Small animals tend to live shorter lives than larger animals. There are a few theories as to why that is, but the one I believe is most popular is: small animals tend to live shorter lives anyway (because of threats from predators), so there are fewer opportunities to evolve to be long-lived.
The American National Standards Institute (ANSI) Class 150 is a system of dimensional standards for weld neck, threaded, slip-on, lap joint, socket weld and blind flanges. Dimensions for facing, bolts and studs are also included in ANSI Class 150. ANSI Class 150 establishes measures for pipe sizes.
ANSI (American National Standards Institute) defined a regular series of paper sizes based around the Letter (8.5 x 11) format, with this becoming the A sizes and larger sizes being B,C,D & E. Surprisingly these ANSI standard sizes were defined in 1995 well after the ISO standard sizes.