public long age(final long currentGeneration) {
		return currentGeneration - _generation;
	}
Return the age of this phenotype depending on the given current generation.

@see #generation()

@param currentGeneration the current generation evaluated by the GA.
@return the age of this phenotype:
         {@code currentGeneration - this.getGeneration()}.
jenetics/src/main/java/io/jenetics/Phenotype.java