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 The only disadvantage of these resources is that they were originally made for molecular data sets.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.