You need to learn better English. If you care to read the question again, you will realize that you did not answer the question. That's your style. We understand. No worries.
The key part of the question is "how" do we know? It does not imply that you cannot be female, or you and @steve are the same person, or otherwise. It is just a simple question of "how". The answer is, there is no way to know.