Because of evolution/population bottlenecks, humans have a very low level of genetic diversity, more in line with a population of fewer than 20,000 breeding individuals. This is well known, and is not a new conclusion

Data from this conference paper which cites multiple studies http://www.understandingrace.org/resources/pdf/myth_reality/long.pdf --- > One clear signal from our genome is that the level of diversity is at odds with the large number of people living today. In fact, it is more in line with a population of fewer than 20,000 breeding individuals. This is not a new conclusion. The nucleotide sequences and STRs discussed here (68) agree with findings from many studies and for many other types of genetic data (1, 19, 24, 31, 36, 41, 44, 46, 47, 60, 69, 71). > > Another robust finding is that the genetic diversity in people outside of Sub-Saharan Africa is for the most part a subset of that found in Sub-Saharan Africans. The STR data confirm that the predominant genetic diversity pattern among populations is one of nested subsets. This pattern is consistent with a model that postulates a succession of ancient founder effects and bottlenecks that occurred as the human species expanded its range and occupied new continents (47). We have this [Venn Diagram from the paper showing the relationship](https://i.imgur.com/WDPlG2u.png) --- > It therefore appears that the vast store of genetic variation shared by all humans owes to the fact that all humans trace back to a common source population that existed recently on an evolutionary time scale. Moreover, the existing patterns of local gene flow have not persisted long enough to reshape the genetic structure of our species