Original Article
CROSS SECTIONAL STUDY OF SECOND AND FOURTH DIGIT RATIO
W ITH PHYSICAL ATTRIBUTES IN SOUTH INDIAN POPULATION
M eera Jacob
* 1, Ramakrishna Avadhani
2, Bindhu Nair
3, Rani Nallathamby
4,
M eril Ann Soman
5.
ABSTRACT
Address for Correspondence: Dr. M eera Jacob, Assistant Professor, Depart ment of Anat omy, Yenepoya M edical College, M angalore, Karnataka, India. E-M ail: meera_jacob83@yahoo.co.in * 1 Assistant Professor, 2 Head of t he Depart ment , 3 Associate Professor 3, 4,5 PG st udent .
Depart ment of Anat omy, Yenepoya M edical College, M angalore, Karnataka, India.
Background: St udy of t he index (2D) and ring (4D) digit rat ios and t heir associat ion w it h som e physical charact erist ics of Sout h Indian Populat ion w as done t o det erm ine t he values of 2D:4D digit rat ios and t heir associat ion w it h ot her ant hropom et ric variables.
M at erials and M ethods: 160 adult s (80 m ales and 80 fem ales) bet w een ages of 18 years and above w ere random ly select ed w it h exclusion of t hose w it h hand def orm it ies. The digit lengt hs w ere m easured from t he basal cr ease t o t he t ips using vernier caliper s. The 2D:4D r at ios w ere det erm ined for each subject w hile height and w eight w ere used t o calculat e t he body m ass index and dat a analyzed.
Results: The result s show ed signif icant diff erence in 2D:4D rat io bet w een m ales and fem ales. (p<0.001). M ean height of m ales exceeded t he m ean height of fem ales and t he m ean w eight of m ales exceeded t he m ean w eight of fem ales .M ean BM I of m ales also exceeded t hat of fem ales. There w as a posit ive correlat ion bet w een t he second digit lengt h and Height and w eight in m ales and fem ales bot h on right and left sides. Ther e w as also a significant correlat ion w eight and second digit lengt h in m ales.The 2D:4D rat io for bot h left and right hand did not show any posit ive correlat ion w it h height , w eight or BM I of an individual f rom people of Sout h India.
Conclusion:The result s show a posit ive cor relat ion bet w een t he digit lengt hs and height in bot h m ales and fem ales and bet w een weight and second digit lengt h in case of males but t he 2D:4D digit rat io had no relat ionship t o height ,w eight or BM I.The analysis also dem onst rat ed t hat t he m ales have great er 2D:4D rat io com pared t o fem ales. The result s of t he st udy can be of im portance in t he field of forensic ant hropology.
KEY W ORDS: 2D:4D rat io,ant hropom et ry,finger,height ,w eight ,BM I.
INTRODUCTION
Int J Anat Res 2015, Vol 3(2):1133-37. ISSN 2321- 4287 DOI: ht t p:/ / dx.doi.org/10.16965/ ijar.2015.177
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Received: 08 M ay 2015 Accept ed: 08 Jun 2015 Peer Review : 08 M ay 2015 Published (O):30 Jun 2015 Revised: None Published (P):30 Jun 2015
Int ernat ional Journal of Anat omy and Research ISSN 2321-4287
ww w.ijmhr.org/ ijar.htm
DOI: 10.16965/ ijar.2015.177
Recent decades have w it nessed an increase in underst anding of t he import ance of prenat al p r ogr am m i n g o n i n d iv i d ual ’s su bseq uen t behaviour, physiology, and phenot ype and also on reproduct ive success. It w as also show n t hat pr enat al st er oids also play a m ajor r ole in programming of lat er life reproduct ive
M ATERIALS AND M ETHODS
fourt h digit lengt h correlat es w it h in ut ero t est -ost erone levels because it is sexually dimorphic and is considered as an indicat or of prenat al sex hormone exposure [3]. The differences in 2D:4D rat io is set before birt h around 14 w eeks of gest at ion [ 4] . This fact rules out any social influences t hat can affect t he digit grow t h. All somat ic sex differences can eit her be due t o androgenic masculinisat ion or due t o effect s of sex chr o m oso m es [ 5] . Pr en at al sexual dimorphism indicat es t hat androgens act before birt h t o affect digit rat ios and t he finding of androgen insensit ivit y syndrome rules out t he role of sex chromosomes in t he sex differences of digit rat ios [5].
There w as possible associat ion of 2D:4D rat ios w i t h sexu al o r ien t at i o n,au t i sm , age at development of myocardial infarct ion, age at developm ent of breast cancer, musical abilit y and different aspect s of cognit ive abilit y and personalit y [ 6] . The skelet al st r uct ure and personalit y are affect ed by sex hormone levels in t he ut erus because t hese hormones carry out t heir f unct ions by evoking responses fr om specific organs or t issues t hat are adapt ed t o react t o minut e quant it ies of such hormones [7-8] . It w as f o u nd t hat t her e w as a d ir ect relat ionship bet w een t he index and ring finger lengt h rat ios and t he amount of t est ost erone in ut ero [9]. In a st udy of M anning et al smaller index finger in men have been associat ed w it h higher level of physical aggression [10]. This associat ion w as proved t rue only for physical aggression and not any ot her t ype of host ile behaviors [11]. The aim of t he present st udy is t o invest igat e t he associat ion of t he index (2nd) and ring (4t h) digit ratios w it h some physical traits in Sout h Indian populat ion.
