Abstract
Neo-Darwinism claims that mutations coupled with natural selection have evolved various immune systems existing in life today from simple to the very complex system in humans. However, the various adaptive immune systems in the animal kingdom are all equally complex, yet with major discontinuities between them. It is improbable that one evolved into another. All multicellular organisms have an elaborate innate immune system, and many animals have one of the two known arms of the adaptive system that produces enormous antibody diversity to destroy specific pathogens. Although very different, all known immune systems are highly effective in dealing with pathogens. No evidence exists for the evolution of the immune system, which appears to be irreducibly complex.