How race is a social construct: it was imposed as an idea for reasons that were not connected to physiological fact (although often claiming the contrary at the time, the claims were the same kind of made up BS as phrenology, another idea from the same time period).

There are biological correlations with inherited genetic lineage. That only has weak correlation with assigned race. Lots of different lineages of people are "black", Africa is big and diverse. Lots of different lineages of people are "white". But for example, if your lineage is from a malarial region, your chances of being a genetic sickle cell carrier are higher. Most people from those areas are dark skinned, so it correlates with being "black".

Also there's the impact of racism, which affects everything from nutrition to poverty to pollution exposure, and does so on an individual, a regional, and a national scale. And this has biological consequences.