I've seen it (incorrectly) described before that native Americans were practically clones from a genetic perspective, so it's a relatively mild strawman. Found

I've seen it (incorrectly) described before that native Americans were practically clones from a genetic perspective, so it's a relatively mild strawman. Founder effects did reduce genetic diversity of native Americans and it takes a long time to rebuild that. We actually use this to track historical migrations. It's also worth pointing out that a very similar process affected everyone outside Africa. That's why the sharpest dropoff in genetic diversity is between Africa and everywhere else. Not all diversity is equal or generates at the same rate either and the highest diversity genes tend to be the ones related to disease resistance /immune system functioning. Native Americans actually have several new alleles here that apparently evolved independently in the new world. When you talk about specific things like the MHC, they're still quite diverse and not too far off from similar European populations.