Dr. Clarke was a very brilliant brother, but in this particular case he was WRONG.
He literally contradicted himself by saying that there was no such thing as race THEN went on to talk about how man invented races and racial classifications!!!!
According to the Cambridge dictionary, race DOES exist:
race noun (PEOPLE)
C1 [ C ]
one of the main groups to which people are often considered to belong, based on physical characteristics that they are perceived to share such as skin color, eye shape, etc.:
People of many different races were living side by side
RACE | definition in the Cambridge English Dictionary
That entry from the dictionary is clear proof of the existence of not only race but MULTIPLE races as a way of categorizing people.
If it didn't exist, there would be no need to define it.