Tuesday, November 22, 2011

Apes (and other primates) on the internet -The digital morphology museum

I’m a huge fan of Internet Databases, such as the Nespos Database, where you can get access to CT-Scans of original fossils as well as recent specimens for your work.. However what always bothers me is that all those databases aren’t completely open to the public. For example to get access to the Nespos Database, you need to explain why you need access to it, you need to be a member of an academic institution and you need to pay for a membership.
These things make it rather difficult, if for example biology teachers want to use these materials during their courses (which would be a really great thing).
This is why I was really excited, when I read on Lawn Chair Anthropology about the “Digital morphology museum” of the university of Kyoto. Here you can take a look at their whole stock of CT and MRT-Scans of a bunch of different Primate specimens and, after a small registration process, you can even download these Scans for free.

Right now I’m thinking about something for which I can use this Database. Perhaps some kind of online course? I don’t know but I’ll come up with something.

If you want to take a look for yourself, you can do it right here.

Wednesday, November 16, 2011

A lot of trees here...

Those few and lucky people who read this blog on a more regular basis probably have realised that  a lot of the stuff I wrote recently dealt in some manner with phylogenetic trees.
On one hand this does not seem to be very suprising since taxonomic questions always were some kind of focus of this blog. However the other reason for this is because I finally found a suitable topic for my M.A. Thesis (yaaaay!). I won't write about the exact topic as of yet simply because I still need to write it down properly, but if you're interested, just look at the comments under this Post, it's mentioned in one of them.

I plan on covering the whole process of me writing the thesis, analysing my data and whatever else I need to do on this Blog. This is going to be my first real scientific work so it might be interesting to see what kind of stupid mistakes I make and in what kind of pitfalls and Problem I might run into. Also, I want to use this blog as a Plattform where I can write down some of the ideas I get while working on my thesis. In fact this is why I wrote my last post and there's another one coming soon.

In other news: This week I'm in Frankfurt at the Senckenberg-Museum to attend a congress about the ecology and organisms of the eocene. Since I'm mostly interested in primates and I don't have that much knowledge about fossil invertebrates and I also have to prepare my Thesis (yaaaay!), I will probably visit the conference only on Friday, since this is the "primate day".
Of course, good ol' "Ida" will be a big topic on this day and from what I can tell from the abstracts, I'm pretty sure the discussions are going to be very "interesting".

Wednesday, November 9, 2011

Some thoughts on the phylogenetic relationships between great apes and humans (and why morphology fails to answer this question)

Taxonomy isn’t a really satisfying branch of evolutionary biology, especially if you’re interested in the phylogenetic relationships between great apes, hominins and humans. You always tend to step on someone else’s toes and sooner or later this other person starts to harass you with critique. One of the standard arguments which are brought up against almost any kind of phylogenetic study is that the characters you used for your phylogenetic reconstruction are misleading, because they’re homoplasies. “Homoplasies” are characters which evolved independently in two closely related species and are usually your biggest enemy when it comes to taxonomic questions. 

fig. 1 Today's topic: The "correct" phylogenetic relationships between great apes and humans and why morphologic characters fail to reproduce these results.

This problem seems to be overabundant in Paleoanthropology, since I have yet to see a single taxonomic paper which isn’t immediately criticized for using homoplasious characters for their hypothesises. This is probably due to the reason that morphological characters in general are having a hard time reconstructing the “correct” phylogenetic relationships between great apes and humans (fig.1), which was established with molecular characters (e.g. Wood & Collard, 2002; Wood & Harrison, 2010; Strait & Grine, 2004). And if your characters aren’t able to reproduce the correct phylogeny between extant species, how can you expect them to get it right with fossil species?
Recently one of my Professors pointed me towards an interesting problem which made me wonder if those difficulties are really due to too many homplasious characters in your datasets.

Imagine a Population “P”
This Population has some characters which are polymorphic, which means that they exist in different states within this population. For the sake of simplicity I will only use two characters. The first character has either the state “+” or “-“
The second character has either the state “circle” or “square” (I’m too inept to put those symbols within this text –sorry).

Now this Population starts to split up.

Shortly after P1 split up from P, the rest of the original population splits into two additional subpopulations (P2 & P3).

