Detailed theoretical analysis, using mathematical modeling, reveals that sex is a very inefficient way of reproducing. The inefficiency lies in making male offspring. In the majority of sexual species, only the female contributes energy and resources to the young. In contrast the males rarely contribute more than the minimum-a tiny sperm carrying genes, but devoid of other resources.
What is said above argues that the male contribution at fertilization is restricted to one half of future embryonic chromosomes. Although inspired by general perception and often perpetuated by popular science, this assumption is incorrect. Besides being a launching pad for the remaining chapters of this tome, the goal of the present chapter is to demonstrate that the male germ cell, the spermatozoon, is well suited to make other important contributions to the zygote and embryo. Studying spermatogenesis allows us to show how the unique, paternally contributed resources are generated during the intricate and fascinating process of spermatogenesis. In a show of male vanity, we decided to take a somewhat unconventional approach to this treatise on spermatogenesis and sperm structure by putting the emphasis of paternal contributions made at fertilization. We thus focus mainly on the later stages of spermatogenesis, during which the haploid, somatic-cell like round spermatid is transformed into a specialized, nearly cytoplasm-free spermatozoon capable of acquiring progressive motility and fertilizing an ovum in the oviductal environment.