There is a statistically average condition, but each variant is as real as any other and there is no ideal condition. This concept of type is unfortunately still very much part of racial thinking and has no place in modern biology. Darwin realized that this natural variation led to differential survival based on that variation. Heredity of most features 2. Heritable Variation in the population 3.
Variation leads to differential rates in survival and reproductive success among the variations.
Differential survival and reproduction leads to a shift in the frequency of characters, leading to a shifting of mode within the species. If this process goes on long enough, parent and daughter species can no longer interbreed. 1. microevolution 2. As an aside, it is worth noting that Darwin initially regarded the fossil record as a bit of an embarrassment. In 1859, there were no fossil intermediate forms known between major groups from the fossil record.