When the earth formed some 4.6 billion years ago, it was a lifeless, inhospitable place. A billion years later it was teeming with organisms resembling blue-green algae.
- How did they get there?
- How, in short, did life begin?
- This long-standing question continues to generate fascinating conjectures and ingenious experiments, many of which center on the possibility that the advent of self-replicating RNA was a critical milestone on the road to life.
- Before the mid-17th century, most people believed that God had created humankind and other higher organisms and that insects, frogs and other small creatures could arise spontaneously in mud or decaying matter. For the next two centuries, those ideas were subjected to increasingly severe criticism, and in the mid-19th century two important scientific advances set the stage for modern discussions of the origin of life.
- Repeated generation after generation, natural selection could thus lead to the evolution of complex organisms from simple ones. The theory therefore implied that all current life-forms could have evolved from a single, simple progenitor - an organism now referred to as life's last common ancestor. (This life-form is said to be "last" not "first" because it is the nearest shared ancestor of all contemporary organisms; more distant ancestors must have appeared earlier.)
by , P#@N!M@#E$#.
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