It's important to clarify that the term "creationist" generally refers to someone who believes in the creation of the universe and life by a supernatural being. This is in contrast to the theory of evolution, which explains the diversity of life through natural processes.

Therefore, there is no scientist who was a "creationist" of organic evolution. The concept of evolution by natural selection was developed by Charles Darwin and Alfred Russel Wallace, who were not creationists. They proposed that life on Earth changed over time through a process of natural selection, where organisms with advantageous traits were more likely to survive and reproduce. This theory is supported by a vast body of scientific evidence and is the foundation of modern biology.

It's worth noting that there are some people who hold creationist views and attempt to reconcile them with evolutionary theory. These views are often referred to as "intelligent design" or "creationism." However, these ideas are not scientifically supported and are often seen as an attempt to inject religious beliefs into scientific discourse.