By comparing the performance of identical twins, who share the same genes, with that of fraternal twins, who on average share about half their genes, researchers were able to determine which skills were linked primarily to genetics and which could be attributed primarily to environment.
(identical twins; share; the same genes) (researchers; were; able to determine which skills were linked primarily to genetics and which could be attributed primarily to environment) (researchers; to determine; which skills were linked primarily to genetics and which could be attributed primarily to environment)
identical twins researchers researchers
share were to determine
the same genes
able to determine which skills were linked primarily to genetics and which could be attributed primarily to environment
which skills were linked primarily to genetics and which could be attributed primarily to environment