As with a lot of science the real answer is probably "we don't know." Although a standard response would be that this is some sort of holdover from our evolutionary past when our ancestors lived in places where spiders were a very real danger to human life. It makes sense to fear certain species that are lethal to humans and it is thus likely that in most people's brain "spider" is a catch all perception, so we fear them all. However, convincing as it may sound this answer may be wrong. A quick search on google scholar revealed at least one scientific paper that suggests fear of spiders is not innate, but cultural - we fear spiders because those around us do. Of course somebody influential would have to have started such a trend, but if this is the case it looks likely to persist.

I personally suspect there is some truth in this as I doubt you would be happy having a harmless, non-biting species crawl across you! What we dislike is something else.

I googled this quickly and it seems that the study you have heard of was undertaken as there was a suspicion that ferrets could see infrared cameras used to monitor wild animals. (These cameras emit infrared light just as normal cameras might use a flash). Although it seems that some ferrets are sensitive to infrared light it is likely right at the end of their visual range and so it is unlikely that they see much. I'm afraid I don't know if such abilities are possessed by other mammals, but  the fact that so many other species can be filmed at night in this way it seems likely that they don't.

Hi Kathleen,

This is more of a gardening question really. I suggest you try something like this site instead: … dener.html

(Or some other gardening web site).

Aside from not letting the cat outside the only thing I can think of is putting a bell on his collar. In theory this will give the skink a warning and hopefully a head start. Otherwise I suggest going to your local pet shop and explaining the problem to them - there may be some novel invention that I am unaware of.

I work in a University, but will soon leave to work in a museum.

(I think a pattern is emerging...)

I think the smaller Earth, denser air and different values for g are extremely implausible. As far as I'm aware none of the known dinosaurs are actually in danger of invalidating the laws of physics. However, you should bear in mind that many dinosaurs show evidence of pneumaticity and a lot of the body volume would actually be nothing more than air and it is generally hard to know exactly how much an extinct animal weighed.

From the Paleobiology Database (


Actually it does. Sort of.

There was great show on British TV a while back about a certain famous soft drink company. If you poll the public they will often say they prefer one of the major cola drink brands over the other, but when the same people are blind tested very few of them can actually tell the difference, i.e. based on taste alone. Furthermore, if they are shown a TV commercial for a particular brand whilst drinking either drink they will say it tastes like the brand they are being shown, even when it isn't. In other words clever marketing fools our brains into thinking we prefer the taste of one brand over another. It could be argued that this is completely abstract from Nature, but as flowers are visual advertisements for nectar, perhaps not.

I don't know if anybody has actually looked at how the keratin structure differs between the various "beaks", but as you are no doubt aware keratin appears in many different guises in the natural world. However, we can confidently say that the various "beaks" out there do not have a single common origin (they are not homologous). Too many species that sit in between these various beak-bearing forms are mostly beakless and it is much more parsimonious to say that the "beak" has evolved multiple times (i.e. convergently) as a general solution to very similar problems.

It is kind of a biology question as fat is a product of biological activity. However, at it's root the answer is probably explained by physical chemistry and I'm afraid this is beyond my personal knowledge.

Hi Roger,

Sorry for the length of time we've taken to get to this - it is usually a good indication that the answer is "we don't know." It may be that nobody has ever looked into this, or that this is a peculiarity of the erect nature of human posture. Don't really know I'm afraid.

Hi Bryan,

Once again your curiosity seems to be beyond our knowledge. Here are my answers:

1. No idea. I doubt anybody does. It is an interesting question though, but I'm not sure how we could set up an experiment to work this out. One for you to think about!
2. I assume they have some sense of taste, it would be dangerous for a vertebrate to not have any way of distinguishing what was good or bad to eat - that is after all there main function. As for the tongue, sense of smell is essentially a sensory system based on chemical traces left in the air, so really the sense is the same regardless whether you 'smell' with your tongue or your nostrils.
3. I think it is essentially the same, but others might disagree. There are actually other named senses (other than the five we possess) besides the obvious (echolocation), but I don't have a good source on this.

Sorry for the lengthy response time.

I think otters have a really high density of hairs in order to maintain their body heat in aquatic environments. I suspect the same is true of other aquatic mammals. Otherwise I think hair density is probably pretty much the same for a moggy or a lion, regardless of age.

I think the killer whale still holds the record for biggest (i.e. heaviest) carnivore of all time.

It is the skull of a fish or rather part of it, that much I'm pretty sure of, but beyond that I will need my colleagues help!

