A break

Lately, I have been thinking about taking a break from blogging now until university starts again in mid-September.

First of all, I want to prepare properly for the second year of university, because now the grades are really important, and I suspect it will be harder than last year. I want to analyse the mistakes I made in the first year, research what they will expect of us this time, and design a strategy to meet those expectations as efficiently as I can. First year was more about testing how far I could reach with only half-hearted efforts; I came really close to a so-called two-one grade, which is the second highest, but now I want to be serious about excelling.

Second, from mid-August, my good friend Hanna will come back to Sweden, so I want to spend as much time as possible with her and Tim, because they will stay here the whole of next year, so will see even less of them than I did last year. Therefore, I basically have until mid-August to make most of the preparations for university.

Third, I want to make a serious effort to get my creative writing started again. I have been half-thinking about some ideas since last summer, but barely got started. But, with my plans to study more intensely and to exercise more, I won’t have much time left for creative writing if I also keep two blogs running. However, I will probably leave the writing to commence for real until after the start of university, so I can judge if I really have the time.

My intention is not to stop writing for any of these blogs, not at all! I will probably throw in a few casual posts per month, writing when I feel inspired or when something noteworthy happens. What I am taking a break from is the efforts to write regularly. So, in a sense, the posts in the near future will only be special ones, haha!  

The scientific method: strengths and limitations (2)

Part Two: Deduction vs. induction

The first part introduced the essence of logics, syllogisms and the concepts of validity and soundness. It was intended to present a fundamental way of thinking philosophically about big words such as truth and certainty, and to emphasise that ‘logical’ does not necessarily mean ‘true’. I would strongly recommend that you read Part One before proceeding. I know it is a long text, but it is also essential to be familiar with the concepts that are discussed there. 

In Part Two, I want to take the discussion a step away from general philosophy and closer to concepts more relevant to science: deductive and inductive reasoning. These are still fundamental to many, if not all branches of philosophy, but inductive reasoning in particular is central to the natural sciences.

Deductive and inductive reasoning are both forms of extrapolation (which was discussed in Part One). Strictly speaking, deduction is the act of reasoning from the general to the particular, while induction is the act of reasoning from the particular to the general. Before you get a headache trying to understand what on Earth that even means, let me talk you through a few simple examples.

Deduction is thinking that if all bananas are sweet, the banana you are about to eat will taste sweet. Induction, on the other hand, would be the reverse: if you eat a banana and find it sweet, you can expect other bananas to be sweet as well. In this case, ‘the general’ refers to all bananas, and ‘the particular’ is the banana you have or ate.

So, knowing that the general (all bananas) has a certain feature or attribute (tasting sweet), you may deduce that the particular (the banana in your hand) might possess that attribute as well. Conversely, observing an attribute (sweet taste) in the particular (the banana you ate) may lead to the inductive conclusion that that feature may belong to the general (all bananas).

If you are observant, you may already be wondering: does induction come before deduction then? How would you know that all bananas are sweet, unless that is a conclusion you have reached inductively by tasting many bananas? Well noted – but do not jump to conclusions! Although that may be true in many cases, there are many exceptions as well. (Trick quiz: was that inductive or deductive thinking?)

The main type of deduction that does not rely on induction is based on definitions. A classical example of something that is true by definition is that all bachelors are unmarried men. This is because the word bachelor means unmarried man. Thus, if you meet someone you know is a bachelor (he may have presented himself as such), you can deduce that he (!) is an unmarried man. This is not because you have met many bachelors and they have all turned out to be unmarried men, but because if he is not an unmarried man, then he is not a bachelor (or… maybe he is lying to you).

You may recall this example from Part One as the first example of a syllogism. I repeat it here because it is not only a sound syllogism, but also one that illustrates deductive reasoning:

     P: All bachelors are unmarried men

     P: Peter is a bachelor

     C: Therefore, Peter is an unmarried man

Here, we go from the general (all bachelors) to the particular (Peter). We know something about the general, something that applies to all of them; and from that, we reason that this something is true also for every particular individual or unit in this general group. We reason from the general to the particular in deduction.