Eventually all those three subpopulations will evolve into three different species

If we look at the pattern in which those Populations split from each other, we can see that P2 and P3 are closer related, because they got separated after P1 split away.
Now imagine that we weren’t able to witness this pattern and instead we have to reconstruct it with a cladistic analysis, which is usually the case if you want to know how extant species are related to each other. The problem here is that there is no clear signal. Instead your results depend highly on the character you’re using. Here we are in a situation where we have three equivocal hypothesises just because you had an polymorphic, ancestral population which split up so fast, that it wasn’t possible to fixate one character state within the whole population. Instead the ancestral polymorphic state was carried into those new subpopulations and the trouble we encounter if we want to use those characters for phylogenetic reconstruction is simply because of this incomplete lineage sorting and not because the character were homoplasious.

Of course I came up with this example, because we can see the exact same phenomenon if we look at molecular studies which dealt with the phylogenetic relationships between great apes and humans. Satta et al. (2000) found that out of 46 genetic markers, only 60% supported the “true” phylogeny (see fig. 1), the other 40% either supported a Human-Gorilla dichotomy, a Gorilla-Chimpanzee dichotomy, or a trichotomy.
Salen et al. (2003) came to similar result as they used “Alu-SINEs” to reconstruct the great ape phylogeny. Although Alu-SINEs are probably the best characters you can use to resolve any kind of phylogenetic relationship within primates, simply because it’s highly unlikely that they independently occurred at the same place on the DNA. Nevertheless they found one Alu SINE which humans and Gorillas had, but Chimpanzees didn’t.

But how polymorphic was the ancestral population of Gorillas, Chimpanzees and Humans on a phenotypic level?
This question is almost impossible to answer, at least for now. we have no Idea how the genotype relates to the phenotype as long as we aren’t able to close this gap we’re not able to make anything more than vague assumptions about this question. Looking at this whole story of Neanderthals and “Denisovans” interbreeding with modern humans (Greene et al., 2010; reich et al., 2010), which probably means that we have to broaden up our own species to include at least the Neanderthals if not even Homo heidelbergensis, I think we can see that a species can vary pretty much on a phenotypic level without interfering with reproduction.

This whole story definitely doesn’t make things easier since we now have two problems: Convergent evolution and incomplete lineage sorting. But I think we can at least try to differentiate things a little bit more. Although we have no Idea how much incomplete lineage sorting has affected the phenotype of the African great apes and humans we can’t rule out that it had no effect at all. Therefore it’s pretty much futile to make any assumptions about the “quality” of certain characters, since we have no idea to what extent those characters were affected by incomplete lineage sorting. As we could see, characters can be pretty much invulnerable to parallel evolution and still indicate wrong phylogenetic relationships (Salen et al. 2003).
Maybe we should instead explicitly look at each and every character, especially those which support the “correct” tree and test, if they share a common origin.


Collard M, & Wood B (2000). How reliable are human phylogenetic hypotheses? Proceedings of the National Academy of Sciences of the United States of America, 97 (9), 5003-6 PMID: 10781112
Green, R.,et al (2010). A Draft Sequence of the Neandertal Genome Science, 328 (5979), 710-722 DOI: 10.1126/science.1188021
Reich, D., et al. (2010). Genetic history of an archaic hominin group from Denisova Cave in Siberia Nature, 468 (7327), 1053-1060 DOI: 10.1038/nature09710
Salem, A. (2003). Alu elements and hominid phylogenetics Proceedings of the National Academy of Sciences, 100 (22), 12787-12791 DOI: 10.1073/pnas.2133766100
Satta Y, Klein J, Takahata N (2000). DNA archives and our nearest relative: the trichotomy problem revisited. Molecular phylogenetics and evolution, 14 (2), 259-75 PMID: 10679159
Strait DS, Grine FE (2004). Inferring hominoid and early hominid phylogeny using craniodental characters: the role of fossil taxa. Journal of human evolution, 47 (6), 399-452 PMID: 15566946
Wood, B., Harrison, T. (2011). The evolutionary context of the first hominins Nature, 470 (7334), 347-352 DOI: 10.1038/nature09709

P.S.: I just realised that used almost the exact same formulation for the title of this Post as I used for my last title. I'm deeply sorry for my lack of creativity. (11.10.2011)

Saturday, October 29, 2011

The debate that should not be: Some thoughts about creationism, intelligent design and other "alternative explanations"

If you blog about human evolution there’s one topic which is really hard to avoid. I’m of course speaking about creationism, or “intelligent design” or some other kind of unscientific explanation about human evolution. So far I tried to avoid this topic as best as I could, since I don’t feel competent enough to actually write something about it. However, last week I received an Email from one of my German readers which forced into writing something about it. 

