Saturday, 24 September 2011

A Creationist Misconception About Transitional Forms

Palaeontology is just the study of old bones and all we can know about them is that something died. It is surprising how many people have that view of the fossil record, with no idea that we can study the lives of many fossil organisms in a lot of detail, even able to determine their behaviour. When it comes to studying evolution using the fossil record we can learn quite a lot about what happened. The creationist misconception I intend to clear up is not the impoverished understanding I just mentioned, but the idea that in order to claim a fossil as a transitional form we must demonstrate that this particular organism reproduced and passed on its genes. This is an unreasonable request based on a misunderstanding of palaeontology.

What is a transitional form?

The public often use the term "missing link" when talking about fossils which plug a gap in our knowledge. This term is a useless tautology because a missing link is always missing by definition. Not to mention, whenever a "link" is found, that just creates two more smaller gaps which need filling. The correct term is transitional form which is used to refer to fossils which possess traits which fit them between two taxonomical groups (intermediate form is roughly synonymous with transitional form). Technically all fossils are transitional forms, but that assumes evolution and so will not pacify creationist attacks. What creationists seem to request is those transitions between major groups which grab the headlines and fortunately we have many.

One thing to keep in mind is that transitional forms should not be put in a chain of ancestor-descendent relationships. This cannot be done with the fossil record because it creates untestable hypotheses and becomes nothing more than story telling. Transitional forms should instead be thought of in terms of the traits they possess, as they indicate the latest possible time that trait could have evolved (the traits in question are shared, derived characteristics, which can get confusing when taken in isolation and with convergence taken into account). The traits should also not be expected to evolve at the same rates or in a sequential order; there can be overlapping.

So, did transitional forms reproduce?

It is safe to assume that they did and here is why.

  1. Fossilisation is rare. Small populations are unlikely to be preserved in the fossil record, even just an individual. The larger the population, the more likely it is that an individual will become part of the fossil record and will be discovered by a palaeontologist. It is therefore safe to assume that a transitional form was not some atypical individual, but part of a large population.
  2. Evolution functions by the spreading of genes in the gene pool of a population. Populations reproduce, so even if the individual which was preserved did not reproduce, it was part of a population which did reproduce. 
  3. If, somehow it was a "freak of nature", then it is unlikely that it was physically very different to the population average as survival to adulthood would also be unlikely. 
Some transitional fossils are clearly part of a population, as numerous fossils have been found. Archaeopteryx is a key example considering its fame, as there are several fossil examples. Clearly these Archaeopteryx individuals were part of a large population and even if they did not reproduce themselves, the population contained many reproducing members. They are transitional forms which bridge the gap between non-avian dinosaurs and birds.
8 of the 9 Archaeopteryx specimens
A more recent example is Darwinopterus, a transitional pterosaur which fills the gap between the two major groups. It is known from numerous specimens which have yielded a wealth of information, providing evidence for sexual dimorphism in pterosaurs. One of the specimens has an egg preserved, showing unequivocally that they were capable of reproduction and the numbers demonstrate that it was part of a population.
The famous female Darwinopterus with egg.
Some transitional forms are, of course, represented by a single individual which is also often fragmented. A good example is the now well known Tiktaalik, which has been labelled as a "fishibian" due to its mixture of fish and amphibian traits. It is so clearly transitional that when its discoverer, Neil Shubin, took a model of it into an infant school class and asked them what they thought it was, some said it was a fish, some said a crocodile, whereas others recognised that it could be both. Only an unthinking pedant would claim that they are wrong. Only one specimen is known, but it is not the only organism which is part of the fish to amphibian transition. Whenever Tiktaalik is brought up, it makes sense to think of the other forms it fits with too, showing the evolution of key traits: 
This applies to all transitions. They should not be taken in isolation, but viewed as part of the whole evolutionary narrative, alongside the other transitional forms. Check out the evolution of whales or the early evolution of mammals, as there are numerous species known for each transition and all should be seen as part of a population in the deep past. 

Probabilities mean that it is extremely likely that transitional forms found were part of a population which involved reproduction. The individuals themselves need not have reproduced because evolution functions in populations, not a string of individuals. If a creationist demands evidence that the individual reproduced they are making a claim based on ignorance of palaeontology. 

