Geographical influence on digit ratio (2D:4D): a case study of Andoni and Ikwerre ethnic groups in Niger delta, Nigeria.

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1 Journl of Applied Biosciences 27: ISSN Geogrphicl influence on digit rtio (2D:4D): cse study of Andoni nd Ikwerre ethnic groups in Niger delt, Nigeri. Gwunirem, Isrel U 1 nd Ihemelndu, E. C 2. Deprtment Of Antomy, College Of Helth Sciences, University Of Port Hrcourt Deprtment Of Antomy, College Of Medicine nd Helth Sciences, Abi Stte University. *Author for correspondence e-mil: gwuniremisrel@yhoo.com Originl submitted in November Published online t on Mrch 8, ABSTRACT The role of geogrphicl loction on digit rtio (2D:4D) in ethnic groups within the sme geogrphicl loction ws investigted. One thousnd four hundred nd twosubjects drwn from Andoni nd Ikwerre ethnic groups in the Niger Delt region of Nigeri were rndomly selected for this study. These comprised 702 (50.07%) Andonis of which 350 (24.96%) were mles while 352 (25.11%) were femles nd 700 (49.93%) were Ikwerres of which 461 (32.88%) were mles nd 239 (17.05%) femles. A digitl venier cliper ws used to mesure the lengths of the second digit (2D) nd fourth digit (4D). The rtio 2D/4D ws then clculted for ech subject. The results obtined showed positive significnt differences (p<0.001) in the lengths of 2D nd 4D between mles nd femles in the two ethnic groups. It lso showed significnt (p<0.001) sexul nd ethnic differences within sme geogrphicl loction. This suggests tht 2D:4D is inherited but not necessrily influenced by geogrphicl loction. INTRODUCTION Digit rtio commonly known s 2D:4D is the rtio of the index finger (2D) to ring finger (4D) (Mnning et l, 2002). Digit rtio hs been reported by mny workers to show sexul dimorphism with women hving higher rtio thn men (Mnning et l, 2002; Phelps 1952,, George, Mnning et l, 2002 reported tht, for mles, the index finger is generlly bout 96 percent of the length of the ring finger, which gives n verge digit rtio for mle of Femles hve digit rtio of bout 1.0. The sexul dimorphism in 2D:4D is influenced by prentl secretion of testosterone nd estrogen. Testosterone negtively correltes with 2D:4D while estrogen correltes positively with 2D:4D (Mnning et l, 2002). Fertility nd humn behvior (Mnning et l, 2002), ggression nd ssertiveness ( Wilson G. D; 1983) nd (Allison et l, 2004), personlity fctor nd hnd skill nd medicl conditions such s brest cncer, utism nd Congenitl Adrenl Hyperplsi (Windy M. Brown 2002) hve lso been explined with digit rtio study. Mnning, 2002, reported significnt rcil nd ethnic vritions mong Cribben Jmicns nd white Cucsins. Oldipo et l, 2006 reported tht there is no ethnic vrition in digit rtio between Igbo nd Urhobo nd between Igbo nd Yorub ethnic groups of Nigeri respectively. They however recommended tht tribes tht re more distnt be investigted to estblish if ny exist. Andoni nd Ikwerre ethnic groups though in the sme geogrphicl loction, nd shring some common culturl vlues, hve different ncestrl origins. Andonis re Cmeroonin descent (Enemugwem, 2006) while the Ikwerres re believed to be descent of Arochukwu nd ncient 1736

2 Benin Kingdom respectively (Akobundu, 2000). This study seeks to investigte whether the environment or loction would hve modified their MATERIALS AND METHODS A totl of 1402 humn subjects between the ges of 15 nd 60 were recruited by rndom smpling. Those hving ny form of hnd deformity were excluded. Seven hundred nd two were Andonis (50.07%). Out of 702, 350 were mles (24.96%), 352 were femles (25.11%). 700 were of the Ikwerre tribe (49.93%). Out of this number 461 (32.88%) were mles while 239 (17.05%) were femles. Digit length ws mesured on RESULTS The results of this study re presented on tbles 1-4 nd figures 3-6. Tble 1 nd figure 1nd 2 show the men nd stndrd error of 2D nd 4D for both Andoni nd Ikwerre mles. Tble 2 nd figure 3 nd4 show the men nd stndrd error of 2D nd 4D for both Andoni nd Ikwerre femles. Tble 3 nd figure 5 show the right nd left digit rtios for mles in Andoni nd Ikwerre ethnic groups. Tble 4 nd figure 6 show the right nd digit rtios over time since it ws reported by Mnning et l, 2003 tht geogrphicl loction influences digit rtio. the ventrl (inferior) surfce of the hnd from the bsl crese of the 2nd nd 4th digits to the tip, using Venier clipers mesuring to 0.01cm minor reding (. Vlues obtined were recorded, then 2D:4D clculted for ech hnd. The dt ws nlyzed with descriptive sttistics: Men, stndrd error nd Anlysis of Vrince (ANOVA) using SPSS softwre progrmmer. left digit rtios of the Andoni nd Ikwerre ethnic groups. There ws significnt difference (p< 0.001) in 2D, 4D nd 2D:4D between mles nd between femles in the two ethnic groups. These differences confirm tht 2:4D is sexully dimorphic. It lso shows tht 2D:4D exhibited ethnic vrition within the sme geogrphicl loction. Tble 1: shows the lengths of second nd fourth digits in mles of Andoni nd Ikwerre tribes. PARAMETER AND./CM IKWERRE/CM F-RATIO SIG. LEVEL R2D±SEM 7.199± ± L2D±SEM 7.40± ± R4D±SEM 7.589± ± L4D±SEM 7.795± ± SAMPLE Tble 2: Men nd stndrd error of the lengths of second (2D) nd fourth (2D) digits for femles of Andoni nd Ikwerre tribes PARAMETER ANDONI IKWERRE F-RATIO SIG. LEVEL R2D±SEM 6.987± ± L2D±SEM 7.205± ± R4D±SEM 7.260± ± L4D±SEM 7.475± ± SAMPLE

3 Men vlues R2D L2D Andoni Ikwerre Figure 3: R2D nd L2D for femles s7.3 e lu 7.2 v7.1 n e 7 M R4D L4D Figure 4: R4D nd L4D for femles Andoni Ikwerre 1738

4 TABLE 3: Digit Rtio of mles in the two tribes PARAMETER ANDONI IKWERRE F- RATIO SIG. LEVEL R2D:4D 0.95± 0.96± L2D:4D 0.95± 0.96± Digit rtio vlues Mles Femles Digit rtio of Andoni Mles nd Fem les Figure 5 Tble 4: Digit Rtio of femles in the two tribes PARAMETER ANDONI IKWERRE F-RATIO SIG. LEVEL R2D:4D 0.96± ± L2D:4D 0.96± ± F i g u r e 6 : R i g h t 2 D : 4 D n d L e f t 2 D : 4 D f o r f e m l e s A n d o n i I k w e r r e 1 s e lu v n e M R - 2 D : 4 D L - 2 D : 4 D 1739

