Sorry but you are wrong. The AR15 is not nor was it ever a direct descendant of military design. It was a completely fresh start design with using lighter composit materials and smaller caliber projectile. It was originaly made for commercial purposes not military. It wasn't until Colt obtained the rights that it transitioned to military status and was standardized as the M16.
Shooter's Bible: Guide to AR-15: According to Ezell, however, the leaders intrigued by the AR-10's design included CONARC's commander, Gen. Willard G. Wyman. In 1957, Wyman personally asked Stoner to design a 5.56mm rifle for the Army similar to the AR-10. That scaled-down rifle would go on to become the AR-15. Wiki: The first confrontations between the AK-47 and the M14 came in the early part of the Vietnam War. Battlefield reports indicated that the M14 was uncontrollable in full-auto and that soldiers could not carry enough ammo to maintain fire superiority over the AK-47.[28][31] And, while the M2 Carbine offered a high rate of fire, it was under-powered and ultimately outclassed by the AK-47.[32] A replacement was needed: A medium between the traditional preference for high-powered rifles such as the M14, and the lightweight firepower of the M2 Carbine. As a result, the Army was forced to reconsider a 1957 request by General Willard G. Wyman, commander of the U.S. Continental Army Command (CONARC) to develop a .223 caliber (5.56 mm) select-fire rifle weighing 6 lb (2.7 kg) when loaded with a 20-round magazine.[8] The 5.56mm round had to penetrate a standard U.S. helmet at 500 yards (460 meters) and retain a velocity in excess of the speed of sound, while matching or exceeding the wounding ability of the .30 Carbine cartridge.[33] This request ultimately resulted in the development of a scaled-down version of the Armalite AR-10, called ArmaLite AR-15 rifle.
Because there is nothing inherent to the design of that weapon that increases its effectiveness against strictly human targets. Dumbass
So it was designed as a direct result of the M14 being inferior to the AK47's wielded by _______? Dogs? Trees? Sport targets?
What makes this weapon better suited to shooting humans instead of horses/dogs/tin cans/watermelons/flying spaghetti monsters? The weapon was designed to be more versatile and easily handled. It is no more lethal, and in fact with 5.56 NATO rounds, it is significantly LESS lethal than any number of weapons. Keep digging, short bus