I don’t want to talk about the exact content of the email or about the (rather short) debate I had with the person who wrote me this Email. What I want to talk about is my point of view on this whole issue and why I think we shouldn’t even have these kinds of debates.
It goes without saying that this text only represents my opinion so don’t interpret the stuff I’m going to write as some kind of general explanation about this topic.
I’m going to split this Post into three different parts to make it a little bit easier to follow my line of argument.

1. Why Sciences and Religion shouldn’t interfere with each other.
To understand this point, first of all we need to define what we understand under the term “God”. This probably is a topic for not one but several posts itself, but for the sake of my argument, let’s put as simple as possible.
“God” is an entity which almighty and which isn’t completely detectable. The first premise directly leads to the latter, because if an entity is almighty then it also has power over those parts of reality which we can’t perceive.
Now, if we want to build a scientific hypothesis, we have to make sure that we can actually falsify it (if you want to know why, I wrote something about it here). But how can we falsify something which isn’t completely detectable? The simple answer is: We can’t.
Therefore, if we try to explain our world due to the work of a non detectable entity, we’re leaving the scientific framework.
The scientific method is not suited for those questions. You simply can’t prove or disprove God due to scientific methods. Or to put it more bluntly: “God doesn’t matter in Science”
This does not mean however, that each scientist is an atheist. You can believe in whatever you want, as long as you don’t try to mix up both “worlds”. Every attempt to do otherwise ends in a logical fallacy.

2. Why, in my opinion, Science produces reliable statements about our world.
Some of the more “advanced” criticisms of evolutionary theory try to show that the theory itself or the scientific method itself is somehow erroneous in some manner.
The interesting thing about the different perspectives on the world, whether they are scientific or more metaphysical is, that all of them need some kind of basic assumptions to actually work. If you don’t make those assumptions you will, at some point during your argument, come to a stage where your own arguments become circular.
But which are those basic assumptions for a scientific world-view?

The first assumption is that we live in a world which consists of laws.
-If there are no laws in nature, then we won’t be able to make any reliable statements about it.

The second assumption is that we’re able to recognize these laws.
-Science is a cognitive process. If we weren’t able to recognize any of these laws, than we couldn’t do any kind of science.

These basic assumptions are the fundamental aspects on which every other scientific theory is build upon and it’s the only context in which they make any kind of sense. The question, whether or not I “believe” in evolution isn’t a real question. It’s simply the explanation which, in the framework I presented here, makes the most plausible. The “question of faith” doesn’t ask itself if you look at separate scientific theories, it’s only important if you look at the basic assumptions of Science. And so far I haven’t found anything which convinced me that those basic assumptions are wrong.
However, this does not answer the question, whether or not science can answer every question. Unfortunately we will never receive a message which says: Achievement get! Explain every law of nature!” Or to say it with the words of Gerhard Vollmer:

"The degree of consistency between our theoretical knowledge of the world and the real world remains unknown to us, even if it's complete."

[From: Vollmer G. (1975) Evolutionäre Erkenntnistheorie Hirzel, Stuttgart, Leipzig, p. 137, (probably horribly) translated])

Ok, after we set the stage for the debate, let’s move on to the original point of this post.

3. What’s that stuff got to do with creationism?
The first point of my argument shows that it’s completely impossible to prove or disprove God within a scientific framework. Therefore any kind of “theory” which tries something like that is making a logical fallacy. This works in both directions. You can’t explain any kind of natural law with the work of God, as well as you can’t demonstrate that God doesn’t exist.

The second point shows that it’s not the question whether or not someone believes in a certain scientific theory, because its validity is the result of the scientific framework. Not “believing” in a certain theory means omitting any kind of ability to recognize laws in nature and therefore this person leaves the scientific framework. Any kind of argument which follows after this point is subject of my first line of argument.

