I think you've highlighted something important. If we look at Africa as an example of blackness then we will see the massive variety in physical characteristics and skin tones. Black people as I've said before are not monolithic exhibiting the same features and behaviours.
I think because of the great variety in those who are considered black the initial constructed boxes or race are becoming harder to define. When I look at my black friends who vary in shade and features I think to myself what makes us black? it certainly isn't culture because to suggest that black people have the same culture makes the assumption they were raised in the same environment.
I look at my friends high cheekbones, low cheekbones, dark and light skin, coloured eyes (yes, and this individual is not of mixed "race"
, and I say to myself what is blackness?
I think blackness is defined by society, you don't look like white skinned people (although some black people do) so you are black. But its weird, because we're all part of the same species- we can reproduce and have fertile offspring (A level biology thankyou) but seriously, why the need to stratify and organise us in certain catergories which lead to obvious discrimination. At the same time, people define your blackness on how you behave- you act white, you act black- which in itself are disgusting statements propagating negative stereotypes and attributing what is considered good behaviour to white people only.
Some regard blackness as living a shared experience- that is why some Asian people identify as politically black. I am not sure of this because the experience of oppression varies between ethnic minorities- the experience is not shared entirely and there is anti- blackness in Asian communities.
I think its a very interesting topic.