We definitely have evidence of cancer being present in the animal kingdom (that includes humans) deep into the fossil record so I might suggest that they are mistaken.
Pruitt, S. (2019, February 11). "How Old Is Cancer? At Least as Old as the Start of the Dinosaurs, Fossil Shows." HISTORY.
Pruitt, S. (2019, February 11). "How Old Is Cancer? At Least as Old as the Start of the Dinosaurs, Fossil Shows." HISTORY.
https://www.history.com/news/cancer-dinosaur-fossil-earliest...