The average size of Americans today is much greater than the size of humans 100 years ago. A visit to any museum, or visits by Americans to any third world country, will easily confirm this. This is a clear case of adaptation to evironment (plentiful food supply), suggesting that at least one hypothesis based on Darwin's theory is true.
Please verify, through rigorous scientific method, that the theory put forth in Genesis is the correct one. By this I mean that the order and timing of creation occurred as it says it did in Genesis.
The Vietnamese Boat People.
Entering our country in the 70's and later with young children in tow, the children's change in diet later caused higher than normal birth weights for the next generation born in the USA. As such, it was necessary for birth to be by C-section since their hip girdle was too small for the greater size of the babies.
It appears that the second and third generation born in the USA may now have larger hip girdles for passing larger babies and C-section is not as common.
Read about the first part around 1980 and more in the later 90's.
Your point is correct, but your example is flawed. The changes in size among humans in the last century are attributable to improved diet.
A better example--unarguable to a creationist--is the genetic size difference between pygmies and bantus, which has ostensibly developed in the 4000-or-so years since Noah's flood.