(posted in Fossils)

Genyodectes, for the benefit of others who might be reading this, is a South American theropod dinosaur known from only a few fragments of the upper and lower jaws of one fossil individual. The fragments vary in size, but the largest (the front part of the left lower jaw) is around 33.5 cm long. A complete lower jaw might have been more like 60 cm, but this is just a rough estimate.

According to the paper published a few years ago that reported the draft sequence of the Neanderthal genome, the proportion of Neanderthal ancestry in non-African human populations is 1 - 4%.

This proportion of ancestry is different from the amount of DNA shared with Neanderthals. A person with three east Asian grandparents and one European grandparent would be 25% European and 75% east Asian by ancestry, but would share over 99% of his or her DNA sequence with any randomly sampled European or east Asian - or with any other person on the planet! This is because most base pairs in the DNA sequence are identical across all humans, including Neanderthals, so ancestry only affects the small percentage of base pairs that do vary within our species.

Imagine a seagull flying not against the wind, but in still air. Its wings will produce lift, which allows the bird to stay airborne by counteracting the force of gravity, and thrust, which propels the bird forwards at a rate of, say, 40 km/h. If the same bird is flying against a 15 km/h wind, it is essentially flying within a stream of air that is carrying it backwards at 15 km/h, like a person running the wrong way on a conveyor belt. In theory, the seagull should be able to fly forwards at 40 - 15 = 25 km/h. Its wings produce enough thrust that it can keep advancing despite the headwind, albeit more slowly, and enough lift to keep it aloft just as in still air.

Now imagine that the wind speed increases to 40 km/h. The seagull is now flying in a stream of air that is carrying it backwards exactly as fast as its wings can propel it forwards. The wings are still producing lift, so the seagull does not fall out of the air, but it hovers in the same place without advancing, as if it were in a wind tunnel. If the wind starts to blow even harder, and the seagull is unable to flap more powerfully in order to compensate, it will theoretically start to be blown backward.

The short answer, then, is that the seagull is not "trying" to remain in the same place when flying against the wind; it is trying to move forward, but the wind is blowing hard enough to hold it in place. Of course, the wind doesn't usually blow at a perfectly steady rate, so sometimes a bird will be "held" by strong gusts but can advance in between gusts when the wind speed is lower.

This is a long way from my area of expertise, but I thought the evidence for menstrual synchrony being a real phenomenon in humans was actually quite shaky. A little poking around on Google Scholar reveals a number of studies that have challenged the idea, including one entitled simply "Women do not synchronize their menstrual cycles":

http://link.springer.com/article/10.100 … 006-1005-z

David, do you have a sense of where the debate stands at the moment?

(posted in Fossils)

The bone you found looks like the astragalus, an ankle bone usually called the talus in humans, of a goat or sheep. Compare your bone, for example, to the one illustrated on this page:

http://museumvictoria.com.au/collection … circa-1880

That bone is a particularly interesting one for a couple of reasons. First, the shape of the astragalus is distinctive in artiodactyls, the group of "even-toed hoofed mammals" that includes sheep and goats along with deer, antelope, cows, camels, pigs, and various other ungulates (but not horses, tapirs and rhinos, which are perissodactyls or "odd-toed hoofed mammals"). In artiodactyls the astragalus forms convex joint surfaces at both ends rather than only one end, giving the ankle some extra flexibility, and you can see this "double-pulley" structure in the bone you found (your second photo shows this nicely - one convex, pulley-like joint surface is to the right, the other to the left).

Second, sheep and goat astragali roll well enough that many cultures have traditionally used them as dice. This Wikipedia page describes some Central Asian games that can be played with them.

http://en.wikipedia.org/wiki/Shagai

And, of course, black hair is not restricted to Asian and African Caucasians by any means - it also shows up even in northwestern European populations, albeit at a much lower frequency than is the case in Asia, Africa and even southern Europe.

(posted in Evolution)

Like David, I'm having trouble grasping exactly what potential role you see for emotion in the evolutionary process. It's certainly true, however, that evolution has endowed humans and other animals with important psychological drives, including the powerful survival instinct that you mention.

...the program devised by R Dawkins.

Richard Dawkins is a brilliant thinker and communicator, but he didn't really "devise" much of modern evolutionary biology. The core of the evolutionary theory that goes into Dawkins' books is a synthesis of Darwin's key insight of natural selection with more recent discoveries relating to the mechanisms of genetic inheritance (which were essentially unknown to Darwin).

Surely if there was no control over evolution, the right thing for nature to do would be to make it possible for the species to feed off all the different foods that were available?

It's a bit misleading to think in terms of "the right thing for nature to do", given that nature isn't a being with needs or any kind of agenda. Nature is just the sum total of the processes that occur in the world without human involvement. Evolution is all about which kinds of fish (for example) successfully survive and reproduce, and which die out. Some fish do indeed eat many different kinds of food, but this requires them to be very versatile. They need "general-purpose" jaws and feeding behaviour that are reasonably good at handling a wide variety of food sources, but are unlikely to be ideal for handling any particular food source. Other fish instead specialise by evolving to handle a single type of food very well, at the expense of their ability to efficiently feed on other types. As long as multiple types of food are available, there are likely to be some generalists and some specialists, taking different paths to potential evolutionary success.

