Factual error: Fitch, who professes qualifications in biology, genetics and biochemistry, says that they made Sil female because she's a natural predator and so she'd be more docile. He should retake his finals. In every single species of predator on earth - every single one - the females are the hunters, aggressors and killers. The males may be socially dominant but they are the 'docile' ones. There are no exceptions - and no human DNA was used to create Sil - they used synthetic DNA based on the instructions transmitted to them.
Other mistake: It's impossible for Sil to wear the conductor's clothes. She's tall and slim around maybe 5'9" while the conductor looks to be 5'5"or so and a little chubby.
Suggested correction: It's not "impossible" in the slightest. Both women were roughly the same height. Natasha Henstridge is about 5'10" and Esther Williams was usually listed around 5'9" or 5'10" before she passed away. And the weight difference also makes sense, as the clothes look baggy and ill-fitting on Sil. (Ex. The jacket is very loose and hanging around her shoulders and arms, and the shirt isn't nearly as form-fitting as it was on the conductor.) It's pretty much perfectly portrayed in the film.
Suggested correction: They never said Sil was a natural predator when they created her. She was half human and half alien and it was their belief that human females are more docile (i.e. more motherly, more gentle, more empathetic, and less aggressive than human males). Although the reply to "more docile and controllable" was "you guys don't get out much", meaning that girls aren't that docile and controllable.
Bishop73