Essentialism is usually used within the sphere of philosophy. It basically states that "things," whatever they may be, share a quality or qualities in common at its core. In short, the essence is held in common. This philosophy, as you can imagine, has been challenged by many. The generalizing tendency of such a point of view may be too much for modern people, who see differences rather than similarities. A more helpful approach may be the idea of "family resemblances" by Wittgenstein. I believe that this approach allows for more flexibility, while retaining the insight that certain things are related.
Essentialism refers to the belief that people and/or phenomenon have an underlying and unchanging 'essence'. Firstly it refers to the use of biological, physiological and, increasingly, genetic, causes as explanations for human social behaviour. A second use of the term essentialism is when generalised statements are asserted that make no reference to cross-cultural differences or previous historical variation. This is also sometimes called universalism. Thirdly, the term essentialism refers to when in everyday conversation or also in academic writing we make use of unified concepts.
Essentialism is a cognitive process which means a spontaneous, unconscious and intuitive mannet to represent things or persons and to consider that their own characteristics are caused by an "essence" of their own category. This substance is clearly fictional and its associated characteristics may be observable realities or, in turn, pure fiction. (modular theory of brain from psychology development and cognitive anthropology).
Cognitive Essentialism lies manifestly in the concept of "soul", that immaterial essence that animate human beings, or all beings in general, regarding the considered religious faith.
Totemism is a form of religious Essentialism.In ancient tribal societies,to each individual was assigned a totem, that was a symbol that results from what clan the individual belongs. This put the individual in relation to ancestors and supernatural forces. This is one of the most rudimentary forms of religious life.
Religion becomes the expression of a cognitive process of categorization, an Essentialism, which is more effective than a simple ranking method based on similarities. It allows us to establish fast connections such as cause and effect when we have no idea about the real causes of the phenomenon we observe.