Gender Identity

Cerebral activity results in a subjective experience of identity, a conscious process of unity, of being oneself in time and space. This experience, which could also be called the Self, has a sex and a gender. This is so because consciousness is formed from the perception of our body and its relationship with space and with other bodies. But the body is not perceived and self-represented in our mind with a neutral form, but with all of its physical attributes, among which the genitals are very important. That is, our identity has a sex and a gender.
The gendered self is nuclear to understanding our nature. It is not just another function among others, it is the genesis of all our behavior, giving it a unity and coherence within our environment. It is the self that endures throughout life. We believe one cannot speak of this identity, the self, without referring to sex and to gender.
This book examines binary (1) gender identity expressed by the consciousness of being a man or a woman, as defined by Stoller in the middle of the last century, and it has two objectives. The first is providing a comprehensive view of the genetic and hormonal bases at work in the generation of our gender identity, and the second presents a model about the participation of cerebral cortex sexual differentiation in the development of gender identity. In summary, for binary people, we propose that sexual differentiation prepares a brain, and, in interdependence with the environment, establishes a gender identity as man or as woman, whether cis- or transgender. As we shall see, the theory is supported by a substantial number of already-published molecular genetics and neuroimaging studies. But there are no dogmas in science and theories are only considered valid while they are not falsified.
As we shall see throughout this book, it is highly improbable that the formation of gender identity lacks a strong biological foundation. In sexually reproducing species, including humans, sexual differentiation of the organism — encompassing gonadal, hormonal, and neural development — constitutes a fundamental aspect of biological organization. This differentiation shapes not only morphology but also patterns of brain development that underlie self-representation and social interaction. Consequently, the emergence of gender identity must be understood within the broader framework of sexual differentiation of the organism, including the brain. As we shall also see, morphological sexual differences are associated with distinct cerebral endophenotypes linked to gender identity.
This affirmation does not mean that the genesis of gender identity is not related to environmental influences. As can be deduced from the following chapters, gender identity is the consequence of the intervention by genetic, epigenetic and hormonal mechanisms. During cerebral differentiation, sexual differentiation has three periods: prenatal life, the early postnatal period and puberty. Differentiation, a process that depends on hundreds of functions and can be influenced by environmental stimuli, is inherently variable at morphological, physiological, and behavioral levels. But what purpose would a sexually differentiated brain serve if there were no models in its environment for it to recognize itself in and align with?
This book is not trying to explain what gender identity is in transgender people as if we already understood what it is in cisgender people. The strategy we have followe...