Are you saying that indigenous people evolved here independently of African origins?
I follow anthropological matters in this area and there is no theory suggesting that. There is some debate as to whether indigenous people arrived up to 15 000 years ago as may suggest or up to 40 000 years ago as some new theories posit.
Let us also not pretend that all of the indigenous communities got along with each other in North and South America. There are suggestions that there were wars between communities before European settlers arrived. The challenge for anthropologists is that there is no recorded history because, apart from Mayans, the many other communities were illiterate and used stories. So, if one indigenous community wiped out another before Europeans arrived, it would largely have gone unnoticed.