Observing the spread of culture, scientists document social conformaty in wild animals for the first time.
Last week we looked at artificial evolution in the lab. By modifying the genetics of yeast, scientists were able to create a complex and illuminating pattern of behavior under specific evolutionary constraints. This week we look at something similar, but quite different: the directed evolution of culture.
Now before you start thinking of ‘culture’ as some sort of expression of society, let’s sort out what it is in biology. Cultural and biological evolution are not the same thing. Culture, as far as biology is concerned, encompasses the behavior and tradition of a group. In contrast, biological evolution is used to describe the changes in a population - everything from their genes to the behavior they display. Frequently, culture and learning can be influenced by evolution: different traits can influence behaviour and how an organism learns and shares their experience. Because of this link, we often observe how animals evolved and produce that behaviour.
So how does cultural evolution work within a species? How does a species 'learn' their behaviour? Why do they prefer certain behaviours over others? A group of creative scientists decided to answer these questions differently than others, who typically sit for hours observing the behaviour of different species. Alternatively, these investigators introduced a new behaviour into the target population, and observed if and how it spread.
They first asked what organism would be best to use in this experiment. Much like the yeast experiments discussed last week, scientists needed to choose a species whose behavior and traits were well-studied. That way any behavioural changes could be spotted easily. They chose a species of bird called Parus Major (P. Major), which is part of a family of birds called Paridae, a large family of passerine, or perching, birds. Their behavior is one of the most observed and well studied in the animal kingdom. P. Major are very creative and social birds who live in a fission-fusion social structure. This means that the population frequently separates to forage and hunt (fission), but then groups together to exchange information (fusion). Those P. Major that live in greatest proximity to humans have been known to alter their behavior to accommodate changes in their surroundings, including human-instigated changes. For example, British birds of this family famously began to pierce the tops of milk bottles to get to the liquid inside.
For this experiment, the scientists chose distinct but similar populations of P. Major and captured males from each. Two males from every group were then put into separate cages, each with a puzzle box that contained food. The first group served as the control group; these were not taught how to use the box to get food. They were only exposed to the box and allowed to discover how to use it on their own. The second group was taught to use the puzzle box by sliding a blue door on the box and opening it. The last group was also taught to slide a door to get food, but they were trained to use the red door on the box, not the blue one. After a few days of training, the birds were released back into the population, which now had puzzle boxes spread throughout their territory.
Pictured above, a diagram of the puzzle box used by scientists to study the spread of culture.
The results were quickly visible among the populations that had the trained males. Using cameras and sensors on the puzzle boxes, the researchers found that up to 75% of the population had learned how to use the boxes. This result was drastically different from the control population, where less than half of the population were seen using the boxes. Not only that, but the populations that had been taught to use the boxes started using them more often and more quickly than the ones that had to figure it out on their own. They also showed that those males that had been trained to favor a certain colored door - red or blue - passed that preference to the rest of their population. That is, the red group continued to use mostly the red, and the blue used mostly the blue side.
To learn how this information was being transferred, the scientists didn’t just study the puzzle boxes. The researchers also set up other bird feeders that contained cameras to record who visited. They found that the birds had social groups to which they adhered. This socialization is how information was carried through the population. In other words, the birds taught the others in their social group how to use the boxes before teaching anyone else. This social transmission showed that the birds do something we humans do all the time: they follow social trends.
If your friend shows you a really cool game on their phone and you begin to use it, they have socially transmitted a learned behavior to you. As you use it, and share it with others, you are continuing the tradition of playing the game. Often, you are teaching them your way of using it. Your way of playing may not be the best or worst way to play or even unique. When you teach someone how to play, you teach them your specific style of gameplay. This is called social conformity: when many people do things and continue to do things the same way because they are taught and because it is popular. That social conformity is exactly what the scientists found these birds were doing. They were learning how to use something a certain way and sharing that way of doing it. Not only that, but they found that over two generations this tradition became even more prominent. Even the next generation did things the same way as their elders.
By taking evolution into their own hands, scientists were able to teach a population how to do something and then observe how that behavior spread. But why? Why bother teaching birds how to solve a puzzle?
The answer lies in human society. We as humans have traditions that carry on over generations. These traditions influence how we think, act, and - consequentially - how we evolve. These cultural norms are taught to us because, socially, they are the most common way of thinking. That makes them easier to teach. This is social conformity. As the author Terry Pratchett wrote in his book The Fifth Elephant, “You did something because it had always been done, and the explanation was, ‘But we’ve always done it this way.’ A million dead people can’t have been wrong, can they?”
This social trait has never been described in any other wild animal and was generally a trait that was thought to belong only to primates such as apes, chimpanzees, and humans. These scientists did something completely new in their field. They showed that wild animals could express and pass along a complex social trait such as social conformity. This discovery gives insight into how we evolved and how we, as humans, developed complex social behaviors. Why do we, as a species, do things in certain ways? Maybe next time you have to make a decision, you can think of why you are doing to do something, instead of just what to do.