IntroductionLife on Earth is entirely about sex. But sex has more to do with our animal instincts than many humans realize. Animals and humans, just like humans, go through unimaginable things to ensure their genes are passed on to another generation. The sole purpose of life for most species is to reproduce so that some part of their DNA or genes can be passed on. It is clear that without reproduction and sex, which are very different terms, the species would disappear. Because of this unavoidable fact, the evolution of sex is a very important subject. We can say that sex determines evolution and evolution determines nature, which in turn places sex at the center of existence. When looking at the evolution of sex, there are many different topics and facts that need to be looked at closely. This article will give a brief description of the history of sexual reproduction and its evolution over the last 600 million years. Next, a discussion of Darwin's theories of natural selection and sexual selection and their role in evolutionary theory will be presented. Additionally, this article will include an in-depth look at different forms of reproduction; the history, current state and future of human sexual reproduction; and various other interesting topics related to the evolution of sex.ReproductionWilson (1975) notes that an individual organism is part of an elaborate device that ensures survival and replication of genes with as little biochemical alteration as possible. Since reproduction is considered one of the main reasons for the existence of many species, it is important to study its role in the evolution of sex. Webster defines reproduction as the act or process by which plants and animals give rise to suckers...... middle of paper ....... (2007). Evolutionary Analysis (4th ed.). Upper Saddle River, NJ: Pearson Prentice Hall. Neiman, M., Hehman, G., Miller, G., Logsdon, Jr., J., & Taylor, D. (2009). Accelerated accumulation of mutations in asexual lineages of a freshwater snail. Molecular Biology and Evolution, 27(4): 954-963.DOI: 10.1093/molbev/msp300Schuiling, G. (2005). On sexual behavior and gender role reversal. Journal of Psychosomatic Obstetrics and Gynecology, 26(3): 217-223The evolution of sexual reproduction. (nd). The Journal of Evolutionary Philosophy - Evolution and meaning. Internet. November 22, 2015. http://www.evolutionary-philosophy.net/sex.html WhyEvolutionIsTrue. Evolve: Sex Story Channel [Video]. (April 4, 2011). Internet. November 20, 2015. http://www.youtube.com/watch?v=gO7Y61bn_MQWilson, E., (1975). Sociobiology: The new synthesis. Cambridge, Massachusetts: Harvard University