The species Ryan has in mind must be Labord's chameleon, Furcifer labordi. Apparently this lizard has a posthatching lifespan of only four or five months, which follows an incubation time of eight or nine months. The following article summarises its life cycle:

http://news.bbc.co.uk/earth/hi/earth_ne … 398679.stm

Using this species for experimental work in evolutionary biology is an interesting idea, but there are some large potential stumbling blocks. In addition to the ones already pointed out by David and Alastair, F. labordi is considered "vulnerable" from a conservation perspective, so removing even a relatively small number of individuals from the wild for laboratory research could be problematic. However, field studies aimed at better understanding the unusual life history and ecology of this species could be very rewarding.

A scientist who has done some important recent work on F. labordi is Kristopher B. Karsten of California Lutheran University. I'd suggest that you look up Professor Karsten's papers for further information on this species.

David,

That page you linked to looks very informative, and I see that it mentions "leaking" or "regurgitation" as a potential problem with the aortic valve. I assume that a similar issue with imperfect closure can arise with respect to the mitral valve, which is normally bicuspid? This might have been what Dmitry was getting at.

At this point English is pretty well established as the international language of science, and universities and other organisations that might employ scientists are likely to be a lot more interested in things like publications, grants and teaching experience than in an applicant's proficiency in languages other than English. So yes, I'd say that the professor who addressed your school was exaggerating a bit if he said that foreign language proficiency was important in ANY career. Of course, it's (unfortunately) more or less essential for a scientist whose mother tongue is not English to develop the ability to publish and present his or her work in English in order to have an international impact.

With that said, proficiency in at least one foreign language is useful even for native English speakers like myself. Scientists need to travel internationally and communicate with foreign colleagues, and facility with languages certainly makes that easier. I live and work in China, for example, and I find myself constantly wishing my Chinese were better than rudimentary. Also, a fair amount of older scientific literature is in languages other than English, although this is more of an issue in some disciplines than others.

Whether French or Spanish is the better choice will depend to some extent on an individual scientist's activities. A palaeontologist who visits France often, collaborates closely with French colleagues and does fieldwork with them in Morocco every summer will probably want to learn some French. However, Spanish has many more native speakers worldwide and is the primary language in many more countries. Important scientific literature has been, and to some extent continues to be, published in both languages. Both are undoubtedly useful, but if you're in school and need to make a choice I would suggest that you opt for Spanish unless you have some specific reason (like thinking you might want to work in a part of the world where French is widely spoken) for choosing French instead.

The following webpage lists a couple of insect species (and one subspecies) that appear to have recently gone extinct as a result of habitat destruction, and claims that 59 species are "known" to have disappeared in modern times:

http://www.endangeredspeciesinternation … ects7.html

Some insect species are confined to small areas, exist in relatively low numbers and/or are vulnerable for ecological reasons (such as dependence on a specific food resource), so I'm sure it's not uncommon for humans to wipe out species accidentally. I don't know of any pest eradication campaigns that have totally eliminated an insect species, but it's interesting that one of the extinct species mentioned on the webpage I linked to was the Rocky Mountain grasshopper or Rocky Mountain locust (Melanoplus spretus), which was a widespread and devastating pest on the American plains during the 19th century. I can't find any indication that it was deliberately eradicated, but I'll bet prairie farmers didn't shed too many tears when it was declared extinct.

Here's an article from the Denver Rocky Mountain News recalling the depredations of the locust, which supposedly "chewed the wool right off sheep":

http://denver.rockymountainnews.com/mil … mile.shtml

Interesting questions. You're entirely correct that humans have always used tools to improve their odds of survival, and that modern medicine just represents a continuation of the same fundamental strategy. If I were to break my leg I could go to a hospital and have it put in a cast, whereas my Stone Age counterpart might have had to settle for a wooden crutch and a splint applied by some obliging fellow hunter-gatherer, but both scenarios involve technology and (just as crucially) social cooperation. We've never, in our history as a species, had to face natural selection alone and with only our bare hands.

When people argue that it's "wrong" to "go against" natural selection, what they generally mean is that using medicine and technology to help people overcome genetically-based disadvantages will allow the genes that cause those disadvantages to survive and become more common in future generations. For example, I'm rather short-sighted, and there was probably a time in human history when this would have decreased my chances of surviving into adulthood. In modern society I can wear glasses, and even without them I wouldn't face much risk of dying as I went about my daily business. Assuming that short-sightedness has a partly genetic basis, the genes linked to this trait are no longer being selected against, and must be more common than they were in the Stone Age.

The proliferation of genes for short-sightedness could be seen as a weakness spreading through the population, but it's not a very important or harmful weakness as long as we can keep manufacturing and distributing glasses. Once we've invented a good medical solution to a genetic problem, it doesn't matter too much if the genes that cause the problem become more abundant, and it no longer really makes sense to think of them as disadvantageous genes at all. They're not disadvantageous in an environment where the solution to the problems they cause is readily available, any more than lacking thick fur is disadvantageous in an environment where one can easily buy warm clothes.

Regarding your last question, Dawkins didn't call genes selfish because he thought that they made people selfish - he called them selfish because the evolutionary success of a gene is only partly linked to the welfare of individual organisms carrying that gene. Rebelling against the tyranny of the replicators just means acting in ways that we find beneficial and fulfilling, rather than working tirelessly to spread our genes. If you're doing something with your life other than raising or preparing to raise as many fertile offspring as possible, and encouraging your close relatives (who will share many of your genes) to do the same, then you're already standing up to the replicators.

Quoth David:

Agreed the genetic data is now incontrovertible - our direct ancestors were apes.

