Heredity has no definition other than mathematical tools used to measure it. Do you say statistics has the power to exclude environment's influence just because

Heredity has no definition other than mathematical tools used to measure it. Do you say statistics has the power to exclude environment's influence just because you made up some definition on the label of the measured variable? Specifically about the twin studies this has been heavily criticized from their outset. Already Flynn (of the famous Flynn effect of IQ increase over time) put out the requirements for proper control of such studies in his 1980 book. Nevertheless in 30 years of conducting new ones it appears none improved the methodology to control more carefully for environment and for culture. Just one facet of their invalidity: adoptive families have been found to be exceedingly intelligent with IQ over 120 on average, which is obviously different than general average (Stoolmiller in Psychol. Bull. 125:392-409).