(posted in Evolution)

I think that most groupings that humans impose on nature are largely due to the pragmatic need to be able to talk about it in a clear way; which is very useful when carrying out and discussing science, but creates a false sense of things being as clearly distinct in nature itself.
Take the evolution of species: for example when one species splits into two, if you were able to be present during the whole process, is there a clear point when the one species becomes two? Most likely you could never point at one single point in time where that happened.
There are many other continua like that, especially in biology.
The origin of life, I would say, is also such a continuum. However abiogenesis unfolded, it seems that the transition from basic chemical reactions to a living cell (especially one at this early point in evolution) would be a gradual affair of increasing compelxity and self-containment. Do we need to draw a clear line at some point in this process beween non-life and life? That probably depends on what you are trying to achieve: if it's for pragmatic purposes (say we want to have a definition of life so we know when we see it on another planet), then that's fine; but in reality, I think being clear that there is not objective distinction in such a scenario is important for our understanding of how it works.
That's not to say that a rock isn't clearly non-living, which a bacterium is clearly living.

the first photo is too out of focus to be sure, but it looks like a mixture of algae, corraline algae and possible bryozoans all encrusting on the stem of another larger marine plant or algae.

(posted in Fossils)

Just to add: the cutoff of 10,000 years was largely established for practical purposes of dividing disciplines into palaeontology and zoology/archaeology, but has no basis in reality (I know, I'm being a bit sarcastic here).
The age is based on the start of the Holocene.

(posted in Evolution)

I think the question is suffering from two pieces of baggage (not of Shawn's making mind you):

The split is largely a hangover from earlier scientific thinking (strictly speaking "organic" and "inorganic" are usually used for chemistry, not so much for "living" vs "non-living"), which in itself inherited some classic (but wrong) categorisations of the world.

The more we know about life, the more we understand that there is no clear cut off (at least going back to the origin of life) between when chemical reactions were just happening, and when they became part of a living organism. Indeed, I think the distinction is missing the point: there is NO distinction. Today we find the distinction mostly clear, but we are looking at billions of years of evolved organisms compared to a rock; but we get confused when we try to categorise viruses.

I think we fall victim to what Richard Dawkins calls the "tyranny of the discontinuous mind": humans have a tendency to need to neatly package the world into separate categories, and we struggle when characteristics occur on a continuum.

Very good question. There are a couple of problems that need to be understood:

The species concept in general is problematic (the definition of how and what separates one species from all others). In fact there are about two dozen quite distinct species concepts, most of them are in use by one discipline or another (check out "species problem" on wikipedia to get a general sense)

Fossil species are very problematic, because it's almost impossible to be certain about their genetics and breeding capabilities.

In the case of H. neanderthalensis and H. sapiens, it appears that the two were probably distinct species, but still so close together that some forms of interbreeding produced reproductive offspring, while others didn't. This is based on the fact that our nuclear DNA contains neanderthal genes, but our mitochondrial DNA doesn't. mtDNA in primates is always maternally transmitted,  which has prompted the hypothesis that whereas female humans interbreeding with male Neanderthals were able to generate fertile offspring, the progeny of female Neanderthals who mated with male humans were either rare, absent or sterile (there is a lot of debate about this though).

Try the Paleobiology Database (http://fossilworks.org), which is aiming to be a comprehensive database of all taxe, grouped into their taxonomic heirarchy.
If you query for a genus for example, the results page should show you things like 'parent taxa', 'sister taxa' and 'sub taxa'. You can also get the full heirarchy for the taxon.
Hope this helps

There are cases where apparent coexistence is recorded in fossils, though it is difficult to confirm if the relationship is symbiotic, commensal, mutualistic or even parasitic; or if it is obligate or facultative.
I know of a Silurian-Devonian marine gastropod (Platyceras) that always is preserved sitting near the anus of crinoids (sea lilies) - it has been interpreted as feeding off the crinoids poo. I'm not aware of any morphological changes, and I would guess that the relationship was mostly a form of commensalism.