The case was pretty much incontrovertible even before the genetic data were available, to be honest. The evidence from the anatomy, physiology and behaviour of living primates, combined with the fossil record, points overwhelmingly to an ape ancestor.

Quoth Peter:

Many of the factors you mention are either anecdotal or equally applicable to apes.

I think this is the key point in this discussion. To expand on it a little, the similarities between wolves and humans mentioned in the original question are mostly real (though I'm sceptical about the one involving long-distance knowledge of dying elks, dying partners and departing mothers). For example, humans and wolves are both social animals, so they do indeed have very broadly similar "pack mentalities". However, chimpanzees and gorillas are social animals too, so this characteristic can't be used to argue that wolves are more likely to be closely related to humans than apes are. To determine whether this might be the case we need to look at characteristics that differ between wolves and apes, and with respect to those features humans are almost without exception more similar to apes than wolves. Apes and humans, for example, have hands that bear fingernails and can be readily used to manipulate objects, whereas wolves have forepaws that bear claws and are mostly for use in walking and running.

(posted in Evolution)

...adhere to the receptors in different concentrations in either nostril...

For clarity, it's worth pointing out that the olfactory receptors aren't in the nostrils per se but farther back on the roof of the nasal cavity, internal to the skull.

The nasal cavity is of course partitioned by a septum, so inflows from the paired nostrils are kept separate and the left and right patches of olfactory receptors could still presumably receive different signals that might indicate direction. However, another reason for having two nostrils might be control of the airflow - given the need to be able to inhale or exhale a given volume of air through the nostrils per breath, it might be that two narrow passages provide smoother, more regular flow than a single wide one would. It also seems possible that a single large nostril would be harder to keep free of large incoming particles and even parasites.

If the new and old species exist together in the cave as distinct, non-interbreeding populations for a period of time before the old one dies out and the new one takes over completely, then sympatric speciation has occurred. This could happen, for example, if some individuals in the original population developed superior climbing ability and began to prefer mating on high rock ledges within the cave that were less accessible to predators. The climbers would then be reproducing primarily with each other, and might eventually form a new species coexisting with the non-climbers. Of course, allopatric or parapatric speciation could also take place in a cave large enough to contain geographic barriers (such as collapsed sections of tunnel) and varying microhabitats.

If there are never two separate populations, but new characteristics simply spread through the original population until its members are different enough from their ancestors to be recognisable as a distinct species, then this is an example of anagenesis rather than speciation per se. Anagenesis is defined as evolution within a single lineage, whereas speciation is usually defined as the branching of a lineage into two distinct ones (also called cladogenesis). One could consider anagenesis to be a special form of speciation, not involving splitting, but the terms "allopatric", "parapatric" and "sympatric" would still only apply in a meaningful way to cladogenesis.

Edited to add: I would probably have tried to think of an example that didn't involve climbing if I'd noticed that this question was posted in "Fishes"!

Your guess was an inspired one, but those aren't lemur bones - for one thing, the lower jaw of a lemur would have at most one large, pointed tooth (the canine), with incisors in front and premolars and molars behind.

I'm going out on a bit of a limb here, but I'm reasonably convinced that your friend spotted the bones of another equally interesting member of Madagascar's subfossil fauna: the extinct crocodilian Voay robustus. The bone above the jaw in your second photo is part of the left side of the rear part of the skull. The semicircular prominence at the very top is the "squamosal horn", a protrusion on the back of the skull. A squamosal horn is not found in Crocodylus niloticus, the only crocodilian that inhabits Madagascar today, but is present in Voay.

The partial jaw doesn't look quite right for a crocodilian, admittedly, but that could be the result of damage combined with the angle of the photo.

The complexity of our nervous system and the amount of information that the controlling organism/infecting agent would need to carry to take control of a mammal would be vast and just does not exist nor can I imaging a scenario that it would.

Doesn't it depend on the nature and precision of the "control"? Rabies is a good example of a disease that "controls" mammals in the sense of altering their behaviour, and Wikipedia (for what it's worth) does describe the hyperaggression that is sometimes characteristic of rabies as an adaptation for facilitating the spread of the pathogen. Is it really that much of a stretch to imagine an easily communicable disease that would make people wildly aggressive?

Of course, wild aggression wouldn't be enough in itself to generate the kind of scenario outlined in the question, because humans don't ordinarily express aggression by clawing and biting each other. They're more likely to punch, kick, strangle, or reach for some kind of weapon, tactics that wouldn't offer much of a route for disease transmission. Also, a disease that caused zombie-like aggression (I'll call the disease "zombosis" for short) wouldn't blossom into an epidemic if the aggression was typically severe enough to kill or seriously wound new victims.

To get around these problems, I think zombosis would have to cause people to scratch and bite without generally continuing the attack to the point of incapacitating the victim. I suppose the latter point would take care of itself if the attack were clumsy enough and didn't involve much grappling - most healthy victims would easily escape after a bite or two.

A disease that would specifically result in clumsy, indiscriminate biting seems less neurologically plausible than one that would simply cause hyperaggression. However, one of my colleagues on the site who knows more than I do about disease and the nervous system might be able to come up with a halfway-conceivable mechanism for inducing the former, and the conventions of science fiction provide a certain amount of leeway in any case. Having zombosis evolve as a variant of rabies might be a good bet, given that rabies already causes hyperaggression in at least some species. It's hard to imagine that "zombies" would have much of a life expectancy once they started attacking people (and maybe each other), so perhaps zombosis would be rapidly fatal and rely on wide transmission as a "strategy".

