I feel like there is enough research now to prove this. It is pretty clear when you look at the skull morphology of the earliest skulls found in the America's.

For example, the Yotzin skull was just recently discovered and has features reminiscent of ancient Australian aboriginals. The same can be said for the Naia woman, Luzia woman skull and the other Lagoa Santa skeletons. All these skulls have features similar to Australian aboriginals, and all date back to a similar period (10-13 KYA). The same can be said for Kennewick man, whom also has morphological traits that are quite different than modern Indians. I can continue with other examples, such as the Angeles Mesa skulls found in California which look extremely similar to the recently found skull in Yotzin. There is the Penon woman, the Metro man, the Chimalhuacan man. All of these paleo-indian skulls are similar to one another, but quite different from the skulls of modern Amerindians. The Kennewick man and other ancient skulls found in what is now modern USA and Canada even look different than the other ancient skulls found in Mexico and south of that (but all similar within that area). They look more Polynesian/Caucasian. This could mean there are three separate migration waves into the America's in ancient times, all within a few thousand years.

These were likely the pre-clovis people which were absorbed by the second (or third) migration of peoples into the America's which came later after the ice sheets melted and opened a corridor from Beringia. The pre-clovis, negroid-polynesian looking people came before that but were replaced by the mongoloids.

The reason the genetic studies link these people to modern Indians is because they are still technically ancestral, but that is because of the absorption into the mongoloid wave which came later. The Australasian signal can still be found in some Amazonian tribes, which happens to be where the Australian Aboriginal looking Lagoa Santa skulls were found.