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ceases. Additionally, different pat
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of the orbit that the eyeball fills
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CHAPTER 7SUMMARY AND CONCLUSION7.1
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margins in this group. The slightly
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classification of dry skulls and as
Page 149 and 150:
Six orbital variables were used to
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A final prediction relating to how
Page 153 and 154:
Nevertheless, orbital traits that c
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etraction could not be evaluated. H
Page 157 and 158:
A statistically significant negativ
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to engage in non-subsistence activi
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comes at a cost to visual acuity ho
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trajectories between the eye and or
Page 165 and 166:
BIBLIOGRAPHYAiello, L., Dean, C. (1
Page 167 and 168:
Bruner, E., Saracino, B., Passarell
Page 169 and 170:
Goldschmidt, E., Lam, C., Opper, S.
Page 171 and 172:
Lam, C., Edwards, M., Millodot, M.,
Page 173 and 174:
Quant, J., Woo, G. (1992) Normal va
Page 175:
Weiss, K. (2002) How the Eye Got it
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