One problem with the scenario, I think, is that the "zombies" would actually be pretty easy to deal with once the authorities were on to them. Lacking any kind of super-toughness, they could easily be shot or perhaps even tasered. It's hard to see how zombosis would spread to enough people to create a truly threatening horde of "zombies" before being nipped in the bud.

I don't actually find zombies to be terribly interesting antagonists in books or movies - I prefer monsters with a lot more agency and intellect. However, it is interesting to think about how a disease might lead to zombie-like behaviour. I agree with David that this site should be about fact rather than fiction, but I don't think that rules out considering how closely a fictional scenario might be approximated in the real world. It's a fun and potentially informative kind of thought experiment.

(posted in Evolution)

In terms of scientific classification, "monkeys" could presumably be either a clade containing the common ancestor of New World monkeys and Old World monkeys and all its descendants (including humans and apes), or a grade containing New World and Old World monkeys plus any other (extinct) primates that are at least as closely related to humans as New World monkeys but no more closely related to humans than Old World monkeys. Either way, the common ancestor of humans and all living monkeys would be a monkey.

An alternative would be to take the view that "monkey" is a vernacular term with no precise relationship to scientific classification. Then the question of whether a given ancestor (if spotted by a time traveller) should be called a monkey really would boil down to "po-tay-to/po-tah-to", except that one option might be more confusing and/or inconvenient than the other.

In this case, I would argue that saying that "humans didn't evolve from monkeys, but share a common ancestor with them" is potentially quite misleading in two ways: it gives the impression that the common ancestor might not have been very monkey-like, and encourages people to think of humans and monkeys as separate groups that diverged from one ancestral species (whereas Old World monkeys are actually more closely related to humans than either group is to New World monkeys). Saying that "humans evolved from monkeys", "humans evolved from among monkeys", or "humans are just modified monkeys" (all of which, in my view, are defensible ways of expressing the same idea) avoids these problems.

(posted in Evolution)

In my opinion it's about time that we biologists stopped beating around the bush (or the evolutionary tree) and admitted that, yes, humans absolutely did evolve from monkeys in the same sense that birds evolved from dinosaurs. It would be more in line with current views of evolution and classification to say that humans are a highly modified kind of monkey, and birds are a highly modified kind of dinosaur, but this is really a bit of quibble.

The bottom line is that the common ancestor of humans and all of the living things that we call monkeys must have been very monkey-like in its appearance and behaviour (though exactly what kind of living monkey it would have most resembled might be an interesting question). Furthermore, some monkeys are more closely related to humans than others, so it's incorrect to think of "human" and "monkey" lineages extending separately from a common ancestor. Rather, monkeys appeared in the geological past and diversified into many different types, and one lineage of those monkeys eventually evolved into an animal that we would recognise as an ape (while other lineages evolved into the various monkey species that are still with us today). Then apes diversified, and one lineage of those apes evolved into humans. Humans didn't evolve from any modern type of monkey, but a time traveller following our own lineage back through geological time would quickly come upon ancestors that no reasonable person would hesitate to describe as monkeys.

You might find Table 1 in the following paper helpful. I think it should be freely accessible. Click on the "full text" or "full text (PDF)" link in the sidebar to see the whole paper.

http://www.jappl.org/content/89/1/81.short

The paper describes a study that measured upper body muscle mass and lower body muscle mass in both men and women, using a sample that was fairly diverse in terms of age and ethnicity. The researchers used a landmark in the lower back (the dividing line between the 4th and 5th lumbar vertebrae) to define the boundary between the lower and upper parts of the body.

On average, women had about 12 kg of muscle in the lower body and 8 kg in the upper body, while for men the corresponding numbers were 18 kg and 14 kg. Absolute muscle mass declined only slightly with age until around the 45 year mark, but muscle mass as a percentage of body weight declined faster because people tend to put on weight as they age.

Regarding literature searches, the best magic words I can come up with are "digestive efficiency". You can combine this with "animal", "vertebrate", or the name of any specific animal group you may be curious about. There does seem to be a fairly substantial literature on the subject, but I don't know it particularly well as I'm not a physiologist.

One complication to keep in mind is that the ability of an animal to extract energy from its food is partly a function of the food, as opposed to the animal. Cellulose is notoriously hard to digest, even with the help of symbiotic microbes, so some herbivores have evolved special tricks for extracting as much energy as possible from plant materials like leaves and grass - anything from ingesting their own faeces for a second round of digestion to having a multichambered stomach, or just a very large set of intestines. However, comparisons of efficiency between animals with very different diets are not really "fair". Comparing apples and oranges might actually be reasonable in this context, but comparing fruit of any kind to either meat or leaves would be more dubious.

Dan said:

What we think of as 'evolution' resulting from drastic environmental change is really only a dramatically obvious change in gene expression that we have noticed because of its coincidence with the change.

I find it difficult to agree with this, actually, though I might be misunderstanding your point somehow. Environmental changes can result in changing selection pressures that affect gene (or rather allele) frequencies, not just patterns of gene expression. Previously abundant alleles can become rare in a population, and vice versa, so in that sense a drastic environmental change can quite genuinely drive evolution.