Recall that deduction and induction are inferences, and as such not necessarily true. Again, what we are concerned about is how we reason when we infer. We want the reasoning to be valid, so we can be certain that the deductive or inductive conclusion is as true as the initial premise. In the above example, the first premise is true by definition, and therefore unquestionable (the only grey area would be a widower, a man whose wife has died) – unless you want to challenge the definition, but then it becomes a matter of language, not the nature of the world. The second premise, however, may or may not be true. As a result, the conclusion is only as certain as the second premise. If Peter is not a bachelor, then he is either married or not a man.

Dinosaur warm-bloodedness: The whole dinosauria (non-avian), Part 3

Evidence for warm-bloodedness in the whole of the dinosaur group was discussed in Part 1 and Part 2. Now, we will look at some evidence against that idea. These have been used to argue that all non-avian dinosaurs (i.e. all dinosaurs except birds) were cold-blooded. We know that birds definitely are warm-blooded, but this evidence suggests that that feature is not rooted deeper in the dinosaur group, i.e. that warm-bloodedness started with the birds, or at least within their closest ancestors.

1. The first arguments relates to water loss associated with warm-bloodedness. Recall from the Part 2 that warm-blooded animals need a high rate of blood flow through their bodies in order to supply all the cells with oxygen required for aerobic food conversion into energy. From Part 1, I hope you could understand that oxygen is supplied to the blood by gas exchange, and that this cannot occur without ventilation, or breathing. Therefore, efficient oxygen supply to the body’s cells requires both high blood pressure, as discussed in Part 2, and high ventilation rates.

Gas exchange is actually not made directly between the air in the lungs and the blood vessels of the lungs. The oxygen and carbon dioxide gas molecules are first dissolved in the thin lining of water that covers the inner surface of the lungs. The dissolved gases then travel across the blood vessel walls and into the blood, where they remain dissolved, of course.

The lining water evaporates as it is heated up by the warm blood that is constantly pumped near it. This is why warm-bloods have a moist breath, which explains why glass windows get hazy when you breathe on them: that is the water vapour that evaporated from within your lungs that came out with your breath and then condensed into tiny liquid droplets on the cool window glass.

Therefore, rapid ventilation, which is needed to sustain the metabolism of a warm-blood, results in considerable water loss. And we know well that water is essential for any organism!

Both mammals and birds have solved this problem independently but in the same way: by respiratory turbinates, which are spiralled sheets of thin bone covered in moisture-trapping tissue, forming a large surface area for absorbing the water from exhaled air. These are located in the nasal cavity (which is why the air you breathe out from your nose is not as moist as that which comes out of your mouth). No dinosaurs have been found with such structures, however.

The four pictures above illustrate this point showing the independently evolved adaptations of the only known warm-blooded animals to avoid water loss during ventilation, and comparing it to crocodiles, a know cold-blood and the closest living relatives to the ancestors of the dinosaurs. Finally, it is shown that the dinosaur skulls that have been studied in this light have shown features similar to that of a crocodile, rather than of definite warm-bloods. Images from http://faculty.plattsburgh.edu/thomas.wolosz/turbinates.htm

Although I would not agree that this “strongly” suggests cold-bloodedness among the dinosaurs, it presents a difficult obstacle to advocates of the warm-blood hypothesis. Of course, there are more than one way of preventing water loss, and some can be expected not to show up in the fossils.

Dinosaur warm-bloodedness: The whole Dinosauria (non-avian), Part 2

Here is the continuation of my account of arguments for warm-bloodedness in the whole of the Dinosauria.

2. The second main argument is that dinosaurs are thought to have had four-chambered hearts, which may be coupled with warm-bloodedness. Both mammals and birds have four-chambered hearts; crocodiles are the only cold-blooded animal group that shares this feature (as far as I am aware!).

We can be fairly confident that dinosaurs had four-chambered hearts because both their closest modern relatives, birds and crocodiles, possess this feature. Modern crocodiles represent the closest living thing to the shared ancestor between dinosaurs and crocodiles, and birds represent what the dinosaurs became at the end, sort of. The crocodiles suggest that the ancestral dinosaurs also had four-chambered hearts, and the birds show that they were not lost during evolution (at least not fully). This type of reasoning is common practice among paleontologists and evolutionary biologists, and is known as the Extant Phylogenetic Bracket (EPB) principle. Of course, it is far from certain, and there is no fossil evidence to support this. If memory serves, the only dinosaur heart ever found was later shown to have been an ordinary rock, deceptively shaped to be mistaken for a heart. But, let us at least consider the implications for warm-bloodedness if the dinosaurs had had four-chambered hearts.