It definitely reminds me of the 'crucifix' fish (look at the lower picture turned 90-degrees anticlockwise and see if you can see a man on a cross). For that reason I would hazard a guess that it is a catfish or close relative. I think the part you have is the palate/base of the braincase.

(NB: the 'nose' end is at left and the 'neck' end at right).

Undoubtedly. It will probably look like this:

These aren't unscientific, but they are partially speculative. I suggest looking at this site:

Sorry Karen, but I want to see the original paper too (this is what I meant by the citation, but thanks for typing that out). Identify the New Zealanders and we will bring our collective insights to bear!

Hi Jeff,

There definitely has been. In fact this kind of data is used to place estimates on stratigraphic ranges (how long a species may have actually been around) as well as correcting for uneven sampling when constructing diversity curves (i.e. calculating the number of species that were around at particular times). This is the point of the Paleobiology Database, for example:

Many species are known from just a few individuals (few actual specimens), e.g. dinosaurs, but others exist in the thousands to millions. Your point about stasis is harder to answer, as you can probably guess, if stasis doesn't exist then if we sample a lineage more than once we might simply recognise two or more different species, but we can never really be sure when this is happening.

Hi Karen, I will do my best!

I'm sorry I had to write a new post I couldn't find a way to reply to the previous one.

Yep, the site is designed so that only we 'experts' can reply to posts, even though it is essentially the code for normal forum sites underneath.

Anyway, yes Graeme I am aware that it has always been taught that prokaryotes came before eukaryotes, I'm a biology major myself and was, like you, shocked.  I'm reading a book called Genome by Matt Ridley, and I came across this passage that said that it has been suggested by a couple of scientists from New Zealand  that the "tree of life" may actually be upside down. I read the passage on and on, and weirdly enough, the explanation made sense.

It would be good if you could provide a citation and then I can look it up! I had thought you meant the paper by Rivera and Lake published in Nature in 2004 where they argue that genomes indicate eukaryotes evolved via the fusion of an archaeon and a eubacterium (or at least, that is how I understood it).

It explained the RNA theory, which states that before DNA and proteins existed there was only RNA. Which makes sense, because in advanced animals such as ourselves, RNA plays a messenger role, it neither holds the genetic code as does the DNA , nor does it perform all of the body's activities like proteins, it is only the link between those two. So more or less, it has a smaller (i won't dare say minor) role than DNA and Proteins. And since evolution strives to the better, this confirms the theory that RNA evolved to DNA and proteins only to become less important.

Yes, this is a hypothetical stage in the evolution of life known as the RNA world and appears in many models of the evolution of life. However, it is not proven (and probably can't be) nor can we really say that "evolution strives to the better." Natural selection may favour the 'fittest', but what qualifies can vary and not everything in life is adaptive. We don't really know why DNA became the only way organisms store genetic information, there are many hypothetical alternatives, but this could be a case of 'lock-in' such that once it happened (perhaps accidentally) alternatives became practically impossible, e.g. like the inefficient QWERTY keyboard.

It is much more acceptable , thus, to say that prokaryotes dropped the RNA (i'm sure you know they do not have RNA) rather than eukaryotes created it.

I'm not a molecular biologist, but I am trying to learn (my training is in geology and palaeobiology). However, from my reading they do have what is known as polycistronic messenger RNA, but this is unique to them. But still, this fits with RNA-first and I don't see a reason to dispute this.

Why did they drop RNA? Most bacteria live in places with extreme conditions- very high temperatures.
So , in order for them to avoid the excess mutations that might occur, they dropped their RNA (and also them having a single DNA makes sense).

It is a theory. If i wasn't clear enough make sure you look it up.

Well, I'm still confused. I will look it up if you post the citation.

And after you get over your disappointment, try answering my questions :)

It's my confusion and ignorance I need to get over!

(posted in Fossils)

I've had a quick trawl of the scientific literature, but can't find a specific mention of this. I'm afraid the book might be your best bet (not in our libraries here in Bristol, or I'd check that).

Not the kind of thing we have floating around in our heads I'm afraid, but you can try sites like this one:

Hi Ken,

We can't really help you with homework questions, but you might want to ask whether the difference is due to wave energy. What else changes between the two environments? After all, because you are collecting from the field there are many other other factors you can't control for.

Hi Karen,

I'm very confused by your post as everything I have read and been taught suggests that eukaryotes are more complex organisms than prokaryotes. (Biologists do not deal in 'more evolved/less evolved', but eukaryotes have larger genomes, more genes, more non-coding DNA, more cell types etc.). Eukaryotes didn't come first, prokaryotes are older (regardless of whether the endosymbiont theory is true or not). I suspect you have simply confused the two!