The populat ion of st udy consist ed of 80 males and 80 female st udent s and staff of Yenepoya M edical College, M angalore. The st udy w as approved by inst it ut ional et hical com m it t ee. Convenient random sampling met hod w as used t o obt ain m easurem ent s of index and r ing f inger w it h t he exclusion cr it er ia t hat t he part icipant s do not have any physical anoma-lies of fingers or had any hist ory of fract ure or dislocat ion of index, middle and ring fingers .The
m i dd l e f i n ger w as used as t h e st an dar d reference. At t he proximal base of index and ring f inger s t here w ere cr eases. In m ost of t he part icipant s, index finger had only one crease and ring finger a band of creases. The m ost proximal crease w as chosen as a point . Wit h t he help Venier Calipers t he lengt h of second and fourt h digit s w ere measured. All measure-ment s w ere made carefully w it h t he digit s fully extended.
Statistical Analysis: The dat a collect ed w ere used t o obt ain 2D:4D rat ios by dividing 2D by 4D lengths. Dat a w as expressed as mean ± st an-dar d deviat ion. St udent t t est w as used t o determine the level of significance. The relat ion-ship bet w een t he par am et er s st udied w as est ab li sh ed u si n g Pear so n Co r r el at i o n t o est ablish t he st rengt h of relat ionship bet w een t he lengt hs of second and fourt h digit s (2D and 4D), t he digit rat ios and ot her ant hropomet ric variables in bot h sexes. St at ist ical significance w as accept ed if p value w as less t han or equal t o 0.001(p < 0.001).
RESULTS
Fig 1a: Digit lengt h in fem ales.
Fig 1b: Digit lengt h in m ales.
4D lengt hs and t heir rat ios for left hand respect ively. The m ean values of lengt hs of index finger (2D), ring finger (4D) and R2D:R4D bet w een males and females w ere st at ist ically signifi-cant (p<0.001) as show n in Table 1 and Fig 1a and 1b. L2D:L4D rat io was no signifisignifi-cant bet w een males and females.
Table 1: Show s t he m ean ±standard deviat ion of 2D, 4D lengt hs and t he rat ios of 2D:4D in m ales
and fem ales.
* * p<0.001-st aist ically significant * p>0.001-St aist ically not signif icant
Table 1 & Figure 1a and 1b indicate M ales have greater 2D:4D rat io in t he right hand compared t o females. In bot h males and females t he 2D:4D rat io w as equal in left hand. Using t t est , in males and females t he 2D:4D rat io w as not significant for t he left w it h p=0.736.M eanw hile t he digit rat io was significant for right hand w ith p=0.001. Result s show s t hat mean height of males exceeded t he mean height of females and t he mean w eight of males exceeded t he mean w eight of females .M ean BM I of males also exceeded t hat of females (Table2).
Table 2: General stat ist ics of t he ant hropom et ric param et ers used.
M ales Females
M EAN ±SD M EAN ±SD
R2D 7.21±0.46 6.72±0.36 7.52 p<0.001* * R4D 7.12±0.59 6.77±0.39 4.31 p<0.001 L2D 7.11±0.53 6.67±0.35 6.07 P<0.001 L4D 7.21±0.49 6.81±0.38 5.69 P<0.001 R2D:4D 1.01±0.06 0.98±0.11 2.38 P<0.001 L2D:4D 0.97±0.12 0.97±0.03 0.34 p>0.001*
Parameters t- value Sig. Level
Parameters Sex M ean±SD M inimum M aximum N
M ale 166±9.60 141 187 80
Female 159±6.28 147 172 80
M ale 63.72±11.74 32 94 80
Female 56.56±10.53 39 90 80
M ale 22.95±4.39 13.42 39.63 80
Female 22.28±4.26 16.4 38.95 80
BM I Height
weight
Table 2 Correlat ion m at rix for t he second and fourt h digit lengt hs and t he ant hropom et ric variables w ere done t o analyze any associat ion bet w een t he digit lengt hs and t he physical at t ribut es. There w as a posit ive correlat ion bet w een t he second digit lengt h and Height and w eight in males and females bot h on right and left sides (Table 3).
R2D P VALUE L2D P VALUE R2D P L2D
Height .428* * 0 .466* * 0 .452* * 0 .598* *
W EIGHT -0.017 0.883 0.024 0.832 .288* * 0.01 0.213
BM I -0.191 0.09 -0.17 0.131 0.05 0.657 -0.145
Parameter FEM ALE
P
0
0.058
0.199 M ALE
Table 3:Cor relat ion m at rix of second digit lengt h w it h ant hropom et ric variables.
* * Correlat ion is significant at t he 0.01 level
Table 4: Correlat ion m at r ix of four t h digit lengt h w it h ant hropom et ric variables.
