WASHINGTON, April 21 (UPI) -- When it comes to the evolution of weapons, designers make things bigger when they can't think of anything else to do with them.

As is the case with animal and human species, very often specialized groups start small and as they prosper, they get bigger. Irish boxers from their home island of Ireland dominated the flyweight and bantamweight divisions for decades in the mid-20th century.

But Irish-American boxers tended to do best in the heavyweight division as early as the time of John S. Sullivan more than a century ago. When the Irish migrated to America, over the generations, they became more prosperous and successful and consequently, a lot bigger.

The same evolutionary principle -- that success begets bigger size, can be seen in a whole host of land, sea and air weapons systems. Today's nuclear powered U.S. super-aircraft carriers dwarf the highly successful -- and in their own day, breathtakingly large -- Essex-class carriers that ruled the Pacific Ocean during World War II.

Modern Main Battle Tanks like the U.S. Abrams M12A and the Russian T-90S dwarf most of their World War II evolutionary grandfathers. The famous World War II single engine, propeller-driven fighters like the British Supermarine Spitfire, the U.S. North American P-51 Mustang, the Yakovlev Yak-3 fighter and the German Messerschmitt Me-109 or Focke Wulf-190 would be dwarfed in size, as well as outclassed in speed and firepower, by a modern F-22 raptor, F-35 Lightning II or Russian Sukhoi Su-30 or MiG-29.