It will vary massively depending on the species of tree the time of year and the maturity of the tree. Some older trees are even net consumers of O2 and their role in saving us all from global warming has been massively overstated. (The sea is a far bigger CO2 'sink'). I suspect the value you saw was an average or an estimate of some kind.

I'm going to speculate wildly here, but I suspect the answer might be surprising little effect. In most ecosystems snakes are at the top of the trophic pile and so nothing really relies on them for food (at least not exclusively). A more probably effect might be a surge in the population of any prey species that could have a knock on effect on vegetation and the like. However, I am deliberately being vague because I am no snake expert, but sadly I think we are currently missing one on this site as they seem to attract a fair bit of interest!

I seriously doubt it. Fossils are just too small and rock formations too big for anything to have high enough resolution and ludicrously high enough power to be remotely economical (or, probably, safe) to do the kinds of things you are suggesting. We continue to rely on good quality geological mapping and a pair of well trained eyes for the most part. However, some workers are using LIDAR to map surface geology, including fossil trackways.

Biology is made up of the words 'bio' meaning life and 'logy' means something like reason, logic or word (it is Greek), so basically a biologist is someone who thinks about life!

I think it is safe to say that we all look at the things we look at because we find them fascinating and beautiful. For a palaeontologist like me it is looking at fossils that I like and a big reason is that they are so old and often very rare and in the case of dinosaurs, very big!

I hope that ansswers your question.

Well you only need to be bitten once to get malaria so the odds of swatting every mosquito are probably not much different to another animal. However, malaria does exist in other species too, so there isn't really a preference for humans. You should probably also know that mosquitoes themselves don't cause malaria they are just a 'vector' for the parasite that does. (Vectors are other organisms that a parasite uses to get into its final host).

I am actually reading an interesting book called Parasite Rex on this topic at the moment, which might be of interest to you.

(posted in Birds)

1. Embryological study usually requires development to be stopped (at differerent stages) before it can be studied and it is also a legal requirement that the embryo not be allowed (for ethical reasons) to reach 'adulthood' - for vertebrates this is the stage when they would start to feed.
2. As far as I know there are no cases of a toothed chicken...
3. ...hence the origin of the phrase, i.e. so rare as to be non-existent.

I couldn't tell you for sure as I am not a chameleon expert, but as far as I am aware all vertebrates have taste buds. Taste is an important sense as it can prevent you from eating things that are bad for you (poisonous and even deadly) so I doubt there are many cases of taste being secondarily lost (hopefully a colleague can correct me if I'm wrong).

The ability to detach a limb or tail in any animal is 'autotomy': 'auto' for self and 'tomy' for cut. However, regenerating a limb is simply regeneration.

Hope that helps.

(posted in Plants & Fungi)

I have a couple of dragon plants myself and I think you probably overwatered them. They are fairly low maintenance plants (and hence very popular) and don't need to be watered too often, in fact this can be bad for them and is probably the reason two of your 'trunks' died. I recommend watering less often, just make sure the soil never goes completely dry.

We can't tell much as the organs usually involved in making sounds are made from soft parts that typically decay and hence leave no record behind. However, the bony crests of some hadrosaur dinosaurs do have tubes inside that look like they would have been used to make a 'honking' sound, although we can only speculate on what such noises meant.

As for T. rex we don't know anything, but it is unlikely that it would have roared just before trying to eat something as this tends to scare away your dinner!

However, we can speculate that is was likely that they did make some noise and probably that they carried the same meanings as modern animals do (e.g. invitations to mate, threats to rivals, alarm calls to a group etc.). After all, dinosaurs gave rise to birds, and perhaps some of them possessed a primitive version of bird song.

Hi Adriann,

Sorry for the delay in answering your question. There was a paper written on this very topic, but I'm afraid I can't remember enough about it to dig it up!

I think the answer to your specific question is essentially "not very likely at all", although this could all be proved wrong by a well-dated fossil (we do have fossils going back at least 2 billion years). Life itself may have had multiple starts, and even competing 'versions', but we do know that all living things now share the indelible stamp of common ancestry - DNA - and it is unlikely that anything else was around long enough to reach the level of complexity of modern ecosystems (after all, the version of life we have, the one that 'won', took some 3 billion years to get to this point).

As for your bonus question, probably not very long. There are 'extremophiles' we know about that can live in temperatures greater than the boiling point of water, but I would risk suggesting that they are already at the limits of what is possible. Of course, life may evolve to live underground, but without photosynthesis most complex forms would die out and probably single-celled organisms would be the most complex things on the planet until they, too, found conditions to harsh. Still, a few billion years to go I think...

