• Women can't do maths (like at all, their brains are tiny and incabable of abstract thought) It's in the nature!
• Men can't look after babies, they'd probably hold them by their heads or something! It's in their nature!
• Jews are only concerned with money, it's in their nature!
• Women lack the mental capabilites for politics and shouldn't be allowed to vote, it's in their nature.
• Women are very emotional, and hence are unsuitable for high pressure jobs (high level political leader, CEO, doctor, military commander), they'd just have some sort of emotional break down when the going gets tough, it's in their nature.
• etc. etc. (I haven't even touched on non-noble people, black people, LGBT people, catholics, prodestands, muslims, etc. etc.)
All of these things have been said about natural differences between various groups, mostly due to what we now realise as massive biases. When one says "men are naturally violent" or "women are naturally caring", the burden is on you to show how this time it's different, rather than it being just another (false) statement born out of bias. All these claims had some sort of evidence behind them. The burden is on you to come up with a standard of evidence that supports your biased claim, but doesn't show that women are incable of high office (say).