Ever since the beginning of recorded history, man has speculated on the origin of life. In ancient times, it was generally believed that organisms originated spontaneously Renaissance from non-living matter. Thus, the ancient Egyptians believed that rats came from garbage. scientists knew better than this, but in the seventeenth and eighteenth centuries AD, it was widely believed that acteria (microorganisms discovered in 1676) originated spontaneously. It was only in 1862 that Louis Pasteur disproved, once and for all, the theory of spontaneous generation
Have you ever wondered how the earth came to be populated by a great variety of organisms? The search for explanations has proved to be challenging. The answers have been found to point to one direction — to evolution, which means the progressive change of living things through time. The idea of evolution was not originated by Darwin in the nineteenth century as some people think (Raven and Johnson: 1986). Some ancient philosophers observed that organisms ranged from very simple to relatively complex ones.
Each group of organisms, according to them, was created by God.
Modern individuals of each group trace their ancestry to the individual created by God. The Judeo-Christian culture also promoted such thinking. Most early scientists believed fully that each kind of organism with all of its individual adaptations was created by God. They studied these organisms, their structures, and the relationships between them as a way of learning more about the creator. In the seventeenth century, for example, the English scientistclergyman, John Ray (1627-1705) clearly declared his belief that each kind of animal and plant had remained unchanged from the day it was created (Raven and Johnson: 1986). All these views are collectively known as the doctrine of fixed species or creationism. It was never convincingly challenged before Darwin.
During Darwin’s time, biology was dominated by natural theology. The natural theologians believed that the variations and adaptations of organisms proved that each species was fashioned by God for a particular purpose. Besides they believed that the earth was only a few thousand years old. For them, this was not long enough for significant evolutionary change. What is your own view? Do you believe in the theory of spontaneous generation or in the doctrine of fixed species? What are your reasons? Gradually, some discoveries led to the revival of discussions on evolution. These include:
A.The discovery of many more kinds of organisms by the first part of the eighteenth century.
B. The study of fossils which was begun in the eighteenth century by Georges Cuvier
Fossils as you might be aware are remains or body impressions of dead organisms that lived in the past. They are usually found within sedimentary rocks, which occur in layers. Cuvier, from his studies, found that different layers of the rocks held different kinds of fossils. Also the fossils appeared in chronological order that is the deeper the layer, the older the fossil it contains. To him, these observations seemed to be boundaries for dramatic change in ancient environments
