The single genetic variant identified that most powerfully predicted height explained all of 0.4 percent--four tenths of one percent--of the variation in height, and all those hundreds of variants put together explained only about 10 percent of the variation. Meanwhile, an equally acclaimed study did a GWAS regarding body mass index (BMI). Similar amazingness--almost a quarter million genomes examined, even more authors than the height study. And in this case the single most explanatory genetic variant identified accounted for only 0.3 percent of the variation in BMI.