Biology is just messy
Some traits, such as adult height, are readily measured. The heritability of this trait is ∼60 to 80%. Attempts to characterize “height genes” have resulted in the identification of tens of thousands of genes, each of which contributes a small amount to this heritability. The plethora of factors is almost inevitable, given the vast number of cellular and physiological steps involved in the development of an adult human being. A model that accounts for ∼40% of height variability predicts individual heights to within 4 cm for 50% of people, but with errors of more than 10 cm for 5%. Thus, a sophisticated genomic analysis can predict height to some extent, but not well enough for use in ordering tailored clothing. Most direct-to-consumer genomic results are based on much less detailed analyses and many involve complex traits, so considerable skepticism is appropriate.
But such sensible comments, will not stem the hype — or the investors.
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