ABSTRACT
A growing body of literature, has associated exposure to prenatal testosterone, to the length second to fourth digit ratios (2D:4D) and this have been linked to several biological traits e.g. fertility, birth weight, cognitive abilities and psychopathology etc. This study was aimed at evaluating the 2D:4D and 2D:4D and aggressionamongst artisans, non-artisansin Zaria, Kaduna state, Nigeria. A cross sectional study was conducted and a total of 700 subjects participated in this study, 548 subjects from different artisan groups and 152 subjects from non-artisan groups respectively. The artisanswere mainly labour workers between the age ranges of 18-65 years while the non-artisans are mainly students between age ranges of 18-56years.Anthropometric measurements were obtained using stadiometer and weighing scale, standard measuring tape, digital vernier caliper, anthropometric variables such as height, weight, finger length, humeral length, foot length and hand length were measured.The study revealed statistical difference in the variables between artisans and non-artisans except in right finger I and III, right 2D:4D ratio, left finger I, III and III, left 2D:4D ratio,hand length and hand breadth.When artisans were categories according to their trade (auto-mechanics, bricklayers, tailors and carpenters) artisans showed various degree of significant difference within the groups and with the non-artisans. The regression equations derived for bothartisans and non-artisan groups separately using height, weight and body mass index (BMI)by means of which these variablescan be accurately estimated using 2D:4D ratio when such body parts are recovered. Relationships between 2D:4D and different scale of aggressions have been established. The linear regression equations for the association of right and left 2D:4D and anger aggression in overall artisan and non-artisan groups is given as Anger = 28.026 – (10.172 * R2D:4D) (R = 0.176,R2= 0.0311, SEE 2.148, P=0.001) and Anger = 28.923 – (11.060 * L2D:4D),R =
xvi
0.173, R2= 0.0300, SEE 2.384, P=0.001respectively. The present study showed significant (p< 0.001) negative relationship between 2D:4D and all forms of aggression. In conclusion right and left 2D:4D ratio could be applied for estimations of height, weight, BMI and forms of aggression in artisans and non-artisan groups of Kaduna state. Also differences of 2D:4D ratio estimation between the different groups of artisans and non-artisans has been established in this study, indicating population specificity in 2D:4D ratio based on occupation in Kaduna state, Nigeria.
TABLE OF CONTENTS
Title Page …………………………………………………………………………………i
Declaration ………………………………………………………………………………………………….. ii
Certification ………………………………………………………………………………………………… iii
Acknowledgements ………………………………………………………………………………………..iv
Dedication …………………………………………………………………………………………………….vi
Table Of Contents ………………………………………………………………………………………. vii
List of Tables ………………………………………………………………………………………………… x
List Of Figures ………………………………………………………………………………………………xi
List Of Appendices ……………………………………………………………………………………… xiv
Abstract ……………………………………………………………………………………………………… xv
CHAPTER ONE ……………………………………………………………………………………………. 1
1.0Introduction ……………………………………………………………………………………………… 1
1.1Background of The Study ………………………………………………………………………….. 1
1.2Statement of Research Problem ………………………………………………………………….. 6
1.3Justification/ Significance of the Study ………………………………………………………… 6
1.4Aims and Objectives ………………………………………………………………………………….. 7
1.4.1Aim of the Study ……………………………………………………………………………………… 7
1.4.2Objective of the Study ………………………………………………………………………………. 7
1.5Hypothesis ………………………………………………………………………………………………… 7
2.0Literature Review ……………………………………………………………………………………… 8
2.1Assessment of Digit Ratio …………………………………………………………………………… 8
2.2History of Digit Ratio Research ………………………………………………………………….. 8
2.3Evidence of Androgen Effect on Digit Ratio……………………………………………….. 10
2.4Geographic and Ethnic Variation in Digit Ratio …………………………………………. 12
viii
2.5Correlation Between Digit Ratio and Traits ……………………………………………….. 13
