Millions of animals were killed with bows and arrows, atlatls, spears, and/or rocks before man ever heard of KE, FOC, etc. Terry recently had a thread on here about trad archery not being Popular Mechanics, and it is true. Most of us do this because it is challenging, but is also technically pretty simple. If you are into charts and graphs and tables, they are certainly there to be looked at, but the bottom line is Sharp Head+Stuck in Right Place=Meat On the Table. Pointy sticks kill efficiently when tipped with sharp blades placed strategically in an animal's boiler room.