The Purple Earth Hypothesis

A cool Youtube video about an intriguing hypothesis.

For some weeks, I have been following the Youtube-channel PBS Eons. On this channel you ‘join hosts Hank Green, Kallie Moore, and Blake de Pastino as they take you on a journey through the history of life on Earth. From the dawn of life in the Archaean Eon through the Mesozoic Era — the so-called “Age of Dinosaurs” — right up to the end of the most recent Ice Age.

They produce great videos and I can recommend all of them. But their latest video – on the ‘Purple Earth Hypothesis‘ – really intrigued me. For two reasons:

  1. I have never heard of this hypothesis before, so I was eager to learn more about it.
  2. The colors of my favourite Belgian football team – Anderlecht – are purple and white.

I won’t give too much away about this ‘Purple Earth Hypothesis’. Just check out this video!


Why is today #WorldSeabirdDay?

While browsing through my Twitter-feed, I realized that today is World Seabird Day. But why is this day – the 3rd of July – dedicated to seabirds? Because on this day in 1844, the last Great Auks (Pinguinus impennis) were seen (and killed) on Eldey, of the coast of Iceland. Hopefully, we can avoid that other seabird species suffer the same faith.

specimen great auk
Specimen of Great Auk and replica egg in Glasgow, Scotland (from

The species went extinct due to human exploitation, mostly because of its down. An account from 1794 by Aaron Thomas, who worked aboard the HMS Boston, illustrates the cruelty that the Great Auks had to cope with and eventually drove them to extinction:

If you come for their Feathers you do not give yourself the trouble of killing them, but lay hold of one and pluck the best of the Feathers. You then turn the poor Penguin adrift, with his skin half naked and torn off, to perish at his leasure. This is not a very humane method but it is the common practice. While you abide on this island you are in the constant practice of horrid cruelties for you not only skin them Alive, but you burn them Alive also to cook their Bodies with. You take a kettle with you into which you put a Penguin or two, you kindle a fire under it, and this fire is absolutely made of the unfortunate Penguins themselves. Their bodies being oily soon produce a Flame; there is no wood on the island.

The Great Auk – commonly regarded as the penguin of the northern hemisphere – stood about one meter tall and weighed approximately five kilograms. It had a wingslength of no less than 15 centimeter, which is obviously too short to fly. From an evolutionary point of view, the Great Auk is probably most closely related to the extant Razorbill (Alca torda).

Great Auks by John James Audubon in The Birds of America (from

The scientific journal of the American Ornithologists’ Union is named The Auk in honor of this bird. I am proud to have published at least one paper in this journal (you can read it here). My way of honoring this iconic bird.

These trees lean towards to equator!

When you walk along a line of Cook pines (Araucaria columnaris), you might think that a tornado just passed. Most trees of this coniferous species are leaning in the same direction. Researchers from the California Polytechnic State University also noticed this. In fact, travelling around the world (something that scientists tend to do), they started seeing in pattern. In their paper, published in Ecology, they write:

We first noticed A. columnaris leaning south in California and Hawaii, where it is a common horticultural plant. Our observation from Australia, though, suggested that A. columnaris lean north in the southern hemisphere.

This observation triggered their curiosity. They sampled 256 trees on five continents and recorded the orientation of their lean. And it turned out that they ‘uncovered a surprisingly consistent pattern of hemisphere-dependent directional leaning in A. columnaris.’ Indeed, in the northern hemisphere, trees lean south, and in the southern hemisphere they lean north. But why they do it? Nobody knows…

cook pine.jpg


How to survive the tsunami of scientific literature

As a scientist, it is important to keep up with the latest developments in your field. One way of doing this is by reading the most recent scientific papers. But in the constant bombardment of papers, it can be tricky to choose which ones to read and which ones to ignore. In this blog post, I will quickly guide you through my system.

My way for dealing with the mind-boggling amount of scientific literature encompasses three steps:

  1. Look for scientific papers and save PDFs based on title
  2. Read abstract, summarize and classify
  3. READ!

1. Look for scientific papers

The first step is quite straightforward. Before you can read papers, you have to find them. You can do this by visiting the websites of journals in your field and browse through the contents of their latest issues. I mostly have a look at journals such as Evolution, Journal of Evolutionary Biology, Biological Reviews, Current Biology, ect. In addition, you can subscribe to the newsletters of these journals. Another possibility is creating a keyword alert using websites such as Scopus or Web of Science. For example, I receive weekly mails with papers that include the keywords “introgressive hybridization”.

Based on the title (and sometimes the abstract if the title is not very informative), I save a PDF of the paper on my laptop. I link this PDF to a reference in the software EndNote. In Endnote, I have created several folders to store the newly found papers. The first folder – Avian Hybrids – contains papers that are relevant for my website on Avian Hybridization, where I gather the scientific literature on (you guessed it!) avian hybrids. The second folder – General Papers – contains the rest of the papers that I find online.

2. Read abstract, summarize and classify

Next, I have a look at the abstract. While I do this, I open another program: Evernote. This software can be seen as a giant electronic notebook. Instead of wasting paper, I prefer to save my notes digitally. In Evernote, I have created a notebook called ‘Paper Administration’. Every time I dive into my pond of scientific literature, I take some notes. I briefly summarize the paper based on the abstract and (if applicable) write down some additional comments or thoughts. For example, this paper could be interesting for idea X or this papers reminds me of another paper.

