The literature I've read says hormones are "involved in the creation of the brain".
"Steroid hormones are a dominant and pervasive source of sex differences by mediating developmental processes that are enduring and establish adult physiological and behavioural responses relevant to the reproductive constraints of each sex."
From Multifaceted origins of sex differences in the brain, 1 February 2016, an open access article.
"Animal models have also allowed us to move beyond hormones and to an appreciation of the important role of sex chromosomes. Study of these mice has revealed important roles for chromosome complement on body weight and feeding, aggression and habit formation, to name a few."
And section 8:
"Some argue it is pure folly to study neuroanatomical sex differences with the hope of understanding sex differences in behaviour as the connection between anatomy and behaviour is often weak or even non-existent [50]. Indeed, the most celebrated sex difference in the brain, the SDN, has not been clearly tied to any specific behavioural or physiological endpoint, although see above discussion regarding sexual orientation. While it is true that anatomical or physiological differences in the brain often do not map onto clear differences in behaviour, does this mean they are not important or even, not real? Many studies of sex differences in brain anatomy or neural functioning are perfectly sound, meaning they are fully powered and technically executed using well vetted and accepted approaches, yet a strong correlation between variance in anatomy and variance in behaviour is about the best one can hope for in establishing a causal relationship."
I never said that hormones were the only influence, in fact I agree that genetics is also important.
Regarding behavior, and specifically the SDN, consider, for example:
The volume of a sexually dimorphic nucleus in the ovine medial preoptic area/anterior hypothalamus varies with sexual partner preference. Endocrinology. 2004
"In addition to a sex difference, we found that the volume of the oSDN was two times greater in female-oriented rams than in male-oriented rams."
Wired on steroids: sexual differentiation of the brain and its role in the expression of sexual partner preferences. Front Endocrinol (Lausanne). 2011
"Development of female-directed partner preference in the male is dependent on exposure of the developing brain to gonadal steroids synthesized during critical periods of sexual differentiation of the central nervous system"
The development of male-oriented behavior in rams. Front Neuroendocrinol. 2011
"Although our understanding of the biological determinants and underlying neural substrates of sexual attraction and mate selection are far from complete, compelling evidence is discussed that supports the idea that neural substrates regulating sexual partner preferences are organized during prenatal development"
"Steroid hormones are a dominant and pervasive source of sex differences by mediating developmental processes that are enduring and establish adult physiological and behavioural responses relevant to the reproductive constraints of each sex."
From Multifaceted origins of sex differences in the brain, 1 February 2016, an open access article.
http://rstb.royalsocietypublishing.org/content/371/1688/2015...