Spiders see with their eyes! Most spiders have four pairs (eight eyes). However, not all eyes are the same and the different pairs often perform different functions.

This page provides a good summary: … ry/see.htm

(posted in Fossils)

There are two possibilities here:

1) Their geology is wrong and the rock is not metamorphic, or
2) The rock is actually very low-grade metamorphic

There are other examples of fossils in metamorphic rocks, although the only specific one that comes to mind is ammonites in Portrush on the Northern coast of Ireland.

However, the geology one seems more likely. People who use stone commercially tend to have a different set of names for things. I have lost count of the number of supposed 'granite' worktops people have installed in their kitchens. These are rarely granite (which is normally pinkish) and are usually some much darker igneous or metamorphic rock. Ordinary limestones also tend to be misclassified as 'marble'.

(posted in Fossils)

Their have been claims of fossils being as old as 3.5 billion years, but such materials have no recognisable features. Instead they are simply carbonaceous blobs that have an isotopic signature that may, or may not, be indicative of a biotic origin. The oldest unequivocal fossils are about 2 billion years old, but these are only microbes. (So yes, there are fossilised microorganisms). Most palaeontologists only work with fossils from the Phanerozoic (540 million years ago to present) as this is when animals with readily fossilisable hard parts (shells and bones) have been around.

As far as I know, nobody has ever claimed to have found a fossilised virus and I am very sure that such a thing never could be found in the normal sense of the word 'fossil', i.e. an organic thing turned to stone. However, there are, I believe, samples of HIV that are now decades old and that are completely different to the 'living' forms. So I guess, in some sense, these might be considered fossils.

Wow! This is an interesting question and I'm sure you'll get plenty of responses, but here are a couple of my thoughts:

1. We can get DNA from things like mammoths and Neanderthals, yes, but these are always heavily fragmented. There is, however, a project underway to put enough of these fragments back together to make up a complete Neanderthal genome. So in principle what you suggest ought to be possible, but I'm sure there are many complications that my colleagues will point out.

2. However, even if it were possible I suspect that this kind of experiment would be highly illegal in most countries (at least those with legislation covering this kind of thing). I'm sure you can appreciate the moral implications of bringing a human back to life!

3. Finally, even if we did it I seriously doubt it would tell us too much about what our human predecessors were like, beyond how hairy we were! I suspect the more interesting cultural aspects (tool use and the like) are unlikely to be genetically 'stored'.

Strictly speaking the answer is "we don't know", but I think the most common explanation is that they are analogous to the tentacles of hagfishes, which are used as sensory organs.

That's an interesting question!

In terms of the number of individual fossils there are probably countless billions. Most large Natural History Museums will have a collection of several million. However, as you probably know there will be multiple specimens for most species. For example we have lots of different fossils of T. rex, these even have names like 'Sue' and 'Jane'. The number of different kinds of fossils (species) is much less, I think the figure is a few hundred thousand. In reality there were probably many more species in the whole history of life, but many of these never left a single fossil and others have yet to be dug up!

I think that it is technically speaking, at least according to the Oxford English Dictionary. However, I know the English palaeontologist Colin Patterson was a keen fan of the use of 'fishes' for the plural.

It appears that the creators of this site have gone with the latter! (See above).

Turtles certainly go back as far as the dinosaurs, in fact the earliest turtle and earliest dinosaur are both around the same age (some 230 million years old). Snapping turtles just about overlapped with dinosaurs, with the oldest fossil found from the Maastrichtian (some 70 million years old), just before they went extinct 65 million years ago.

Hi David,

Sorry for the delay, I guess this isn't something most of think about. I'm certainly not an expert. But you might want to try this site:

I'm sure you'lll get lots of answers to this, but one problem with transitional forms I can think of is that it is actually somewhat erroneous to look at them as transitions, i.e. that they are 'on the way' towards some living animal. Truthfully, this is a bias of hindsight, of seeing the present as the 'end' of evolution. Such ideas of progressive change in evolution (the technical term is orthogenesis) has been widely refuted. We can't think of dinosaurs purely as protobirds, just waiting around to evolve wings - I'm sure you can see why this would be silly!

