The first amphibians appeared in the Paleozoic era during the Devonian period. Before amphibians, fish were the only backboned animals. During the evolution of amphibians, both physical structure and behavioral adaptations had to occur. Some of the ancestors of amphibians developed lungs in place of gills. For example, a lungfish can get oxygen through its gills and also through rudimentary lungs by gulping air. As the marshes they lived stagnated or dried up, primitive lungs were an adaptive step toward survival on land. British paleontologist W.E. Swinton pointed out, "The vertebrates which could survive the prolonged dry spell of the late Devonian period which dried out the marshpools, were those kinds which had developed means of both breathing and eating."

The lobe-finned fishes that lived in shallow waters developed limbs strong enough to support their weight on land. As the waters alternately receded and flooded, these animals could not find food on land during the prolonged droughts of the Devonian, prevailed. The stronger limbs also helped these transitional organisms to navigate water and land better, thus they eluded predators more effectively as well. This transition from water to land took at least fifteen million years. Amphibians, having found their niche on land, were both carnivores and herbivores.

The swampy, moist conditions of the Carboniferous period allowed amphibians to flourish. The food was plentiful, insects and spiders abounded, and the warm temperatures were favorable. A vast variety of amphibians developed. However, during the Permian and Triassic periods, conditions deteriorated for amphibians. Two hundred and fifty million years ago, many amphibians died off, though they are still around today.