Shells are typically found along the shorelines of oceans, so why are seashells and fossils found in the middle of the Sonoran Desert? Ten million years ago the Imperial Valley was the northernmost extension of the Gulf of California. Countless floodings of the Colorado River brought millions of tons of silt and debris from the Grand Canyon, which eventually resulted in an earthen dam that cut the sea off from the Valley. Sea life remained in this new inland lake and, over the next 7 million years, fossilized and was discovered by the first peoples of the Imperial Valley, the Kumeyaay. The Kumeyaay utilized these resources not only in Imperial Valley, but along the Pacific coast in modern day San Diego as well, where some bands would settle during summer’s hotter months.

Dinosaur fossils have been dated to be anywhere from 66 million to 210 million years old. In San Diego, the most common fossils that can be found are of sea life. The oldest fossils found along San Diego’s coast were 151 million year old clams found by Perry Crampton. Around 66 million years ago in the Cretaceous Period, San Diego had a much more tropical climate, which explains the plentiful shellfish resources available to the Kumeyaay. They collected and manufactured these shellfish into jewelry and tools. The best examples of such are Rudist clams and Olivella (dwarf olive) beads, the latter of which originate from gastropods (sea snails). Olivella shells were exclusively used as a jewelry bead because they were lighter and easier to manipulate.

Rudist clams, on the other hand, were referred to as “reef builders”; they have heavy and tough shells and were best used as cutting or chopping tools. Although they are relatively brittle compared to stone tools, Rudist shells were more readily available, making them the preferred choice over similarly sized stones.

There are multiple archaeological dig sites along the San Diego coast. The two locations that yielded the most evidence for shell manufacturing (both jewelry and tools) are the Remington Hills and Scripps Estate sites, along the Tijuana River and in La Jolla, respectively. Remington Hills acts as an important location, not only because archaeologists found hundreds of raw and worked shells, but because worked shells could be dated as far back as 8,675 B.C. This dating time frame reinforces the Kumeyaay’s timeline for their habitation of the San Diego coast and Imperial Valley as the “first people.”

While developing the area for housing in the 1920s, more than 200 burial sites were uncovered, resulting in the accidental dig site at Scripps Estate. Wrongfully, these bodies were uncovered from their burials and, in the eyes of the Kumeyaay, “have been rudely returned from their afterlife, their journey interrupted.” Within these burials and their surrounding areas, shell jewelry like the Olivella bead necklace and Pismo clam pendant were found. The number of burials reported at the Scripps Estate site provides further evidence of Kumeyaay habitation and the production of shell jewelry for at least the last 7,500 years.

Once winter was upon the San Diego coast, the Kumeyaay headed inland and settled back in the Imperial Valley. Just as they had shells to collect along the current coast, the ancient coast of the Gulf of California provided the Kumeyaay with resources to manufacture tools and jewelry while in the desert. We currently refer to the area where these fossils and shell remnants can be found as the “Latrania Formation,” which stretches from the southern base of the Coyote Mountains to the east toward Yuma. Many types of shells, from clams, snails, scallops, oysters and Olivella, can be found and the Kumeyaay used them all. Similar to findings in San Diego, the Kumeyaay appeared to mainly produce jewelry out of shells. Shell jewelry was used as a currency and status indicator for Kumeyaay societies. Due to this, the Kumeyaay chose to be buried wearing their jewelry to carry their status with them into the afterlife. Shell tools were used during physical labor and were likely to break. Once a tool broke, there was little reason for it to be kept around, or for archaeologists to see it as anything other than fragmented shell pieces. Therefore, it is much more common for intact Olivella beads to be found than shell tools, since they were better preserved.

Why did the Kumeyaay use shell tools if they were so likely to break? Why not just use stones? One hypothesis posits that since the Kumeyaay were semi-nomadic and moved multiple times a year, they chose to use the most plentiful resources in the areas they settled. Meaning, when they settled along the Pacific coast and the shoreline of Ancient Lake Cahuilla, sea life and shells were an easy product to gather and craft. Evidence also reports that the Kumeyaay had incredibly intricate trading systems with the Northern Chumash tribes, in which shell jewelry was traded for resources only available in the Santa Barbara region. However, once Spanish missions arrived, trading between tribes became much more difficult and for some bands, it was restricted. The Kumeyaay continued to use their shell currency through tribal interactions and for ceremonies.

Rather than buying goods, Kumeyaay leaders, or Kwaapaay, exchanged shells as an invitation to an event or to pay respects to different bands and their Kwaapaay after the passing of a member.

Despite the harsh conditions imposed on the Kumeyaay by the missions, they remained steadfast in their traditions and continued to craft their shells into beautiful art and effective tools.

Sea life continues to thrive off the coast of San Diego and places like Shell Beach, Silver Strand State Beach, and La Jolla Cove are all public spaces where shells are easy to come by, as they simply wash up onto the shore. Shell hunting in Imperial Valley is more complicated; much of the land is under the Bureau of Land Management’s (BLM) protection. This restricts public access, meaning if you do find a shell, you aren’t allowed to simply take it. There are no restrictions on the exploration of the desert for shells, but the BLM guidelines ensure we aren’t destroying shells, fossils, or the environment. The Imperial Valley Desert Museum is in the process of creating a new temporary, “Desert Shells” exhibit, that will be able to provide a visual representation of the information in this article.

The Imperial Valley Desert Museum is located in Ocotillo. It is open Wednesdays through Sundays 10 a.m. to 3 p.m.

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