Generic List No Sense Problem

Hello, i was making my inventory system for my game and then i had a problem, i created a new script just to make some test i face this no-sense problem:

using UnityEngine;
    using System.Collections;
    using System.Collections.Generic;
    public class Test : MonoBehaviour {
        public List<Pig> johnPigList = new List<Pig>();
        public List<Pig> peterPigList = new List<Pig>();
    	void Start () {
            peterPigList = johnPigList;
    	void Update () {
            if (Input.GetKeyDown(KeyCode.G))
    public class Pig
        public int quantity;

ok, i have two generic lists, johnPigList and then peterPigList, at start peter list is equal to john list, thats ok, but then, when i change the quantity variable, the two list changes too, and this on my mind makes no sense because i defined that these two are equal in the start, so then they are two separed lists.

on line 12 you’re setting the reference of peterPigList to johnPigList, this doesn’t clone it just changes the reference (thus losing any reference to the previous peterPigList.

If you want to just clone the list an not change the reference use

peterPigList = new List<Pig>(johnPigList);