Per the "American Heritage Dictionary of Science," there are four empirical attributes of life: growth, reproduction, response to stimuli, and metabolism. Numerous scientific texts document that these attributes are all present at fertilization. Likewise, the genetic composition of humans is formed during fertilization, and as the textbook "Molecular Biology" explains, this genetic material is "the very basis of life itself." In keeping with these facts, the medical textbook "The Developing Human: Clinically Oriented Embryology" states that fertilization marks the "beginning of a new human being." Likewise, the medical textbook "Before We Are Born: Essentials of Embryology and Birth Defects" states that "the zygote and early embryo are living human organisms."