However, and with reference to the original question, I agree that drastic environmental changes aren't required for evolution to occur. Peter's example of sexual selection is a good one, and even in a stable environment a new mutation that makes it easier to survive in that environment might happen to appear. If that mutation spreads through the population, then the population will have evolved, with no environmental change necessary.

There's also the issue of the word "drastic". Slow and gradual environmental changes can drive evolution just as easily as "drastic" ones can, and environments are rarely if ever truly stable on evolutionary time scales. The climate is always getting just a bit warmer, colder, wetter or drier, species are always moving into and out of a given area for a wide variety of reasons, rivers are shifting in their courses and hills are gradually eroding. Environmental change is very much the rule rather than the exception.

(posted in Fossils)

Interesting question! As you say, internet searches for Certhidium portlandicum come up blank, but it turns out that there are some references in the older literature to a gastropod (snail) called Cerithium portlandicum that occurs on the Isle of Portland and is known informally as the "Portland screw". It seems likely, then, that Fowles just got the spelling a bit wrong.

However, newer documents give the scientific name of the "Portland screw" as Aptyxiella portlandica. I'm no expert on fossil gastropods, but I suspect that the species was moved at some point from the genus Cerithium to the genus Aptyxiella, and that the species name was changed from portlandicum to portlandica in order to agree with the feminine gender of Aptyxiella.

In any case, a picture of a "Portland Screw" can be seen on the following web page (if you scroll down a bit). It's a gastropod whose shell forms a rather delicate spiral turret.

http://www.ammonite.free-online.co.uk/fgastro.htm

Alistair: Although the difference is reversed in later life...

To put it rather mildly!

I take your point about the rearing environment being important, and yes, animals may be a lot more cognitively sophisticated than earlier generations of scientists ever gave them credit for. However, I suspect the specific finding that chimpanzees can outperform humans in early infancy says more about the developmental rates of the two species than it does about their cognition per se. Chimpanzees may take an early lead in mental development, but then quickly run out of steam as humans continue on into the far distance.

In my opinion the bottom line is that, while the cognitive gap between humans and chimpanzees was probably overstated in the past, it's still pretty huge. Chimpanzees, thank goodness, are not going to be competing with us for jobs in academic biology departments (or positions as "experts" on this website) any time soon. If that comment seems farcical, well, that's sort of the point - once you get beyond infancy, the idea of chimpanzees even approaching normal human levels of intellectual sophistication is ludicrous, and biologists shouldn't be reluctant to say so. Animal cognition is a fascinating subject, and I'm sure there will be plenty of surprises as research in this area continues, but it's necessary to be realistic about the limitations.

I agree with David that it's important to avoid exaggerating the differences between humans and other primates, but there's no denying the fact that there is a large gap in cognition between humans and even chimpanzees. There is also a large gap in physique, such that humans are much better at bipedal walking (and especially at long-distance running, something the human body may be specifically adapted for) but weaker and less good at climbing.

This demonstrates that genetic differences that look unimpressive, when expressed as a percentage of the genome, can have very substantial effects on anatomy and behaviour. As David says, this isn't unique to humans. The living world is probably full of pairs of related species that share all but a few percent of their genetic code but differ in many observable characteristics. This is partly because the differences might be widely distributed throughout the genome. If every human gene differed by 1% of its sequence from every chimpanzee gene, for example, the total percentage difference between the two genomes would be only 1% (assuming the same rate of variation within the large amount of DNA that does not form genes), but a substantial proportion of the genes might exhibit some kind of functional difference between humans and chimpanzees. In reality, the variation won't be quite that evenly distributed, but much of it might still consist of small but possibly functionally significant changes in many different genes.

Information on the specific genetic variants that distinguish humans from chimpanzees, and ensure that there will never be a chimpanzee that can do philosophy as well as Aristotle, is still very limited. Detecting a difference in the genetic code is a lot easier than working out the effects of that difference, especially considering that some differences might not have any significant effect at all. However, research done over the past several years has identified a gene called FOXP2 that differs between humans and other mammals, including chimpanzees, and seems to be linked in humans to the ability to use language. It seems likely that the "human version" of FOXP2 was favoured by natural selection because it helped our ancestors communicate with one another more effectively, although of course other genes must have been involved in the evolution of language as well. However, this seems to be a good example of a genetic difference between humans and chimpanzees that can be linked at least tentatively to an important aspect of human behavioural and cultural sophistication, namely the ability to talk.

For more information on FOXP2, see this excellent article by the American science writer Carl Zimmer:

http://discovermagazine.com/2011/oct/08 … your-cells

That clarifies the issue, David. Much appreciated.

Dave (Hone):

Our list of experts is ranked strictly by how many answers they have provided (which is also of course linked to how long they have been on the site as well as general productivity).

And some of that "productivity" may be lighthearted chatter, secondary comments and questions on answers provided by other people, and patient explanations that we do not answer homework questions. I approve of all those things, of course, but the point remains that the system is counting all posts (presumably even ones on threads that are "closed" and eventually disappear, though I'm not sure of this) rather than only substantive answers.

I wonder, though, if it might be worth looking at the possibility of presenting the "list of experts" in a random order. That would help to showcase the diversity that exists among the denizens of this site - not just in demographic and geographic terms, but also (and in my opinion more importantly) with respect to areas of expertise and even career paths.

David (Wynick):

You are an Instructor in Biology at Delgado College and have a PhD from Rockefeller University - surely you know (or should know) the answer why our bodies can't store amino acids?!

