This might be true for a lot of species but doesn't apply to humans for a number of reasons. Overall, humanity has extremely low genetic diversity due to the species almost dying out tens of thousands of years ago (potentially down to a very small number of people), and that humanity had a desire to travel all across the globe and communicate with others (clearly a useful quality, as many species similar to humans died out because of staying put in the same place).

We can tell that race is almost entirely a social construct because the idea of it didn't exist before slavery was first questioned, and was used as a means to justify it, backed by pseudoscience like "race science". Before this, ethnicity was only based on things like which gods people worshipped, the food they ate, or the languages they spoke, and travelling between different places would affect which gods people worshipped, which makes sense since ethnicity is derived from culture, with culture being derived from geography and population.