Human nature comprises the fundamental dispositions and characteristics, including ways of thinking, feeling, and acting, that humans are said to have naturally. It is often used to denote the essence of humankind or what it 'means' to be human. The concept has been a central focus of philosophy for centuries and continues to provoke lively debate. There are varying and conflicting normative uses of the expression "human nature," and there are serious disagreements concerning the concept's content and explanatory significance. Some argue that human nature is incompatible with modern evolutionary biology, while others defend the concept as scientifically respectable and meaningful. Human nature is traditionally discussed in relation to the comparative importance of genes and environment in human development, known as "nature versus nurture"