Many people in the 20th century assumed that the average citizen of the 21st century would be taller. However, a smaller (and for our purposes admittedly more entertaining) contingent assumed that advances in chemistry would breed hilariously super-sized babies. Having tipped the scales at ten pounds and ten ounces when I was born, it may be difficult to convince someone like my mother that this wasn't shockingly accurate; but we haven't quite reached Paul Bunyan proportions as a species just yet.
The article below from the November 21, 1937 issue of the San Antonio Light (San Antonio, TX) references the H.G. Wells novel The Food of the Gods. In the book, scientists create a chemical called "boomfood" which causes rats to expand to the size of ponies and makes people grow to be forty feet tall. The piece goes on to explain that Dr. Albert F. Blakeslee had created a new "elixir of growth" called colchicine which may bring about this super-sized world of the future. Of course, colchicine wasn't some magical elixir that would turn people to giants -- nor was it really even "created" by Dr. Blakeslee -- but it's certainly fun to think about what a world overrun with giant killer caterpillars might look like.