Now about the debate on creationism: Both of my arguments show that any kind of argument which is brought up by these people is not part of the scientific framework. This means that their arguments don’t matter in a scientific discussion. But it also means that you’ll never be able to use purely scientific arguments if you want to debate with them. Someone who isn’t convinced that we’re able to recognize laws in nature will never be convinced by scientific arguments, simply because he doesn’t believe them.

In my opinion the only thing you can try to do is to show, that there are no conflicts between scientific and metaphysical (e.g. religious) views on the world, as long as both sided try to stay within their specific framework. Both sides have completely different premises and thus there is no reason for a conflict. Those conflicts only occur if one side tries to interfere with the other, but as I demonstrated, this is logically false.
Trying to debate this stuff on this level is pretty difficult, since you’re leaving the scientific framework and enter a purely philosophical one and I think this is the reason why this whole debate does not take place on this level. This and also because I think there isn’t much public interest in these kinds of debates. The public tends to direct its attention to the loudest participants and those aren’t often the most competent when it comes to actual discussions.

Anyway, this is my opinion about this whole story. I have to admit that I'm not very comfortable with this post. Firstly because I think I left some important questions unanswered and secondly because I’m not very confident that my English is actually good enough for this topic, in fact I’m pretty sure it isn’t. So, if you don’t understand some of my arguments, please tell me and I’ll try to clarify things. Furthermore I would really like to know how other people think about this debate.

Wednesday, September 28, 2011

Where to put Australopithecus sediba?

It took me some time to decide what I should do with Australopithecus sediba on this Blog, in the end I decided to concentrate on the aspects I at least know a little bit of, one of them is taxonomy.

I had to reconstruct a bunch of phylogenetic trees in the last few months and I found  some free online tools which enabled me to do this without using any fancy (and expensive) Computer Programs. The only disadvantage of these resources is that they were originally made for molecular data sets. This made my work a little bit more complicated since I had to modify my morphological datasets in a way that these programs were able to work with them. I won’t talk about the exact process right now; instead I want to show you some of the stuff I did with Australopithecus sediba.
First of all, let’s have a look at a classic tree which illustrates the phylogenetic relationships among the genus Homo. I took the tree from Strait et al. (1997) for this particular example:

Strait et al. (1997)
There’s nothing really special about this tree, sure you could discuss whether or not the shown phylogeny represent the true relationships of these fossils, but discussing this stuff always tends to get boring, since you have to look at the characters and you need to discuss the validity of each of them
To make things a little more interesting, I took the character matrix from Strait et al. and included Australopithecus sediba. The characters for Australopithecus sediba were taken from the initial description of this Fossil (Berger et al., 2010). This is the tree you get, when you run this modified matrix through an Analysis:

Same character matrix but with A. sediba.

Sediba ruined everything!
What in the first tree looked like a nice and clear relationship is now collapsed into something completely indifferent.
To make things clear, the taxonomic position of Homo habilis and Homo rudolfensis never was pretty clear. In fact, the latter species was established, because the initial hypodigm (the total sum of all fossils which describe a species) of Homo habilis was so diverse in its morphology that it was split up into two separate species. The “new” species was then called Homo rudolfensis. I won’t talk up the exact reasons why this was the case, since it would make this post too long, but I will eventually come back to this topic in another post.

Let’s go back to Australopithecus sediba for the moment. It’s not only that the fossil practically ruins the common taxonomic picture of relationships of early homo, it’s also very young. Right now, Australopithecus sediba is dated at about 1.9 million years, this is very young, if you keep in mind that there are fossils of Homo habilis and Homo rudolfensis which are much older then 2 million years. There are also possible fossils from Homo ergaster/erectus which are only slightly younger then the sediba fossils. Now add the about 1.7-1.8 million year old remains from Dmanisi/Georgia to this mess and you can see how complicated this whole story starts to look.
Fortunately the tree I showed you at the beginning of this post isn’t completely useless since it shows that Australopithecus sediba falls somewhere within the relationship of Homo ergaster/erectus, Homo rudolfensis and Homo habilis.

So let’s have look at the possible relationships and the possible consequences of each scenario:

Scenario if A. sediba would share a LCA with the Genus Homo

In this scenario, Australopithecus sediba would share a last common ancestor with the Genus Homo. The only problem which arises from this tree is that you have to discuss what you should do with the Homo rudolfensis and habilis fossils which pre-date the emergence of Australopithecus sediba in the fossil record.