Based on the abstract, I decide whether or not I want to read the whole paper. If yes, I transfer it to a new folder, conveniently called ‘Read whole paper’. If no, I delete the paper from the list and it is saved in my library. One of my fears was forgetting about papers. A paper might not be relevant at the moment, but in a couple of months I might need it. By taking some notes in Evernote, I keep my ideas stored somewhere (instead of my brain, which is not foolproof…). Later on, I can easily search through my notes with the very handy search function in Evernote.

3. READ!

And finally, I read the papers in my folders ‘ Avian Hybrids’ and ‘Read whole paper’ , when I find the time…

PhD read

I hope this post was useful. If you have any questions or suggestions, don’t hesitate to contact me. I will try to read your mail as soon as possible! 😉

Can Stray Golf Balls Influence Duck Evolution?

An evolutionary perspective on ducks getting hit by golf balls. Fore!

Have a look at the video in the following link:

You can see how a golfer tees off and hits an unsuspecting duck clean out of the air. From an evolutionary point of view, this raises the question whether stray golf balls could influence the evolution of ducks. Evolution mainly operates through natural selection, that is differential survival (and reproduction) of individuals. For example, if bigger individuals have a higher chance of survival, they will produce more offspring, and the next generation will exhibit a marked increase in size (given that offspring inherit the large size from their parents).

So, could stray golf balls provide a new selection pressure in duck evolution? Probably not, because the chance of getting hit by a golf ball is too low to have any significant effect on the duck population. Hitting a duck with a golf ball can be regarded as a random event. Somewhat similar to the process of genetic drift where some genetic variants increase or decrease in frequency at random. Here, the duck has been randomly removed from the gene pool by a golf ball. This accident may be dubbed ‘genetic drive’ (the golfer performed a so-called drive: the long distance shot played from the tee box).

I do wonder if this swing also counts as a birdie


Evidence that ancient reptiles were extremely happy

Today I was skimming through some scientific papers on my ‘to read’ list. At the end of a Scientific American paper by Jonathan B. Losos, entitled Adaptive Radiation, Ecological Opportunity, and Evolutionary Determinism, an old drawing filled in the empty space below the reference list. Here is the drawing with the caption:

Ancient Reptiles

Judging from the blissful smile on the faces of these ancient reptiles, they were extremely happy to be alive. Very convincing (although indirect) evidence that life in these times was more relaxed than nowadays! Which reminds me, I should continue finishing my ‘to read’ list…

Code Orange for the Bengal Tiger!

Genetic study highlights challenging conservation of the Bengal Tiger in India.

India not only houses a significant proportion of the human population, it is also home to roughly 70% of the global tiger population. The most numerous subspecies, the Bengal Tiger (Panthera tigris tigris), roams in six areas across India. A study in the scientific journal PLoS ONE assessed the genetic architecture of a population in one of these areas, the Terai Arc Landscape (TAL), a stretch of habitat along the foothills of the Himalayas. The results, based on 13 microsatellites,  are not very reassuring for this endangered cat…

Bengal Tiger (by Kaksbhatt, from Commons Wikimedia)

First, the genetic diversity of Bengal tigers in TAL is lower compared to previous studies. Small populations often exhibit low levels of genetic diversity and are expected to lose more diversity due to genetic drift. This continuous reduction in genetic diversity might make it impossible for these populations to adapt to rapidly changing circumstances.

In addition, the level of inbreeding among these tigers is relatively high (mean inbreeding coefficient = 0.23, for the formula fetishist among the readers). Inbreeding, the mating between close relatives, can have devastating health effects (just look at the royal families in Europe) and often leads to a further degradation in genetic diversity.

Finally, the genetic analysis uncovered two distinct populations connected by moderate gene flow. These two populations, referred to as Corbett Tiger Reserve (CTR) and Rajaji Tiger Reserve( RTR), are connected by a corridor (very originally dubbed the Corbett-Rajaji corridor). The genetic differentiation between CTR and RTR suggests that this corridor is under severe pressure by human disturbance. The loss of another corridor has previously led to the extinction of a western tiger population in RTR. The Corbett-Rajaji corridor needs to be preserved, certainly a challenge in this area of India, which has a higher population density (over 500 people per km2) compared to the Indian average (300 people per km2).

One solution is the relocation of human settlements. For example, the Gujjars, a pastoralist community in TAL, were relocated to the east, creating more room for the tigers. But can the Indian government convince people to leave their homes for a striped cat? The locals certainly wouldn’t move for an insignificant songbird, meaningless moth, or trivial termite. In this respect, tigers can function as so-called ‘umbrella species’, which is a species selected for making conservation-decisions, because protecting these species will indirectly protect other species in their ecological community.

umbrella species


Singh, S., Aspi, J., Kvist, L., Sharma, R., Pandey, P., Mishra, S., Singh, R., Agrawal, M., & Goyal, S. (2017). Fine-scale population genetic structure of the Bengal tiger (Panthera tigris tigris) in a human-dominated western Terai Arc Landscape, India PLOS ONE, 12 (4) DOI: 10.1371/journal.pone.0174371