Answer: The amniotic egg was an evolutionary invention that allowed the first reptiles to colonize dry land more than 300 million years ago. Fishes and amphibians must lay their eggs in water and therefore cannot live far from water. But thanks to the amniotic egg, reptiles can lay their eggs nearly anywhere on dry land.
Explanation:
A change in the sequence of nitrogen bases in the dna is the answer
Image result for In what era did the humans appear
Hominins first appear by around 6 million years ago, in the Miocene epoch, which ended about 5.3 million years ago. Our evolutionary path takes us through the Pliocene , the Pleistocene , and finally into the Holocene, starting about 12,000 years ago.