It's striking how often authors of biology papers in Science and Nature use mechanical metaphors. "Cellular machinery." "Molecular machines." "Molecular motors." "Replication mechanisms." "Mechanisms for maintenance of DNA integrity." And so on.
Life as a machine. The metaphor has been ingrained in scientific thought since the 17th century, when a scientific revolution coincided with a time of mechanical innovation (perhaps not coincidentally).
The mechanical metaphor has some life in it yet. At least, no more fruitful metaphor has come along. But the metaphor is taking on on a new twist: not the 17th-century clockwork of gears and levers, but the silicon chip.
A completely functional digital computer could be made out of gears and levers, but such a machine would be mammoth, cumbersome and slow. What goes on inside an electronic computer is closer in scale -- size and speed -- to what happens inside a living cell. Indeed, the computer has become an indispensable tool of molecular biologists. Only with computers can they begin to give visible representation to the chemical machinery of life. Witness that exquiste image of the foot-and-mouth virus I posted here not long ago.
Many people recoil from the mechanical metaphor for life. They cling to the notion that there is something magical, irreducible and transcendent about living organisms, something that will forever escape the grasp of the molecular biologists with their mechanical models of chemical structures.
Two things to keep in mind:
1) "Life is a machine" is only a metaphor. All understanding is metaphorical -- in science, in poetry, even in theology. No one mistakes the gray-bearded man on the ceiling of the Sistine Chapel for God, but Michelangelo's powerful metaphor evokes awe and understanding of something essential to the believer's idea of God. In science, too, we use the metaphors that most fruitfully advance our understanding.
2) The mechanical metaphor for life does not so much reduce the marvelous to the mundane as it elevates the mundane to the marvelous. "Mundane" comes from the Latin mundus, meaning "world." The more we understand the staggeringly complex molecular machinery of life, the more truly marvelous the world becomes.