There are certainly occasionally discoveries of animals that were thought of as extinct but turn up to be still extant, the coelocanth being the classic example. But more of the 'reports' of mysterious animals are either misidentifications of normal animals, hoaxes, or optical illusions.
It depends which ones you are talking about.

Most of these organs are very different in their developmental origins and functions, as well as constraints.
Most pairs are at least partly due to the bilateral symmetry of most animals, which mirrors organs; but they are also selected for in pairs due to the usefulness that way: pairs of sensory organs to allow 3D perception, pairs of limbs for stability.
The digestive system is a very fundamental part in our development, and develops as one of the very first things in the early embryo (did you know that during gastrulation in Protostomes the mouth developes first, but in Deuterostomes [which we belong to] the anus develops firs); something that is this fundamental is generally not likely to change much in it's basics through further evolution, so all animals have just one mouth and one anus and a single digestive tract between them.
Kidneys and lungs may have explanations as to why they are pairs, but I'm not sure - it may be a form of redundancy for such important organs.

There are several issues that need to be understood in this context:
At the most superficial level: there have been numerous 'mass extinctions' in the geological past, but the classic "Big Five" are the end Ordovician, Late Devonian, End Permian, End Triassic and End Cretaceous events.
These were all recognised originally several decades ago, partly because their pattern stood out quite clearly at the time in the fossil record. But later research has made the distinction between these five and other significant extinctions less clear. But these five have become somewhat entrenched in the literature.
Overall, there has been a decline in what is called the "background extinction rate" over the Phanerozoic: basically, there is a 'normal' rate at which species go extinct at an given interval (similarly there is a 'normal' rate of speciation). Earlier in time, especially the Cambrian, the background extinction rate was relatively high, and some of the Cambrian stages saw extinction rates apparently higher than some of the Big Five; but these events didn't seem to stand our significantly compared to the background rate.
Another factor is that some 'mass extinctions' are not due to an increase in extinction rates, but rather a decrease in speciation rates, giving a similar signal in the fossil record. The Late Devonian event may have been such a 'mass depletion'.
Before the Cambrian the fossil record is very poor, largely due to the lack of multicellular life with hard parts; in addition the number of fossil sites for any geological interval decreases further back in time due to preservation being less likely over time because of erosion etc. This hinders our ability to be able to properly identify abundance and diversity patterns of species further back.
The Cryogenian ice ages likely did have a significant effect on life, but we just don't have the fossils to accurately verify this.

There are numerous things wrong with the idea that we are "going agains natural selection".
FNS is not some monolithic entity that is perfect. NS is simply a name for many mechanisms that tend to keep populations of organisms of a species the fittest.
Note several aspects of that sentence:
"mechanisms" - everything that the organism interacts with affects it's survival and reproduction rate. But these things have no directed purpose, so NS does not in itself mean all organisms evolve towards perfection, just towards "good enough"
"tend" - being based on random processes, sometimes NS will wipe out fitter individuals purely because they were wrong place wrong time. Or sometimes it may wipe out a whole species that would be the fittest one moment, but not the next (think mass extinctions)
"fittest" - this really refers to how well the population fits into its environment (not 'fit' as in 'strongest'). Many species actually modify their environment in order to fit better, and in order for other to fit less well. Humans are superb at this, and have modified environments for millennia to fit better, medicine is just one of those modifications.
Also, medicine could be considered as, what Richard Dawkins termed "Extended Phenotype".

(posted in Evolution)

Regarding the question if fish or dinosaurs would evolve on the new planet: by definition, this is essentially impossible. Evolution will never follow the same exact path again, even if we re-ran the history of live anew on Earth. Too many individual and totally random occurences will very quickly change what species evolve or die out.

(posted in Fossils)

The classic example of sudden new competition bein introduced by colliding continents is the case of the Great American Biotic Interchange, which occurred when North and South America became connected by a landbridge about 3 million years ago. South America had been dominated by marsupial mammals, while North America had only had placental mammals. Most of the marsupials probably died out during this exchange due to competition from the northern placentals; at the same time no northern placental appeared to die out directly due to competition from the southern marsupials.

