This paper reports further results and an extension of the study presented at Complex Systems 2016. Human teeth and fingerprints both arise from genetic/epigenetic/environmental interactions and have embryological pathways with epithelial–mesenchymal interactions. The aims of this study were to determine the nature and extent of sexual dimorphism in teeth and fingerprints of twins at two different ages and to explore whether both systems display the features of complex adaptive systems. Buccolingual (BL) measurements from both primary and permanent teeth and ridge breadth (RB) measurements from fingerprints of the same set of Australian twins (28 males and 31 females aged 8 to 10 years, and aged 13 to 16 years, respectively) were collected and analysed. Sexual dimorphism was observed in both the primary and permanent dentitions, with the latter showing greater differences than the former. There was no observed sexual dimorphism in the fingerprints at 8 to 10 years. However, a few fingers (left index, left ring, and right middle) at 13 to 16-years exhibited significant differences, suggesting that friction ridges expand over time. It is concluded that both the dentition and dermatoglyphics display sexual dimorphism and characteristics of complex adaptive systems.
buccolingual, complex adaptive system, dentition, dermatoglyphics, fingerprints, human development, ridge breadth, sexual dimorphism, tooth size
The authors wish to thank The Australian Dental Research Foundation (ADRF), the NHMRC of Australia, Australian Twin Registry and Australian Multiple Birth Association.
 Guatelli-Steinberg, D., Sciulli, P.W. & Betsinger, T.K., Dental crown size and sex hormone concentrations: another look at the development of sexual dimorphism. American Journal of Physical Anthropology, 137, pp. 324–333, 2008.
 Alvesalo, L., Human sex chromosomes in oral and craniofacial growth. Archives of Oral Biology, 54S, pp. 18–24, 2009.
 Dempsey, P.J., Townsend, G.C. & Richards, L.C. Increased tooth crown size in females with twin brothers: evidence for hormonal diffusion between human twins in utero. American Journal of Human Genetics, 11, pp. 577–586, 1999.
 Ribeiro, D.C., Brook, A.H., Hughes, T.E., Sampson, W.J. & Townsend, G.C., Intrauterine hormone effects on tooth dimensions. Journal of Dental Research, 92, pp. 425–431, 2013. https://doi.org/10.1177/0022034513484934
 Moorrees, C.F.A., Thomsen, S.O., Jensen, E. & Yen, P.K., Mesiodistal crown diameters of the deciduous and permanent teeth in individuals. Journal of Dental Research, 36, pp. 39–47, 1957. https://doi.org/10.1177/00220345570360011501
 Ribeiro, D., Sampson, W., Hughes, T., Brook, A. & Townsend, G., Sexual dimorphism in the primary and permanent dentitions of twins: an approach to clarifying the role of hormonal factors (Chapter 5). New Directions in Dental Anthropology: Paradigms, Methodologies and Outcomes, ed. G. Townsend, E. Kanazawa, H. Takayama, University of Adelaide Press: South Australia, pp. 46–64, 2012.
 Garn, S.M., Lewis, A.B., Swindler, D.R. & Kerewsky, R.S., Genetic control of sexual dimorphism in tooth size. Journal of Dental Research, 46, pp. 963–972, 1967. https://doi.org/10.1177/00220345670460055801
 Acree, M.A., Is there a gender difference in fingerprint ridge density? Forensic Science International, 102, pp. 35–44, 1999. https://doi.org/10.1016/s0379-0738(99)00037-7
 Taduran, R.J.O., Tadeo, A.K.V., Escalona, N.A.C., & Townsend, G.C., Sex determination from fingerprint ridge density and white line counts in Filipinos. HOMO - Journal of Comparative Human Biology, 67, pp. 163–171, 2016.
 Brook, A.H., Brook O’Donnell, M., Hone, A., Hart, E., Hughes, T.E., Smith, R.N. & Townsend, G.C., General and craniofacial development are complex adaptive processes influenced by diversity. Australian Dental Journal, 59S, pp. 13–22, 2014. https://doi.org/10.1111/adj.12158
 Nanci, A., Ten Cate’s oral histology: development, structure, and function, 7th edition, Elsevier Health Sciences: Missouri, pp. 16–107, 2008.
