For a long time, we thought of tool use as the thing that made us human, but we actually share the ability with many other primates, as well as surprising animals like crows and sea otters. Some archaeologists are interested in studying sea otters' tools.
Archaeologists have studied the history of human tool use, through the physical things our ancestors left behind, for decades. In recent years, some archaeologists have started using the same methods to study chimpanzee tool use by looking at the tools they discard, and even the waste that gets left behind when a chimpanzee makes a tool. Now, a small group of primate archaeologists wants to take a look at sea otters.
Sea otters are one of handful of non-primate species in the world that uses tools. From a young age, some sea otters learn to use rocks to crack snail shells to get at the soft, edible bits inside.
Recently, biologists realised that how often sea otters use tools, and even whether they learn the skill at all, varies from place to place. That seems to be linked to the kinds of food that's most common in each area; sea otters who mostly eat sea urchins, for instance, are less likely to learn to use tools than those whose local diet is more snail heavy. In other words, sea otters may have something like culture that varies from place to place.
They also found that knowledge spreads quickly among sea otter populations. One animal may discover a new method, like eating a type of fish that's new to the area, or smashing a snail shell against a boat hull, and within weeks or months, other otters will have learned the same behaviour. That points to tool use as something more complex than simple instinct (although biologists think instinct plays a role in the ability to learn it).
That's why archaeologists are interested. If researchers learn more about how, when, and why tool use evolves and spreads among other species, they might also learn something about what we have in common with chimpanzees, crows, sea otters, and others -- and what sets us apart.
Sea otters present a special challenge for archaeologists, though. Otters drop their tools and the smashed shells into the ocean when they have finished. On the sea floor, a rock that's just been used to smash a snail shell looks like every other rock.
That's why archaeologists may be turning to ancient sea otter skeletons to study the evolution of tool use in the sea. Snail shells are hard enough to crack the otters' teeth if they just try to bite into them. Isotopic analysis of the bones can tell scientists what sea otters likely ate, and it's a reasonable leap of logic to conclude that otters who ate snails but didn't have broken teeth were probably tool users.
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