2.6Body Mass Index, Weight, Height and Digit Ratio ……………………………………… 15
2.7 Digit Ratio and Risk Taking…………………………………………………………………….. 16
2.8 Male-To-Female Transexual People …………………………………………………………. 17
2.9Digit Ratio and Development ……………………………………………………………………. 17
2.10Aggression …………………………………………………………………………………………….. 17
2.10.1 Violence …………………………………………………………………………………………….. 18
2.10.2Domain Specific Theories of Aggression ………………………………………………….. 18
2.10.3Cognitive Neoassociation Theory ……………………………………………………………. 18
2.11General Aggression Model ……………………………………………………………………… 21
2.12Biological Bases Of AggressioN ……………………………………………………………….. 22
2.12.1Behaviour Genetics ……………………………………………………………………………….. 22
2.12.2Ethology and Evolutionary Biology …………………………………………………………. 24
2.13Hormones and Aggression ………………………………………………………………………. 27
2.14 Reported Findings on Occupation and 2D:4D Ratio …………………………………. 29
3.0Material and Methods ……………………………………………………………………………… 33
3.1Research Participants ………………………………………………………………………………. 33
3. 2Study Location ……………………………………………………………………………………….. 33
3.2.1The Climate of Zaria ……………………………………………………………………………….. 34
3.2.2Natural Vegetation ………………………………………………………………………………….. 35
3.3 Methodology ………………………………………………………………………………………….. 37
3.4 Ethical Approval …………………………………………………………………………………….. 42
3.5 Inclusion and Exclusion Criteria ……………………………………………………………… 42
3.5.1Inclusion Criteria ……………………………………………………………………………………. 42
3.5.2Exclusion Criteria …………………………………………………………………………………… 42
ix
3.6Statistical Analyses ………………………………………………………………………………….. 43
4.0Results ……………………………………………………………………………………………………. 44
4.1Anthropometric Variables and 2D:4D Ratio ………………………………………………. 44
4.2 Correlation Between Anthropometric Variables ……………………………………….. 55
4.3Linear Regression Models of the Anthropometric Variables ………………………. 59
4.4Scatter Disgrams Andregression Lines for Artisans and Non-Artisan Population Groups ……………………………………………………………………………………………………….. 62
5.0Discussion……………………………………………………………………………………………….. 85
6.0Conclusion And Recommendations …………………………………………………………… 91
6.1Conclusion………………………………………………………………………………………………. 91
6.2Recommendations……………………………………………………………………………………. 91
References …………………………………………………………………………………………………… 93
Appendix …………………………………………………………………………………………………… 112
CHAPTER ONE
1.0 INTRODUCTION
1.1 BACKGROUND OF THE STUDY
Digit ratio commonly known as 2D:4D is the ratio of the index finger (2D) to ring finger (4D) (Manning, 2002). Digit ratio has been reported by many investigators to show sexual dimorphism (Manning et al., 1998; Danborno et al., 2007; Ibegbu et al., 2012) with women having higher ratio than men (Manning et al., 1998; Danborno et al., 2007).
For males, the index finger is generally about 96 percent of the length of the ring finger, which gives an average digit ratio for males of 0.96 and females have a digit ratio of about 1.0 (Manning et al. 1998).The sexual dimorphism in 2D:4D is influenced by prenatal secretion of testosterone and estrogen (Zhang and Martin, 2011). Testosterone negatively correlates with 2D:4D while estrogen correlates positively with 2D:4D (Manning et al, 2002; Putz et al., 2004). A plethora of biological trait, have linked 2D:4D as reported by earlier investigators e.g, Zhang and Martin, 2011 fertility and human behavior (Allison et al, 2004), aggression and assertiveness (Wilson, 1983; Allison et al., 2004; Danbarno et al., 2008; Kilduff et al., 2013), personality factor and hand skill and medical conditions such as breast cancer, autism and congenital adrenal hyperplasia (Brown,2002; Manning, 2002) have also been explained with digit ratio study. Manning, (2002), reported significant racial and ethnic variations among Caribbean Jamaicans and white Caucasians. Oladipo et al. (2006) reported that there is no ethnic variation in digit ratio between Igbo and Urhobo and between Igbo and Yoruba ethnic groups of Nigeria respectively. They however recommended that tribes that are more distant be investigated to establish if any exist. The high value placed by females on male ability to acquire resources has been well documented (Buss, 1989).
