Difference between the old and the new cryptokitties' geneScience smart contract

ck.diff

diff --git a/old.sol b/new.sol
index 0184107..1419bcd 100644
--- a/old.sol
+++ b/new.sol
@@ -1,16 +1,35 @@
 pragma solidity ^0.4.18;
 
-
+contract KittyCoreInterface {
+    function cooAddress() public returns(address);
+}
 
 /// @title GeneScience implements the trait calculation for new kitties
-/// @author Axiom Zen, Dieter Shirley <dete@axiomzen.co> (https://github.com/dete), Fabiano P. Soriani <fabianosoriani@gmail.com> (https://github.com/flockonus), Jordan Schalm <jordan.schalm@gmail.com> (https://github.com/jordanschalm)
+/// @author Axiom Zen, Dieter Shirley <dete@axiomzen.co> (https://github.com/dete), Fabiano P. Soriani <fabianosoriani@gmail.com> (https://github.com/flockonus), Jordan Schalm <jordan.schalm@gmail.com> (https://github.com/jordanschalm), Abhishek Chadha <abhishek@dapperlabs.com> (https://github.com/achadha235)
 contract GeneScience {
     bool public isGeneScience = true;
 
     uint256 internal constant maskLast8Bits = uint256(0xff);
     uint256 internal constant maskFirst248Bits = uint256(~0xff);
 
-    function GeneScience() public {}
+    // This is the privileged birther address. If this is set to 0, privileged birthing is disabled
+    address internal _privilegedBirther;
+    // Privileged window size for birthers, set to 5 blocks.
+    uint256 public privilegedBirtherWindowSize = 5;
+    KittyCoreInterface _kittyCore;
+
+    function GeneScience(address _privilegedBirtherAddress, address _kittyCoreAddress) public {
+        require(_kittyCoreAddress != address(0));
+        _kittyCore = KittyCoreInterface(_kittyCoreAddress);
+        _privilegedBirther = _privilegedBirtherAddress;
+    }
+
+    /// @dev set the privileged birther address
+    /// @param _birtherAddress the new birther address
+    function setPrivilegedBirther(address _birtherAddress) public {
+        require(msg.sender == _kittyCore.cooAddress());
+        _privilegedBirther = _birtherAddress;
+    }
 
     /// @dev given a characteristic and 2 genes (unsorted) - returns > 0 if the genes ascended, that's the value
     /// @param trait1 any trait of that characteristic
@@ -99,7 +118,14 @@ contract GeneScience {
 
     /// @dev the function as defined in the breeding contract - as defined in CK bible
     function mixGenes(uint256 _genes1, uint256 _genes2, uint256 _targetBlock) public returns (uint256) {
-        require(block.number > _targetBlock);
+        if (_privilegedBirther == address(0) || tx.origin == _privilegedBirther) {
+            // Allow immediate births if there is no privileged birther, or if the originator
+            // of the transaction is the privileged birther
+            require(block.number > _targetBlock);
+        } else {
+            require(block.number > _targetBlock + privilegedBirtherWindowSize);
+        }
+
 
         // Try to grab the hash of the "target block". This should be available the vast
         // majority of the time (it will only fail if no-one calls giveBirth() within 256