In that book, Schwartz hearkens back to earlier theories that suggest that the Darwinian model of evolution as continual and gradual adaptation to the environment glosses over gaps in the fossil record by assuming the intervening fossils simply have not been found yet. Rather, Schwartz argues, they have not been found because they don't exist, since evolution is not necessarily gradual but often sudden, dramatic expressions of change that began on the cellular level because of radical environmental stressors--like extreme heat, cold, or crowding--years earlier.
Determining the mechanism that causes those delayed expressions of change is Schwartz's major contribution to the evolution of the theory of evolution. The mechanism, the authors explain, is this: Environmental upheaval causes genes to mutate, and those altered genes remain in a recessive state, spreading silently through the population until offspring appear with two copies of the new mutation and change suddenly, seemingly appearing out of thin air. Those changes may be significant and beneficial (like teeth or limbs) or, more likely, kill the organism.
Why does it take an environmental drama to cause mutations? Why don't cells subtly and constantly change in small ways over time, as Darwin suggests?
Cell biologists know the answer: Cells don't like to change and don't do so easily. As Schwartz and Maresca explain: Cells in their ordinary states have suites of molecules-- various kinds of proteins--whose jobs are to eliminate error that mi
Source:University of Pittsburgh