According to a recent National Geographic article on twins, 75% of your intelligence is derived from your genes.
Eugenics is considered immoral today, even though there more evidence than ever before that the science behind eugenics is correct. It says many good things about society today that, even with today's scientific knowledge on the role of genes, we still believe it to be immoral.
Here UBS a quote about the importance of twin studies.
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We forget that 50 years ago things like alcoholism and heart disease were thought to be caused entirely by lifestyle. Schizophrenia was thought to be due to poor mothering. Twin studies have allowed us to be more reflective about what people are born with and what's caused by experience."
