I just happened upon this article that relates to our discussion. This is ca. 12,000 years ago:
“Soul Train Hypothesis?” AKA the “hippest trip to America”
What has not been considered here is panspermia. Interstellar transportation of early life to NA
is not out of the question. As evolution is in the habit of evolving, the growth to man having taken possibly billions of years could have happened in NA, from start till now. Panspermia could have been the kick start of a shorter or quicker version of our accent in our native lands.
Our family tree may have a unique branch from much further away than Asia, Europe or even aboriginal Africa.
Your contention is that two completely separate groups of humans evolved on earth while separated by oceans, and billions of years later they were just lucky to be almost exactly identical and to be able to successfully reproduce?
There’s a very good reason why it isn’t considered. It’s absurd and there’s no evidence to suggest it ever happened. It’s a new-age fantasy.
Actually, we have sufficient information to know that this did not happen. DNA mapping shows a continuous flow of minute changes originating in Africa and extending around the world. There is no abrupt leap in DNA from Eurasia or Africa to the Americas. Instead, we find the slow accumulation of differences steadily moving from Africa into Eurasia, then into Australia and Oceania and into the Americas. In addition, we have not found any fossil evidence of humanoid precursors in the Americas.
In the early 1950s, before we understood just how fundamental DNA is, we could entertain notions of polygenesis and a panspermian origin of that polygenesis could be conjectured. (Even then it was only a wild conjecture that had little to support it.)
However, ever since the discoveries of Crick, Watson, Wilkins, and Franklin the notion of polygenesis began to be shown to be less of a possibility until decades ago it finally lost any hope to be any more than a dead end branch of speculation.
It is, actually, based on all available evidence.
Much like Mr. Twain, you repeat yourself…
I would leave luck out of it but yes, that is my contention.
Thank you both tomndebb & Colibri for directing my thinking to more empirical thinking.
Can we rule panspermia out by saying there was no original life landing of alien bacteria-virus in Africa where man evolved from?
Jayjay, you, I, and the esteemed Mr. Twain, have been around here too long. 
I believe I read in 1491 by Charles Mann that there might have been peoples that migrated from Australia to South America 10’s of thousands of years ago. I no longer have that book. Is there any DNA to support this?
IANAAnthropologist, but I don’t believe so. Interestingly, Thor Heyerdahl showed that migration in the opposite direction (S. America to Easter Island and on to Polynesia) was possible, but that doesn’t mean it was accomplished, let alone common. Considering the difficult, extreme distances across the Pacific Ocean compared to the relatively easy coastal-following north-south routes, it seems far, far, far less likely.
Whether or not panspermia occurred, we can rule out separate colonization events on different continents. All life on Earth has a single origin, and certainly has not been evolving separately on different continents for billions of years. The continents themselves did not exist in their present form billions of years ago, and South America and Africa were part of the same continent as recently as 120 million years ago.
The idea is contradicted by everything we know about genetics, evolution, Earth history, and paleontology.
I’ve read speculation that these sites may be the resut of a single-event crossing from Australia. I do not believe there is evidence to support that, though.
Australia has been peopled for at least 40 000 years, and probably had at least three waves of migration. As the theory goes, the circumpolar current around the Antarctic is fast, stable, and would take someone lost at sea south of Australia pretty straight from Australia to South America. Such as crossing would be very hard to survive, but if you did, thats where you’d end up.
The late colonization of New Zealand argues against this theory.
After reading the great responses to this thread, I am inclined to believe that most of them were on the coast at the time and are now underwater and all traces are gone.
Here’s an article on some of the evidence. All of the evidence I am aware of is skeletal, which is more difficult to interpret than genetic data. To date, all the genetic evidence indicates the colonists of the Americas came from northeast Asia.
While Australoid-type peoples made it by boat to Australia, the Philippines and to the islands of Melanesia, you would think that if they were capable of reaching the Americas they would have left some evidence on the Polynesian islands in between. If Australoids did reach the Americas - which I consider possible - I think it would more likely to be by the coastal route later followed by the northeast Asian colonists.
There aren’t a lot of Polynesian islands between Australia and the Americas, and New Zealand doesn’t appear to be populated that early.
Native Americans share some teeth root thing with Asians. Both have four roots on a tooth that Europeans have two, as I recall. Do they share that with Polynesians?
I would like to mention the Beringia Isolation Hypothesis, just for the sheer coolness.