What Lies Beneath California’s Coast Is Changing How We See Ice Age History

There are remains of a much older landscape that existed during the Ice Age beneath California’s coastline today, when sea levels were lower, and the environment looked very different. A number of submerged village sites were discovered by archaeologists, as well as fossil remains of large animals that lived thousands of years ago. These discoveries are beginning to show how humans and megafauna once lived along the California coast

A Jefferson’s ground sloth bone that was discovered in the Santa Cruz Mountains, along with a mammoth tusk found on Santa Rosa Island, provides evidence of a region that was once rich in wildlife and human activity, writes The Archaeologist. The Santa Cruz Museum of Natural History presented several of these findings through its “Pleistocene Pop-Up” exhibit in late 2025. A Jefferson’s ground sloth bone was found by children during a hike, and is considered one of the most notable discoveries in the area.

A Paramylodon bone was also discovered by researchers during construction work nearby, which was dated to around 85,000 years old. These fossils help us understand that large mammals had once occupied this region in larger numbers and greater diversity than we see today. The exhibit also featured a reconstructed mastodon skull, which gave the visitors a clearer picture of the kinds of animals that lived in California during the Ice Age, reports Santa Cruz Museum.

Researchers have also identified submerged village sites that were once used by Indigenous groups such as the Kumeyaay off the coast. These settlements existed during a time when the coastline extended much farther out because of lower sea levels. These areas were gradually submerged as oceans rose, which preserved some parts of human history underwater. Archaeologists are now studying these sites to understand how early communities adapted to changing environments and shorelines that kept shifting.

This work tells us that coastal populations were closely connected to marine ecosystems and were dependent on them for survival (The Archaeologist). California’s tar pits and coastal cliffs continue to reveal fossils, and these natural features quite often preserve bones of animals such as mammoths and saber-toothed cats. Erosion along the coastline sometimes exposes new remains, which researchers must document quickly before they are lost. These discoveries give us important insights into prehistoric ecosystems and how species interacted with each other in the past (The Archaeologist).

A mammoth tusk dated to more than 100,000 years ago was uncovered, which is another important find from Santa Rosa Island. The mammoths were able to reach the Channel Islands, probably during periods when sea levels were lower. The discovery helps scientists in tracing migration patterns and understanding how animals adapted to changing climates during the Ice Age (Cal Geographic). Researchers have also stated the role of local communities in these discoveries. The sloth bone found by children shows us how public awareness and participation can contribute to scientific research. Numerous educational programs and museum exhibits are helping people realise the importance of these findings and report them properly (Santa Cruz Museum).

However, scientists are still discussing the possible causes for the extinction of these giant creatures. One theory is that a cosmic event caused sudden changes in the environment, while another theory suggests that climate change and human involvement could have been the cause. It is possible that all these factors contributed to the extinction of the creatures. The California coastline is revealing an ancient story that is much older than its current appearance. This research connects the history of human beings with the lives of Ice Age creatures and how they adapted to a changing world. More discoveries may be made on how this ancient landscape evolved into the current scenery with more research.