Thursday, 22 September 2011

I am a "paleontologist"

A friend linked to this video on Facebook earlier, I thought I would share:

A look through the comments sees someone lamenting that this would be considered politically incorrect due to the mention of evolution. What utter nonsense, palaeontologists study evolution, this should not be kept quiet (rant over).

Tuesday, 20 September 2011

Could it really be? A news round-up?

I've not done one of these for ages and it is about time I got back into the habit. I have been posting interesting news articles on my Facebook profile for a while now and could very easily have linked to them here. So here are the news items which have piqued my interest:

Jurassic Park is back!

Next month sees the release of the Jurassic Park trilogy on Blu-Ray, but before that the first Jurassic Park film will be shown as a limited run at the cinema again. On September 23rd the roar of the Tyrannosaurus will be heard throughout UK cinemas, and I will most certainly be going to see it (provided the loan is through). I remember when I first saw it, I even remember my anticipation of first seeing it. All I knew about it was that my mum's friend had seen a dinosaur film which he said was so realistic that it felt like the dinosaurs were going to burst out of the screen. I was around seven years old at the time and nothing was more exciting. I went to see it with my dad and sister, climbing up onto his knee during the famous raptors in the kitchen scene. We went to see it again, allowing me to be braver second time round. I collected every toy I could get my hands on and still own them all, hidden away in my asbestos-riddled loft. I watch the films a couple of times per year. When my ex-girlfriend suggested that we cuddle up and watch them all together, I instantly thought I was onto a winner (though sadly I was not allowed to say the lines along with the film). I could go on and on about the memories I have from this film, but instead I will just have to go watch it at the cinema again and create yet another memory. See here for an article about the re-release, including a trailer.

Dino Feathers in Amber

If you haven't heard about this, then I have to ask where you have been. I've had people talking to me about this loads, wanting to know if I had heard about it. A friend even randomly phoned me from home just to talk about it. Amber is rather good for preserving three dimensional fossils of things which would not normally be fossilised, such as soft parts. In this case numerous feathers have been preserved in amber dating back to the Late Cretaceous, a time when birds and non-avian dinosaurs lived side by side, both sporting feathers (it is a shared trait due to ancestry). These fossil feathers show an evolutionary range, from primitive feathers through to highly derived feathers which match those of modern birds. There is also yet more information on pigmentation in Mesozoic feathers, giving us more of an idea of the colouration of dinosaurs and early birds. It will soon be common knowledge that the colours of dinosaurs are not complete fantasy any more, though there is still a long way to go and a lot more to learn. See here for the BBC article on this well known discovery.

Sometimes spiders can be cool...

This is not a news item, though it was for me. I found a picture of a spider which interested me, rather than making me shudder and squirm as most do:
It also allows me to put another picture in this blog, as it was feeling a bit text heavy (despite that I am keeping the news short).

DNA regulation in the news again

Whenever I discuss evolution with people in any sort of detail I put emphasis on gene regulation. Genes code for proteins and are flanked by regions of DNA which determine where and when the gene in question will be expressed in the developing embryo. It is through changes in gene switches that you get changes in development, resulting in changes in morphology which can be as gradualistic as natural selection requires. This is how something such as the tetrapod limb has become so diverse; just think of wings, such as the wings of birds, bats and pterosaurs, as they are all variations on the same bones. Gene regulation changes have caused some bones to become longer, some shorter, some fuse, some are different shapes, some disappear entirely (though gradually). Evolution uses what is available and modifies it, often resulting in new combinations which allow for novel form and function. This information is important to our understanding of evolution, yet it gets overlooked a lot. This recent bit of news is the identification of the oldest known regulatory region in vertebrates and invertebrates, see here. Back in August a study was published looking at diversification events in vertebrates based on gene regulation, see here.

