Our conscious experience exists. In fact, it's the only thing you can directly observe, as everything about reality and how we perceive it is filtered through how our brains process stimuli and information. You are the only one who can define who and what you are.

Don't get me wrong, I am a materialist who believes the universe exists in the absence of beings who can observe it from an intelligence standpoint, but we are all collections of atoms, our function governed by chemical processes, not perfectly replicated by the process of birth.

Our means of DNA replication is imprecise because of billions of years of random evolution. We are on one branch of many, and there is countless variation in how all living beings are formed, and how we classify traits of those creatures, including sex and reproduction methods.

It would be an error to say that people who are intersex and/or transgender are the results of mistakes or errors in reproduction, because it implies DNA is "trying" to create a binary model of people and sometimes gets it wrong. It doesn't "try" to do anything; DNA != conscious.

Rather, our biological blueprints are not precise, and this is true for all living things. We can crossbreed plants and animals because of that imprecise nature, it's responsible for what we perceive as the "races" of people, etc. We can observe variation everywhere.