There isn't one single "father" of radiation biology. The field grew through the contributions of many scientists from various disciplines. However, some key figures who made significant contributions and are often associated with the early development of the field include:

* Pierre Curie and Marie Curie: Their groundbreaking work on radioactivity in the late 19th and early 20th centuries laid the foundation for understanding the effects of radiation on living organisms.

* Henri Becquerel: His discovery of radioactivity in 1896 paved the way for the Curie's research.

* Wilhelm Conrad Röntgen: His discovery of X-rays in 1895 opened up a new field of research and applications, leading to the early investigations of radiation effects.

* Thomas Hunt Morgan: He was one of the first to study the genetic effects of radiation, using fruit flies as a model organism.

* Hermann Joseph Muller: He made significant contributions to understanding the genetic effects of radiation, particularly its mutagenic properties. He was awarded the Nobel Prize in Physiology or Medicine in 1946 for his work.

* John G. Trump: He developed the first high-voltage X-ray generator, used for medical and industrial applications, and was a pioneer in the field of radiation therapy.

These individuals, among others, played pivotal roles in shaping the field of radiation biology. It's important to recognize that the development of this field was a collective effort, building upon the knowledge and contributions of many scientists over time.