I'm not familiar with the regional geology of Nurthumberland, but the rock looks finely crystalline, like an igneous rock (solidified out of molten rock), rather than a sedimentary rock (which is where fossils would occur). So very unlikely to have any fossils preserved.
Also, it looks like a well-worn pebble, so any structured would have likely been abraded.

This question reminded me of a study a few years ago that showed how essential whales are for ocean productivity: basically some species that feed deep and poop in the shallow ocean help enrich nitrogen, which would otherwise be a limiting factor for life in that reagion.

The updated version of Darwin's theory of evolution, to include things like genetics, is often called "Neo-Darwinism".

As you mention, the Bdelloid Rotifers have been able to maintain asexual reproduction for a long time, probably for up to 80 million years. But apparently they manage it by hijacking DNA from other species (http://www.wired.com/wiredscience/2012/ … dna-trick/), which allows them to add genetic variation.

The whole class of Bdelloid Rotifers are exclusively parthenogenic (reproduce asexually), and have been for up to 80 million years. This was not expected to be possible for such a long time, until it was discovered recently that they manage it by hijacking DNA from other species (http://www.wired.com/wiredscience/2012/ … dna-trick/).

The Blue Whale is really the largest top predator. Its sole food is krill (animals), which makes it by definition a predator. In the same way, some of the earlier fossil whales were probably larger than C. megalodon.

It looks like Acetabularia, which is a single-celled(!) green algae. I remember learning about them in undergraduate University courses, and then later I saw them growing on the sides of stromatolites in Shark Bay, Western Australia - it was an item on my science bucket list to see them live. Very cool.


If you mean someone who draws scientific reconstructions of fossils, then this is a very useful profession (though unlikely to be a full-time occupation for most). I know several people who do very good illustrations of ancient life for scientific publications and museum exhibitions (to name a few).

Peter Trusler started as an artist, but did a degree in science and now creates highly respected reconstructions of extinct Australian animals, for which he does a lot of his own detailed research on the actual fossils.

Brian Choo was a palao PhD student who was also good at drawing, and he was comissioned to do quite a few illustrations for other researchers. (eg do a google images search for: Brian Choo Materpisces)

(posted in Evolution)

This article might help with the maths: Wilf HS, Ewens WJ (2010) There's plenty of time for evolution

http://arxiv.org/PS_cache/arxiv/pdf/101 … 5178v1.pdf

This blog post may help with the process as well: http://scienceblogs.com/pharyngula/2010 … networ.php

(posted in Fossils)

The look like crinoid (sea lily) stems. The various angles at which they are cut gives the different shapes. Not sure though what the age or provenance would be.

(posted in Fossils)

Under the right circumstances shells can fossilise (or at least lithify, turn to rock) very quickly, in a matter of a couple years or even less. In our collection we have crab and lobster carapaces that were found near mangroves in northern Queensland, and the species are identical to one living within the mangroves. It turns out that the water chemistry around the mangroves is such that sand and shells can become cemented by calcite very quickly. Some have even speculated that, as the crab carapaces are moults (the outer shell they shed in order to grow larger), the individual the shed the 'fossilised' carapace may still be living nearby.

In other cases there are fossils that are more than half a billion years old in Siberia of Ediacaran animals that are still so soft that you can scratch them with your finger nail.

Due to their great diversity, new species of insects and arachnids are being discovered all the time, including in seemingly well-investigated regions like Europe and the US. You would have to get a good idea of the species that are already known to occur in your area, and then you may be able to recognise ones that noone has described yet.

Capturing a specimen is the best way to identify it (show it to your local natural history museum's or university's entomologists). A photograph may not show sufficient detail to distinguish it from other similar species, but it can help.

Sounds like it could be freshwater bryozoan colonies, probably Pectinatella magnifica.

Speaking of kangaroos: The 2m tall Propleopus oscillans was carnivorous and lived during the Pleistocene in Australia, may have still been around when the first Aborigines arrived in Australia.

(posted in Evolution)

As long as the resources needed to grow the bone are not significantly detrimental, then there is not selection pressure against it. But it could still disappear via genetic drift, which is quite a powerful evolutionary driver.

