EGU Blogs


A thought on impact factors

OK, bear with me on this one. It’s a bit of a thought dump, but it would be interesting to see what people think.

You can’t go anywhere in academia these days without hearing about impact factors. An impact factor is a metric assigned to a journal that measures the average number of citations per article over the preceding two year interval. It was originally designed to help libraries select which journals were being used by academics in their research, and therefore which ones they could not renew subscriptions to. However, in modern day academia, it is often used to measure the individual ‘impact’, or quality, of a single paper within a journal – that is, the metric assigned to a journal is used as a proxy for the value of each article inside. It doesn’t make much sense on the face of things, especially when you here stories about how much impact factors are gamed (read: purchased) by journals and their publishers (see link below), to the extent that they are at the least meaningless, and at the worst complete lies.

The evidence suggests that the only thing that an impact factor, and journal rank, is reflective of is academic malpractice – that is, fraud. The higher an impact factor, the higher the probability that there has been data fudging of some sort (or higher probability of detection of such practice). A rather appealing option seems to be to do away with journals altogether, and replace them with an architecture built within universities that basically removes all the negative aspects of assessment of impact factors, at the same time as removing power from profit-driven parasitic publishers. It’s not really too much a stretch of the imagination to do this – for example, Latin America already uses the SciELO platform to publish its research, and is free from the potential negative consequences of the impact factor. University College London also recently established it’s own open access press, the first of its kind in the UK. The Higher Education Funding Council for England (HEFCE) recently released a report about the role of metrics in higher education, finding that the impact factor was too often mis-used or ‘gamed’ by academics, and recommended its discontinuation as a measure of personal assessment. So there is a lot of evidence that we are moving away from a system where impact factors and commercial publishers are dominating the system (although see this post by Zen Faulkes).

But I think there might be a hidden aspect behind impact factors that has often been over-looked, and is difficult to measure. Hear me out.

Impact factors, whether we like it or not, are still used as a proxy for quality. Everyone equates a higher impact factor with a better piece of research. We do it automatically as scientists, irrespective of whether we’ve even read an article. How many times do you hear “Oh, you got an article in Nature – nice one!” I’m not really sure if this means well done for publishing good work, or well done for beating the system and getting published in a glamour magazine. Either way, this is natural now within academia, it’s ingrained into the system (and by system, I include people). The flip side of this is that researchers then, following this practice, submit their research which they perceive to be of ‘higher quality’ (irrespective of any subjective ties or a priori semblance of what this might mean) to higher impact factor journals. The inverse is also true – research which is perceived to be less useful in terms of results, or lower quality, will be sent to lower impact factor journals. Quality in this case can refer to any combination of things – strong conclusions, a good data set, relevance to the field.

Now, I’m not trying to defend the impact factor and it’s use as a personal measure for researchers. But what if there is some qualitative aspect of quality that it is capturing, based on this? Instead of thinking “It’s been published in this journal, therefore it’s high quality”, it’s rethinking it as “This research is high quality, therefore I’m going to submit it to this journal.” Researchers know journals well, and they submit to venues for numerous reasons – among them is the appropriateness of that venue based on its publishing history and subject matter. If a journal publishers hardcore quantitative research, large-scale meta-analyses and the sort, then it’s probably going to accrue more citations because it’s of more ‘use’ – more applicable to a wider range of subjects or projects.

For example, in my field, Palaeontology, research typically published in high impact factor journals involves fairly ground-breaking new studies regarding developmental biology, macroevolution, extinctions – large-scale patterns that offer great insight into the history of life on Earth. On the other hand, those published in lower impact factor journals might be more technical and specialist, or perhaps regarding descriptive taxonomy or systematics – naming of a new species, for example. An obvious exception to this is anything with feathers, which makes it’s way into Nature, irrespective of it’s actual value in progressing the field (I’ll give you a clue: no-one cares about new feathered dinosaurs any more. Get over it, Nature).

So I’ll leave with a question: do you submit to higher impact factor journals if you think your research is ‘better’ in some way. And following this, do you think that impact factors capture a qualitative aspect of research quality, that you don’t really get if you think about what impact factors mean in a post-publication context? Thoughts below! Feel free to smash this thought to shreds.

They might be giants, but how could they live with each other?

Sauropod dinosaurs are the biggest animals to have ever walked on land. They are instantly recognised by their long, sweeping necks and whiplashed tails, and nearly always portrayed moving in herds, being stalked by hungry predators.

