Many Western countries experienced better health, nutrition, and hygiene in the last century. One of the effects is height. The Europeans are 10 cm higher than their ancestors on average. If you look for a better gene, height is one of the cues. But, of course, not only one.
What makes this research great: This is unique research because: (1) it covers more than hundred years of data, (2) it covers not only one country but 9 countries, so we can compare between countries.