All other scenarios basically ruin our contemporary picture of the Genus Homo:

Two of the possible relationships if A. sediba would be place somewhere within the Genus Homo
 No matter which scenario we look at, none of them shows the Genus Homo as a monophyletic group. This means that either we have to include Australopithecus sediba within the genus Homo which I’m not very fond of since it would lead to an even weaker definition of it. Or we have to exclude Homo habilis and/or Homo rudolfensis from the genus Homo. The Genus Homo would then begin with Homo ergaster/Homo erectus and everything before that species would be either inside the genus Australopithecus or in a complete new genus.
Personally, I have no Idea what I should make out of this stuff. Right now everything seems to contradict itself and I think we need to have much more knowledge about this certain period of time. This means of course more fossils from this period but also more research on the already known fossils.
What I think we can safely right now is that the emergence of the genus Homo didn’t happen in a gradualistic fashion where one species slowly evolved into the next one. I think what we have here is a series of, possible independent, speciation events. This would explain why we have that many species that look similar to another but who overlap in spatial as well as temporal aspects and whose phylogenetic relationships are completely unclear. I have some more thoughts on this matter and I will write another Post where I go into much more detail. For now, all I can say is that, although Australopithecus sediba completely ruins the contemporary phylogeny, it might help us to really understand what happened back then.

 Berger, L., de Ruiter, D., Churchill, S., Schmid, P., Carlson, K., Dirks, P., Kibii, J. (2010). Australopithecus sediba: A New Species of Homo-Like Australopith from South Africa Science, 328 (5975), 195-204 DOI: 10.1126/science.1184944
Strait, D., Grine, F., Moniz, M. (1997). A reappraisal of early hominid phylogeny Journal of Human Evolution, 32 (1), 17-82 DOI: 10.1006/jhev.1996.0097

Monday, September 26, 2011

Back from Leipzig

Well, the Congress is over and after a very long and very weird train ride, first there was someone who decided to jump in front of another train, which led do a 45 minute delay and after that, some Idiot decided it would be a good Idea to forget his suitcase within the train. And since some other Idiots decided to fly two airplanes into some buildings 10 years ago, a forgotten suitcase in a train is a case for the police. To make a long story short: I arrived in Mainz with a total delay of around two hours yesterday and was as exhausted as I was the days before.

The conference itself was great. I’ll have to admit that I thought I would be able to participate in the discussions there, but I saw pretty quickly that most of the other People there were on a completely different level then I was. This bothered me for quite some time, but then I realised that, as an undergraduate student, I don’t need to know all this stuff by now. So instead of showing off my tremendous knowledge (which I didn’t had) I started to enjoy listening to the stuff other people said and there was a lot of really interesting stuff going on.
In the end, the days in Leipzig were a very exhausting, intimidating and humbling experience, but I’m glad I went there. I saw how much stuff I still need to learn to really understand this field but I also realised that I really want to learn all this stuff. The last days gave me even more motivation to continue my studies so that maybe by the same time next year, I have something to present at the next ESHE Meeting, or somewhere else.
I’ll try to write about some of the stuff I heard in Leipzig within in the next weeks and there’s also this stuff about Australopithecus sediba which I wanted to write. I hope to get this Post done within this week.

At last I want to thank Anna Barros and Tracy Kivell who were both kind enough to answer a bunch of my questions and listened to some of my weirder thoughts during the Poster session on Friday.

Friday, September 23, 2011

Eric in Leipzig: Lessons from the first day

Scientific congresses are, especially if you're a little student a place to learn a lot of new stuff. So far I learned the following lessons:

1st Lesson: Don't be cheap.
I wanted to save 12,50€ for an addional night in a bed in a cheap hostel and decided to arrive at Leipzig the day the conference started. Only Problem: The conference started at 10am. This forced me to spend my night in a train, which lead to the nice fact, that I had around 1 hour of sleep in the night from Wednesday to Thursday.

2nd Lesson: Don't attend to a course on geometric morphometrics when you're deprived of sleep.
Lesson 1 leads directly to Lessen 2. I remember some of the stuff that was mentioned in this course yesterday but the most parts of it, and I think those were the more important parts, I forgot about five minutes after they were told.

