diff --git a/Runtime/Scripts/Core/Cluster.cs b/Runtime/Scripts/Core/Cluster.cs
index e516491..3f8275e 100644
--- a/Runtime/Scripts/Core/Cluster.cs
+++ b/Runtime/Scripts/Core/Cluster.cs
@@ -564,28 +564,6 @@ namespace NanoBrain {
             return allInstances;
         }
 
-        // public void Backpropagation(Func<Cluster, float> Observer, float target, float learningRate) {
-        //     foreach (Nucleus nucleus in this.instances[0].nuclei) {
-        //         if (nucleus is not Neuron neuron)
-        //             continue;
-
-        //         foreach (Synapse synapse in neuron.synapses) {
-        //             List<Neuron> allSynapseNeurons = GetAllInstances(synapse.neuron);
-
-        //             Vector3 dSSRdW = Vector3.zero;
-        //             for (int clusterIx = 0; clusterIx < this.instances.Length; clusterIx++) {
-        //                 Cluster clusterInstance = this.instances[clusterIx];
-        //                 Neuron neuronInstance = allSynapseNeurons[clusterIx];
-
-        //                 // Simple case, without receivers...
-        //                 dSSRdW += (Vector3)(-2 * (Observer(clusterInstance) - target) * neuronInstance.activation);
-        //             }
-        //             synapse.weight += learningRate * dSSRdW.magnitude;
-        //         }
-        //     }
-
-        // }
-
         #endregion ClusterArray
 
         /// <summary>
diff --git a/Runtime/Scripts/Core/Neuron.cs b/Runtime/Scripts/Core/Neuron.cs
index a528f4d..efb0594 100644
--- a/Runtime/Scripts/Core/Neuron.cs
+++ b/Runtime/Scripts/Core/Neuron.cs
@@ -807,6 +807,7 @@ namespace NanoBrain {
             this.lastUpdate = Time.time;
             this.bias = inputValue;
             this.parent?.UpdateFromNucleus(this);
+            this.resetStimulus ??= ResetStimulus;
 
             if (autoResetDelay > 0) {
                 long now = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds();
diff --git a/Runtime/Scripts/Core/Population.cs b/Runtime/Scripts/Core/Population.cs
new file mode 100644
index 0000000..29c3ced
--- /dev/null
+++ b/Runtime/Scripts/Core/Population.cs
@@ -0,0 +1,118 @@
+using System.Collections.Generic;
+using UnityEngine;
+
+namespace NanoBrain {
+    public class Population {
+        public class Member {
+            public Member(Cluster cluster) {
+                this.brain = cluster;
+                this.performance = 0;
+                this.initialized = true;
+            }
+            public Cluster brain;
+            public float performance;
+            public bool initialized;
+        }
+        public List<Member> members = new();
+
+        public Member AddMember(Cluster brain) {
+            Member newMember = new(brain);
+            this.members.Add(newMember);
+            return newMember;
+        }
+
+        /// <summary>
+        /// Generational update
+        /// </summary>
+        public virtual void Update() {
+
+        }
+
+        public void NewGeneration() {
+            foreach (Member member in this.members) {
+                member.initialized = false;
+            }
+        }
+
+        protected List<Member> SelectElite(float percentage) {
+            return SelectElite((int)(members.Count * percentage));
+        }
+        protected List<Member> SelectElite(int count) {
+            List<Member> selectedMembers = new();
+
+            SortMembers();
+            for (int i = 0; i < count; i++) {
+                Member member = this.members[i];
+                if (!member.initialized) {
+                    Debug.Log($"Selected {i}: {member.performance}");
+                    member.initialized = true;
+                    selectedMembers.Add(member);
+                }
+            }
+
+            return selectedMembers;
+        }
+
+        private void SortMembers() {
+            members.Sort((a, b) => a.performance.CompareTo(b.performance));
+        }
+
+        protected List<Member> GenerateMutants(List<Member> elite, float percentage) {
+            return GenerateMutants(elite, (int)(members.Count * percentage));
+        }
+        protected List<Member> GenerateMutants(List<Member> elite, int count) {
+            List<Member> selectedMembers = new();
+            int i = 0;
+            int n = 0;
+            while (n < count && i < this.members.Count) {
+                Member member = this.members[i];
+                if (member.initialized == false) {
+                    GenerateMutant(member, elite);
+                    member.initialized = true;
+                    n++;
+                    selectedMembers.Add(member);
+                }
+                i++;
+            }
+            return selectedMembers;
+        }
+
+        protected void GenerateMutant(Member member, List<Member> ants) {
+            System.Random randomGenerator = new();
+            int n = ants.Count;
+            int parent1 = randomGenerator.Next(0, n);
+            int parent2 = randomGenerator.Next(0, n);
+            Debug.Log($"Mutate from {members[parent1].performance} and {members[parent2].performance}");
+
+            member.brain.CopyWeightsFrom(ants[parent1].brain);
+            member.brain.ProcessWeightsFrom(ants[parent2].brain, Average);
+            member.brain.GaussianAdditiveMutation(1e-1f);
+        }
+
+        private static float Average(float a, float b) {
+            return (a + b) / 2;
+        }
+
+        protected List<Member> GenerateRandom() {
+            return GenerateRandom(int.MaxValue);
+        }
+
+        protected List<Member> GenerateRandom(int count) {
+            List<Member> selectedMembers = new();
+            int i = 0;
+            int n = 0;
+            while (n < count && i < this.members.Count) {
+                Member member = this.members[i];
+                if (member.initialized == false) {
+                    Debug.Log($"Randomized {i}: {member.performance}");
+                    member.brain.InitializeRandom();
+                    member.initialized = true;
+                    selectedMembers.Add(member);
+                    n++;
+                }
+                i++;
+            }
+            return selectedMembers;
+        }
+    }
+}
\ No newline at end of file
diff --git a/Runtime/Scripts/Core/Population.cs.meta b/Runtime/Scripts/Core/Population.cs.meta
new file mode 100644
index 0000000..2d9d7fa
--- /dev/null
+++ b/Runtime/Scripts/Core/Population.cs.meta
@@ -0,0 +1,11 @@
+fileFormatVersion: 2
+guid: a820ab88a63bed6e881dbb82eae0a824
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: