Biological responses to climate have led climatologists to recognize bio-evidence as one of the most appropriate patterns of studying past climatic developments. Biostatic evidence includes plant, animal and human evidence. Plant evidence includes plant remains and annual growth rings of trees. Animal evidence can be studied and evaluated in aqueous and terrestrial areas, as well as in dry or humid regions. The habitations of the early humans, caves, agricultural lands remaining from ancient civilizations, types of livestock and livelihood of primitive human beings in every place indicate the climatic conditions of that place in each period.
Tracing and recreating climatic conditions of distant past based on evidence in the African Continent (Sahara), Europe, the United States and Asia have shown acceptable results with regard past climate changes.
The findings from the study of past biological conditions have been confirmed by other methods. Therefore, biological methods of studying past developments are among the most useful methods for examining climate change.
It should be noted that the methods of studying distant-past climates utilize the results of research in other scientific fields as well, and, along with other methods of study, provide with a more satisfactory image of the past climatic conditions.