While football players have gotten bigger, stronger, and faster in general over the last few decades, the variety of body shapes in the league is actually higher than it has ever been.

Journalist Noah Veltman made a great visualization of how NFL body sizes have changed over time. Notice how the spread of types has gotten larger and the density of specified height-and-weight combinations has gotten lower:

In 1920, most players were roughly the same size. While they continued to get taller and larger over the years, that relative lack of variation in body type stayed around until the late 1970s — when the league began to rise in popularity and player salaries skyrocketed.

By 2014, we are firmly in the era of specialization. Ideal body types for each position have evolved as the sport grew and the financial incentive to find better players exploded. Offensive lineman are now tall and heavy. Cornerbacks are short and light. Wide receivers are tall and light. Different positions serve dramatically different purposes on the football field, so naturally each position has its own specialized type.

The most dramatic change since the 1980s is the rise of the jumbo lineman. Now, the cluster of players who are at least 6'3" tall and 300 pounds is one of the most popular body types.

That player didn't exist in 1980:

To this 34 years later: