Race is definitely real, how a society chooses to divide/group people will vary but there are very real biological differences between different groups.
To say it’s man made is obviously false and just because people of the same race historically never aligned with each other that doesn’t prove race doesn’t exist. Somalis were slaughtering each other over pastures for god knows how long, Afars too. Are rival Somali clans not Somali now? Because they killed each other they’re not the same people anymore? Of course not, they are still the same folk and it would be silly to argue otherwise. Habeshis fight each other, are Tigrayans and Tigrinya Eritreans not the same race?
Also you are just plain wrong many Europeans despite not liking each other did feel kinship with one another on the basis of racial similarities. And the idea that no sub Saharan Africans considered themselves black is also another lie many of them did.