3rd Lesson: Speak more english!
I think that I understand english fairly well, be it spoken or written. I think I'm also able to write in english in a at least partially understandable way. But my spoken english is abyssimmal. I have next to zero practice in speaking english and therefore my pronounciation is just bad and unsophistacated. And as you might guess, it's pretty hard to ask intelligent questions if hearing yourself speaking gives you nausea.

Well, those are the lessons I learned yesterday. I also learned something anthropological, but nothing of it is related to this congress and besides, I learn something about Anthropology almost all the time.

Let's see what interesting stuff happens today.

P.S.: I'm pretty sure, the english in this post isn't very good as well. But please keep in mind that it's around 7am and I'm still a little bit tired.

Tuesday, September 20, 2011

Sediba Post: Status report

I said I was going to write something about Australopithecus sediba, and believe it or not, I still intend to. However there were two things which mainly kept me from doing so within the last weeks:

1. Time:
In the last two weeks, my studies kept me from doing anything related to A. sediba other then reading the papers.

2. My Head:
To make things worse, I got a really good Idea what I can do with this fossil. There's something really neat which I wanted to demonstrate for quite a long time now, and I think the sediba fossils are the perfect objects for this little project. However I will need some time to prepare this post properly.

And at last, I'm about to go to Leipzig at Wednesday evening, where I will have the pleasure of walking around on a scientific congress until sunday. So don't expect something related to Australpithecus sediba until next week, but I might write something about this congress if I find something interesting.

Until then, why not read something about Australopithecus sediba at "Lawn Chair Anthropology"?

Sunday, September 11, 2011

Australopithecus sediba: First (small) information dump

I didn't had enough time to completely dig through all the information towards Australipithecus sediba, but I intend to do so tomorrow. Until then, why not heare some words about Australopithecus sediba by some people who are far more competent then I am?

For example, you can read/hear an Interview with Lee Berger on the Science Podcast: Right here

Or you can read/hear an Interview with Lee Berger and Bernard Wood at NPR: Over there

Friday, September 9, 2011

The slump is over!

(well, at least kind of...)

Sometimes it's funny how things turn out in the end. Just as I'm about to finish the Assignment that ate up all my further interest in anything even remotely related to science so I could get started to get back into maintaining this Blog, Science released a bunch of Papers regarding Autralpoithecus sediba. This species was first announced last year, an announcement I somehow completely ignored back then, probably because the authors didn't put any effort into making some waky claims that could've set me up.
Anyway, I haven't looked much into the articles but I intend to do so within the next few days and report on what I think about them.

And since I have a little more time at my hands, I'll try to write about some of the other stuff that circles in head as well.

Wednesday, July 20, 2011

Speculation on Speciation

There is one topic which somehow touches almost every major debate in Paleoanthroplogy and this is the question about how speciation actually works. There were a lot of very smart people, who already wrote about this stuff, and I even read some of them. But a large proportion of what I’m going to say about this topic comes from my own thoughts on this topic. So if someone finds a mistake in my arguments, please let me know.

When it comes to speciation, there are basically two different opinions on how speciation could work. The first one is sometimes called “punctualistic” or “phylogenetic” and says that speciation usually results in a split in which the ancestral species splits into two different “offspring-species” (there is probably a more suitable term for it, I just can’t remember the English translation).

The second one is called “gradualistic” or “anagenetic” speciation and says that one species can, if there is enough time; evolve into another species without any form of splitting.

Now although there are many species concepts out there, the main criterion to recognize a species is, if their members are able to interbreed with other animals. This means that no matter what type of speciation process we propose, at some point during this process there has to be some kind of “breeding barrier” (once again, I’ve no Idea how to translate this term), be it either geografical, behavioural or otherwise.

Now let’s take a look on how this stuff actually works in case of a punctualistic speciation:
Exdample for a punctualistic speciation: Assume a Species "A" lives in a certain habitat "X". Now due to some reasons (e.g. a geological event), a barrier arises in said habitat. This barrier changes the enviroment on both of its sides and furthermore prevents the now separated populations of "A" to exchange their genes. With time, those two sperate populations will adapt to their new enviroments and will become two distinct species.

