In the article, Growth Spurt for Height Genetics by Jocelyn Kaiser, she describes the impact genetics plays in people's height. Studies of fraternal and identical twins show that 80% of their variation in height is genetic. However, data from more 4 million people from 200 studies by the genomewide association (GWA) shows that genetics has less of an impact in the general population than the twin populations studied. These studies show that genetics alone is only responsible for 40-50% of the variability in the population. They also show that common variants make up most of these differences. This didn't explain why genetics were more important in twins' height though. Peter Visscher suggested that the extra 30% came from rare variants that twins would be more likely to share than two people in the general population would. I thought this was interesting because we only know the DNA makers responsible for our differences in height, not the actual genes yet. Also, I always assumed height was almost all genetic, I didn't know that environmental factors had such a big impact on our height.