There have been massive disruptions of the biosphere in the geological past, and the recovery from these may give some idea of how long it may take to recover from humans. At the moment I think human impact is still not as massive as, say the Permian/Triassic or the Cretaceous/Cenozoic mass extinction events, but if we keep going at the current rates, I think we'll achieve similar impact in a couple of decades.

The biosphere took a long time to recover full from those mass extinction events. After the Permian (which may be a bit similar to today in that it ended in a massive Greenhouse climate) there is for example a 'reef gap', where no coral reef structures formed for at least 10 million years. Similarly there is a 'coal gap' of similar length where apparently the vegetation struggled to regain a footing, thus no coal deposits formed. Although life in general seemed to recover relatively quickly, only generalist species (ones that can survive in all sorts of environments - what we would probably call pests and weeds) dominated, such as Lystrosaurus. It too a long time for complex ecosystems to redevelop.

Ecosystems tend to be quite similar each time they recover (though often new complexities may be added); but similar niches are occupied by quite different species that convergently evolve to exploit the same resources.

(posted in Fossils)

The orange band look like they are Liesegang Bands (probably iron laid down by repeated water flowing through the rock), rather than sedimentary layers.

The globe-like structure could be a mould of some animal like an echinoid, but I'm not certain.

are you able to attach a couple of photos of this critter? The description alone may not be enough.

As far as I understand it, sexual reproduction probably evolved in single celled eukaryotic ancestors of plants, fungi and animals. Thus there are was no nervous system yet to produce what we understand by 'pleasure' and 'pain'.

(posted in Evolution)

Bwtween Africa up until the archipelagos of what is today Indonesia etc, there is continuous land, so no problem there. Jumping between these island would not have been too difficult as the sea level at the time was much lower. Humans reached Australia at the latest about 30,000 years ago, during the last glacial maximum when sea level was about 100 meters lower than today. They probably had some basic boat technology by this time.

http://en.wikipedia.org/wiki/Early_huma … _Australia

(posted in Evolution)

I'll focus on the question in the heading: why life?

It is likely that life originated simply by the physical and chemical interactions inherent in pre-existing organic molecules, like amino-acids. There was nothing that 'wanted to live', it just happened. Evolution (basically the stochastic selection of collections of these molectules that could better maintain their structure and harness energy and produce accurate replicas) drove these aggregates to become more complex on average. Still no will to live needed. So the dynamics of populations of living organisms don't require individuals to live forever for them to be successful, indeed, it's probably a bad situation where every individual lives forever, but at the same time continues to reproduce; you end up with overpopulation very quick, plus it makes a species much slower at adapting to changing environments. Programmed death is probably itself an evolved trait, rather than something that we just haven't overcome yet.

Remember also that avery single cell alive today (be it all those in your body or just that of one bacterium) are the direct descendent of the very first life-form. In other words the very first life-form never died, and neither did any organism that is an ancestor of today's organisms (in multicellular organisms it's just one cell (egg or sperm) that continues living, but still pretty amazing).

Why do we strive for life? Well, and organism that didn't do that would be unlikely to live to reproductive age, and thus would be rather insignificant in the story of life.

The ribbed shells are indeed brachipods, probably of the family Spiriferidae (or closely related). I would guess that the age is Palaeozoic, probably between 200 and 400 million years old (a more precise age may be possible if we knew the area where it was collected)

Aparently there's a component of your salva that helps your skin actually heal, called histatins. They encourage epithelial cells to migrate to the wound area and start the healing process.

the risk of infection: your mouth always harbours a huge diversity of
microorganisms, which are pretty harmless in the oral environment, but
may cause problems when introduced into other areas. The majority of
these are not harmful, and in a healthy person the potentially harmful
ones are kept at very low levels, so licking a superficial wound should
not be a problem. But problems may occur in deeper cuts as the bacteria
can invade tissue that is normally protected by the outer layers of
skin. It's even more problematic for immunocompromised people, which
have very little defense.

Looks like the centipede Scutigera coleoptrata, but it could be a related species.