2
This is evident in pre-industrial human societies, where males exhibit a positive relationship between status and number of surviving offspring. Such observations have been made across the continents of Africa, South America and Asia (Kaplan and Hill, 1985a; Pennington and Harpending, 1993; Smith, 2004). It has been suggested that the same is true of contemporary Western society; increasing income has been shown to have a significant effect on male reproductive success and desirability as a marriage partner (Buss, 1989: Pollet and Nettle, 2008: Buunk et al., 2002; Nettle and Pollet, 2008). Prior to agriculture, hunting may have represented an important means by which male resourcefulness could be demonstrated. Food is inexorably linked to status in many cultures around the world (Weissner and Schiefenövel, 1996), and there is evidence that superior hunters enjoy social prestige within the community (Altman and Peterson, 1988). Indeed, successful hunters have been shown to enjoy higher reproductive success (Kaplan and Hill, 1985b). Hunting may therefore be motivated by male-male competition (Hawkes et al., 2001). Smith (2004) has reviewed quantitative links between hunting ability and fitness-related factors such as fertility, offspring survivorship and number of mates, and qualitative links between hunting success and knowledge of hunting ability within communities. However, it is not clear whether it is the high social status of hunters (which reflects their ability to acquire resources), or the actual resources they obtain, that provides the mechanism linking hunting success with reproductive fitness. The 2D:4D ratio has been studied in the context of reproductive success (Manning et al.,2000), sex-typed behavior (Csathó et al., 2003a), spatial/cognitive abilities (Coolican and Peters, 2003; Csathó et al.,2003b; Kempel et al., 2005), adult personality characteristics (Austin, et al., 2002; Fink et al., 2004; Bailey and Hurd, 2005a), and more recently in the context of psychopathology (Arato et al., 2004; Bailey and Hurd, 2005b; McFaddenet al., 2005;Klumpet al., 2006; Walderet
3
al., 2006). Generally, digit ratios show positive correlations with female-typical behaviors and negative correlations with male-typical behaviors (Putzet al., 2004). Intrauterine environment appears to play a role in the formation of 2D:4D, twin studies have indicated a significant additive genetic and non-shared environmental influence on digit ratios (Rubolini et al., 2006; Gobrogge et al., 2008).It is generally assumed that this difference is established during early prenatal development under the influence of sex hormones. This view was illustrated by the recent experimental mouse work of (Manning, 2011; Zheng and Martin, 2011). They revealed that the sex differences in 2D:4D were the results of prenatal testosterone (PT) and prenatal oestrogen (PE) signalling in a narrow developmental time window in utero. Furthermore, an evidence suggests that in the human male, foetus starts to produce testosterone in week 8 and testosterone peaks at about week 11 or 12 to 14 (Scott et al., 2009). The 2D:4D ratio is probably fixed during this tight time (Mallas et al., 2006). Because of this, there has been increasing use of the 2D:4D ratio as an index of prenatal hormone exposure, and extensive studies in humans have found correlations between digits ratios and a variety of physiological and psychological conditions, including fertility, season of birth, athletic ability, sex-biased diseases, social behaviours, and sexual orientation (Henzi et al., 2003;Fisher et al., 2010; Zheng and Martin, 2011; Sadhaer et al., 2014;Danborno and Danborno, 2015; Wang et al., 2016).
Many studies showed that low 2D:4D ratios correlated with athletic ability (Taylor and Manning 2001; Manning et al., 2007b;Honekopp and Schuster, 2010;Longman et al., 2011, 2015) and male aggression (Bailey et al.,2005a; McIntyre et.al., 2007; Danbarno et al., 2008; Honekopp and Watson, 2011).Manning and colleagues have shown that
4
2D:4D ratios vary greatly between different ethnic groups (Manning et al., 2004). In a study conducted among the Nigerian population, showed males have a significantly negative relationship between right and left 2D:4D ratio with birth weight, while females show positively significant relationship in both right and left hands. This means that association exists between 2D:4D ratio and birth weight which could be predicted most especially from the left hands (Danborno et al., 2010). Recently, researchers have been trying to investigate the relationship between 2D:4D and traits like coronary heart disease (Fink et al, 2006; Wu et al., 2013), gym-based physical fitness (Honekopp et al., 2006), development of psychopathology (Fink et al., 2007), cooperative behaviour (Millet and Dewitte, 2006), attention deficit hyperactivity disorder (Stevenson et al., 2007). There are some findings on health related outcomes, specifically, an association between smoking and digit ratios was detected by Borkowska and Boguslow, (2013). Using a sample of students they found a positive relationship with female smoking. Manning and Fink, (2011) found a positive association between national means of 2D:4D and number of cigarettes consumed per capita per nation. Another side of health related outcome concerns sports. Particularly, 2D:4D was found to be related to performance in endurance running by Manning et al. (2007b). It was shown that higher level of prenatal testosterone (lower 2D:4D) positively correlates with performance in endurance running.