A four-chambered heart is basically divided into two halves with two special chambers, an atrium and a ventricle, on each side. Blood enters the heart via the atrium, and leaves through the ventricle. When the atrium muscles relax, the chamber expands and blood is sucked in (just like with air in the lungs, see Part 1). Next, when the ventricle muscles relax and the atrium muscles contract, blood is forced from the atrium into the ventricle. Finally, the ventricle muscles contract, forcing the blood out from the heart; at the same time, the atrium muscles relax, sucking in new blood into the heart. That way, the two chambers create a smooth flow of blood in and out of the heart.

If I am not mistaken, this process is basically the same in two- and three-chambered hearts as well, but the four-chambered heart is special in that it enables two separate blood circuits, with different blood pressures! This is essential for an active animal, which needs a high pressure levels for the blood to reach all parts of the body, and deliver oxygen and energy-storing molecules (e.g. ATP; see the post on the meaning of warm-bloodedness). But, the blood vessels in the lungs are very narrow and thin, a design to maximise their ability to take up oxygen and give off carbon dioxide to the air inside the lungs; these would explode if they were subjected to as high pressure as is present in the other blood vessels of a warm-blooded animal.

In other words, it is impossible to maintain a high enough blood pressure for efficient transport of oxygenated blood in the body without destroying the blood vessels in the lungs, which is where the oxygen is replenished. If all blood vessels in the body are connected in the same circuit, the blood pressure would be limited to what the lungs can handle without bursting.

A four-chambered heart makes it possible to keep the blood circuit from the heart to the body separate from the circuit from the heart to the lungs. We refer to them as the systemic circulation (heart-body) and pulmonary circulation (heart-lung). Because the atria and ventricles are separated from one another by valves, it is possible to change the blood pressure between incoming and outgoing blood.

So, if blood coming from the body enters the right atrium with high pressure, when it is pumped into the right ventricle, the right valve closes it off from the behind it. The blood is then pumped out from the right ventricle, with more gentle pressure, toward the lungs. The blood then goes from the lungs to the left atrium, and then the left ventricle, from where it is pushed out to the rest of the body with high pressure, until it eventually returns to the right atrium. 

Thus, having a four-chambered heart makes it much easier to be an active animal, which we from previous arguments know is intimately linked with warm-bloodedness. I dare not claim that a four-chambered heart is strictly necessary for a warm-blooded animal, but as with the parasagittal limb posture, it would be highly advantageous.

However, a strong counter-argument to the link between the four-chambered heart and warm-bloodedness is that very large animals would also need high blood pressure in their systemic circulation for the blood to reach out, especially to its head. And many dinosaurs were very very big! In fact, it is the smaller dinosaurs that are most certain to have evolved warm-bloodedness.

Since the use of a four-chambered heart can be explained by the size of the dinosaurs, that feature is rendered weak as evidence for warm-bloodedness. We know the dinosaurs were big, but whether they were warm-blooded or not is more doubtful, so the most rational thing to do is to assume that the four-chambered heart was needed/used primarily because they were large animals.

Moreover, the fact that the cold-blooded crocodiles also have four-chambered hearts casts further doubt on the link to warm-bloodedness. I am not sure of why crocodiles would need this, but I can imagine that they were at least not disadvantaged. As you can see, there is yet more mystery here…

3. The final piece of evidence for warm-bloodedness is about special features in the microstructure of dinosaur bones: it has been discovered that some had dense secondary Haversian bone, which is a product of bone growth (or, bone remodelling, actually). A lot of it indicates fast bone growth, and fast growth is characteristic of mammals and, especially, birds. Dense secondary Haversian bone has been found in fossil dinosaurs, pterosaurs and therapsids (mammal ancestors), all good candidates for warm-bloodedness.

I have little understanding for any of this, but apparently, from what I can gather from various sources, it has later been shown that production of dense secondary Haversioan bone is not as strongly linked to BMRs as previously thought, but is more affected by age and size, among other factors. It seems, then, that the relationship between this bone feature and warm-bloodedness is rather weak. Moreover, it seems to be absent in small modern mammals and birds, which are known to have the highest relative BMRs of all.

