help please. I wrote a mergesort algorithm that does nothing.

public class mb_Mergesort : MonoBehaviour {

 public int[] numbers = new int[7] {1,2,4,4,3,1,2};

 void Start () {
     for (int i = 0; i < numbers.Length; i++) {
         Instantiate (new Tile (numbers [i]).image, new Vector3 (i, 0, -1), Quaternion.identity);
     }
     Mergesort (numbers, 0, numbers.Length - 1);
     for (int i = 0; i < numbers.Length; i++) {
         Instantiate (new Tile (numbers [i]).image, new Vector3 (i, 2, -1), Quaternion.identity);
     }
 }

 void Mergesort(int[] input, int startIndex, int endIndex){
     int splitIndex;
     if (startIndex < endIndex) {
         splitIndex = (startIndex + endIndex) / 2;
         Mergesort (input, startIndex, splitIndex);
         Mergesort (input, splitIndex + 1, endIndex);
         Merge (input, startIndex, splitIndex, endIndex);
     }
 }

 void Merge(int [] input, int startIndex, int splitIndex, int endIndex){
     int[] duplicate = new int[input.Length];
     int leftPointer = startIndex;
     int rightPointer = splitIndex + 1;
     int duplicatePointer = startIndex;
     while (duplicatePointer <= endIndex) {
         if (leftPointer > splitIndex || rightPointer < leftPointer) {
             duplicate [duplicatePointer++] = input [rightPointer++];
         } else {
             duplicate [duplicatePointer++] = input [leftPointer++];
         }
     }
     duplicatePointer = startIndex;
     for (int i = startIndex; i < endIndex + 1; i++) {
         input [i] = duplicate [i];
     }
 }

}

when i run the code it just prints the original array twice. I'm running it through Unity which is why I have instantiate statements. I'm making an image of the number on the screen..