This is when ancient animals would gradually change forms over a long period of time.the first land animals appear on earth? About 417 million years age during the Devonian era. As for creationism there are skeletons of humans who are much older than 6000 years.ence it is the first plant as well as first animal. Some millions of year back. The first known fossils of what is possibly animal life appear in the Ediacara biota just prior to the Cambrian era.