Collins Lab Blog

What is most probable, most probably happens

In this paper, I was really struck by the visual representation of the data shown in Figure 2. The data report a quantitative evaluation of Prussian Blue positive cells (indicative of iron-rich content) to reveal the three dimensional distribution of iron-rich cells within an anatomical region, the upper beak of the pigeon.

Figure 2: Number and distribution of PB-positive cells in the upper beak.

This figure displays an enormous quantity of information, anatomical data, distances, cell numbers, individual birds, both male and female. It displays all this information in a masterful manner that is accessible, communicative and elegant.

The scientific conclusions arising from this study are that the majority of the iron-rich cells in this region are in fact macrophages and not neurons. The significance of this conclusion is that it eliminates a possible source/location for the elusive sensory neurons that pigeons use for navigation according to magnetic stimuli.

This particular scientist does not have the expertise to accurately judge the data presented in this paper, although it is interesting to note that it is still quite rare for a major journal to publish a manuscript that almost wholly communicates a negative conclusion. The reason for this is that it is very difficult to satisfactorily demonstrate a negative, there always remains the concern that there is, somewhere, just some other explanation, some type of experiment that is waiting to be done to disprove the negative conclusion. It’s a little bit like losing a key, at first, you’re sure that you left it in a particular location, but then you thoroughly search that location and you have to admit that you obviously didn’t leave they keys where you thought and you need to come up with other possibilities. Of course, it could be that the keys were in the original location and that the search you claimed was thorough was just subpar….

As the authors put it:

“Although we cannot exclude the possibility that a small number of sparsely distributed magnetoreceptors reside at an unknown location in the upper beak of pigeons, this study finds no evidence to support the existence of a subepidermal magnetic sense system that consists of iron-containing dendrites at six specific bilateral loci.”

At SOME point, however, it is reasonable to suppose that if something is most probably not the cause of a phenomenon, it is time to stop and move on to a new investigation. What is most probable, most probably is happening (or happened)!

 

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