I hope I'm not going to be sent to the back of the class for this, but the whole premise of the question confuses me. Aren't we, in a sense, storing amino acids whenever we combine them into a protein and integrate the protein into our tissues? Kindly help a bemused palaeontologist overcome his ignorance.

Many of the kangaroo and wallaby skulls on the following page, including the swamp wallaby, do have very large styloid processes similar to the ones in Bryce's specimen.

http://museumvictoria.com.au/bioinforma … umbmar.htm

Bryce, comparing your skull carefully to the images might help you work out whether it is indeed a swamp wallaby.

Paolo, any idea what the huge styloid processes in these critters are actually for? They're remarkable structures.

Also, I didn't know there were any wallabies that actually had Wallabia as a genus name. That's rather charming.

It's definitely the back half of a mammalian skull. The two bulbous swellings you can see at the top of the upper right image, between the "horns", are the condyles that form the joint between the skull and the first vertebra. Next to them is the foramen magnum (literally, in Latin, the "big hole") through which the spinal cord would enter the skull. You can also see the roots of the zygomatic arches, curving forward, that form the boundary of the temporal fenestrae (equivalent to the human "temples"). The front part of the skull, including the snout and upper jaw, is broken away.

The two photos on the left side of your composite image actually show the underside of the skull, so the "horns" project down rather than up. My guess is that they're very large styloid processes, protrusions from the lower surface of the skull for muscle and ligament attachment. In humans (and presumably other mammals), the styloid processes can be pathologically enlarged, and that might be what we're seeing in your specimen. The other possibility is that the skull might be from a species in which the styloid processes are just very big, although I don't know what species that might be (I'm no expert on mammalian skull anatomy). Or perhaps I'm wrong, and they're not styloid processes at all. My colleagues on this site may be able to help further.

In any case, congratulations on an interesting discovery!

Personality could be defined simply as variation in behaviour patterns within a species. If Irene the Iguana is consistently a little more aggressive than Igor the Iguana, then the two of them have different personalities, at least at a rudimentary level. I can say from personal experience that variations like this exist in reptiles, and I wouldn't be surprised if they occur in fish and amphibians. I agree with Brent that octopuses belong on the list as well.

In principle, it seems possible that variations in behaviour might exist even among very simple organisms. Are some individual amoebas quicker than others to approach and engulf a particle that might be edible, and therefore more "adventurous" (or greedy)? I don't know of any evidence for such "personality" differences among amoebas or other single-celled creatures, but I wouldn't rule out the idea. The genes that influence their behaviour, through whatever comparatively crude mechanisms, should be able to vary in a population just like any other genes.

It's worth pointing out that in Canada and the United States, and possibly some other countries, an undergraduate degree usually takes four years to complete and a PhD takes five or six. Some students also take a couple of additional years in between to earn a master's degree, although my impression is that this is becoming less common.

I agree with David that the main perk involved in being a biologist is getting to do interesting work. The job has its tedious parts, but whenever they start to feel intolerable I think to myself, "come on - you get paid to study dinosaurs!" (I'm a palaeontologist, or in other words a biologist who works mostly on long-dead organisms rather than live or recently dead ones). Other perks, which exist in academic settings but I suppose not necessarily in corporate ones, are a high level of flexibility in one's daily activities and occasional opportunities to travel to conferences (and sometimes also to field sites, museum collections, etc., depending on one's specialty within the wider world of biology).

There is no special property of human flesh that protects it from the acid and enzymes present in the stomach. Human flesh consumed by a cannibal will be digested just like beef or chicken.

Your question about why the stomach does not digest itself is a good one. The answer is that the wall of the stomach is covered in a layer of mucus that protects it from the action of the digestive juices. If a small gap, called an ulcer, forms in this layer of mucus, the acid can attack the stomach wall at that one specific point.

(posted in Mammals)

For what it's worth, the following paper tentatively places elephants among the mammals that are able to vomit, but scrupulously notes that the presence of vomiting is "based on a single clinical report".

Sanger, G. J., Holbrook, J. D. and Andrews, P. L. R. 2011. The translational value of rodent gastrointestinal functions: a cautionary tale. Trends in Pharmacological Sciences 32: 402-409.

The intriguing title refers to differences in gastrointestinal function between rodents and humans, including the inability to vomit in rodents. Therefore, information obtained by experiments on the rodent digestive system cannot always be considered applicable to humans.

Some palaeoanthropologists do consider neanderthals to be a subspecies of Homo sapiens (Homo sapiens neanderthalensis) rather than a separate species of Homo (Homo neanderthalensis). Especially when dealing with extinct organisms, it's often very difficult to decide whether distinguishable but closely similar "kinds" should be considered species, subspecies or "races" (a fuzzy term that I've rarely, if ever, seen applied to non-humans). Even the classic test based on the ability to breed and produce fertile offspring is not really decisive, because in some cases members of what are clearly different species turn out to be able to interbreed occasionally.

More important than exactly how science classifies neanderthals, however, is what science actually knows about them: that they were close relatives of modern humans who were similar to us in many ways, were different in a few others, seem to have interbred with us occasionally, and went extinct tens of thousands of years ago. I would personally favour calling them a subspecies of Homo sapiens, rather than a distinct species, but the difference between these alternatives is not very important from the point of view of understanding what neanderthals were really like.

Evolution can only do so much to limit complex patterns of behaviour like child abuse (a term whose definition is very broad, and changes with time). For one thing, much of human behaviour is learned and flexible rather than genetically hard-wired, so it's unlikely that natural selection could instill an instinct that would completely prevent people from hurting their own offspring. It's even less likely that the instinct could be sufficiently finely tuned to prevent real harm (i.e. abuse) but still leave parents with enough psychological flexibility to impose normal discipline on their children.

Another consideration is that, in prehistoric societies even more than today, people probably needed a certain capacity for anger and aggression in order to defend their family units and meet the basic challenges of life. It might be almost impossible for evolution to maintain the ability to act on those emotions while simultaneously ensuring that they were never directed at a person's own children.

Precise body size information for large wild animals is often hard to obtain, which might seem surprising until you consider the effort involved in catching (or killing) and then weighing enough individuals to get a clear idea of minimum, maximum and average adult body masses for both sexes.

Clauss et al. (2003) cite one source that gives the mass of adult gaur as 650-1000 kg, and another stating that female and male gaur respectively average 590 and 880 kg and have maximum masses of 700 and 940 kg. The Leslie and Schaller paper you referred to mentions mass estimates for adult male yaks that include 1,200 kg, ">800 kg", and "as high as 1,000 kg", but notes simply that adult females are "about 350 kg".

These numbers suggest that male yaks may get at least a little larger (in terms of mass) than male gaur, whereas female gaur are considerably larger than female yaks. This is perhaps a good example of how measurement problems and natural variation often frustrate, or at least complicate, straightforward comparisons of size and other parameters among different species.

References:

Clauss, M., Frey, R., Kiefer, B., Lechner-Doll, M., Loehlein, W., Polster, C., Roessner, G. E. and Streich, W. J. 2003. The maximum attainable body size of herbivorous mammals: morphophysiological constraints on foregut, and adaptations of hindgut fermenters. Oecologia 136: 14-27.

Leslie, D. M. and Schaller, G. B. 2009. Bos grunniens and Bos mutus. Mammalian Species 836: 1-17.

(posted in Mammals)

Daeodon, called Dinohyus in some older books and scientific papers, was a large, carnivorous member of a group of pig-like mammals called the entelodonts. It was apparently among the last entelodonts, living in North America during the late Oligocene and early Miocene (around 20-30 million years ago).

Early, primitive entelodonts, known from the Eocene of Asia, were considerably smaller than Daeodon and less adapted for meat-eating. So Daeodon and other advanced entelodonts probably evolved from smaller, less specialised entelodont ancestors that lived in Asia. Going further back, entelodonts as a whole are closely related to hippos and whales according to at least some recent studies, and would then share a close common ancestor with these groups.

English does have standard gender-neutral terms for most family relationships. A hermaphrodite of any species could be described as a child, a sibling and (if capable of producing offspring) a parent. Similarly, it could be a grandparent, a grandchild and/or a cousin. There are no gender-neutral terms that mean "niece or nephew" or "aunt or uncle", but these are the only problematic exceptions that I can think of at the moment.

David, would a hermaphroditic rabbit necessarily be capable of fertilising itself? I was under the impression, possibly mistaken, that an individual with both male and female reproductive organs would quality as a hermaphrodite even if it couldn't self-fertilise. That said, I agree that a "diagnosis" of hermaphroditism in a pet rabbit merits careful double-checking!

(posted in General Biology)

A quick e-mail exchange with my colleague Brian Choo, who studies fossil fish, has confirmed my impression that it's actually a bone called the "parasphenoid" that forms part of the underside of the braincase (the part of the skull that encloses the brain). The parasphenoid is covered by the skin and other soft tissues of the roof of the mouth.

It does indeed come from a fish, though it's hard to tell exactly what kind. Of course, fish are animals, a term that also encompasses insects and other invertebrates.

Congratulations to your daughter on an interesting find.

I'm always a little hesitant to link mythical animals (like werewolves) to imaginative or superstitious interpretations of real ones (like lemurs or baboons), unless the myths include details that clearly support the link. If eastern European folk tales said that werewolves had brightly coloured rumps and lived in Africa, I'd believe that the folk tales were based on baboons.

Traditional stories about people turning into animals (or vice-versa) are so common that I don't think there's any real need to look for something in the natural world that could have inspired the idea of lycanthropy. Of course, sightings of lemurs, baboons and very hairy people might have reinforced the myths and added to their credibility.

But yes, werewolves are completely imaginary.

Based mainly on the bone's curvature, large size and thin, plate-like proportions, it looks like a neck (or cervical) vertebra from some sort of whale. The preserved part is the body (or centrum) of the vertebra, but the bases of the snapped-off arches that would protect the spinal cord and vertebral arteries are also visible.

In some whales the neck vertebrae are fused together, but your bone clearly comes from a species in which they remain separate. I don't know which specific whales belong on this list, however, so I can't narrow the identification down any further. One of my colleagues on the site may be able to help with this.

To complement the link John provided, here's a paper discussing the age of consent in pre-modern times:

http://www.tandfonline.com/doi/abs/10.1 … 6v16n02_03

You probably won't have access to the paper unless you're at a subscribing academic institution (I don't have access to it myself), but the abstract can be freely viewed and contains some interesting information. The main point seems to be that the age of consent (although that term might not have been used) was set in the early teens (12-14) in Western societies until fairly recently, when it tended to be raised at least slightly.

