You can stick your head in the sand over what genetic testing tells us about the actual sexual behavior of men and women versus whatever rules they play lip service to, but, well, facts are facts, and the ancient Hebrews were as polygynous as any of their modern closely relate semitic descendants.
Science has proved that gender is based on the structures and chemical amounts in our brains, to put it simply. It’s not as cut and dry as this, but basically, transwomen actually have the brain patterns of ciswomen. It has little to do with genitals, however, most society sees the genitals and simply follows the strict gender binary where each gender must adhere to their peers in dress and mannerisms. And we did evolve, but transpeople (and even transgender-like behaviors in some animals) have been recorded since forever, so no one really knows when it started to happen regularly.