 Kücken, M. & Newell, A.C., Fingerprint formation. Journal of Theoretical Biology, 235, pp. 71–83, 2005.
 Taduran, R.J.O., Ranjitkar, S., Hughes, T., Townsend, G. & Brook, A.H., Complex systems in human development: sexual dimorphism in teeth and fingerprints of Australian twins. International Journal of Design & Nature and Ecodynamics, 11, pp. 676–685, 2016. https://doi.org/10.2495/dne-v11-n4-676-685
 Townsend, G., Bockmann, M., Hughes, T., Mihailidis, S., Seow, K.W. & Brook, A., New approaches to dental anthropology based on the study of twins (Chapter 2). New Directions in Dental Anthropology: Paradigms, Methodologies and Outcomes, ed. G. Townsend, E. Kanazawa, H. Takayama, University of Adelaide Press: South Australia, pp. 10–21, 2012.
 Hughes, T.E., Townsend, G.C., Pinkerton, S.K., Bockmann, M.R., Seow, W.K., Brook, A.H., Richards, L.C., Mihailidis, S., Ranjitkar, S. & Lekkas, D., The teeth and faces of twins: providing insights into dentofacial development and oral health for practicing oral health professionals. Australian Dental Journal, 59S, pp. 101–116, 2014. https://doi.org/10.1111/adj.12101
 Brook, A.H., Griffin, R.C., Townsend, G., Levisianos, Y., Russell, J. & Smith, R.N., Variability and patterning in permanent tooth size of four human ethnic groups. Archives of Oral Biology, 54S, pp. S79–S85, 2009.
 Brook, A.H., Smith, R.N., Elcock, C., al-Sharood, M.H., Shah, A.A., Khalaf, F., Robinson, D.L., Lath, D.L. & Karmo, M., The measurement of tooth morphology: validation of an image analysis system. 13th International Symposium of Dental Morphology. E. Zadzinska, University of Lodz Press: Lodz, pp. 475–482, 2005.
 Schneider, C.A., Rasband, W.S. & Eliceiri, K.W., NIH Image to ImageJ: 25 years of image analysis. Nature Methods, 9, pp. 671–675, 2012. https://doi.org/10.1038/nmeth.2089
 Mundorff, A.Z., Bartelink, E.J. & Murad, T.A., Sexual dimorphism in finger ridge breadth measurements: a tool for sex estimation from fingerprints. Journal of Forensic Sciences, 59, pp. 891–897, 2014. https://doi.org/10.1111/1556-4029.12449
 Ządzínska, E., Karasínska, M., Jedrychowska-Dánska, K., Watala, C. & Witas, H.W., Sex diagnosis of subadult specimens from Medieval Polish archaeological sites: metric analysis of deciduous dentition. HOMO - Journal of Comparative Human Biology, 59, pp. 175–187, 2008. https://doi.org/10.1016/j.jchb.2008.04.004
 Girija, K. & Ambika, M., Permanent maxillary first molars: role in gender determination (morphometric analysis). Journal of Forensic Dental Sciences, 4, pp. 101–102, 2012.
 Griffin, J.E. & Wilson, J.D., Disorders of the testes and the male reproductive tract (Chapter 18). Williams Textbook of Endocrinology, 10th edn., eds. P.R. Larsen, H.M. Kronemberg, S. Melmed & K.S. Polonsky, W.B. Saunders Company: Philadelphia, pp. 709–770, 2003.
 Reyes, F.I., Boroditsky, R.S., Winter, J.S.D. & Fairman, C., Studies on human sexual development. II. Fetal and maternal serum gonadotropin and sex steroid concentrations. Journal of Clinical Endocrinology and Metabolism, 38, pp. 612–617, 1974. https://doi.org/10.1210/jcem-38-4-612
 Knickmeyer, R.C. & Baron-Cohen, S., Fetal testosterone and sex differences. Early Human Development, 82, pp. 755–760, 2006. https://doi.org/10.1016/j.earlhumdev.2006.09.014
 AlQahtani, S.J., Hector, M.P. & Liversidge, H.M., Brief communication: the London atlas of human tooth development and eruption. American Journal of Physical Anthropology, 142, pp. 481–490, 2010. https://doi.org/10.1002/ajpa.21258