The First Americans – a story of wonderful, uncertain science

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https://aeon.co/essays/the-first-america...in-science

INTRO: The debate over how people first arrived in the Western Hemisphere continues to roil archaeology in the United States – and to capture public attention. Today, the scientific community is contending with significant amounts of new genetic and archaeological data, and it can be overwhelming and even contradictory.

These data are coming from new archaeological excavations but also from the application of newly developed tools to re-analyse prior sites and artefacts. They’re coming from newly sequenced genomes from ancient peoples and their contemporary descendants, but also from re-analysis of prior sequence data using new modelling tools. The generation of new data at times feels as though it’s outpacing efforts to integrate it into coherent and testable models.

Did humans first populate the Americas 100,000 years ago, 30,000 years ago, 15,000 years ago, or 13,000 years ago? Did they come by boat or by an overland route? Were the ancestors of Native Americans from one population or several? The answers to these questions would help us understand the grand story of human evolution.

We know that the Americas were the last continents that anatomically modern Homo sapiens – humans like us – entered, but we don’t know exactly how this happened. These long-ago movements give us hints about the challenges ancient peoples across the world had to contend with during the Last Glacial Maximum (LGM), a prolonged period of coldness and aridity, when animals, plants and humans retreated to environmental ‘refugia’ for several thousand years.

How did we survive this Ice Age? What technological and biological adaptations arose as the result of these environmental conditions? These questions capture the popular imagination and challenge the scientists working to uncover the details of individual lives thousands of years in the past.

To their Indigenous descendants, the stories we tell about these First Peoples of the Americas are highly relevant for additional reasons. Their deep ties and claims to the lands have often been ignored or expunged by governments, media and corporations across North and South America in order to make room for narratives that are more palatable, exciting or convenient to certain non-Native groups.

The historical exclusion of Indigenous peoples from making decisions about research on their own ancestors and lands has caused significant harms to Native communities and individuals; when Native scientists and community members are full participants in the research process, the stories that emerge are not only more respectful but also more accurate.

Archaeological evidence establishes that Indigenous peoples were present in the Americas at least 15,000 years ago. Scientists don’t agree, however, on when people first arrived. Some archaeologists claim it must have been much, much farther back, citing evidence such as flaked stones in layers dating to ~30,000 years ago at the Chiquihuite Cave site in Mexico, bones with cut marks in layers dating to 34,000 years ago in Uruguay, flaked stones in layers dating to 30,000-50,000 years ago in Brazil, and even broken mastodon bones dating to 130,000 years ago in California. All of these claims are heavily disputed... (MORE - details)

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These ancient stone weapons may link the ice age peoples of North America and Northeast Asia
https://www.sciencefocus.com/news/ancien...rica-asia/

INTRO: These ancient stone weapons may link the ice age peoples of North America and Northeast Asia

A selection of stone ‘projectile points’, which were most likely attached to darts, have been found to be 3,000 years older than any similar examples found in North America.

The remarkable discovery by Oregon State University (OSU) archaeologists, who have been carbon-dating the razor-sharp artefacts, will help to fill in gaps in the history of how early humans crafted and used stone weapons.

Prof Loren Davis, an archaeologist at OSU and head of the group that found the ancient artefacts, points out how the discovery of these projectile points is revelatory, not just because of their age, but because of their similarity to items found in Hokkaido, Japan – dating from 16,000-20,000 years ago.

The presence of the weapons in modern-day Idaho gives more weight to the theory that there may be early genetic and cultural connections between the ice age peoples of Northeast Asia and North America... (MORE - details)

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My understanding is that earlier hominins like Homo erectus never made it to the Americas. The first humans here were anatomically modern humans.

And own guess (based on Cavalli-Sforza) is that humans arrived in the Americas in three distinct waves, associated with the beginning and end of the last ice age. (Cavalli-Sforza hypothesized that climactic conditions at the height of the ice age were too severe to allow crossing of the Bering land bridge.)

The first wave arrived ~30,000 years ago when the ice age was just gathering force but the crossing was still passable. These people spread throughout the western hemisphere very quickly, reaching Chile in just a few thousand years. This earliest group were the ancestors of most of the American Indians today.

A second group arrived around the end of the last ice age, ~10,000-15,000 years ago, when conditions in Beringia were gradually improving. These were the ancestors of the Na-Dene speakers among the American Indians. This group is found from Alaska to western Canada, and very prominently in the southwest United States where the Navajo and Apache belong to this group. That's as far south as this wave penetrated, perhaps because the earlier group slowed their expansion.

And a third linguistically and genetically distinct group arrived some 8,000-10,000 years ago, also associated with the end of the last ice age, and are the ancestors of the Eskimos and Aleuts.

It's all controversial of course. But this hypothesis, or some variant on it, seems most likely to me.

Cavalli-Sforza believed that both archeological and genetic evidence supported this hypothesis. We know that the Navajo intruded from the north into land occupied by the ancestors of the Hopi within the last few thousand years. And Cavalli-Sforza argued that there is genetic evidence that the Na-Dene speakers are a distinct group. And the Eskimos maintain the most genetic similarity to groups remaining in northeast Siberia.