On Earth, Among Millions Of Lineages Or

Evolution ... Is Opportunistic, Hence Unpredictable.

It Seems To Me That For Darwin The Pulsing Of Evolutionary Rates Was A Strictly Vertical Phenomenon.

New Gene Pools Are Generated In Every Generation, And Evolution Takes Place Because The Successful Individuals Produced By These Gene Pools Give Rise To The Next Generation.

The Reduced Variability Of Small Populations Is Not Always Due To Accidental Gene Loss, But Sometimes To The Fact That The Entire Population Was Started By A Single Pair Or By A Single Fertilized Female. These 'founders' Of The Population Carried With Them Only A Very Small Proportion Of The Variability Of The Parent Population. This 'founder' Principle Sometimes Explains Even The Uniformity Of Rather Large Populations, Particularly If They Are Well Isolated And Near The Borders Of The Range Of The Species.

Evolution Thus Is Merely Contingent On Certain Processes Articulated By Darwin: Variation And Selection.