Sure there are. An easy example is Australian aboriginals. They were geographically isolated for tens of thousands of years. Their subgroups are more related to each other than to other subgroups.
That is one relatively isolated group. The existence of small isolated groups does not mean the whole species has a small number of distinct subgroups. The smallness here is intended to apply to the number of groups, with the size of the groups being correspondingly large.
The boundaries between groups may be blurred, but surely a person whose ancestors lived in location A for the last 10 thousand years will be genetically more similar om average to other people from that location than to people in location B on the other side of the planet.