Bird bones are not necessarily lighter overall than for example mammal bones of similar size; they may be almost hollow, but they are also made of significantly denser material, which can make them stronger but heavier per unit bone. This may be one reason why there's no pressure on other land vertebrates to evolve hollow bones; or put differently: thi smay be one reason why bird ancestors found hollow bones advantageous, as they would otherwise be too heavy (this assumes that the denser material evolved before the hollowness).

They characteristic to make bones hollow probably originated in birds' ancestors at some point in the Triassic Period (about 230 million years ago). At this time in earth's history the atmosphere apparently contained much less oxygen than today (dropping below 15% after the Permian/Triassic Mass Extinction; as opposed to today's 21%). The group of dinosaurs that bird belong to, the Sauriscia, evolved at around this time, and all of them had hollow bones to some extent (including the giant sauropods). One theory is that as the air sacs that filled these hollows are a part of the lung system, the extra surface area allowed them to get more oxygen out of the depleted air. This came in handy later when oxygen levels rose and they could afford to use the extra oxygen for the very oxygen-intensive activity of flying.

After having said all that though, beware that these may simply be "Just So" Stories.

Predicting the path that earth's evolution will take in the future is a very tricky prospect. Remember that evolutionary theory usually cannot predict specific outcomes, except perhaps in very well-defined circumstances. So we may be able to predict that E. coli will evolve to digest citrate (natural strains can't do this) if raised in a medium where citrate is the main nutrient (*), however we can't predict when or how they will do this. And this is a very well constrained experiment, with not too many variables; think how complex a whole ecosystem is in comparison, let alone the whole bosphere.

But the when and how can be fundamental variables when trying to predict the future course. Therefore Stephen Jay Gould argued that the path the evolution takes is largely dependent on 'contingency', or 'historical accidents' (basically completely random, and therefor unpredictable circumstances can have a major effect on the evolutionary course).

This doesn't mean you can't have a stab at a very coarse grained prediction, but even then you have to make assumptions about some of the major contingencies that you expect to occur in the future, such as the timing, location and effect of another major asteroid impact.

Regarding your specific issues:

Humanity's progression will depend on factors such as the continued existence of civilisation (not a given considering that the more sophisticated a civilization, the more prone to collapse - and we are very sophisticated now), the expansion of genetic engeneering within our species, etc. You're walking in sociology territory there :)

There is probably a major extinction event going on right now, due to humanity itself. Each of the major mass extinctions of the past appears to have had a completely different root cause(s) and therefore also different affect on biodiversity. The current one is different again, and predicting the outcome is therefore quite difficult.

You may be aware of the series "The Future Is Wild" (somewhat dodgy in my opinion), and books like "Future Evolution" that attempt such predictions.

(*) see Lenski's experiment: http://en.wikipedia.org/wiki/E._coli_lo … experiment

(posted in Evolution)

New species evolve all the time, and existing ones go extinct all the time as well; this occurs at a so-called background rate. Mass extinctions are characterised by the extinction rate significantly exceeding the speciation rate. This can be due either to the extinction rate rising (a true mass extinction) or the speciation rate dropping (a mass depletion). The causes of each are probably always major environmental changes, such as massive and rapid climate change that outstrips many species ability to adapt. But the end results are the same: a large amount of ecological niches may open up (note that a nich is not something that just exists waiting to be filled, it is largely 'created' by a species interacting with the environment). This may result in a rise in speciations after the causes of a mass extinction have settled down, but not necessarily.

So, speciation occurs all the time, even without mass extinctions (remember that a new species may arise simply when a previous species changes significantly enough; it could be argued that the old one never went extinct, but simply changed, yet a new species arose anyway).

This is probably impossible, as the human reproductive system is geared to developing a human embryo to maturity, which requires quite different processes than that of a cat. At the most basic a human takes 9 months to mature in the womb, while domestic cats take about 2.5 months. It's also likely that because they belong to an unrelated species the immune system would reject it (it's a balancing act already for a human foetus not to be rejected as a foreign body).