Table 3 Weight and second digit lengt h also show ed correlat ion in case of males. There was also a st rong correlat ion bet w een t he fourt h digit lengt h and height in bot h in males and females bilaterally (Table 4).
R4D P VALUE L4D P VALUE R4D P L4D
Height .248* 0.026 .351* 0.001 .498* * 0 .444* *
W eight -0.166 0.142 -0.93 0.412 .258* 0.021 0.283
BM I -.264* 0.018 -0.236 0.035 -0.031 0.786 0.003
M ALE
Parameter FEM ALE
P
0
0.011
Table 5: Correlat ion m at rix of R2D:4D w it h t he ant hropom et ric param et ers used.
Table 5 show s t he correlat ion mat rix of R2D:4D w it h t he ant hropomet ric parameters. There was no posit ive correlat ion (p<0.001) bet w een t he R2D:4D and height , w eight and BM I.
Karl Pearson correlation coefficient
Karl Pearson correlation coefficient
r Value r Value
Height .235* 0.036 -0.279 0.012
W eight 0.89 0.431 -0.027 0.81
BM I -0.012 0.917 0.157 0.165
Parameters
Females (R2D:4D) M ales(R2D:4D)
P Value P Value
Table 6: Correlat ion m at rix of L2D:4D w it h t he ant hropom et ric param et ers used.
Karl Pearson correlat ion
coefficient
Karl Pearson correlation
coefficient
r Value r Value
Height 0.135 0.233 0.036 0.75
W eight 0.188 0.095 -0.095 0.402
BM I -0.126 0.266 -0.106 0.35
M ales(L2D:4D)
P Value P Value
Param et ers
Fem ales (L2D:4D)
Table 6 show s no posit ive correlat ion bet w een L2D:4D and height , w eight and BM I.
DISCUSSION
Det erminat ion of finger lengt h rat io (2D:4D) was done in cross sect ion of sample of Sout h India and t he result s w ere compared bet w een males and females .according t o previous researches done in t he field show s t hat t he digit rat io values are consist ently reliable in determinat ion of sexual dimorphism. According t o Brow n et al, considerable proport ions of normal males have low digit rat ios compared t o females [12]. It w as al so sho w n t hat m en had r elat ively sho r t second digit s t han fourt h digit s [13]. In our present st udy, males had greater 2D:4D for right hand and almost equal digit rat io for t he left hand. According to Est her et al, a low 2D:4D rat io in gir ls is highly pr edict ive of pr esence of aut ist ic feat ures and a low rat io can be used as a diagnost ic predict or in m edicine [14]. The p r esen t st ud y w as do n e t o est ab li sh t h e r elat ionship bet w een t he m ale and f em ale finger lengt h rat ios (2D:4D) and t o ascert ain if it has any correlat ion w it h height , w eight and BM I. The r esu l t s sho w ed t h at t her e w as corr elat ion bet w een R2D:4D and height in f em ales if t he p value w as less t han 0.05. Ot herw ise t here w as no significant correlat ion betw een the digit rat ios and other anthropomet-ric variables. M anning et al report ed t hat t here w as no significant correlat ion bet w een height
and w eight and digit rat ios for 69 men and 62 w omen w it h t he except ion of posit ive correla-t ion becorrela-t w een correla-t he w eighcorrela-t and 2D:4D racorrela-t ios for t he right hands [10]. According t o Tester and Cam pbell t her e w as a negat ive associat ion bet w een t he height and digit rat io (regression coefficient -.25) w hich is close t o t he present dat a [15]. Present st udy show ed a negat ive correlation bet ween R2D:4D and height (-.27).On t he ot her hand, Hurt and VanAnders reported a large negative correlat ion of -.49 betw een height and digit rat ios aft er cont rolling t he gender [16]. The results of t he present st udy have great prac-t ical applicaprac-t ions in prac-t haprac-t iprac-t could useful in prac-t he field of forensic ant hropology and in forensic medicine as a means of ident it y.
CONCLUSION
The 2D:4D lengt h rat io in males is great er t han in fem ales. Result s obt ained from t he t ot al sample of 160 part icipant s have show n t hat males have show n to have higher or equal 2D:4D rat ios in bot h right and left hands respect ively. The follow ing observat ions w ere derived from t he st udy
- Present st udy showed t hat t here w as a posit ive correlat ion bet w een second and fourt h digit l engt h an d h ei gh t in m al es an d f em al es b i l at er al ly. Th er e w as al so a si gni f i can t correlat ion bet w een w eight and second digit lengt h in males
- Results showed no positive correlation between t he 2D:4D rat ios and height , w eight and BM I of t he st udy populat ion.
Result s from t he present st udy indicat e t hat 2D and 4D lengt hs is a proxy indicat or of height w hen it is difficult t o measure height direct ly. Since t he st udy is limit ed t o Sout h India, furt her st udies are recommended t o be carried out wit h larger populat ion and ot her et hnic groups for great er ut ilit y value of 2D:4D as a indicat or for physical at t ribut es.
Conflicts of Interests: None
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