It's not a simple case of "follow the leader" when it comes to baboons on foot, traversing their home range. Based on prior research, scientists had a few theories as to why the animals fall into such structured formation and travel in what looks like an orderly line. But what they found was a surprise, and something that can help us better understand human behavior, too.
Researchers from Swansea University were curious about why baboons travel as they do, in a line known as a "progression," as they traverse their home range – especially given that previous studies had delivered conflicting answers. But understanding this behavior, although it may seem trivial to some, can offer broader clues about interspecies and intraspecies relationships. Which in turn can inform conservation and the welfare of animals in captivity.
Previous studies landed on either side of the one coin: the formation was random, or that the animals deliberately took up positions that protected vulnerable animals from attack.
Now, flipping the science on both those theories, high-resolution GPS tracking of wild chacma baboons (Papoo ursinus) in South Africa has found that rather than forming strategic formations for the protection of individuals, or it being random, the animals were simply following their best friends.
Using the tracking system, the team looked at 78 progressions spanning 36 days and were able to show that the order in which the animals were walking was not at all random. Then, testing for other hypotheses – protection from threats, resource competition, "follow the leader" theory and patterns emerging from social relationships (social spandrel hypothesis) – the researchers found that the baboon's travel formation was not just influenced by but solely driven by social relationships.
“Surprisingly, the consistent order we see for the baboons we studied isn’t about avoiding danger like we see in prey animals when they position themselves in the middle of their social group, or for better access to food or water like we see in like we see in the movements of plains zebra," said Andrew King, Associate Professor at Swansea University. "Instead, it’s driven by who they’re socially bonded with. They simply move with their friends, and this produces a consistent order."
On a broad scale, baboons that live in large social groups have strong social ties and behaviors that reflect and reinforce those, and studies have shown this is also associated with larger brain volume. But fascinatingly, the structured order in which they walk is not to demonstrate the social relationships, but a byproduct of them.
“We know that strong social bonds are important for baboons – they’re linked to longer lives and greater reproductive success," said Marco Fele, the study’s lead author and PhD student at Swansea University. "But in this context, those bonds aren’t serving a specific purpose. The travel order we see is simply a by-product of those relationships, not a strategy with immediate benefits. Our study highlights the potential for these kinds of spandrels in collective animal behavior.”
Spandrels, most recognized in architectural terms, are spaces between features – such as two arches – that end up making their own distinct order as a byproduct of the deliberate designs. In evolutionary biology, a spandrel is in a way the same – a formation that exists as a byproduct of some other dominant aspect of structure. And it's a rather controversial theory, given that it flies in the face of Darwinism in particular. But if you want to go down that rabbit hole, this seminal 1979 paper by Jay Gould and Richard Lewontin is the one to read. Essentially, though, they argued that not all traits we observe are specific adaptations – in this instance, why baboons have this structure in their progressions – but can be incidental rather than intentional.
“In the baboon group we studied, the more socially connected, higher-ranking individuals usually walk in the middle of the group, while lower-ranking baboons are often out in front or at the rear," said King. "During these group movements – like heading to a familiar sleeping spot – it’s likely that the group already knows where they’re going. So, the baboons at the front aren’t really leading; They’re just out ahead.”
If this study seems a little niche, consider it this way: Humans and baboons share around 94% of their DNA, so it’s not a stretch to think similar spandrels show up in our complex behaviors. The researchers found that the baboons’ orderly line formation isn’t a coordinated strategy – it just occurs when individuals walk near their social partners. Kind of like how friends naturally form a line in a busy crowd; we're not trying to make a deliberate formation, but one occurs naturally as a byproduct of our familiarity with each other.
Ultimately, spandrels remind us that what looks like intention or design can sometimes just be the side effect of other instincts – a pattern that emerges, not a strategy that evolved. (As much as it pains this evolutionary biologist to write that.)
"This non-random structuring of individuals during progressions can be considered a side-effect or outcome of underlying social forces acting among individuals, providing an example of a ‘social spandrel’ in collective animal behavior," the researchers concluded.
The study was published in the journal Behavioral Ecology.
Source: University of Swansea