Ah, the classic conundrum involving fossils and genes

When looked at broadly the genetic data and the fossil data match up nicely, both showing that evolution is the explanation for how they appear. When we look closely, we find areas of conflict which are difficult to resolve. One of those problems has apparently just been solved (I haven't read the journal paper, so I don't know if their confidence has been justified). One of the problems is that we only have the genomes of recent organisms to study, giving us information only about the survivors. Each genome we have comes from lineages which got through every mass extinction; we lack the genetic information for those which perished. When we look at current genetic diversity it looks like the end result of diversification, because if there are six species in a genus it will look like that was the peak of diversity. The fossils, however, tell a different story. After mass extinctions there is often a boom in diversity, with large increases in the number of species, but as with any boom this then goes bust. Many of those species go extinct, so the fossils may show that those six species are what remains of a genus which once contained ten species. The genetic data would not be able to show this, yet the fossils do. Additionally, sometimes the fossil data is so poor that it can't tell us anything useful (such as when soft tissue is not preserved) so the genetic data is all we have. A new technique has been created, making up for this problem. See here.

Epigenetic changes are short-lived

Anyone who is interested in evolution must pay attention to epigenetics these days. Epigenetic changes do not involve the genome directly, but instead are changes which occur during the life of an individual which can affect how genes are regulated and expressed. I personally know little about epigenetics, so I may go wrong in talking about it. The recent study has shown that these changes are rarely lasting, so they play a small role in the variation available in evolution (though people still love to claim that Lamarck has been vindicated it seems). See here for more information. Also, keep in mind this other bit of news from earlier this year, as a study has shown that lasting evolutionary change takes around a million years to become fixed. Evolution in the short term can be rather fast, much like if you recorded your weight change throughout the day using extremely sensitive scales, as you would see clear changes with every meal and trip to the loo. If you do the same with a child you would find no trends in any discernible direction, until you stepped back and looked at the data over a long period, as you would clearly see growth. One of the difficulties in studying evolution is that gap from short-scale to long-scale is difficult to bridge.

Terra Nova!

This was announced a while ago and got me very excited. Next month will see the release of Spielberg-produced TV series Terra Nova, in which an apocalyptic future sees people travelling back to the Mesozoic to seek paradise and live without the problems which an ever-growing population have caused. I don't know about you, but this is right up my alley. Incredible locations, an apocalyptic future, and of course, dinosaurs.

Now that is how you do micropalaeontology!

During my recent dissertation fieldwork, which I have yet to blog about, I met a palaeontologist from Keele University, Michael Montenari. When I got back I looked him up on his university website and found this awesome image:

That's him, magnified thousands of times, studying fossil extremophiles. If only it were that easy.

Catholics Going Backwards?

I've been lazy all day. I've been doing very little and could have been blogging, but never got the motivation. Until I saw this article on CosmOnline. I was shocked to say the least. I get involved in the science-faith debate/discussion as much as I can, having posted on this blog about it and delved into discussion boards. I intend to make that involvement more academic some day, as I have a lot to say. I feel like I know a lot when it comes to this topic, but every so often I find a surprise.

Anyone who has looked into this subject even slightly will know that the Catholic Church has made mistakes in the past, citing their own authority over science and rejecting discoveries which we now take as given. They've done a fair bit of forgiving over the years and in the past century seem to be making amends. It is well known that Catholics are rarely creationists, that they can accept evolution and many prominent theistic evolutionists are Catholic scholars. The Big Bang theory, repudiated by creationists of many stripes, was first proposed by a Catholic priest. Yet they are not without their crazies when it comes to science. Enter Robert Sungenis and co.

Sungenis is a conservative Catholic who believes that Galileo was wrong, the celestial bodies really do revolve around the Earth! (Terry Pratchett would probably use five exclamation marks there as a sign of insanity.) Geocentrism is still alive, though naturally an extreme fringe view (I do wonder if it has as many followers as the flat earth believers). Sungenis makes me think of Kent Hovind, with the way he emphasises his Ph.D despite the fact that it is from an unaccredited university (he even wrote his thesis on geocentrism). He typically writes books about it and I wonder if anyone is mad enough to take him seriously:
If you want to check out this lunacy for yourself, see here. I have nothing more to say on this, I'm more than a little incredulous.

Tuesday, 13 September 2011

I should try this

Just a brief little news article, have a read, as a man sent a letter of complaint after he was over-charged for a sandwich and said he wanted a dinosaur drawing as a refund. He got it. See for yourself.

This is my first post since fieldwork and I intend to keep it up. Naturally my fieldwork itself needs writing about at length, but for now you simply get the cartoon dinosaur.