Friday, May 20, 2011

If you need to fight, stand upright.

Did our ancestors began to stand on two legs, because it gave them an advantage in beating up their rivals? Well at least this is what David Carrier tried to find out in his most recent study, as he looked at how hard people were able to punch when they stood upright and when they didn’t.

First of all, how does someone come to this kind of idea? Carrier explains that an upright stance is a common behaviour seen ion other mammals when they want to threat/fight their opponents and that especially apes often display this kind of behaviour.
And indeed, an upright posture is more effective when it comes to smack people in the face, but does this mean that male to male aggression has anything to do with the evolution of human bipedalism?

It’s funny that my last post was about how we’re able to build up testable hypothesises in evolutionary biology and which kind of problems you face while doing so, because this study completely made some huge mistakes in this regards. First of all, the study only relies on data from present day organisms. We have little knowledge about how our earliest ancestors (or their ancestors) even looked like, which makes it even more difficult to make any serious assumptions on how they behaved. Therefore evolutionary models solely relying on behavioural evidence from extant animals are almost untestable via the fossil record. But we need to test those models with fossil evidence if we want to avoid telling “just so” stories. I have mantra that I picked up from one of my teachers: “The past is a foreign country, they did things differently there.” Surely we need observations on recent animals to build up our models, but they can never be a complete substitute of the fossil record.

Papers like this make me wonder if I might get something wrong in how I approach this field. In my eyes it completely omits all standards of how to build a scientific theory in favour of making some wild assumptions on human evolution and I don’t understand how this can happen or how such stuff gets published in the first place.


Carrier, D. (2011). The Advantage of Standing Up to Fight and the Evolution of Habitual Bipedalism in Hominins PLoS ONE, 6 (5) DOI: 10.1371/journal.pone.0019630

Tuesday, May 3, 2011

The "Stop"-Button does not open the door: What going by bus can teach us about Science.

I don’t have driver’s license and therefore have to rely on public transport (mostly the bus) to get around. Although it’s sometimes annoying, there are a lot of interesting behaviours you can witness by taking the bus.

Usually, there are three kinds of buttons in the busses around here: One that signals the driver to stop at the next Bus stop, one for people in wheelchairs to “order” a ramp and one (usually at the last door) which opens the door once you press it. The last button is important, since it’s the only one that actually opens a door; the other doors are controlled by the bus driver.

As you can see, when it comes to door-opening, we're encountering two different conditions:

One time the action “press button” is followed by the reaction “door opens” and the other time it isn’t.
The Problem with these conditions is that people who, for example push the "stop" button next to one of the other doors, don’t get the feedback that their action didn’t do anything. Instead the door, unrecognised by the person who pushed the “stop” button, is opened by the bus driver.

So instead of the (right) connection:
Button on the last door opens it.

They're learning something like this:
Every button next to a door opens it, no matter what it says.

You can say that they've built up a false theory about how the doors in the bus work.

The question now is how they find out that their theory is wrong. The bus driver always opens the first two doors of the bus and somehow this action will always coincide with their action of pressing a button, so people won’t be able to recognize their mistake by verifying their current theory. The only way to show that their theory is wrong is by falsification.
So instead of always pressing a button, let’s see what happens if one never presses a button when he/she wants to exit the bus. After a short while, they would recognize that on some cases the door will open without their actions and sometimes it won’t. This procedure might lead to the conclusion that only the last door of the bus is controlled by a button.
Through constant observation and the falsification of their own theories, people would learn the “true” principle of how the doors in the bus are controlled. By this method, people would not only stop looking like pavlovian dogs when they want to exit the bus, they would also learn how science works.

Whether you want to learn how the doors in the bus work, as I did back when I was still going to school, or if you want to be a scientist: The only reliable way to get a better knowledge about the world is to try to falsify already existing theories. You can never be sure if the causal principle you described is true. It could be controlled by something completely different, like the bus driver in my example. The only thing you can be sure of is that if a theory is wrong, it stays wrong. So the only true way to get to reliable knowledge about our world is by ruling out any alternative explanations.

This stuff sounds pretty easy and if we’re looking at sciences like physics, it’s quite easy to execute. But if we look at evolutionary biology, things become pretty difficult.
Evolutionary theory itself is, from a philosophy of science-perspective, a pretty nasty theory (to explain why would need some elaboration) and what’s really problematic is that most hypothesises drawn from it are retrospective in their nature.
You cannot simply make an experiment on whether or not the evolution of our bipedal gait is connected to a more open habitat or the emergence of pair bonding. The only way to test these theories is by looking for clues in the fossil record and by reconstructing the environment in which the postulated transition happened. Therefore all hypothesises regarding a certain evolutionary scenario, or the relationship between two groups of animals, need to be connected somehow to the fossil record to make them testable.
In some cases it’s not that difficult but if we’re looking at the evolution of our behaviour and cognitive abilities, the margin between science and story-telling is very thin. Unfortunately a pile of bones doesn’t help very much if you want to find out how our ancestors behaved, if they were able to talk or how far developed their cognitive abilities were. Fossils don’t talk and unfortunately bones do not yield much information on the exact behaviour of their represented species.

This leaves a lot of room for speculation in those fields and therefore they’re often prone to be interpreted in an ideological fashion. We always have to keep in mind that making assumptions on the evolution of our species is not only of scientific importance; by doing this we’re also making a philosophical statement on what defines us as human beings. That’s why I think it’s important to know the limitations of your field and how you’re able to build “good” scientific theories.