Can it be within human nature to be inhumane? Conversely can it be "unhuman" or going against human nature to be genuinely humane?

You're probably just getting hung up on the root word behind humane and inhumane. Humans do inhumane and humane things constantly every day, regardless of whether they do those things directly to a human or not, under the right brain chemistry and external conditions we're capable of it all, good and bad.

human nature doesn't dictate what is humane. Humane morals that we are taught to function as a society dictate that. I'm sure there are vegans that legit think people are monsters for eating meat. If we were all taught for the last 5000 years eating meat was wrong and a random person murders an animal and eats it, pretty sure we would all consider it an atrocity like we would if it was done to person and not a chicken.

I'd put every characteristic in big air quotes. Especially 'human nature'. There's too much relative variables to conclude any result.

I'd say of what people usually call humane acts, many of them include some attention, sacrifice or effort 'to make things right'.

If that's not the norm across us, humans, I guess it's not a 'human nature'.

Being inhumane is almost exclusively the realm of humans, so yes; it can be within human nature to be inhumane.

I think the terms you're looking for are narcissism and empathy. Narcissism is the inhumanity, empathy the humanity. Can a narcissist have empathy, and vise versa? I can't say I've ever heard of an empathist, having too much empathy.

The Range of human nature is equal to the range of human imagination. Anything you as an individual human can imagine is well within the range.

There is no definitive "human nature", so I would say it is in some individuals nature to be inhumane.

The term “human nature” has two uses: it can be normative or descriptive. Your answer will depend on which one you intend.

Inspiring Philosophy lays out the whole issue here: https://www.youtube.com/watch?v=Ei0gPoqx_bQ

I know it's age-blocked due to some of the content, so if anyone knows where to find the youtube-alternative link that would be awesome.

i think the piece youre missing is that humans uniquely (and theoretically) have a choice that other animals do not. we do not have to be the animal... the instinct... we can choose the humanity. not that we always do, we often act inhumane, but at least we have the option.

Humane is a word designed to chastise people based on human societal morality. Humans evolved as a social cooperative species, and in a cooperative environment, selfish and exploitative entities are a drawback to others.

However, being selfish and exploitative of others is extremely useful for the entity behaving that way, as long as it is not ejected from that group.

The word humane is an expression of that ejection. Kindness, compassion and benevolence are good in a cooperative environment and benefit others and the whole group, thus we would like everyone around us to be "humane". Labeling this behavior "humane", good, and making the opposite, "inhumane" a very bad thing, serves to ensure these behaviors across a group of people based on societal pressure, thus making it more likely that people in general try to act humanely (or at least appear to).

Ultimately, every biological organism is entirely selfish, only "interested" (not in an actual conscious motivation kind of way, but in the total way they are built) in propagating its genetic material. Theoretically, in a cooperative context, the optimal way to achieve this is by taking resources from others all the time, giving nothing back, but having everyone else actually give. Obviously, that is not sustainable, since the giving entities will notice this behavior and thus stop their giving of resources. The result of that is a balance between selfish and altruistic behavior.

And thus follows, of course we all behave humanely and inhumanely. We are selfish and altruistic, some more this other more that. So yes, both behaviors are completely within human nature, the labeling of "humane" (i.e. someone who doesn't act humanely is disgusting, not even a human) is an extension of this struggle of getting everyone to behave altruistically, while selfishness exploiting that altruism is not a bad strategy.