It's important to be precise when talking about "doctrines" of evolution. The word "doctrine" implies a set of beliefs held by a specific group, often with a religious or philosophical context.

While the theory of evolution is a cornerstone of modern biology, it's not a doctrine in the traditional sense. It's a scientific theory, supported by an immense body of evidence, that describes the process of change in life forms over time.

Here's a breakdown of the core principles of evolutionary theory, often referred to as the "modern synthesis" of evolution:

1. Variation: Individuals within a population show variations in their traits (e.g., size, color, behavior).

2. Heritability: These variations are, at least partially, heritable, meaning they can be passed down from parents to offspring.

3. Natural Selection: Individuals with traits better suited to their environment are more likely to survive and reproduce, passing on those advantageous traits. This leads to a gradual shift in the characteristics of the population over time.

4. Genetic Drift: Random fluctuations in gene frequencies can also occur, especially in small populations. This can lead to changes in a population's traits that are not necessarily related to adaptation.

5. Speciation: Over long periods, populations can diverge significantly, leading to the formation of new species.

Important Points:

* Evolution is not a belief system: It's a scientific explanation backed by extensive evidence.

* Evolution is ongoing: It's not a completed process but a continuous change in life forms.

* Evolution is not about "progress": It doesn't have a specific goal or direction. Species simply adapt to their environment.

It's also crucial to remember that while the core principles of evolution are well-established, scientists continue to refine our understanding of the mechanisms and processes involved.