Yes, human beings are extremely diverse in abilities, in appearance, and many things. From this, you extrapolate that then gender must be along a spectrum. Do you apply this logic to, say, mortality? Do some people die, some people die a little bit, and some not die at all? Is there a "mortality spectrum," or is it binary? You're making a faulty generalization, concluding that if A, B, and C occur on spectrums, D must also be on a spectrum. Any evidence you might try to furnish will be from gender theorists, not biologists or neurologists.