The gradual change from simple to complex life forms, or from ancient organisms that lived millions of years ago to contemporary species, is known as evolution. Simple life forms undergo changes, improvements, and modifications during evolution. The remains or impressions of species that existed in the distant past are known as fossils. The existence of fossils demonstrates that the current animal descended from earlier species through ongoing evolution. An organism’s evolutionary history can be traced using fossils. The distribution pattern of fossils shows that the ancient fossils present in the bottom rocks are simple, while the most recent fossils found in the upper strata are more highly evolved. It means fossils form and become more and more complex as we proceed from the earliest to recent rocks. It gives us an idea of the time in history when different species were formed or became extinct. Thus, fossils provide us with evidence in support of evolution.