I hope you begin to see a common pattern in the weaknesses of these arguments: they are based on correlations that do not seem to hold all the way; there are exceptions, and alternative explanations. The challenges should be met with special explanations for the exceptions (if they are different from the rest, explain why they are special, rather than abandoning the whole idea), or show that the alternative explanations do not work, if that is the case. So, this is not the end! Although these hypotheses have their weaknesses, they can all be strengthened, and the counter-arguments can be challenged too!

Part 3 will be about a few arguments against warm-bloodedness in the whole dinosaur group – well… except those closest to birds.

The cheekbone case: Note from an article about a new ceratopsian

Well… it was new in 2006… but I read the article not long ago, and first now thought of what it means.

The discovery was a fairly complete specimen of a new primitive ceratopsians, named Yinlong downsi (gen. et sp. nov., which is short for new genus and species, in latin… and, again, it was new when the article was published). The article A basal ceratopsian with transitional features from the Late Jurassic of northwestern China describes the find and attempts to place it within a larger context. From what I gathered when reading it, the article proposes two main ideas, apart from describing the fossil, but only one of has a bearing on the cheekbone case.

The thing about the ceratopsians is that their heads evolved ‘forward’ into a more specialised form, while their bodies evolved ‘backward’ to a more basic body plan. Based on some advanced analysis of the sequence the characters were developed within the Ceratopsia, the authors suggest that they developed their specialised skull form before their bodies evolved into a more primitive shape.

The key word here is before, though. Regardless of in which ‘direction’ they evolved, the point is that the skulls developed earlier. It means that they became what they became because their heads started changing to suit their environment. The body changed appropriately too, but it followed later.

I interpret this as emphasising that the skull is indeed the important feature of the ceratopsians. And, the peculiar jugal (cheekbone) protrusion is one of the first skull features they evolved! It seems it was there from the very beginning, and perhaps was one of the things that made them gradually more and more successful, until rivalled only by one other group of dinosaurs, the hadrosaurs (duck-billed dinosaurs).

Sadly, the article does not go into any detail about the jugal of Yinlong, so it has not done much more than further spur my conviction that that bone played a significant role in making the ceratopsians what they were.

However, I have finished reading another scientific article, one that goes into detail about the skull form and function of another basal ceratopsian, Psittacosaurus gobiensis. It is much more important for my cheekbone investigation, but also very complicated, and, as usual, not directly meant to be relevant, so I need to pick out the evidence and puzzle them together in a way that helps me understand just what it means. That will be for the next time…!

Dinosaur warm-bloodedness: The whole Dinosauria (non-avian), Part 1

The central hypothesis in this series of posts on the debate about whether the dinosaurs were warm-blooded or not is that actually some types of dinosaurs were more warm-blooded and others were less; i.e. that there were different degrees of warm-bloodedness among different parts of the dinosaur group.

This idea calls for an in-depth analysis of all the different subgroups in the Dinosauria, but first I want to give an account of some of the evidence that has been used to argue about all dinosaurs as one. (Note that I naturally exclude the birds here: we know they are all fully warm-blooded.) I hope this both serves as an introduction to the main lines of reasoning, and also gives you an idea of why it makes more sense to split the diverse dinosaurs into smaller groups rather than treating them all equal.

I will start off with evidence in favour of warm-bloodedness in the whole Dinosauria, then move to evidence against, and finish off with an argument that warm-bloodedness must have at least evolved in one dinosaur group: the one close to true birds.

Something you need to understand about how paleontologists gather evidence for such things as warm-bloodedness is that there is no way of measuring it directly from fossils. Recall from the post explainingthe different types of ‘wam-bloodedness’ that the term refers to animals with stable body temperature (homeotherms), internal heat source (endothermic), and/or a high basal metabolic rate, or BMR (tachymetabolic); usually ‘warm-blooded’ comprises all three in combination. It is not possible to measure the live body temperature or metabolic activity of a dead animal that was turned into solid rock millions of years ago. So, there is no way we can truly show conclusively that the dinosaurs fit into any of these categories. What we can do is look at other features – features we can tell from the fossils, and that we have reasons to suspect are related to warm- or cold-bloodedness. We do this by examining differences between the modern animals we know are warm-blooded (mammals and birds) and those we know are cold-blooded (the rest), thinking about which differences could be linked to warm-bloodedness and why, and finally seeing if we can find the same features in the fossils. In other words, all evidence here is indirect evidence. It is important to be aware of this, because it poses a strong, inherent limitation to the quality of the evidence; but then again, it is the best we can do!

