(Editor's Note: This column is a synopsis of a talk given recently in Great Neck before REAP-2.)
Evolution, the formation of new species, occurs when chance, random, or accidental mutations (genetic changes in fertilized eggs) happen to make the mutant progeny better able to survive in their communal environment than their non-mutated siblings. In evolution, survival of the species (not the individual) is all-important. Individuals are merely means by which their genetic strains (species) are passed along from generation to generation.
If the survival advantages gained by the altered offspring are slight, evolution will take a long time, myriads of generations, to manifest itself as the more successful mutant genes slowly increase numerically while spreading through successive non-mutated sibling populations and slowly replacing them as they die out. Here, the more fit mutants are the 'winners' that take over the habitats shared with the less able non-mutant siblings; eventually forcing the latter 'losers' into extinction. If the mutants' gained advantages are profound, new species will appear rapidly in ensuing populations as much better environmentally-adapted mutations spread more quickly throughout future generations with concomitant faster extinction of non-mutant stock.
While evolution takes place slowly in stable unchanging environments and rapidly in unstable changing environments, it occurs explosively during and after mass extinctions, seven of which have been recorded in rocks, the geologic records of past events in Earth's history. Mass extinctions are caused by catastrophic environmental upheavals such as those due to asteroids colliding with Earth, widespread volcanic ash and lava eruptions, extensive earthquakes and major tectonic events, including land that submerges to become seafloor, and seafloor that emerges to become land.
The seven recorded mass extinctions associated with enormous environmental chaos occurred at the ends of these devised geologic time intervals: PreCambrian- 570 mya (million years ago), Ordovician- 440 mya, Devonian- 365 mya, Permian- 250 mya, Triassic- 200 mya, Jurassic- 140 mya, and Cretaceous- 65 mya. The present mass extinction is being caused by intentional and unintentional human activities.
Enormous environmental modifications kill off most previously-existing species that were well-adapted to survive in the old environments, but were not able to adapt to the new tremendously-altered ones. While most deleterious mutations within fairly stable environments eventually die out due to incompatibility with the existing habitats, flawed species with genetic characteristics that enable them to survive mass extinction and adapt to available habitats created by cataclysmic events, become the precursors of innumerable new species that evolve immediately as they fill new or abandoned environmental niches.
Mutations that are deleterious in desirable environments, such as ventral fins of fast-swimming fishes that mutate to tetrapod legs in offshore aqueous habitats, enable the faster non-mutated finned siblings to drive the poorly-swimming legged mutants into extinction within their existing habitat (winners beating losers), or forcing them into dangerous shallow coastal waters in their habitat fringe areas, and then chasing them entirely out of the water onto land.
Their fortuitous tetrapod leg mutations which were harmful in the former water environment, became by pure chance beneficial in the new land one which the mutants were compelled to enter, reluctantly. This is a case of evolution by less able "losers" in an old habitat becoming more able "winners" in a new environment they were compelled to enter reluctantly. This shows that evolution is not always "survival of the fittest," but sometimes is "survival of the unfit."
The extensive but incomplete fossil record in ancient rocks and sediments is constantly being added to by new paleontological discoveries. Paleobiological information correlates well with breakthroughs in contemporary biology, biochemistry and genetics.
Darwin explained evolution clearly in his classic 1859 publication, The Origin of Species and in other later books. He also wrote a book about earthworms and their importance to farmers and gardeners in aerating soils. The worm book earned him more money than all his books on evolution put together. England, after all, is a nation of gardeners.