Here's why:

* Creationism: This is the belief that the universe and life on Earth were created by a supernatural being (typically a god) in a relatively recent past.

* Evolutionary Biology: This is the scientific theory that explains the diversity of life on Earth through a process of change over time. This change is driven by natural selection, where organisms with traits that better suit their environment are more likely to survive and reproduce, passing those traits on to their offspring.

While there are many different versions of creationism, they all fundamentally oppose the core tenets of evolutionary biology.

It's important to note that:

* Evolutionary biology is a well-supported scientific theory, backed by a vast amount of evidence.

* Creationism is a religious belief, not a scientific theory. It is not supported by scientific evidence.

Instead of "opposite," you could also use terms like:

* Scientific explanation of life's origins

* Biological evolution

* Naturalistic explanation of biodiversity

Remember, these terms all describe the scientific understanding of the origin and diversity of life, while creationism offers a religious explanation.