Evidence for warm-bloodedness

1. The reason the idea of warm-blooded dinosaurs was proposed in the first place is actually not that palaeontologists realised that they were closely related to birds, as you might think. Warm-bloodedness was suggested already in the 1980s when the comparative anatomist Sir Richard Owen noticed that the dinosaurs had an upright (or parasagittal) limb posture, a feature today only seen in birds and mammals, the only living warm-bloods. The other land vertebrates typically have a sprawling posture, their limbs splaying out to the sides, the upper part being closer to horizontal.

The main types of limb posture of land-living vertebrates. Sprawling is seen in most amphibians and ‘reptiles’, erect in dinosaurs (including birds) and mammals, and the pillar-erect in rauisuchians, ancient relatives of crocodiles, but extinct today. Image from http://en.wikipedia.org/wiki/File:Sprawling_and_erect_hip_joints_-_horiz.png

 

Of course, it is not enough to base such a claim on pure correlation: there needs to be a link between a parasagittal limb posture and warm-bloodedness. (In scientific terms, there must be a causal relationship between the two features.) And there is! It might be a bit complicated though, but bear with me and I will try to guide you through.

Recall from the postexplaining aerobic and anaerobic metabolism that the aerobic variant is about twenty times more energy-efficient, but demands and consumes oxygen, while anaerobic metabolism works in oxygen-free conditions, but produces much less energy. Warm-blooded animals, which use a large proportion of the energy they gain from metabolic processes to convert into heat to warm their bodies from the inside, therefore require a metabolism that is predominantly aerobic. Otherwise, they would not gain enough energy from their metabolic conversion of food to fuel their internal heat machine.

Thus, warm-bloods must rely on a predominantly aerobic metabolism, and therefore need a large and constant oxygen supply, in order for their aerobic metabolism to work. If they do not get enough oxygen, they will need to resort to anaerobic metabolism to get the energy, but that will consume twenty times as much food, which will run out quickly. 

Warm-blooded animals then need an efficient respiratory system – i.e. a system to get oxygen from the air into the cells of their body.

Vertebrates have lungs, sacs of highly vascularised tissue attached to muscles around the ribs. The millions of tiny, thin blood vessels in the lungs make up a huge surface area for exchange of gases between the blood and the air inside the lungs. The blood that enters the lung vessels has passed through the body, delivering oxygen for the cells to maintain themselves and taking up carbon dioxide they leave as a waste product. Therefore, that blood has plenty of dissolved carbon dioxide but little oxygen. When it comes in contact with the air, which has relatively less carbon dioxide but more oxygen, both gases are exchanged. They move from where there is plenty to where there is less, in order to balance out between the two sites. In effect, the blood gets rid of some carbon dioxide and picks up essential oxygen.

However, after gas exchange, the air in the lungs has as much carbon dioxide and oxygen as the blood, so when new blood enters the lungs, they will already be balanced and no more exchange will take place! For that reason, we need to replace the air in the lungs with fresh air from the outside. We call this ventilation, or breathing; for that, we use the ribs.

The rib muscles perform cycles of contractions to alternately expand and compress the torso, and, in effect, the lungs as well. When the lungs expand, the air pressure inside becomes lower than the pressure of the air outside. This pressure difference causes air to flow from the outside into the lungs. (Air always flows from a region of high air pressure to where the pressure is relatively lower; this is what causes wind, for example.) When the lungs contract, they force out some air from the lungs. This is how we get fresh air in and used air out. Without ventilation, gas exchange will not occur, and we will quickly starve our oxygen supplies, and, as a result, not be able to carry out aerobic metabolism.

Now you must be wondering what this has to do with having straight or bent legs. I will come to that just now! The thing is, except those with a parasagittal limb arrangement, all vertebrates move forward primarily by waving their bodies sideways. We all know that fish swim that way, and that set a precedent for their close land-living descendants. Maybe you have not thought about it, but most amphibians and reptiles in general move this way as well. I will not go into detail on their biomechanics (mostly because my understanding is not great), but, basically, their limbs are not flexible enough to reach far forward and backward, so their strides would be very short if they only used the limbs. By also turning their limb girdles, they achieve a considerably longer stride length, allowing fairly efficient locomotion.

This mode of moving is not only a residue from their fish ancestors, but is kept also in advanced amphibians and reptiles that have lost their limbs, e.g. caecilians (a very worm-like type of amphibians) and snakes. Exceptions to this include frogs (which jump rather than stride) and chameleons (which actually have more of a parasagittal limb posture than most reptiles, but this is because they are fairly large lizards moving around on rather narrow tree branches, so they need to have their limbs straight in order to achieve sufficient… narrowness to get a decent grip). However, these are special cases; they do not have a wave-like body motion for special reasons, unlikely to be related to their metabolism.

The importance of this locomotion style has to do with how they turn their limb girdles: the muscles on the sides of the body, between the front and hind legs, contract and relax alternatingly. When the trunk muscles on the left side contract, the left hind foot is moved forward, closer to the left front foot, and the right front foot is moved forward, away from the right hind foot. The next step is to let the trunk muscles on the right side contract, while those on the left relax. If the animal keeps the left hind foot and right front foot still in the ground, the remaining two feet will be moved forward, this time taking the left front foot further away from the left hind foot, and bringing the right hind foot closer to the right front foot. The animal moves forward by repeating these steps again and again, in a cycle.

I hope that made sense, but if not, do not be alarmed, it is not essential to grasp this. Actually, if you just look up some videos of walking reptiles on YouTube, I’m sure it will become much clearer. Regardless, the key thing to note is that half of the body contracts with every step. This contraction compresses the lung on that side of the body, forcing air out. 

Wow! So they breathe by moving!... You might think so, but that is a hasty conclusion. While one lung is compressed, the other is not expanded (I think… might need to check this up, actually…), so air is not sucked in there. And, even if it did, it would still mean that they only use half their lung capacity while moving. This puts a severe restriction on their maximum oxygen intake. Since oxygen is needed for aerobic food conversion, their ability to perform this is equally limited. As a result, most amphibians and reptiles become completely exhausted after a few minutes of strenuous activity, because anaerobic food conversion is so inefficient.

Now, this means that these sprawling-gaited animals are not very active animals. Because their energy production is so inefficient while they are moving, they spend most of their days resting. (In general, they are active for only a few hours every day, during which they forage for food, carry out domestic chores, etc.)

Now, here is where the argument might get quite confusing: because they are not particularly active, they would not gain much from having an active metabolism (i.e. having a high BMR; tachymetabolic). An active metabolism here means a metabolism that is predominantly aerobic – i.e. the bulk of the food is converted into energy aerobically. As explained in the previouspost on this topic, such a metabolism provides stamina in the form of a fairly high and continuous energy production, while the alternative – a predominantly anaerobic metabolism – normally has low energy output, but is capable of mobilising vast amounts of energy very rapidly, thus granting impressive burst speed. As a result, predominantly aerobic animals can be active for longer periods of time. That is the main advantage of such a metabolic strategy, but the sprawlers would still be restricted on this very aspect due to their less efficient walking style. They would gain little from having an aerobic metabolism, as the advantage it would grant would still have been limited due to their poor oxygen intake.

The advantage of aerobic metabolism is manifested when the animal is active. But this is also when the oxygen intake of amphibians and reptiles is as lowest, meaning that they will not be able to rely on an aerobic metabolism during activity. In other words, their particular gait thwarts the aerobic processes at the precise point where they would have been effective.

The disadvantage of a predominantly aerobic metabolism is that the metabolic rates are also elevated at rest. This means they consume more food during physical inactivity compared to animals relying on an anaerobic metabolism, which have very low rates of energy production (and thus also energy usage) during rest. Having a high energy production while not using any energy is simply a waste, as there is no gain, only higher costs of food.

To summarise, the way most amphibians and reptiles move severely limits their oxygen intake by compressing one of their lungs with every step. If they had been warm-blooded – i.e. had an active metabolism – this problem would have thwarted the advantage of stamina during activity. With the main advantage removed, the only effect of having such a metabolism would be suffering the main disadvantage of higher food consumption while at rest. 

This is the reason why a sprawling limb posture is associated with cold-bloodedness. Conversely, it is also the reason why a parasagittal limb posture is thought to have a connection with warm-bloodedness. Having the limbs straight under the body allows them to swing forward and backward comfortably using only muscles from the limbs and girdles. No other parts of their body need to contract or expand during such movement, so no lungs are compressed; they can breathe to their full capacity even while running, and, as a result, an aerobic metabolism would prove advantageous for them!

Now, a keen critical thinker would realise that the argument that dinosaurs were warm-blooded because they had a parasagittal limb arrangement is based on the assumption that dinosaurs would have evolved warm-bloodedness simply because it would have granted them an advantage. This is just as valid as arguing that ancient apes would have evolved brains of size and complexity rivalling that of humans because it would have granted them an advantage. Clearly, that did not happen.

Evolution just does not work like that. A human-sized brain is arguably an advantage to any animal (except sessile or planktonic filter-feeders… but let us not go there now…), but it is only us, among all the billions of species of animals that have ever evolved, that successfully achieved such cognitive complexity. Why? Because we had the genes for it! Without the necessary genetic material, the trait cannot develop in the first place.

This is why one cannot assume that dinosaurs would have developed full warm-bloodedness just because it would have been advantageous, not without having any reason to suspect they had the necessary genetic background. The fact that birds are warm-blooded gives us a clue that this genetic background at least evolved somewhere within the dinosaur group, but perhaps not necessarily at the base of it, i.e. not necessarily at the same time as they evolved a parasagittal limb posture.

The only difference these limb posture variants make is that if any sprawling-gaited amphibian or reptile had acquired the necessary genetic material to achieve full warm-bloodedness, their limb posture means they would not have gained any advantage from it, but rather a big disadvantage, and so it would not have become prominent in these groups. Dinosaurs, on the other hand, had the potential to gain an advantage from being warm-blooded. That is all.

Dear God, this discussion got far longer than I would have expected. I wanted to keep it brief and simple. But, my desire to explain it from the most basic level made it necessary to describe all parts of the argument thoroughly. Therefore, I decided to actually cut here, or the post would be dauntingly long. The remainder of the arguments for dinosaur warm-bloodedness will be the topic of Part 2.  

Should finish what I've started...

Thinking back on all those projects I have started and never gotten down to finish, I'm beginning to suspect this it has developed into a habit... a bad habit.

The unfinished projects eventually become too many and I end up rarely having time to get anything beyond a good start. I'm trying to think of any project that I have started, lost steam for, forgotten about, much later remembering and finally finshing... I know for sure that there is none that I have started and finished in one flow, hahaha!

So, from what I can recall, on this blog, I have at least the dinosaur warm-bloodedness and cheekbone case projects. The latter started rather recently, so I want to keep it up, for the sake of doing something unusual! But I remember leaving the warm-bloodedness halfway through the draft of the second post... shame, shame shame!

It will be interesting to see if this is manageable, especially as I recently engaged in a collaborative project about open-mindedness together with my good friend Hanna on my other blog, The Bluest Ice, and on Hannas much more enthusiastic A Little Blog About Words. I also want to get The Bluest Ice kick-started for real!

This might be an interesting time indeed... For the sake of challenging myself, I feel a good effort needs to be made! Maybe I should design a weekly schedule...?

Skill... what is that anyway?

One of the things I noticed during my first year in the UK is that there is an almost ludicrous emphasis on skills. At least among the academics, much of what you hear is all about having skills, skills, skills and skills…

I must admit that I find this both amusing and a tad annoying. There is more to life than being skilled, in my opinion. Not saying that a solid set of skills is not useful or desirable, but this nagging about skills is extremely off-putting for me.

But, rather than judging too hastily, I thought maybe the problem is just that I do not know what they actually mean by ‘skills’. I had a good idea of what the word means and implies, but was not sure if I actually understood every aspect of the term.

So, one night I finally got down to looking it up (haha), and, when I got absorbed into the various divisions or types of skills, before I knew it, I found myself doing surprisingly keen research and even taking notes! Naturally, this had to be made into a post on this blog. It does not have much to do with paleontology, but rather with professional life in general.

Before we begin, I just want to mention that this clearly shows what type of academic I am. I found learning about skills interesting because of the many theoretical groupings of types of skills and the implications their respective demands and values have on education theory. Nothing of this has made me more eager to gain any ‘skills’; that does not appeal to me in the same way. I am a theoretical person, not practical.

What on Earth is a skill, then? What is it really?