In recent years, a huge amount of taxonomic effort from scientists has vastly increased the number of known species of sauropod. What we now know is that in many areas we had two or more species co-existing alongside each other.

A question that arises from this, is how did we have animals that seem so similar, and with such high energy and dietary requirements, living alongside one another? Was there some sort of spinach-like super plant that gave them all Popeye-like physical boosts, or something more subtle…?


Hi there, Camarasaurus! One of the iconic dinosaurs of the Morrison Formation (source)

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The early evolution of birds – more complicated than trying to untangle your headphones..

Birds are a phenomenal story of evolutionary success. As modern-day dinosaur descendants, they occupy almost all environments and ecosystems around the globe, and are truly animals that capture our imaginations. However, how did they become so diverse, both in number and form? This is something only the fossil record can divine for us.

Birds first appear in the Middle to Late Jurassic of China and latest Jurassic of Europe (hello, Archaeopteryx), around 160-150 million years ago. Their first radiation, in terms of increasing species numbers, appears to have occurred in the Early Cretaceous of China, based on the fossil graveyards of the 125 million year old Jehol Biota. However, it has been argued that the timing of this radiation is strongly influenced by ‘the Lagersttäten effect’ – that is, periods of exceptional preservation in the fossil record. For the early evolution of birds, this is complicated by the fact that the earliest Cretaceous (around 145 to 125 million years ago) fossil record of birds is known from only rare and fragmentary material.

One of the earliest known birds, Archaeopteryx, from the infamous Solnhofen beds of Bavaria, Germany. (source)

One of the earliest known birds, Archaeopteryx, from the infamous Solnhofen beds of Bavaria, Germany. (source)

At some time around then, however, it is though that birds underwent a phase of rapid diversification of body forms, particularly geared towards increasingly small body sizes. This has important implications for the evolution of flight, but that’s another story.

A possible trigger for this diversification might have been with an extinction event at the end of the Jurassic, 145 million years ago, which saw the decimation of smaller-sized pterosaurs (their non-dinosaurian, winged cousins), particularly those known as rhamphorhynchids. Ecologically speaking, this would have opened up ‘ecospace’, for other animals to radiate into and occupy. Animals, such as birds.

What you would expect to see if this is the case, is increasing diversity of birds, which we do see, as well as increasing diversity of their body forms, their morphology, and ecological variants.

Were pterosaurs duking it out against birds for millions of years? (source)

Were pterosaurs duking it out against birds for millions of years? (source)

However, is this what we the fossils record for us? A recent study has shown that, despite the high diversity represented by the Jehol Biota, we actually see constrained levels of morphological diversity – known as disparity.

Much of the Jehol bird fauna seems to have been comprised of ground foragers, which is curious as they would all have been flight capable. Interestingly, this seems to be at odds with the local pterosaur fauna. These chaps were still owning the skies, and diversifying into an increasingly bizarre suite of forms.

Could it be, perhaps, that there was a sort of ‘fight for the skies’ happening at this time? Perhaps while both pterosaurs and birds radiating, they were competing to constrain the extent to which the others could evolve, and restricted them to particular ecologies. This hypothesis is certainly appealing, and tells of a sort of ‘fight for the skies’ in the early origin of birds.

Understanding why this was happening, and which roles birds were most successful in, is important for understanding their survival through the end-Cretaceous mass extinction and the demise of non-avian dinosaurs, as well as their rise to fame in modern times.


Mitchell, J. S. and Makovicky, P. J. (2014) Low ecological disparity in Early Cretaceous birds, Proceedings of the Royal Society, Series B: Biological Sciences, 281, 20140608. (link)

Palaeontology in the 21st Century

Palaeontology is the study of the history of life on Earth. Whenever I get asked what I do, my answer always gets a predictable response: either “Oh, like Ross from Friends?” “So Jurassic Park?” or “So you dig dinosaurs?”

Neither of these are close to what myself, my colleagues, or the broader field are doing. Well, apart from the digging dinos. We have to have some perks (not that I’ve actually ever been on a dig…).

What I want to highlight are a couple of recent developments in the field that show that palaeontology is just as technically advanced as any other major domain of science out there. They both involve the genesis and analysis of large data sets that we’re constantly using to test large-scale patterns and processes through time – known as macroevolution. Trying to decipher the patterns and processes of evolution leading towards the modern, extant fauna we have today is key in predicting their future as we destroy the planet.

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