But, an important point scientists have discovered is that the DNA of fish ,although has gene for limb formation, it lacks the genes for the formation of the digits, this was proved when scientists inserted the fish Hoxd gene in transgenic mice embryos, during the development of which the inserted gene was active only in the arm region but not in the digits. This evidence proves that the formation of limbs in land animals is the result of modification in genetic material of ancestral water animals.