The study of 2D:4D and other digit ratios, as well as their variation among population groups and among individuals may serve as a useful tool for establishing their values as biomarkers. (Ghosh and Garth, 2005; Eachus. 2007;Kyriakidis and Papaioannidou.
5
2008;Okampaet al., 2015) 2D:4D and other digit ratios appear to be attractive anthropometric traits that probably deserve attention by anthropologists, scientists, and clinicians since these digit ratios have continued to show promise as biomarkers of health and diseases (Manning, 2002; Oyeyemi, et al., 2014; Mitsui, 2015). One’s personality, outlook and degree of optimism may also be relevant indicators of preference and motivation for public service. Standard measures of personality and outlook, respectively, are the Big Five Inventory (BFI) devised by John (1990) and the Aspiration index (AI) constructed by Kasser and Ryan, (1996).More recently, there has been more work that tries to get at the effects of prenatal T, as proxied by 2D:4D, on life outcomes. For example, Coates et al., (2009) have shown that lower 2D:4D (higher prenatal T) correlate with much greater earnings for participants engaged in high-frequency bond trading as compared to their colleagues with higher 2D:4D (lower prenatal T). There is also evidence that suggests that the effects of 2D:4D may be non-linear and sex-differentiated (Manning et al., 2010; Hell and Paessler, 2011; Branas-Garza, et al., 2012; Nye et al, 2012; Nye et al., 2015). For instance, Nye et al. (2012) show that for academic achievement as measured by grades or school GPA, 2D:4D seems to have a clear and significant quadratic effect for women, but the effects are either mildly linear or even insignificant.
Nyeet al., (2012) also tends to confirm the general findings of Manning et al. (2010) with regard to the differences in the effects of 2D:4D for women in more stereotypically masculine vs. more stereotypically feminine occupations. Hell and Paessler, (2011), who only record desired rather than actual occupations, find that female 2D:4D is correlated with an interest in things and weaker interest in people or social professions.
6
This dichotomy between results that sometimes seem to show correlations for male, and other times for female, subjects may be related to measuring actual occupation versus stated interests or preferences.
1.2 STATEMENT OF RESEARCH PROBLEM
The ratio of the length of the second to fourth digit (2D:4D ratio) presumably reflects prenatal exposure to sex hormones. The 2D:4D ratio is sexually dimorphic, and males consistently have a slightly lower value. It is associated with many behavioral and biological variables, including fertility and sexual behavior as well as occupation. There has been no report of studies on the relationship between occupation and 2D:4D and aggression in Zaria, Kaduna state, Nigeria. This study intends to investigate these phenomena.
1.3 JUSTIFICATION/ SIGNIFICANCE OF THE STUDY
Digit ratio has been reported by many workers to show sexual dimorphism with women having higher ratio than men. This study intends to provide information about the digit ratio amongst artisans and non-artisans, which can serve as reference database for the association between 2D:4D ratio, profession and aggression. The result of the present study will also show the influence of anthropometric indices anddigit ratio on occupation and aggression.Therefore the need to correlate 2D:4D ratio among artisans. Results of this study may provide reference for the use of 2D:4D ratio in occupational counselling.
7
1.4 AIMS AND OBJECTIVES
1.4.1 Aim of the Study
The aim of this study is to evaluate the 2D:4D, amongst artisans and non artisans and the relationship between 2D: 4D,some anthropometric variableand aggression in the sample population.
1.4.2 Objective of the Study
The objectives of this study are to investigate:
i. the differences of 2D:4D ratio between artisans and non-artisans.
ii. The differences of 2D:4D between different group of artisans
iii. the relationships between 2D:4D ratio and other anthropometric characteristics amongst artisans and non-artisans.
iv. investigate the relationships between 2D:4D ratio and aggression among artisans and non-artisans.
1.5 HYPOTHESIS
There will be no difference in 2D:4D of artisans and non-artisans, but level of aggression will significantly correlate with 2D:4D in both artisans and non artisans.
8
Do you need help? Talk to us right now: (+234) 08060082010, 08107932631 (Call/WhatsApp). Email: [email protected].
IF YOU CAN'T FIND YOUR TOPIC, CLICK HERE TO HIRE A WRITER»
