Edit: this question has been answered now. Thank you to everyone who took the time to help me understand.
the premise that race is not a natural, biologically grounded feature of physically distinct subgroups of human beings but a socially constructed (culturally invented) category that is used to oppress and exploit people of colour.
Okay… But we can take a DNA test and get our ancestry, telling us what percentage of what races make up our overall ethnicity. So how is race a social construct and not a biological feature, when we have a scientific method to determine our race? This part of the philosophy has been bothering me ever since I read it, and I’ve been hesitant to ask because of how offensive people get when you question this system.
The social construct of race is which features we consider important enough by which to categorise people. So in the USA, this is white, black, asian or hispanic. Maybe native. Those categorisations are based on real observable traits, but we could choose other categorisations. It notably groups together traits which we can easily distinguish and pull out as subdivisions, such as south-east Asians.
We could redraw these groupings: we could for example together north Africans, middle-easterners and Indians, separating out those from southern and central Africa. We could separate Europeans so that Scandinavians, Finns and Slavs are together, separately from western and southern Europeans.