So lets look at the evidence:
OUTLIER DATE:
This site is an outlier among archaeological sites in terms of the date. The date given for Californians according to this research is 130 000 year ago.
As far as I am aware, the earliest recorded human site outside of Africa is one in China 120 000 years ago.
And even that site is an outlier because human migration into the middle east began happening 120 000 -100 000 years ago, 60 000 years ago into Asia, and and 45 000 years into Europe.
Now that in itself is not conclusive, maybe there are older sites that we haven't found and this discovery pushes back human migration. Except there are other problems here.
LACK OF HUMAN REMAINS OR HUMAN ARTIFACTS
So the scientists say the rocks have markings that look like they had been used as a hammer and anvil and there are some mastodon bones near it.
Now no actual human bones were found near this site. Which is certainly not impossible for these kinds of sites. More problematic is that there were no obvious stone tools other than rocks with markings that look like they'd been hit.
With ancient humans, especially ones capable of hunting mastodons, you would expect them to make sharp stone points by flaking (hiting one stone against another). This should leave flakes and tools on the ground. Yet, at this site, there were no stone tools of this sort found anywhere at this site.
LACK OF CUT MARKINGS ON BONES
Further, once ancient humans killed the mastodon, you would expect them to cut pieces of flesh off with a stone knife so that it could be eaten. This process would leave marks on the bones where the flesh had been cut. The article tells us that no such markings were found on these bones.
> Yet there were no cut marks on the bones showing that the animal was butchered for meat.
AVAILABILITY OF ALTERNATIVE EXPLANATIONS
None of these factors itself is fatal, but all three combined, the outlier date (way to early considering the mainstream evidence shows that our species were just getting set up in the middle east at this time,) the absence of human tools nearby, the absence of cut marks on the bones, the absence of any human skeletons or remains in the area. All of these lead me to think there must be another explanation.
It's not impossible that the bones of dead mastodons can get trampled or broken. Under the right circumstances, it's not impossible that trampling can cause rocks to smash against one another or leave marks on the rock. Maybe there was a cliff in the area many years ago and the bones and the rocks took a deep fall. In any event, there are alternative explanations and it is not inconceivable that this happened through natural means. This is hardly smoking gun evidence of human in California 130 000 years ago.
USE OF WEAK EXPLANATORY MECHANISMS
And I think the weakness of this evidence is belied by the unusual explanatory leaps made by the discoverers. When pointed out that there is no evidence that the remains had been butchered for meat, he responds:
"The suggestion is that this site is strictly for breaking bone, to produce blank material, raw material to make bone tools or to extract marrow." Seriously? Why would they break bones without butchering the meat and eating it? Why would you have a separate site just for bone marrow? That makes no sense.
EVIDENCE THAT IS ANYTHING BUT CLEAR LABELED AS CLEAR
>He says the rocks showed clear marks of having been used as hammers and an anvil.
Really, I mean they have pictures of the rocks on the site. It doesn't seem that clear to me that they were hammer and anvil stones. Are they clear to anyone else? They could just easily be old worn rocks. I would expect humans that could make it from Africa or wherever all the way to California 130 000 years ago to be somewhat advanced enough that they have tools more advanced than just two random pieces of rock to bang together. This was the age where humans had started molding rocks for suited purposes by flaking them. Why they would just use two natural rocks instead of created rocks is questionable. If you type in acheulean tools into google, you can see the sophisticated flaked tools (sharp looking leaf shaped blades) our ancestors were making 1.7 million years ago . . . yet ones that traveled all the way to California and kill mastodons are still stuck banging random un-molded rocks against each other for marrow- why?
I have nothing against pushing back migration to Americas, but this site is probably more wishful thinking on part of its founders than legitimate discovery.