Journal of Biology and Life Science ISSN 2157-6076 2015, Vol. 6, No. 1 www.macrothink.org/jbls 139 Human Lateralization among Monozygotic and Dizygotic Twins in Koya Town Karim Jalal Karim Depart. Medical Microbiology, Koya University University Park, Daniel Mitterrand Boulevard, Koya KOY45 AB64, Kurdistan Region-Iraq Tel: 964-750-492-5814 E-mail: karim.jalal@koyauniversity.org Saifadin Khder Mustafa Depart. Medical Microbiology, Koya University University Park, Daniel Mitterrand Boulevard, Koya KOY45 AB64, Kurdistan Region-Iraq Tel: 964-750-753-9290 E-mail: saifadin.khder@koyauniversity.org Kewan Kamal Ahmad Deputy Head of Biology Department Faculty of Science & Health, School of Science, Dept. of Biology, University Park Daniel Mitterrand Boulevard, Koya KOY45 AB64, Kurdistan Region-Iraq Tel: 964-750-112-3722 E-mail: kewan.kamal@koyauniversity.org Received: December 15, 2014 Accepted: January 4, 2015 doi:10.5296/jbls.v6i1.6776 URL: http://dx.doi.org/10.5296/jbls.v6i1.6776 Abstract At present, we do not understand how human handedness arose. Although much attention has been paid to several genetic theories, some studies involving twins have indicated that the influence of genetic and environmental factors on handedness may be minimal or nonexistent. The incidence of left-handedness amongst males is higher than with females, according to a large body of research. People who are ambidextrous are more likely to start to write with their right hand, even when they are not forced to do this. The left hemisphere of the brain is also lateralized when compared to the right hemisphere and vice versa. Our research examined handedness in dizygotic and identical monozygotic twins in Koya