Abstract

Species is one of the most basic concepts for almost all branches of biology, and it is also one of the most controversial concepts. An important aspect of "the species problem" is the question of "what the ontological status of species is". Traditionally, the answer to the issue about "the ontological status of species" is biological essentialism. Biological essentialism claims that species is a "natural kind", which argues that all and only the members of a species have a common essence. Each species is separated from all others by a sharp discontinuity. However, Darwin's evolutionary theory argues that species are gradual, and the boundaries between species are vague. This view conflicts with biological essentialism. With the continuous transmission of Darwin's theories, biological essentialism was gradually abandoned by philosophers and scientists. In recent years, some philosophers try to resurrect biological essentialism by using new biological resources. Their theories are known as New Biological Essentialism, which mainly includes three different approaches: The Barcode Theory of DNA, Relational Essentialism, and HPC Theory. However, there are so many defects in their theories that they don't provide a successful defense for biological essentialism. By analyzing these theories, I try to point out that the dilemma and failure of new biological essentialism dues to the conflict between its ontological presupposition and modern biological practice. The conflict leads to the tension between essentialism and biology. Further, I argue that the best way to eliminate the tension between biology and essentialism is to regard species as “heterogeneous kinds”. This new understanding of species abandons biological essentialism at the ontological level but retains the value of epistemology of regarding the species as “natural kinds”.