Humans drive macaques to invent new tools

Macaques have had their environment changed by humans.But they’ve adapted to their new surroundings, inventing new tools to better exploit the environment


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Humans suck. We’ve been changing the environment for our own benefit for tens of thousands of years. Often, our primate cousins suffer as a result. One of these victims are the long-tailed macaques (Macaca fascilularis) from Ao Phang-Nga National Park, Thailand. You know, that one where they film all those movies. 

Although the park has remained fairly pristine, some of the surrounding area (which the macaques still visit) has been replaced by palm oil plantations. Since humans build these to grow a single type of plant, they tend to lack biological diversity. This includes many of the species the macaques feed on.

However, the long-tailed macaques aren’t a group to give up easily. Faced with this human-created environment, they invented some new macaque-created tools. Now, they can easily exploit the new food source we provided for them.

Of course, this isn’t just good news for the macaques. It also sheds light on primate innovation, perhaps helping us figure out how our own ancestors invented their tools.

Macaques on the prowl

As I said earlier (I hope you were paying attention) the monkeys in question live in a Thai National Park. Specifically, they live on an island within the park. They spend most of their time close to the shore, which remains fairly pristine. However, palm oil plantations were been built further inland in 2000. Lacking the biological diversity many species need, you’d think this would keep the macaques restricted to their thin coastal zone. And for the most part, you’d be right. The monkeys still spend most of their time by the coast where they eat shellfish, sea almonds, and other wholesome primate foodstuffs.

However, at a place called Lobi Bay things were a little bit different. The local palm oil plantation was abandoned. But within the detritus of the old plantation was the tell-tale sign of nut cracking tools. Hammers and anvils that showed damage from being smacked against palm oil nuts. Had the monkeys developed new technology to exploit the man-made environment?

It was difficult to confirm this, as the abandoned plantation was no longer producing any nuts. The macaques still visited the area, but they just pass right through. So the scientists set about restarting the plantation to see if the monkeys would take advantage of it again. Whilst I would like to imagine this was a montage involving various farmer work; it mostly consisted of taking palm oil nuts off local active plantations and placing them in the monkey’s old stomping grounds.

It didn’t take long for the monkeys to realize the palm oil was back. And sure enough, they were seen using rock hammers and anvils to crack open the nuts and get at the sweet treats inside.

Invention or translation?

Many primates around the world use rocks to crack open nuts. My favourites are the capuchin monkeys. However, before the palm oil arrived at Lobi Bay there was no record of these macaques doing this. It’s an innovation brought on by the new environment humans created.

Or is it? Remember how I said these macaques typically live near the coast? Well, there they eat shellfish which also come in a hard container. So the monkeys crack them open with a hammer and anvil. They do the same thing to a few other tough pieces of seafood they like to eat.

As such, it would be wrong to say this is a brand new invention by the macaques. Rather, it represents them figuring out that their existing toolkit can be applied in a new scenario. This is good because it shows they aren’t just smart. They don’t just know how to solve puzzles. Their behaviour is also flexible. They don’t have to rely on brute forcing a solution to a problem but can think and adapt their existing knowledge to new situations.

The researchers who discovered this suggest that such flexibility is a key part of culture. Thus, with time we might see the macaques developing their own cultural toolkits. Chimps, orangutans, and obviously humans show this sort of group variation but it doesn’t seem to have been seen in macaques. Might they soon be joining the party? It’s certainly possible, although behavioural flexibility alone isn’t enough for culture develop. You also need some social learning; which this research failed to find.

Some of the chimp cultures currently identified, along with the behaviours practised by each (you’re probably going to want to click to see a bigger image)

Informing human evolution

Of course, this is a website all about the filthy monkey men we evolved from. We’re an egocentric species. How does a bunch of macaques breaking nuts help us understand our own evolution?

Well, it suggests that many primates – our ancestors included – can recognise when a new situation might be aided by the use of an existing tool. That their technology would be quite flexible. This would have been particularly useful at a key moment in our evolution, roughly 3.3 million years ago.

oldest stone tools found

The Lomekwian. Possibly the most significant find in all of human history

That’s when the oldest stone tools were manufactured (rather than existing stones in the environment simply being used). A bunch of hominins were cracking nuts and realised the sharp pieces of rock debris produced would make good cutting tools. The result is the Lomekwian industry, and the starting steps towards all the manufactured technology we know and love.

For the hominins in question to make this leap they would have had to recognise both the benefits of the cool new sharp rocks and the fact that their existing tools could easily produce them. In short, they would have had to display that same sort of behavioural flexibility as these macaques. Recognising that smashing stuff with a rock can be put to other purposes (smashing other stuff for macaques, smashing the rocks until pieces come off for us).

This would mean that the cognitive evolution needed for the Lomekwian to take off would be very minor, perhaps even non-existent. Existing primates, with their tendency for flexibility, could perhaps have kicked things off.

Our big shift to manufacturing stone tools might not have been a watershed moment of evolution. Rather, just some primates in the right place at the right time to put 2 and 2 together.

References

Harmand, S., Lewis, J.E., Feibel, C.S., Lepre, C.J., Prat, S., Lenoble, A., Boës, X., Quinn, R.L., Brenet, M., Arroyo, A. and Taylor, N., 2015. 3.3-million-year-old stone tools from Lomekwi 3, West Turkana, Kenya. Nature521(7552), pp.310-315.

Luncz, L.V., Svensson, M.S., Haslam, M., Malaivijitnond, S., Proffitt, T. and Gumert, M., 2017. Technological Response of Wild Macaques (Macaca fascicularis) to Anthropogenic Change. International Journal of Primatology, pp.1-9.

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