Ok, this was quite easy wasn't it? But how about gradualistic speciation? Her I'll have to admit that although I spent quite some time on this question, I just could come up with one scenario:

1. Let’s assume the species we’re looking at is restricted to one habitat

2. Let us further assume that all population of said species are able to exchange there genes with on another.

3. Now the habitat of said species changes and due to the wonder of natural selection the species adapts to those changes.

4. As time goes by the species within that habitat would differ significantly from the species we had before this process started, so that we could safely say that we have discovered a new species.

There is only one big problem with this model. If we assume a constant gene flow between the seperate populations of our example species, than this means that there never was any kind of mating barrier at any point in time. So how can we be sure that the species we witnessed at the end of that process isn’t able to interbreed with the species we observed before this whole thing started? Sure, we could assume that since both “forms”, as I might call them right now, are so different that they probably wouldn’t have interbred, if they would’ve lived at the same time.
This assumption is pretty similiar to the concept of a “Chrono-species” which defines species solely after their chronological appearances in the fossil record.
The Problem here is that we’re not able to test, whether or not, those species really weren’t able to interbreed. It is as always when we have to deal with extinct species, we simply can’t be sure about it. In the end the only safe thing we can say is that every model on the evolution of a certain species, which relies on a gradualistic model of speciation, is highly speculative.

There are two recent examples within Paleoanthropology where this Problem occurs. The first one is the possibility to draw a direct line from Australopithecus anamensis to Australopithecus afarensis (Kimbel et al. 2006, Haile-Selassie et al. 2010). The other one are the genetical evidences of interbreeding between modern Humans and Neandertals (Green et al. 2010) and modern Humans and those strange people from the Denisova Cave (Reich et al. 2010).
In both cases we have clues, if not even hard evidence in the second example, of constant gene flow between several populations over a long period of time.
The interesting question now, is what we should do with these findings. Should we just keep these different species and use some kind of dodgy chrono-species concept or should we lump all those different species into one or probably two?

I have to admit that, due to my education, I am a little bit biased towards the “lumping” part.
Right now I am not convinced that gradualistic speciation is possible, or to be more precise, that it is detectable by us. So the scientifically safer way for us right now, is to stay cleer of this concept unless we can find some way to test it.
Surely, the last word isn’t spoken on this one, and right now a can think of several flaws in my own argumentation, but I’m still convinced that it is the preferable way of thinking.


Kimbel, W., et al. (2006). Was Australopithecus anamensis ancestral to A. afarensis? A case of anagenesis in the hominin fossil record Journal of Human Evolution, 51 (2), 134-152 DOI: 10.1016/j.jhevol.2006.02.003
Green, R., et al. (2010). A Draft Sequence of the Neandertal Genome Science, 328 (5979), 710-722 DOI: 10.1126/science.1188021
Haile-Selassie, Y., et al. (2009). New hominid fossils from Woranso-Mille (Central Afar, Ethiopia) and taxonomy of early Australopithecus American Journal of Physical Anthropology DOI: 10.1002/ajpa.21159
Reich D., et al. (2010). Genetic history of an archaic hominin group from Denisova Cave in Siberia. Nature, 468 (7327), 1053-60 PMID: 21179161

Monday, July 18, 2011

I'm still alive!

Unfortunately this isn’t a Post with any real content. In fact, it’s one of those “I’m just writing something to show that I still intend to write something”-like Posts.

The last weeks were pretty boring on when it came to interesting paeloanthropology-related news and those Posts I tried to write were in fact so bad, that I didn’t finish them. And at last, right now I’m desperately trying to finish my studies and unfortunately even this isn’t going as easy as it used to be. I even thought (and tried) to write about the stuff I’m working on right now, because it’s indeed quite interesting, but I just couldn’t find a suitable way to write about it, yet.

Anyways, things are looking a little bit brighter in the near future since I’m going to two conferences later this year. The first one is the meeting of the “European society for the study of human evolution”, which is held in Leipzig by the end of September. I have no idea about the exact program of this meeting, but I’m always excited to get in touch with other people from my own field, so I think it’s going to be pretty interesting.

The second one is the one I’m really looking forward though, partly because it’s held in Frankfurt which means that I can sleep at home and not in some cheap hostel. The topic is also quite interesting since it’s about ecology of the eocene and the early evolution of primates. Giving the fact that there was a lot of noise around Ida in the last two years I’m pretty sure, that this meeting won’t be very boring. I intend to write something about those meetings, be it in preparation for them, or while I attend them, so keep looking forward to it.
I’m still trying to write something within the next weeks though. I have some Ideas which could be suitable for interesting posts, so let’s hope that I can at least finish at least two of them.