However, I think the question you are asking already has an answer in the use of 'stems' and 'crowns'. So, taking the bird example the total (whole) group of birds is all living birds and all extinct animals that are more closely related to birds than any other living animal (i.e. dinosaurs and probably pterosaurs too). Within this total group the 'crown' is all the species that are alive and all the extinct species who are descended from the same common ancestor as all living birds. An example of an extinct crown bird would be the giant Moa. The other portion, or 'stem' group consists of what is left (e.g. Archaeopteryx and most Mesozoic birds (Ichthyornis etc.), all the dinosaurs, pterosaurs and a few 'dinosauromorphs'). These are always extinct and have a common ancestor older than the one for the living group (crown). Sorry, a bit technical I know...

Hmmmm. Well I am afraid this would have to be wild speculation. Drepanosaurids certainly aren't at all closely related to chameleons, so if they did evolve such anatomies and behaviours it would have to have been independently.

There is very limited evidence for colour in fossils. However, we can detect so-called 'structural colour' (think the kind of iridescent 'shinyness' of some fish scales) in Burgess Shale arthropods - this can be preserved as 'grate'-like structures on the hard parts of the animals. (See Andrew Parker's book "In the blink of an eye"). There are also famous examples of 'stripey' trilobites, e.g. Isotelus maximus. We can assume that these animals were colourful because predators, competitors and/or females had colour vision (i.e. they were for camouflage, warning, threat or sexual display).

However, for vertebrates with endoskeletons such traces are less likely to be found, although there is plenty of speculation for what ceratopsian and stegosaurid dinosaurs were doing with their frills and plates respectively. It is likely that drepanosaurids did have some kind of colour vision and that they did reproduce sexually (not all lizards do - thus they would have no need for sexual display, be it showing off to females or warning off other males - in fact some lizards have no males!). However, behaviour can only be guessed at. The best evidence for this comes from trace fossils, but I don't think we have any for drepanosaurids.

There are many so-called 'species concepts' out there, but the standard 'biological species concept' defines a species as a reproductively isolated group - i.e. a group whose members can, or do, only reproduce with other members of the same group.

In reality many species can interbreed (e.g. ligers and tions), but this doesn't happen naturally - given the choice lions breed with other lions and vice versa.

In palaeontology, however, this concept breaks down as we don't know who was breeding with who. Instead, fossils are assigned to species based on the overall shape and appearance (morphology), but there is no 'amount' of difference that distinguishes a species - this is decided by the palaeontologist describing the fossil (and often there are disagreements between different palaeontologists). Palaeontology suffers from other problems as well, imagine one palaeontologist has a skull and another a neck bone found in roughly the same area, but not together. These might be named as two separate species, but in reality they could belong to just one. (Of course there are other clues that help us decide, but sometimes it can be tricky).

I don't know the answer myself, but there is a great series of field guides available for US wildlife that might - try typing "The National Audubon Society Field Guide to North American Reptiles and Amphibians" into or look for it in your local library/book shop. (I might be wrong, but I don't think there are any snake experts on here that will be able to help).

Or, if you're up for some online research then you can try:, particularly the snake page:

I hope that helps!

As far as I'm aware we know next to nothing about this, although the natural world is replete with such case studies of complex tasks being performed near perfectly the first time and without parental (or other) teaching. I know there is a species of bird where the adults leave the new born chicks to make a major migration then just a few weeks later the juveniles follow on taking exactly the same route, even stopping in the same spots.

I suspect that this is exactly the kind of thing that will elude concrete explanation for quite some time as devising appropriate experiments would be very difficult. For example, iteratively 'knocking out' genes until you produce a spider that can't make a web doesn't mean you've isolated the 'web-making gene'. (If you actually did this you'd probably find lots of genes that stop a spider from making a web - as they are genes that would fundamentally stop it from living!).

I hear that Richard Dawkins book The Extended Phenotype, which deals with things like spider webs is very good and you might find some better answers there.

People certainly are interested in where life may have started. Understanding the environment of origin would greatly constrain the mechanism by which such a momentous event could occur.

However, I seriously doubt even the hardiest of the 'extremophiles' you hint at could have survived at the temperatures and pressures present in the depths from which volcanic rocks originate.

Most evidence points to an oceanic origin for life. But how do we arrive at such conclusions?

Life in a basic sense is just a collection of complex chemical reactions that work in tandem to perpetuate itself; something chemists call autocatalysis. Because such reactions only work under precise conditions of pressure and temperature we can use family trees to estimate what kinds of reactions would have occurred in a primitive ancestor and then infer the temperature and pressure this ancestor probably lived in.

One recent paper ( … 0.html#abs) suggested a temperature of a little over 70-degrees Celsius near the origin of life, a value that closely fits geologists estimates of ocean temperatures at the time, but is way to low for volcanism.

However, you are certainly right to point out that the Sun was unlikely to have been important here. By all accounts photosynthesis came later.