In general, the assumption in the past seems to have been that people were ready for sex as soon as they had gone through puberty and were biologically capable of engaging in intercourse and (in the case of girls) becoming pregnant. The abstract of the paper I linked to says that the reasons for raising the age of consent beyond this level "have not always been clear", but among the current arguments for keeping the age of consent relatively high are that adolescents may not be psychologically ready to engage in sex in a responsible way and that they need to be legally protected from being pressured into sexual activity by adults.

There are also risks associated with early teenage pregnancies, so it could be argued that there are straightforward public health reasons to prevent adolescent girls from having sex. The added risks might not have been clear in pre-modern times, when pregnancy was somewhat dangerous and infant mortality relatively high regardless of the age of the mother.

I'm basing this entirely on pictures and descriptions I found online, plus hazy memories of an ichthyology course I took as an undergraduate, but it looks like your fish might be a type of whiting (Menticirrhus). There are apparently a couple of species of this genus in Texas waters, as described on this web page:

http://www.texasgulfcoastfishing.com/whiting.html

The chin barbel, single short anal fin and low rear dorsal fin seen in your fish all fit this identification, as do the general size and shape and the form of the tail. The colouration looks about right as well, as far as I can tell from the photo.

Some of my colleagues on this site know much more about fish than I do, however, so one of them may well come along to correct me.

(posted in General Biology)

According to the following web page, there have been several recorded cases of quintuplet births consisting of a set of identical twins and set of identical triplets, including some from the 19th century. You'll be able to zero in on them fairly quickly if you search for the word "identical" in the text of the page. Unfortunately, there's no indication of where the information comes from, so it's hard to say how reliable this list is.

http://www3.telus.net/tyee/multiples/worldquints.html

I think births of this type ought to be referred to as "full house quintuplets".

I know that object looks very skull-like at a glance, but it's actually the pelvis of a bird. I'm not sure what kind, although one of my colleagues on this site might be able to tell you. The round openings visible in the first and last of the photos you posted represent, respectively, the right and left hip sockets.

One complication attached to this question is that Scannella and Horner (2010) argued that ceratopsian specimens assigned to Torosaurus, which is normally considered a slightly larger close relative of Triceratops, actually represent very mature Triceratops individuals. This might be correct, but would require significant and rapid changes in the structure of the skull as the animal reached full maturity, so some palaeontologists (including me) are sceptical of the idea.

Scannella and Horner stated that the largest skulls traditionally identified as Torosaurus "approach three meters in length", implying that they do not actually reach or exceed 3 m. They also referred to a skull that is "extremely large" among those traditionally identified as Triceratops, with an estimated length (the length could not be measured precisely because the skull is damaged) of 2.5 m.

The largest Triceratops skulls, then, probably measure about 2.5 m, but might be closer to 3 m if Scannella and Horner are correct that the specimens that have been called Torosaurus really belong to Triceratops. It seems unlikely that they quite reached 3 m in either case, however.

Reference:

Scannella, J. B. and Horner, J. R. 2010. Torosaurus Marsh, 1891, is Triceratops Marsh, 1889 (Ceratopsidae: Chasmosaurinae): synonymy through ontogeny. Journal of Vertebrate Paleontology 30: 1157-1168.

So is it just a coincidence that Rutpela is an anagram of Leptura, or did someone decide that rearranging letters would be as good a way to come up with a new genus name as any? I don't think I've ever seen that done before, although there's a Permian critter called Llistrofus from near Fort Sill, Oklahoma.

(posted in Mammals)

That's not at all surprising, now that you mention it. I didn't even think beyond the word "cat", even though it was prefaced with the word "genet"!

(posted in Mammals)

The paper Ryan found deals with estimating rates of oxygen consumption at different speeds, rather than trying to determine maximum speeds. From the graphs (Fig. 1b), it looks like the domestic cats in the study got up to a little less than 6 metres per second (about 13.5 mph), whereas the genet cats barely managed 2 m/s (4.5 mph). The researchers clearly weren't trying to get the animals to run at top speed.

I'm not a wildlife biologist, but I imagine that persuading a big cat to run at top speed in a straight line over clear terrain for long enough to allow a measurement to be made is a lot harder than it might sound. Putting a captive animal on a treadmill would be another possibility, but I wouldn't want to be the one responsible for convincing the Siberian tiger to stay on the treadmill (doing that kind of thing with juvenile alligators as a graduate student was bad enough!). Beyond that, even biologists who study locomotion are not necessarily all that interested in measuring maximum speed as opposed to, for example, understanding the physiology and mechanics of running or walking at normal speeds. The paper Ryan linked to is a good example of this.

(posted in Fossils)

The original question makes much more sense now that we know it was prompted by Dawkins' comments about the thylacine. As John said, tetrapods can have a number of different openings in the palate. In mammals and some other groups, to complicate matters even further, the palate proper is actually covered by an additional layer of bone (the "secondary palate") that separates the cavity of the mouth from the nasal passages.

The openings in the marsupial palate that Dawkins referred to in "The Greatest Show on Earth" are called "palatal vacuities", and penetrate the secondary palate in front of the internal opening of the nasal passages (located at the rear edge of the secondary palate). They're a characteristic feature of marsupials, though apparently some other mammals have similar openings.

I'm not sure which openings you're referring to in Hylonomus, but reptile skulls commonly have "suborbital fenestrae" (also called "palatine fenestrae" or "postpalatine fenestrae"), paired openings that lie behind the palatine bones in the primary rather than the secondary palate. They're present in at least some sauropods, although they tend to be quite small.