Eugene Shubert
Valued Senior Member
As described by Scott Freeman and Jon C. Herron (2004), Evolutionary Analysis 4th Edition, Darwin's theory rests on four postulates:
Does common descent follow logically from Darwin's four postulates or is common descent a logically independent fifth postulate?The postulates, which apply to populations of organisms, are as follows:
If these four postulates are true, then the composition of the population changes from one generation to the next. The logic is clear: If there are differences among the individuals in a population that can be passed on to offspring, and if there is differential success among those individuals in surviving and/or reproducing, then some traits will be passed on more frequently than others. As a result, the characteristics of the population will change slightly with each succeeding generation. This is Darwinian evolution: gradual change in populations over time. (Freeman and Herron (2004) Evolutionary Analysis pp. 72-73).
- Individuals within populations are variable.
- The variations among individuals are, at least in part, passed from parents to offspring.
- In every generation, some individuals are more successful at surviving and reproducing than others.
- The survival and reproduction of individuals are not random; instead they are tied to the variation among individuals. The individuals with the most favorable variations, those who are better at surviving and reproducing, are naturally selected.