The belief that mammalian cells have infinite division capacity was based on contaminated chicken cell-derived food, leading to misinterpretation.

“at the time in the early 1960s it was widely believed that cells from us from mammals could had infinite capacity to divide and this was made famous by Alexis Carrel who goes back decades before that the leaders in the field all believed this and it turns out this was the result of the fact that the food that was being fed to these cells which was derived from chickens was contaminated with chicken cells so every time cells were fed food they were also fed other cells and it gave this impression that these cells were dividing forever”