This is some groundbreaking news. The consensus had been that Siberians colonised the Americas around 15,000 to 14,000 years ago. This was not only supported by archaeology, but also but genetics, as the Q1a-M3 lineage of Native Americans was formed some 15,000 years ago. Pushing the date back to 33,000 years ago would mean that this first colonisation event, which reached as far south as Mexico, was conducted by a completely different group of people. Haplogroup Q did not even exist back then.

Evidence of human occupation in Mexico around the Last Glacial Maximum, Ardelean et al. (2020)


The initial colonization of the Americas remains a highly debated topic, and the exact timing of the first arrivals is unknown. The earliest archaeological record of Mexico—which holds a key geographical position in the Americas—is poorly known and understudied. Historically, the region has remained on the periphery of research focused on the first American populations. However, recent investigations provide reliable evidence of a human presence in the northwest region of Mexico, the Chiapas Highlands, Central Mexico and the Caribbean coast during the Late Pleistocene and Early Holocene epochs. Here we present results of recent excavations at Chiquihuite Cave—a high-altitude site in central-northern Mexico—that corroborate previous findings in the Americas of cultural evidence that dates to the Last Glacial Maximum (26,500–19,000 years ago), and which push back dates for human dispersal to the region possibly as early as 33,000–31,000 years ago. The site yielded about 1,900 stone artefacts within a 3-m-deep stratified sequence, revealing a previously unknown lithic industry that underwent only minor changes over millennia. More than 50 radiocarbon and luminescence dates provide chronological control, and genetic, palaeoenvironmental and chemical data document the changing environments in which the occupants lived. Our results provide new evidence for the antiquity of humans in the Americas, illustrate the cultural diversity of the earliest dispersal groups (which predate those of the Clovis culture) and open new directions of research.

Here is the BBC's article on the topic. They explain that the North America before the Last Glacial Maximum would not be a welcoming place. But neither was Siberia where the migrants originated.

Between 26,000-19,000 years ago, sea levels were low enough for people to cross easily from Siberia to America via the Beringian land bridge. But what about during earlier times?"Before 26,000 years ago, the latest data suggest that Beringia might have been a rather unattractive place for humans to be. It might well have been boggy and very difficult to traverse," said Prof Higham.
"We still think the most likely scenario is for people to have come on a coastal route - hugging a coast - perhaps with some kind of maritime technology."