Ok, I can see that, but it's pretty hard to argue we are actually evolving (a growing ability, as maxi said) into a morally better species considering the state of the world at the moment. Seems a bit over optimistic to me.
I'm not saying it's evolving in the sense you mean - that the entire species is somehow changing in any way.
the first thing I'm saying is that the moral structure that exists in our mind developed as part of human biology and is essentially the same for everyone as we are all the same species.
and the second thing is that when people then develop concepts such as human rights, that reflects those people's ability to understand that moral structure that already exists within everyone.
for example, to recognise that all human beings have an equal right to life and not just our own tribe. the people who recognise that are accessing (via reasoned arguments and moral philosophy - not a biological change) a preexisting moral structure in their minds. the people who disagree with that statement, I'm arguing, are failing to access the same moral structure to the same degree. but the moral structure in their minds is exactly the same i.e. they have the potential to reach the same position but are failing in their reasoning.
human rights is just a concept that attempts to define the inalienable moral rights that all human beings have. at the most basic level, I think we'd all agree that every person has a right not to be murdered for example. the right to life. and then everyone can argue over which other human rights exist, and which things described as "human rights" shouldn't be.
then human rights law is a way of enshrining the things we've decided are human rights into law. those laws can be written well or badly, which is a separate issue. and then they can be enforced or implemented well or badly, which is another separate issue.