I encourage you to read the wikipedia article on the settlement of the Americas, mostly because it's fun[0].
The landbridge theory has its supporters, but what's really interesting is the gaps in knowledge, and other theories about multiple waves of settlement, or settlement directly from seafaring peoples.
It's really just a fascinating mix of fields. You do yourself a disservice by reducing the settlement of the americas to 2 sentences like that.
I do believe the claim of less genetic diversity amongst indigenous Americans is correct. The excellent book "1491" even discusses how this could have contributed to the spread of disease: less genetic diversity meant less overall population protection.
The landbridge theory has its supporters, but what's really interesting is the gaps in knowledge, and other theories about multiple waves of settlement, or settlement directly from seafaring peoples.
It's really just a fascinating mix of fields. You do yourself a disservice by reducing the settlement of the americas to 2 sentences like that.
I do believe the claim of less genetic diversity amongst indigenous Americans is correct. The excellent book "1491" even discusses how this could have contributed to the spread of disease: less genetic diversity meant less overall population protection.
[0] https://en.wikipedia.org/wiki/Settlement_of_the_Americas