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

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.

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.


References:

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

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.

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.




References:



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

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.

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.



References:

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