def sortedbyAge(self):
		'''
		Sorting the pop. base of the age
		'''
		ageAll = numpy.zeros(self.length)
		for i in range(self.length):
			ageAll[i] = self.Ind[i].age
		ageSorted = ageAll.argsort()
		return ageSorted[::-1]
Sorting the pop. base of the age