11. From RNA to Protein
12. When Mistakes Happen
13. Dividing DNA Between Dividing Cells
14. Mendel and His Pea Plants
15. How Sex Leads to Variation
16. Genes and Chromosomes
17. Charles Darwin and "The Origin of Species"
18. Natural Selection in Action
19. Reconciling Darwin and Mendel
20. Mechanisms of Evolutionary Change
Although biology in its modern form is a relatively recent development, sciences related to and included within it have been studied since ancient times. Natural philosophy was studied as early as the ancient civilizations of Mesopotamia, Egypt, the Indian subcontinent, and China. However, the origins of modern biology and its approach to the study of nature are most often traced back to ancient Greece. While the formal study of medicine dates back to Hippocrates (ca. 460 BC â€“ ca. 370 BC), it was Aristotle (384 BC â€“ 322 BC) who contributed most extensively to the development of biology. Especially important are his History of Animals and other works where he showed naturalist leanings, and later more empirical works that focused on biological causation and the diversity of life. Aristotle's successor at the Lyceum, Theophrastus, wrote a series of books on botany that survived as the most important contribution of antiquity to the plant sciences, even into the Middle Ages.