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.

Wednesday, April 27, 2011

I don't want to be a Bonobo

This Post is a reaction on the Post  from “Ariel Cast out Caliban” by Eric Michael Johnson.

There are many things in the world that annoy me: People in the bus who desperately hammer on the “stop” button to open the door, Professors who seem to know where my exact interests are although they haven’t talked in years and stupid ideologies which use biological examples to justify their view on the world.
Although I’d love to talk about all those things (especially the first one) let’s stick to the third one for now.
Every now and then, I encounter the following sentence in some way or another: “We should be like Bonobos.”

What’s really interesting is that the extremes of what could be called “human nature” are represented by our closest living relatives: Chimpanzees and Bonobos, at least if we rely on popular representations of those two species. Chimpanzees are usually presented as egoistic, brutal and aggressive. Whether Bonobos are the ultimate pacifists, their groups are led by the female individuals and conflicts and stress are usually resolved by some way of sexual interaction -instead of just bashing the head of a rival or tearing apart a helpless Colobus Monkey.
One of my favourite German biologists, Hubert Markl wrote in 1983 that all models on human nature usually have two aspects. The first one is the description of the present state of human nature, which is always pretty negative. The second one is the ideologically tainted vision of how humanity should be.

If we use this model on our closest relatives, the Chimpanzees represent our present state, while the Bonobos is the Vision of what we should become. From time to time I encounter this case, be it in the media or from people I meet and it might come up again in the next time, after some of the results of this study from Perelman et al. (2011) get more public attention.
This study, which deals with the Phylogenetic relationships of all primates, found that after the split between Chimpanzees and Bonobos, there was a higher rate of Change within the Genome of Chimpanzees as within the one of Bonobos. To make a long story short: This higher rate of change could lead to the conclusion that Bonobos are closer related to us, then Chimpanzees. Until now it was assumed that both species are equally related to us.
This of course changes everything! Our closely related living relative is the ultimate example for altruism and cooperation. The true picture of our own nature! Once again, Man cut himself from his own natural heritage. Now we simply have to return to our own biological roots and all our problems are solved! I’d bet a large amount of money that someone will write something like that, just a little more elaborated and maybe a little more esoteric. Maybe I should write this stuff myself, put in a book and sell it to bolster my very slim budget.

Jokes aside, my point is as follows:
Both Chimpanzees and Bonobos are just models for our own ancestors. Those Models fit in some cases more and in some cases less well on our past. We can’t just transfer our observations on present day animals into the past, just to help us to support some kind of weird ideology, as we can’t use them to justify acts of brutality against ourselves.
Furthermore, these genetic differences between chimpanzees and Bonobos are by now just statistical differences. We have no Idea if those differences are within regions which are related to behaviour or not.
If we look at ourselves, we can see that we’re capable of both extremes: exceptional brutality as well as exceptional altruism. Bonobos and Chimpanzees could help us to understand how we acclaimed those behaviours and how they’re funded in our own biological heritage. Sure, there’s no potentially World-saving conclusion within this stuff, but we need it, if we want to understand our biological “nature”.

Ideologies are always made by humans; and Primates, especially apes, were always used as a screen on which we can project ourselves on. The Chimpanzees were used for all that’s negative about us, while the Bonobos stand for everything positive. But we must not forget that both species are not “unfinished humans” or “almost human”, they are Apes. They got their own history, as we do. Their history might help us to understand our own history, and therefore our “nature”, in a much better way, but as closely as we’re related to them, they can never be role models for us.


Markl, H. (1983) Wie unfrei ist der Mensch? Von der Natur in der Geschichte. In: Markl, H. (ed.). Natur und Geschichte. R. Oldenbourg, München, Wien. p. 11-40.
Perelman P, Johnson WE, Roos C, Seuánez HN, Horvath JE, Moreira MA, Kessing B, Pontius J, Roelke M, Rumpler Y, Schneider MP, Silva A, O'Brien SJ, & Pecon-Slattery J (2011). A molecular phylogeny of living primates. PLoS genetics, 7 (3) PMID: 21436896