5 DISCUSSION In this study, second digit lengths in mles were found to be shorter thn fourth digit lengths nd significntly different between the two ethnic groups. This grees with the reports of George (1930), Phelps (1952), Mnning et l, (2000) who reported tht second digits in mles tend to be shorter thn fourth digits. These digit lengths re influenced by testosterone nd estrogen in utero (Mnning et l, 2000). Ikwerre femles hd pproximtely the sme lengths for second nd fourth digits similr to observtions of Mnning et l, (2002. Andoni femles hd shorter second digit different from erlier reports (George, 1930, Mnning et l, 2000). In this study 2D:4D hs been found to be sexully dimorphic with femles hving higher digit rtio compred to mles. This observtion is in line with erlier reports by Phelps 1952, George 1930, Mnning et l, 2000, Mnning et l, 2002, Mnning et l, 2003,, Oldipo et l, This sexul dimorphism in 2D:4D is influenced by prentl testosterone concentrtions. This hormone is thought to modify developmentl rte such s epiderml ridges of the digits (McEwen, 1981; McLusky nd Nftolin, 1981; Brdin nd Cterll, 1981; Geschwind nd Glburd, 1985). High concentrtions of fetl testosterone indicte low 2D:4D rtio which therefore indictes high prentl testiculr ctivity. On the other hnd 2D:4D is positively correlted with oestrogen in men nd women. A high estrogen level indictes high digit rtio in both men nd women. The sexul dimorphism of 2D:4D hs been reported in different prts of the world: United Sttes of Americ (Mles 0.96, Femles 1.0), Michel nd Mnning 2002, United Kingdom (Mles 0.98, Femles 1.00). In Nigeri it vries ccording to the ethnic group. Among the Igbos: Mles 0.96 ± 0.02, Femles 1.0 ± 0.06 (Oldipo et l, 2006), Urhobos: Mles 0.96 ± 0.02, Femles 1.0 ± 0.02 (0ldipo et l 2006), Ikwerres: Mles R0.96 ± 0.003, L0.96± 0.002, Femles: R1.0 ± 0.001, L1.0 ± 0.005), Andonis: Mles R 0.95± 0.002, L0.95 ± 0.002, Femles R 0.96± 0.002, L 0.96 ± 0.002) (present study). The observed ethnic vrition ws similr to those of Mnning et l. (2003) who reported tht 2D:4D shows strong ethnic differences but contrdicts Oldipo et l, 2006 nd 2009 tht there is no ethnic correltion in digit rtio. In this study, digit rtio ws found to be n inherited trit from the ncestrl origins nd thus showed remrkble ethnic differences in the sme geogrphicl loction. This observtion disgrees with Mnning et l, (2003) who reported tht 2D:4D is influenced by geogrphicl loction. For instnce the digit rtios of the Igbos (Mles 0.96, Femles 1.0) nd Urhobos (Mles 0.96, Femles 1.0) (Oldipo et l 2006) from where the Ikwerres re believed to originte re the sme. This suggests tht 2D:4D is inherited. If digit rtio does not exhibit substntil ethnic vrition, then the ethnic groups in question possibly hve common ncestrl bckground. In conclusion, 2D:4D showed strong sexul dimorphism nd substntil ethnic vrition within the sme geogrphicl loction. This suggests tht 2D:4D is inherited but not necessrily influenced by geogrphicl loction. REFERENCES Akobundu, Nsirim, Mrk (2000). An Economic History of Isiokpo (Ikwerre) Lnd: (From Erly Times to BA History Project (Unpublished). Pp24. Allison, A., Biley, Peter L. Hurd (2004). Finger Length Rtio (2D:4D) Correltes with Physicl Aggression in Men but not in Women. Journl of Biopsychology Brdin, C. W. nd Cterll, C. F.(1981). Testosterone: mjor determinnt of extrgenitl sexul dimorphism. Science Enemeugwem, J. H. ( 2006 ). Obolo nd the peopling of the Niger Delt. Otukpo: Aboki Publishers. Pp George, R. (1930). Humn finger types. Ant. Tec. 46, Geschwind, N. nd Glburd, A. M(1985). Cerebrl lteriztion. Biologicl mechnisms, ssocition nd pthology: hypothesis nd progrm for reserch. Arch. Neurol; 43, McLusky, N. J. nd Nftolin, F (1981). Sexul differentition of the nervous system. Science, 211, McEwen, B. S. (1981). Neurl gondl steroid ctions. Science, 211, Mnning, J.T; Trivers, R. Singh, D. (2000). The 2nd: 4th Digit Rtio nd Asymmetry nd hnd 1740

6 Performnce in Jmicn Children.Hormone nd Behviour Mnning, J.T; Scutt, D. Wilson, J. nd Lewis-Jones, D.I (2002). The Rtio of 2 nd to 4 th Digit Length: A Predictor of Sperm Number nd Concentrtions Testosterone, Luteinizing hormone nd Oestrogen. Humn Reproduction. 13: Mnning, J.T.; Bundred, P. E; Newton, D.T. nd Flnign B.F. (2003). The Second to Fourth Digit Rtio nd vrition in the Androgen Receptor Gene. Evolution nd Humn Behviour 24: Oldipo, G. S; Olotu E. J. nd Gwunirem I. U. (2006). Ethnic nd Sexul Differences in the Second to Fourth Digit Rtios (2D:4D) of Igbos nd Urhobos in Nigeri. Journl of Biomedicl Sciences in Afric Phelps, V.R. (1952). Reltive Index Finger Length s sex Influenced Trit in Mn. Americn Journl of Humn Genetics Wilson, G. D. (1983). Finger-Length s n Index of Assertiveness in Women. Personlity nd Individul Differences Windy, M. Brown Meliss Hines, Brioy F. Fne nd S. MrkBreedloves. (2002) Msculinized Finger Length Ptterns in Humn Mles nd Femles with Congenitl Adrenl Hyperplsi. Hormones nd Behviours. 42: