(posted in Mammals)

I would not recommend vegan dog food for dogs, or cats for that matter. Unlike humans, which are omnivores and have a wide range of food choices, they are carnivores and not designed to eat plants. While they may do so on occasion, they can't digest it and get little to no nutritive value from it as they do not have the enzymes to break down the cell walls.

The few vegans I know that tried to put their dogs on vegan diets wound up having their dogs sent to the vet or even having the poor dog die (the dog that died was fed little but tofu-based food and it starved to death, despite eating the food). It was a hard lesson for them that carnivores eat meat not because they want to, but because they have to. A dog forced to be vegan will be at best sick and miserable. I know of no one that has been able to keep their dogs on a truly vegan diet on a long-term basis and keep the dog healthy and I know quite a few vegan/vegetarians with dogs.

That's a very good question. Much has been talked about concerning a "gay gene", although little has come of it scientifically. While it is still not completely clear, the current thinking is that homosexuality is mostly a result of epigenetics. That is, homosexuality is not caused by genes specifically, but how they are regulated. Thus, it falls outside of most commonly discussed evolutionary paths.

The key, I think, in understanding homosexuality is that it appears homosexuality occurs through genes that control attraction, but not in the way that most people think. It is obviously important for people to be attracted to each other for reproduction. Thus, there are genes that affect behavior which aid in creating that attraction or in some way increasing fertility, allowing more reproductive success. The gene Xq28, for instance, increases fertility in women, making it an evolutionarily desirable gene. Normally, that gene and/or others like it cause women to be attracted to men.

But what if those genes were expressed differently? If they are expressed at low levels, or not at all, then the woman would not be attracted to men and may be either attracted to women or just asexual, not attracted to anyone. Men also have these genes, but they are normally not expressed like they are in women. If they are, then that man would also find men more attractive.

The point is that these are perfectly normal genes doing perfectly normal and evolutionarily required jobs. But a tweak in their regulation can make big changes. Some of these tweaks may be genetically encoded, but many will not be, possibly being introduced during development as a fetus due to numerous different factors or sheer random chance (I know of no evidence indicating that these tweaks may be introduced after the fetus develops, it appears to be set by the time of birth, nor do I know of any research indicating choices by the mother during pregnancy make any clear difference in this regard, a mother can't make their kid homosexual or not). Thus, evolution can't get rid of homosexuality without reducing reproductive success in the whole population. That of course, would spell the end of that species.

Von Baer published his work in the 1820s mostly, Before Darwin, whereas Haeckel published his work in the 1870s and later, well after Darwin. Thus, Von Baer was much earlier. Both happened to be wrong, at least in terms of what embryology could say about evolution. Von Baer was flat out against it, while Haeckel was a proponent. However, Von Baer was more correct in terms of embryos not converging on adult appearances, but rather having similarites to embryos of other animals, and having general characteristics appearing before more specific ones. Haeckel was correct in terms of saying embryology is a very important tool for helping to delineate evolutionary relationships, but the truth is much more subtle and nuanced than the overly simplified story Haeckel tried to make it out to be. So I can't really say either one disproved the other. von Baer didn't see the implications of where his research ultimately led and Haeckel went too far by simplifying to the point he actually became wrong, not to mention idealizing his drawings to the point of falsification. The comparison between von Baer and Hseckel is actually a great example of the pitfalls Haeckel fell into. The real comparison between the two researchers and their ideas is more complex and nuanced than who was right, which is probably a big source of your understandable confusion between the books. It's not simple and straightforward, but I hope this helped.

It is an unresolved question, but the best suggestion I've seen is that of "porpoising," or leaping out of the water at a good speed. If done correctly, it allows breathing at a high speed. According to Richard Cowen, it would allow a physiologic capability similar to a dolphin. http://mygeologypage.ucdavis.edu/cowen/ichthyosaur.html

The general consensus now is that Dilophosaurus was a coelophysoid and not a ceratosaur. Carrano and Sampson published a paper on the phylogeny of the Ceratosauria in the Journal of Systematic Paleontology (2008, vol. 6(2), pg. 183-236). While it is hard to say exactly where a group originates or who was ancestral to whom in the current methodology, your suggestion that Dilophosaurus or some other coelophysoid led to the ceratosaurs and the rest of the theropods is within the realm of possibility. It is unlikely that Dilophosaurus itself was directly ancestral, as the possibililty that any one particular fossil species is directly ancestral to another is low, but it is not impossible and very hard to determine with any certainty. All we can say is that it is a possibility and fits the data we have. Unfortunately, so do several other possibilities. We just need to find more data to make better determinations.

The evolution of the dog is not as straightforward as you might think. While it is generally thought that dogs evolved from the gray wolf, it is also thought that it was not just once, but several times, from different wolf  populations, with backcrossing hybridization that finally led to the original breeds of dog, which then underwent strong directed selection. Here is an article that discusses it nicely, I think.

Honeycutt, Rodney. 2010. Unraveling the mysteries of dog evolution. BMC Biology, 8:20

http://www.biomedcentral.com/1741-7007/8/20

Did Aves take the same route? We don't know. We just don't have the resolution in the relationships to be able to answer that question. We can say that it is almost certain that Aves descended from a small subset, possibly one, species of maniraptoran dinosaurs, but exactly how that happened has not been worked out yet. As it stands right now, I think most paleontologists would favor the one species hypothesis for modern avians, but that is simply an educated guess until we find more species and the relationships get worked out in finer detail.

I doubt it. First, one small thing, there is no Pterodactyl species, there is a Pterodactylus species, though. It's a picky, minor point, not a big deal.

My bet, and I think most would agree with me, is that it would have been a troodontid, as they were the "brainiest" of the dinosaurs. Pterosaurs were brainy as well, but they seem to have been slowly losing out to the avian lineage and I think would have eventually been supplanted, if not completely, at least by dominance inthe skies.

Birds diversified greatly and have developed into a few very intelligent species, the gray parrot and crows being quite intelligent. It is likely that even without the asteroid impact, the maniraptorans would have continued to diversify and achieved dominance.

But let's be clear, there is no "true" here, this is all speculation and we really can't say for sure what would happen. We can only speculate on what we think might have happened. The jestor exemplifying random chance, of which the asteroid is a great example, is a potent player on evolution and that is unpredictable.

Ruben is incorrect in this instance. There have in fact been several papers that have come out in the last few years showing great similarities the the pulmonary system between avians and other theropods. The crocodile comparison is a red herring because the crocodilian pulmonary system is a derived system adapted for their particular lifestyle that seems to have appeared after the split between crocodilians and dinosaurs.  Here are a few papers you might be interested in.

O'Connor PM (2006) Postcranial pneumaticity: an evaluation of soft-tissue influences on the postcranial skeleton and the reconstruction of pulmonary anatomy in archosaurs. Journal of Morphology 267: 1199–1226.

O'Connor PM, Claessens LPAM (2005) Basic avian pulmonary design and flow-through ventilation in nonavian theropod dinosaurs. Nature 436: 253–256.

O'Connor PM (2004) Pulmonary pneumaticity in the postcranial skeleton of extant Aves: a case study examining Anseriformes. Journal of Morphology 261: 141–161.

Claessens LPAM (2005) The evolution of breathing mechanisms in the Archosauria [Ph.D. thesis]. Cambridge: Harvard University.

Claessens LPAM (2004) Archosaurian respiration and the pelvic girdle aspiration breathing of crocodyliforms. Proceedings of the Royal Society of London B: Biological Sciences 271: 1461–1465.

Claessens LPAM (2004) Dinosaur gastralia; origin, morphology, and function. Journal of Vertebrate Paleontology 24: 89–106.

Sereno P, Martinez RN, Wilson JA, Varricchio DJ, Alcober OA (2008) Evidence for avian intrathoracic air sacs in a new predatory dinosaur from Argentina. PLoS ONE 3: e3303.

Farmer CG (2006) On the origin of avian air sacs. Respiratory Physiology & Neurobiology 154: 89–106.

Cleassens,LPAM (2009) J. Exp. Zool. 311A:586–599

As long as you stopped if you saw signs the chimpanzee was upset by it and you didn't break any zoo rules like climbing over a fence or anything stupid like that, I don't see any problem. The very fact that you would ask such a question about it though, indicates that you are unlikely to do anything stupid. The zoo should be glad that you are willing to volunteer some time to see about the welfare of the chimp.

According to Dr. Padian (Paleobiology, 33(2), 2007, pp. 201–226), opisthotonic neck posture is not known outside of mammals, birds, pterosaurs, and dinosaurs. But honestly, I don't know if anyone really knows the extent of the susceptibility to tetanus (and by that I mean to the toxin secreted by Clostridium tetani, which causes tetanus) in other animals outside of a few common test animals like mice. I think it an excellent question.

(posted in Fossils)

I recommend you check out this paper and look up the follow up papers, both pro and con.

Schweitzer, M., Zheng, W., Organ, C., Avci, R., Suo, Z., Freimark, L., Lebleu, V., Duncan, M., Vander Heiden, M., Neveu, J., Lane, W., Cottrell, J., Horner, J., Cantley, L., Kalluri, R., & Asara, J. (2009). Biomolecular Characterization and Protein Sequences of the Campanian Hadrosaur B. canadensis Science, 324 (5927), 626-631 DOI:10.1126/science.1165069

Generally, the fossilization process does destroy that sort of thing. Nevertheless, proteins from dinosaurs have been reported, as well as melanosomes, the organelles within cells that create the pigmentation that determines the color of the skin. These are of course debated and not everyone agrees.

No intact DNA has been found. It degrades fairly rapidly, so intact DNA strands do not survive long after the death of the organism.

We can also study certain aspects of the osteocytes within the bones because the spaces that they occupied have been preserved in the bones.

Even without studying them directly, we can and have studied living relatives. By studying the cells of crocodilians and birds, we can get a good estimate for what they may have been like histologically, at least well enough to determine the likely range of possibilities.

A bigger population would not reduce the chances of a mutation staying in the population. What it would do is reduce the chances that it would become fixed; that is, completely replace the original allele. Every population of any real size carries numerous mutations that are harmful, but so long as both alleles from each parent are not that mutation, it usually doesn't matter.

You are correct that the larger the population, the more likely a mutation would arise, simply due to the larger number of chances.

Of course, there are so many nucleotides that make up the DNA in organisms that it is virtually guaranteed that mutations will occur each and every time there is a cell division. It is just that very few mutations make a diffeence.

There is a physical limit to the spectral range of the eye. Our eyes have three types of cone cells, each specialized to detect a specific range of light. Between the three, the cells cover the visible spectrum, so named because that is the part that is visible to us, obviously. To increase  our range of vision in the eye itself, we would have to add new types of cells.

We could, theoretically, bypass the eye with some other detector and hardwire it into the optic nerve or visual cortex of the brain. But it is not at all clear that the brain would recognize the input from the detector. The wiring in the brain is plastic to a degree though, so it may figure it out over time.

Anotther possibility is gene therapy to introduce new cell types into the retina of the eye.

These techniques are a bit beyond what we can do right now, but there is nothing to say we won't figure it out in the future.

Certainly social mores have a role, but in terms of strictly Darwinian evolution, it makes sense without needing to resort to cultural explanations. Communities which have high mortality rates tend to push the breed early and often mentality, as one would expect in order to ensure sufficient survival of the next generation to reproductive age. In communities which have low mortality but higher competition for resources, breeding tends to be delayed to allow more time for the acquisition of resources. this is not only seen in humans, but all across the biological spectrum. We are not so different from the rest.

Just as a few examples, I spent part of my youth in a poor, rural community, in which girls were considered "old maids" if they had not gotten married and had their first kid by the time they were 20. They were also expected to have large families, despite not having the resources to care for them all because they had to have a high enough replacement to account for early mortality as well as providing workers for the farm. Higher education was considered anathema to them because it reduced the pool of workers for the farm. This sort of behavior seems nonsensical to many of those I am now around, which have nice jobs which depend upon high levels of education to get. In this environment, getting the resources for that education (and other social things) is far more important than the need for workers and replacements.

In a similar vein, there are numerous fish that will delay breeding for a year if they are of insufficient size to compete effectively. If they are big enough as soon as they mature, they go ahead and breed. If they are smaller than others, they delay breeding until they are bigger. The name of the game is resource allocation.

As to your question about competing interests, yes, that is very common. The literature is full of articles detailing the competing interests of parents versus offspring and male versus female. These sorts of issues make working out reproductive strategies for populations very complex. For humans, one might look at it this way. The parents have a vested interest in providing for their offspring as well as their grandchildren. As such, it makes more sense for them to conserve resources to provide for all of them. The offspring on the other hand, have avested interest in monoplozing their parents resources, even to the detriment of their siblings. For them, it is better to have children early enough to have their parents contribute to them before their siblings have children. For the parents of course, the longer the delay for having grandkids the more resources they can provide, not just to one child, but all of their children. Does it all sound a bit mercenary and short-term thinking over the long-term oftentimes? Welcome to the wonderful world of reproductive ecology and evolutionary psychology.

Of course, we are talking about populations, NOT predictive of any one person's behavior. Your mileage may vary.

David, you state eggs from females have a much higher rate of mutation/abnormality that the sperm from males, ifI understand you correctly. Compared to what, precisely? Are you referring to a comparison between the final zygote and its immediate precursor or to the initial DNA sequence at the time of conception? I can see the egg as having a higher number of abnormalities due to degradation over the years. However, the male zygotes have been busily dividing millions of times over during this time. I would expect then that as the male ages, the sperm would incorporate more mutations during that time becaue they are NOT derived from fetal spermatocytes, but a derived population. Of course, only the ones that make it into a viable offspring really matter, but there is rather intense selection going on during this time ("into every generation, there is a chosen one" to paraphrase Joss Whedon), which should, I think, drive the appearance of more potentially beneficial mutations than seen in the egg. Not my field of expertise though, so if I am screwing something up here, please let me know.

There is some thought that the vibrations sent out by earthquakes can confuse a whale's sense of direction or potentially scare them into going into shallow water where they wind up getting beached. But as far as I know, it's all pretty much speculaton at this point. I don't think it really damages them, though. It is unlikely an earthquake could cause a sufficient concussive force wave to damage them directly.

(posted in Birds)

You're right, there does seem to be a lot out fairly recently. I would start with the recent works by Kenneth Dial at Montana State University and Stephen Gatesy at Brown University and go from there. Those are my goto guys for avian flight literature. If anyone else has any suggestions, please feel free to add more or specifics.

I am not an expert on Nile crocodile geography by any means, but I have heard a bit about that work. From what I recall, both C. niloticus and C. suchus are sympatric regionally, in that they live in the same river. However, they tend to occupy different specific habitats within the river. There are morphologic and behavioral differences between them that people living there have apparently long recognized, but has only fairly recently been confirmed by the genetic tests. Many scientists had apparently had the same initial doubts as you, how could two such similar species live so close together, but apparently they do so by taking advantage of the heterogeneity of river environments and utilizing different habitats within the river. As I recall, C. suchus is smaller and less aggresive, but I am not entirely sure on that.

I have also read that about the crocodiles of Madagascar. I have not studied them so I can't really say whether they are or not. But salties have a much larger range in saltwater than most people realize and it is not entirely inconceivable that they could have made it there at some point and established a viable population. They are exceptionally hardy animals. So I would say it is a plausible hypothesis. Whether actually true or not remains to be seen.

Unfortunately, there is not a whole lot of good references on postcranial crocodilian anatomy of which I am aware. There is the classic Laboratory anatomy of the alligator from R.B. Chiasson from 1962, and "The axial tail musculature of recent crocodiles and their phyletic implications," by E. Frey, J. Reiss, and S. Tarsitano in American Zoologist, vol. 29, issue 3, pages 857-862 from 1989; but I don't know of much else that has a lot.

Drs. Holliday and Witmer have started a great 3D alligator website which will (it is to be hoped) include the entire animal, but right now only has the head. Hardly surprising they started with that, as they both specialize in the head for their research. I assume this is what you were referring to? They will appreciate hearing their efforts are reaching people.

Thanks Owen, I oversimplified a bit by just saying somatic and germline and made the situation a bit more black and white than it really is. Most cells in the body have limited to no replicative ability and the amount of telomerase activity is correlated with the self renewal potential of the cell type, such as that seen in stem cells and some immune cells.

Other animals have nose hairs, we are not special in that regard. The amount varies, but I couldn't say anything about how much exactly.

We don't lack turbinates. We have three sets, an inferior, middle, and superior. They are not as well developed as in some others, like say dogs and seals, but we have them and they are very important in helpig us to limit water loss through our nasal passages and to a small degree in helping to cool the brain (ok, only by about half to one degree, but still).

Most people think we evolved in a more open, drier climate, which was probably dusty, so it is possible we were selected for bushier noses than our more forest-bred ape relatives, but I don't know of any real studies on that.

(posted in Fossils)

Bacterial metabolism is part, but there are several other things as well.

First off, when the body decays, it releases a variety of acids and digestive enzymes that help to dissolve bones. The pH in a fresh body is as a result low (acidic). Usually these acids get neutralized quickly enough that they don't have a major effect on the bones though.

Secondly, in addition to bacteria and arguably more important for bone dissolution is fungi, which are major decomposers. They will secrete acid to dissolve and burrow through bone as they extrct its nutrients.

Thirdly, carbonic acid is very common in the environment. When carbon dioxide dissolves in water, it creates an acid. This is actually causing problems with coral reefs around the world as they are trying to cope with the oceans becoming increasingly acidic as the oceans absorb carbon dioxide from the air. Anyway, as a result of carbon dioxide in the air, most surface water is typically slightly acidic.

Interestingly, without something to protect the bone from the environment, the bone will dissolve away due to the natural acids I talked about. One big way bones are protected by this is from the very bacteria that are decomposing the body. Many bacteria create mineral precipitation as a result of their normal metabolic processes. They pump out such things like ammonia, which raise the pH and cause carbonates and other minerals to precipitate in and around the bone, which creates a protective covering. This is not something the bacteria are trying to do, it protects the bone from themselves as well. It is just natural chemistry in action.

We have two different major types of cells in our body. The somatic cells are almost all the cells in your body and they don't increase their telomeres. They get reduced every time the DNA undergoes mitosis. When they get short enough, the cell dies, usually through apoptosis, a regulated cell death, a cellular assisted suicide if you will, to prevent all the cell enzymes from being spread throughout the local cellular environment. Fortunately, the telomeres are long enough usually to last through a standard lifetime of replications. If they aren't, you get early aging syndromes (short telomeres are a component, but these syndromes also have other problems as well, so it's not quite this simple, but then few things are so simple).

The second type of cell is the germline, these are the sperm and ova. These cells create a special enzyme called telomerase, which adds more telomeric DNA to the ends of the telomeres, constantly resetting the clock and keeping them youthful, so to speak. This is why babies have full length telomeres.

The downside to the telomerase is that if this is activated in a somatic cell, you get cancer. We want the germline to grow constantly and be immortal, but it would be disastrous for the other cells in our body to be immortal and grow out of control.

One advantage to using tyrannosaur rather than Tyrannosaurus in a story is you don't need to italicise tyrannosaur, as the others have mentioned. What I would suggest for a story, and what I do even in my nonfiction, is to clarify initially whether I am talking about a specific Tyrannosaurus or particular grouping of tyrannosaurs and then just use tyrannosaur thereafter, unless my meaning changes. It just makes things easier and less likely to create errors if you can avoid italics or any other special font as much as possible. It also makes the question of the proper plural fairly self-evident.

We don't really know for sure, but through the work of Andy Farke and others, we can make some good guesses. It all depends on what exactly you mean by charging. It is clear they at the very least locked horns during combat with each other. But it is also likely that if they charged each other like muskox or bighorn sheep, they would probably snap horns off. The horns simply weren't built for that kind of stress when one considers the size of these animals. However, antelope use their horns very effectively against predators and those horns aren't built for powerful charges either. Triceratops almost assuredly lowered his head and gored a too close predator from time to time. Just because that may not have been the primary purpose of the horns, nothing would not have prevented a triceratops from using them defensively. But it would have been more likely to have been a powerful thrust rather than a galloping rhino-like charge.

There was a question just like this in August, answered by Peter Falkingham (is that the article you were referring to?). He suggested something like the helicopter damselfly. While the family of insects in which that particular damselfly is in is not found in the Channel Islands, there are other damselflies that are found there and likely look pretty similar when in flight. So I would suggest starting there in an effort to identify what you saw.

Guesses for what this sound is are many and varied and they all have thing in common: they are all speculation. Nobody has any real idea what it is. This should not surprise us though, as there  are lots of things in the oceans we don't understand yet. The bloop doesn't sound conclusively like anything we know. But since we know very little about the the activities and lifestyles of most of the organisms we are familiar with, the fact that it doesn't sound like something we already know doesn't mean a lot. Add in all the sounds from inorganic processes, how they are altered traveling through different densities of water, reflections, interference with other sounds, and it makes it practically impossible to identify a sound unless you have a recording of something that you are witnessing at the time.

This is an area that could really use more research. So what are you doing for the next 50 years?:)

To begin with, there is nothing magical about the activity levels of
mammals. Birds on average run higher metabolisms than mammals and
some birds put mammals to shame. But these are large groups and
comparing mammals to dinosaurs is comparing apples to oranges. It
would not be appropriate to compare hummingbirds to sloths for
instance. A more appropriate comparison might be hummingbirds with
shrews, both of which run exceptionally high metabolisms and are
comparable body sizes. So yes, dinosaurs could have higher
metabolisms and higher activity levels than mammals, at least some of
them.

I want to hit the diversity issue again because it puts
the question into perspective. Saying anything about dinosaurs in
general is like saying something about mammals in general. It is even
worse than that because birds are dinosaurs. Metabolic rates among
mammals vary enormously, so much so in fact that arguably not all
mammals are endothermic and certainly not all mammals are
tachymetabolic (high energy levels). A large portion of that
variation is due to body size. The larger the animal, the slower it's
metabolism on a pound for pound basis. One big reason for this is
that large animals have a smaller surface to mass ratio, so they
retain heat better. Multi-ton animals retain heat exceedingly well.
This is the reason some people have suggested gigantothermy for
dinosaurs, saying they did not need high metabolisms to stay warm,
equating temperature with activity levels.

There are numerous problems with the gigantothermy hypostesis. The first
and most obvious one is that a lot of dinosaurs were far too small to
utilize gigantothermy and this  only counts the adults. Every
dinosaur species started out too small to be a gigantotherm. So this
hypothesis requires changes in fundamental metabolic activities that
I think are beyond what I think can realistically be done. You will
run across papers that claim chickens start out ectothermic and
become endothermic as thy grow, but this is bunk, based on a complete
misunderstanding of physiology. Human babies can't regulate their
body temperature very well either, but I don't hear anyone claiming
that humans start out ectothermic. Another big problem with the
gigantothermy hypothesis is that metabolism is more than just heat.
It is the production of usable energy that can be used. Gigantothermy
indicates that a normal reptilian metabolism can create enough energy
to maintain a high mammalian level of activity if only it didn't have
to worry about creating excess heat. Basically, it is saying that
there is not any fundamental differences in the molecular physiology
between the two. This is wrong,wrong, wrong. It is possible to
substantially alter the metabolic rate of cells by transplanting the
cell membranes, such as between alligators and mice for instance. Two
researchers by the name of Hurlburt and Else have done some
fascinating work on this topic. In summary, a large reptile is not
going to behave the same as a mammal no matter how big it gets. The
activity levels will converge, but the reptile will never achieve
mammalian levels of activity.

Fortunately, we have quite a bit of evidence that many dinosaurs did indeed reach mammalian levels of activity. Does this mean they had mammalian levels of metabolisms? Not necessarily. Certainly some did, some even had higher. Birds are proof of that. But remember that the Mesozoic was by and large warmer than the Cenozoic and more moderate in temperature fluctuations (yes, I am making big generalities here, but
it holds up for the most part). Thus,they did not need to create as
much energy, so they did not have the selective pressures to create
the level of control that most mammals demonstrate.

Internal control over metabolic rate is really where the important discussions lie,which all the temperature talk is a proxy for. Not all dinosaurs were capable of mammalian metabolic control almost certainly. But they didn't need to be. Moreover, we know that SOME dinosaurs DID
develop that control.

Hope this helps. This is a hugely complicated discussion and I only
briefly touched on some of the issues here.  Please ask more if you
would more information on any of the points discussed here.

I amnot sure that it is all that uncommon. The skull shape of horses is not that dissimilar from antelope, elk or deer. They all have elongate skulls. To that matter, the horse skull is similar in broad form to that of a diplodocus or stegosaurus, which both also had elongate skulls (although the dipldocids only had teeth in the front and the length of the snout had nothing to do with tooth placement, so that answer doesn't hold up across the board). The length of the jaw in cows is similar to that of horses, but the skulls are not as elongate because cows have more jaw musculature. 

So why do cows have a broader jaw? Because they chew more. Cows and other ruminants extract maximal amounts of energy from the food they eat. Extensive chewing to break down the foodis part of this process. Horses on the other hand, take the high throughput route. They are very inefficient digestors, being what's called hindgut fermentors,  but they make up for it with eating a lot. Thus, they don't chew nearly as much as they just bite and swallow for the most part, with grinding the food being fairly minimal. The food is gritty, so it still wears their teeth down quickly, but the jaw musculature required is much less. Thus the elongate jaw.

(posted in Mammals)

I don't think they have a particular hatred of each other that goes beyond the intense competition between two top predators in an area of very limited resources. Lion prides will do the same thing to other lion prides, just to demonstrate the level of competition in the area. So I think the behaviors you are referring to are just normal ecological levels of competition in that environment. I would point out that humans, as a top predator, are very intolerant of other large predators and have a huge tendency to try to eliminate anything that might compete with them or be dangerous to them. I wouldn't say that we have a particular hatred for wolves, but as a species (I'm speaking broadly here) we have a long history of trying to exterminate them.

I do believe, although I can't back this up with evidence, that if they were raised together from birth in an area that provided abundant resources, they would get along just fine, just like cats and dogs can live together in the same house where they aren't having to worry about where their next meal is coming from.

It looks like a horse to me. While they don't ordinarily live up there, people do ride them up to that elevation. 

Since you are in Colorado, you may be interested to know that there is a vertebrate paleontologist at UC Boulder who specializes in mammals, coincidentally named Dr. Eberle, who may be able to help you with identifying bones you run across like this. There are also several knowledgable people at the Museum of Nature and Science in Denver that would be happy to help as well. Actually, Colorado in general is quite wealthy in terms of knowledgable people in this regard who can be found at many of the museums and universities, so you can find many people within a short drive that can help you with bones and all of them that I know are very friendly and helpful.

Am I reading your posts sloppily? Possibly. You presented the Martinez article as showing a sauropod in sleeping position. I was refering to that article, as I stated. I was not referring to any comments about sauropods in general, so no, I was not creating a straw man argument. Perhaps I am not the one reading sloppily? Perhaps you care to explain what I said that was a strawman argument?

'nuff said is a statement made by someone unwilling to consider any other view point. Surely as a scientist, you prefer facts over personal comments and are indeed willing to hear other ideas.

While it is true that the brain itself does not have pain receptors, the dura mater does. The brain is surrounded by layers of connective tissue, of which the dura mater is part. It is this that feels the pain. You can also get headaches from compression or stretching of nerves in the scalp. Another way to get headaches is hypertension causing pressure in the blood vessels in and around the head.

In short, there are many things that can cause headaches, but what you are feeling is around the brain, not within the brain itself. It is just that our bodies are not always that good at localizing the pain to specific areas.

Dimetrodons are pelycosaurs,a type of early synapsid, which is the lineage that all mammals are descended from. Thus, dimetrodons are more related to mammals than they are to reptiles. However, this doesn’t mean that mammals descended directly from them, only that they were an early branch off the lineage leading to mammals. We don’t know if Dimetrodon was a direct ancestor or a side branch, but likely it was a side-branch with another unknown direct ancestor, much like your cousins are related to you, but only indirectly through your parents siblings.
Currently, the earliest eutherian mammal we know of is Eomaia, a small mammal found in the Lower Cretaceous in China. Eutherians are the placental mammals, so Eomaia was after the marsupials and monotremes split off.
The earliest true mammal that we know of may be Adelobasileus, a small animal from the Dockum Formation in Texas, from the late Triassic. Again, we don’t know if this is a direct ancestor or a side-branch and is most likely a side-branch (the chances of identifying a direct ancestor are small), but it is the closest we have for now.

While Heinrich may not have liked your question, it is probably the most common type of question that gets asked of paleontologists. As someone who participated in Jurassic Fight Club, while I agree that the science is less than stellar, the shows have their purpose other than just getting money off a TV audience. The people making the shows aren't exactly rolling in money. I have witnessed firsthand the interest the shows create and that interest has allowed me to discuss the real science to people that otherwise would not have heard it, so I can't criticize them too much (even though I do wish they would be more careful to present correct information).

To answer your question, let's look at what we know of the animals. Allosaurus was smaller and had a primitive brain compared to T.rex, so we can toss him out.
Spinosaurus may have been bigger than T. rex, but he was comparatively more lightly built and also had a much smaller brain in comparison. So I would toss him out as well.
Giganotosaurus is the only one I think would really pose a challenge, despite what JP3 showed. Even here though, Giganotosaurus was comparatively lightly built, with less robustness in the jaw. Giganotosaurus appears to be more like Allosaurus in being designed to tear flesh from the carcass. T. rex on the other hand, had a powerful skull and could bite through bone. He also had the biggest brain in comparison to any of the others, as shown by CT scans by Larry Witmer.

Thus, I think T. rex is still the reigning champ.

Heinrich is certainly right in that these animals would never have actually fought and this is all sheer speculation, but speculations such as this can in a fun way make us think about the animals in an informative manner. Most any question can increase our knowledge base, so don't be afraid of asking stupid questions!

Heinrich,

There is not enough information in Martinez's paper to conclusively state whether the animal was sleeping or even alive during burial. I think stating this is a sleeping posture is premature, so I have to agree with John.
As to how it flexed the hindlimbs if it collapsed that way? The answer is what you gave, the center of mass is over the limbs. If the animal is going to collapse from exhaustion, it will likely collapse by its back legs collapsing into a flexed position under its body. As someone who is very familiar with collapse due to muscle failure, that's the way it works. For a quadroped of this shape, the back legs will collapse first, as they carry the most weight. While it is possible to collapse with the front legs first, it is not nearly as common. The front legs will then often stay extended as the body falls backward onto its haunches. However, in the figure, the front legs are extended backwards, not frontwards as would be expected.

In truth, assuming the animal was alive at the time of burial, it looks to me like the animal got caught in an avalanche, with the head downstream. The weight would then push the animal down and forward, causing the front limbs to be splayed out behind, the back legs collapsing secondarily underneath the body as dictated by center of mass and flow physics.

This is of course speculation, but it seems to me more plausible than a sleeping position.

Also, Padian's point about the opisthotonic position was that the animal was tachymetabolic, as opposd to bradymetabolic, as only tachymetabolic animals animals show such death positions. Thus, it is not a taphonomic signal, but a physiologic one, so you are right. I think what John meant though, is that this is an example of why it is difficult to conclude behavioral patterns from carcass position. We need to be really careful before we make statements about behavior before we have ruled out other mechanisms first and this is incredibly hard to do with fossils such as this.

But back to how sauropods may have slept. I think it is likely that they slept on their bellies with their legs folded under them, much like a cow. They probably also slept standing up, but I know of no animal that sleeps that way all the time. So they likely were the same, using more than one sleeping posture. What we can rule out is that they didn’t sleep in trees :)

(posted in Mammals)

Comparatively, it's not too difficult to create a unicorn the way Brent describes, by removing one horn bud from an embryonic two-horned animal and shifting the remaining one towards the center. It has been done a number of times. But so far no one knows how to create one that will breed that way.

One of the biggest issues is that it is not just the genes you need to understand, but the timing of development, which makes a huge difference in how structures grow and develop. We just don't know enough about the genetics and developmental timing of horns to do this yet. But it is at least theoretically possible.

One thing to keep in mind as well is that a sigmoidal growth chart somewhat obscures what is really going on. The amount of mass an animal can add is dependent on its weight. The same amount of growth for a 1 kg animal is vastly different than a 1 ton animal. Consider a 1 kg baby tyrannosaur that can grow at 5% a month. After a decade, that animal will be just under 350 kg. But at a continuing 5% growth, in just four more years, that same animal will be over 3800 kg. In that first decade, the tyrannosaur will have increased its weight almost 350x. In the next four years, despite having added almost 3500 kg, it will have only multiplied its weight by 71x.
Thus, if you look at strictly how much weight is added, you have an animal that grows very slowly initially, then virtually explodes in weight. But if you look at the percentage change per time, the growth never changes.

Isn't math fun?

Of course, this growth can't continue at this rate. The older an animal gets, the slower it will grow, thus the leveling off of the curve.

There actually has been work done on croc blood and human diseases. Crocodiles have very powerful antibiotics in their system to deal with the extremely bacteria laden lifestyle they live. Mark Merchant and Adam Britton have done some work on the use of antiobiotics extracted from croc blood on HIV and found it to be extrememly effective. I don't know how far that work went, but it at least looked very promising a few years ago.

I would quibble with Paolo's answer a bit here because paraphyletic groups can still serve some purpose as grade level designations that, while not cladistically valid names, suffice to identify a group of organisms. An example of this would be basal therapsids. This is not a valid clade as it contains several groups, but does not refer to crown group mammals. But if you were to say therapsid to most people, they would generally understand you are talking about a particular collection of related animals, but not the descendants of said group. We do this all the time. Virtually everyone accepts Aves is nested within Dinosauria, but always saying "non-avian dinosaurs" is rather awkward, so when we talk about dinosaurs, we can generally expect that our audience is not going to be thinking about birds.

But back to the question about Insectivora. The original Order Insectivora contained many groups that were found to be unrelated. They could even be considered to be related in grade level because the groups arrived at their forms convergently, rather than as successive branches of the same line.
Thus, Insectivora is polyphyletic, not paraphyletic and so serves no good purpose at all other than as an informal terms describing a lifestyle, which should better just be called insectivores without attaching any thought about a common heritage.

Jonathan is quite correct that it is very unlikely they would ever fight in the wild.

However, assuming they did, I don't see any way a panther of any type could win against a full grown, healthy grizzly. While panthers are quite powerful, they are not nearly as powerful as a grizzly. Adding to their strength advantage, grizzlies have long, powerful claws and powerful jaws for offensive weaponry. But the biggest advantage the grizzly has I think, is that they are hard to hurt. They have thick fur, thick and strong bones, and well protected organs. The panther would have a hard time penetrating the hide of a grizzly with sufficient ease to inflict serious harm before the grizzly killed it. The panther on the other hand, has significantly thinner fur, thinner bone, and is more easily damaged. Panthers would have a speed and agility advantage, but bears are faster and more agile than most people give them credit for, so the advantage is not as high as you might think.

Thus, bears have a significant advantage.

I don't know of any research about maximal diversity in the polar regions that would answer this question, but I would hazard a guess that the answer is no, simply because biodiversity worldwide is dropping at a high rate and there is little reason to think the polar regions are immune to this. When one considers that global warming is affecting the higher latitudes disproportionately greater than lower latitudes, it is likely that biodiversity has dropped there.

As to the algae, it would be impossible to derive nutrients just from ice, as ice is just frozen water. However, most ice in the natural environment is far from pure, containing a wide range of bacteria, viruses, organic debris, and other particulate matter. Therefore, it is possible to collect sufficient nutrients from what is in the ice. There are indeed certain types of algae that make their living this way.

I expect it developed as a consequence of what could happen in the dark. Humans are very visually oriented creatures, so we don't work well in the dark. At one time, we were also not at the top of the food chain. Our predators were much more capable of operating in the dark. When being eaten by predators you can't see until they attack you, being afraid of the dark is a reasonable precaution. The dark also makes it much harder to detect venomous snakes and the like.

This is likely also the reason that so many religions have incorporated evil as being more comfortable in the dark. It is a throwback to that primal fear of the unseen predator.

Nowadays of course, our chances of being jumped by a lion or running across a venomous snake is vanishingy slim, but there is always the threat of a human predator jumpng us (this is of course highly variable on where you live). So it makes sense that a fear of the dark is retained. But hopefully we can reason out when and where such fear is warranted.

I might suggest removing the density as a factor by using equalizing volumes, not numbers. You can't use biomass, as some have done in studies of this type, because you are dealing with molluscs, in which much of their mass is effectively inert and much denser than the soft tissue, so their weight would not be a reasonable comparison with worms with no comparable shell. Even within the molluscs, the amount of shell will vary.

Get an average volume for each species and then pick one as you base reference, say the oysters. Then you can determine "oyster equivalent volumes" for each of the other species. This will equalize biodensity and you can look at just the effects of diversity. You could then vary the composition of each species as you liked, keeping the density the same. You could also, an probably should if you can, look at density effects of the heterogeneous community by altering the overall volume, in which you would reduce each species by their proportional equivalents.

Measuring the volumes is easy. You just plunk them in a graduated cylinder partially filled with water and see how much the water level rises. The only catch is doing enough so that you have a handle on the population variance. If the sizes within each group are very similar and you aren't doing many different trials, you can also measure a group of individuals of a given species at once.

Yes, physics absolutely gives hard limits on what evolution is capable of producing. The biggest issue is that living organisms are complex, with many structural complications. So, while we can give estimates, we can't really say yet precisely where thoe boundaries are.

For your hypothetical  80 meter tall creature, one of the biggest problems it would have is that the strength of its bones is not going to increase as fast as the weight being placed upon it as it gets bigger. By the time it got to that size, its own weight would literally crush it, unless the bones were created with something other than bone and/or designed completely differently than living organisms. Is this possible? Sure, there are quite a variety of invertebrates that reinforce their exoskeletons or cell walls with other mineral structures. But we haven't seen anything like that in vertebrates. It could happen, we just haven't seen it yet.

It would also ahve problems with its heart, as you mentioned. As it stands, Roger Seymore has calculated the stresses on the heart for the large sauropods to raise their heads high and they appear to be beyond the physical constraints of the heart, so he inferred that sauropods had to keep their heads fairly low. There is other evidence that they did in fact hold their heads high, so the argument continues. What we know is that they had to do something remarkable.

Metabolic distribution issues might be a problem. Insects are currently limited in size because they depend for the most part on passive diffusion of gases through a trachea system of tubes that run through their bodies. As a result they can't get much beyond 6" in our atmosphere. They got much bigger in the past, but during those times, the oxygen content in the atmosphere was higher, which allowed diffusion to function better. Vertebrates can simply grow more blood vessels, but then you have to pump more blood through, putting more stress on the heart, which is already overworked simply from the height differences and fighting gravity.

One good thing about getting bigger is that the amount of energy needed gets proportionately smaller. Pound for pound, a large animal doesn't need to burn as much energy as a smaller animal. Its sheer size insulates its internal body from the outside environment. But then here again you run into problems trying to get rid of the heat that is created. No matter how low you reduce the metabolism, you would still need to find some way of dumping a lot of excess heat.

Biology is definitely constrained by the laws of physics. You can't simply scale up a creature to gigantic sizes and have it work. This doesn't mean the problems are insurmountable. But it does mean you will have to change the biological patterns.

Cold sweats generally are a result of some type of stress, either shock, illness, or psychological. It is triggered by your sympathetic nervous system, which activates what is often called your "fight-or-flight" response. I would speculate that the stress causes your body to prepare for action to respond to the stress and the sweating is a preemptive measure to counteract the inevitable heat created by the active response. It could also be that it is simply created simply as part of the flight-or-fight response, that the cascade is triggered as a whole unit and not as a separate response. Obviously, you don't sweat every time you feel any stress at all, so there is likely a threshold that you need to pass before the full effect is felt. Note these hypotheses are not mutually exclusive.

To expand on Alistair's excellent response, this goes to one of the most common errors in thinking that everyone falls prey to, which is why scientists are usually very careful before declaring a link between two events: we remember the hits far more often than we remember the misses. We also are hardwired to find patterns, so we really go out of our way to find patterns, even when they aren't there. This sort of thing happens all the time. We see some whales beach and then we hear of an earthquake and think, aha, there must be a connection. We forget of course that earthquakes happen every day all over the world. If whales beached themselves every time an earthquake happened, they would be extinct.

It could be that whales only beach themselves if the earthquake is large enough and close enough, but where do you draw the line? How far away does it have to be to count as evidence? How close in time? Does it count if it happens within a day? A week?

While I haven't seen any research on whales, there has been research done on other animals and thus far, no one has found any evidence that animals could predict earthquakes beyond anecdotal evidence, which really isn't evidence at all for numerous factors, not the least of which human memory is just not very reliable without supporting evidence that can be checked beyond just what somebody says they remember. Many, many studies have been done that have shown just how fallible our memories are.

These are part of the reasons that lay people accept many things that scientists don't. Scientists are generally happy to say, "maybe, but I don't see the evidence", but it takes a decent amount of verified evidence for us to say, "yes, that seems to be true."

There is an interesting book titled, "Don't believe everything you think" by Thomas Kida, that provides extensive discussion on 6 basic errors in thinking that everyone makes, but which we try to guard against.

There has been reported dinosaur protein that was able to be sequenced by Jen Schweitzer and her colleagues. While I think her data is convincing enough to lead me to think they may have it, it is not by any means universally accepted and until some other group independently reports a find, the jury is still out.

As to how it would preserve, there are two things one would need. First, it would have to be protected from any organism that would like to eat it. Second, it would have to be protected from water, which will break it down without other proteins protecting it. Amber is a possible candidate, but as yet has not proven to be up to the task of preserving DNA. Other possibilities include the way that Schweizter found hers. They found it dep within a bone that has been permineralized (all the pore spaces filled in by mineral deposition) quickly after burial, so that original material was locked away within a mineral coat from the external environment and protected from being degraded. Between the bone itself and the mineral coating, it MAY be possible to preserve small fragments. Retrieving significant lengths though would be astronomically more difficult for anything as old as a dinosaur.

It would be difficult to put a megapixel count on the eye. For one, as Corwin stated, each receptor does not have its own neural receiver. Near the fovea, for the cones, it is a 1:1 relationship, but as one gets farther away with the rods, you get get up to a 1:20 relationship between receptors and nerves (i.e. 20 rods feeding into one neuron). Then all the input from these receptors gets filtered through several layers of cells that pick up only certain aspects of the view. Some cells will pick up only horizontal lines, others only movement, etc. Our eyes do not function at all like cameras. Even after that, the image still needs to be interpreted by the brain, which asembles all these inputs into an image. That image is very patchy because the eye moves rapidly from point to point and it dos not pick up an image in between. Think of the eye as a high speed camera taking several shots a second which the brain then puts together into a panoramic view. The numerous gaps between shots are filled by what the brain expects to be there. This is one of the main ways that magicians fool people is by playing to those expectations and then secretly changing them.

Because the eye and the brain work so fundamentally different, I can't see a justifiable way of comparing them in terms of megapixels.