Every human being, after the first few days of his life, is a product of two factors: on the one hand, there is his __________ endowment; and on the other hand, there is the effect of environment, including _________

There is a clear-cut contrast in the sentence which is clear from the presence of the phrases 'on the one hand' and 'on the other hand'. The word in the first blank has to be connected with something that is present at the time of birth - thus 'congenital'. However, the effect of the environment qualifies 'education'.