Many fossils are found each year, but you would only know if it is a new species after a specialist has had a good look at it. Such specialists usually work at natural history museums, or at universities (either in the geologiy or zoology department, though rarely these days). At my museum we get lots of fossils brought in by the public for identification, and occasionally they turn out to be something new: some years ago a surfer dude (official term) noticed some bone in the coastal cliffs where he surfed and alerted our museum. It turned out to be an ancient whale skull, and a PhD student ended up working on it as his thesis topic (he described a new genus, Janjucetus and named the species after the guy who found it). If you do find a fossil, one of the most important things you can do is not down precisely where you found it, as this will allow the specialist to determine what geological age the fossil is from.

Actually there are a large number of animals that are indeed green: on land insects especially, but also vertebrates such as reptiles and amphibians; in the oceans there are numerous groups like corals and sea urchins to name a few. What you may be thinking of is that there is a lack of green mammals. Indeed there appears to be not a single example of a mammal with actual green fur (the closest to green is the sloth, but the green colour is due to algae growing in its fur). It appears that mammals are only capable of producing two types of skin pigment: the black/brown melanin, and a reddish/yellow one. It's not clear what the evolutionary reason for this is, as the common ancestor with 'green' groups like reptiles and birds was likely able to produce green pigments (note that there's also no blue).

It may be that the animals that use green as camoflage are relatively small (think of the size of insects and most frogs), and so could actually hid on an indivisual leaf. Mammals on the other hand are on average larger, and therefore would need to camoflage against a more varied background, which may include soil and bark. This, of course does not explain why there is what seems to be an inability in mammals to produce green colour. After all, birds which are also quite large, quite often have green feathers, in many cases more for display rather than camoflage.

Also, remember that not all animals have the same colour vision that we humans do. Some see different parts of the light spectrum. Interestingly, most mammals apart from primates have very poor color vision, and so could be considered 'colour blind' (they are able to see blue and yellow, but not red). Considering that camoflage is generally to hide from predators, and predators of mammals are often other mammals, this may have an evolutionary effect.

EDIT: just noticed this quite thorough answer: http://www.hhmi.org/askascientist/answe … ample.html

I guess the distinction lies in the word "research", meaning that such a biologist actually carries out research (be it field work to collect new species or someone who analyses databases for biological trends or other things), as opposed to someone who maybe simply teaches biology or applies their knowledge to advise government policy or manage a national park, etc. The difference is probably ver fuzzy though.

You are correct: animals such as corals do not have cell walls. I suspect it was a bit of lazy terminology that slipped through there.

This differentiates animals from the other major eukaryotic groups like plants and fungi, which have 'cell walls', but in each group the structure and chemistry of these cell walls are quite different, and are thus thought to have evolved separately.

Following on from that: birds are only closely releated to the therapods, which belong to the Order Saurischia. The other major group are the Order Orthithischia (like the ornithopods and stegosaurs). So it would seem like comparing kangaroos with whales.

Well, not really, of course, as we would look for features in the dinosaur's skeleton to see if it compares with modern vertebrates. The most obvious is looking at the teeth of T. rex and eing quite certain that it ate meat. This is to some extent due to converent evolution, where a similar ecological niche (i.e. way of living) will require similar adaptations.

 It gets more complicated with some of the more exotic dinos that have no good modern analogue, such as the sauropods (apparently giraffes are not a good analogue)

(posted in Evolution)

I agree, it would require more documented data than "it is often said" to make anything worthy of explaining. But even if it is on average true (and disregarding the likelihood that in humanities early evolutionary history, a peaceful death of old age was probably a rare event), you need to be wary of developing "just so story" hypotheses when it comes to evolution. Many features of organisms are actually not directly due to any evolutionary adaptive cause.

(posted in Evolution)

It doesn't support creationism, it simply shifts the abiogenesis event to another planet.

My mother actually has no wisdom teeth. They didn't just not erupt, they simply aren't there. Has baffled quite a few dentists over the years.

Regarding the statement about Uniformitarianism: as you say, it assumes that the same processes and natural laws that opperate today also opperated at any given time in the past (and future). This does not mean that the same things that occurred in the past will also occur today, as the environment on earth today is nothing like what it was 3500 million years ago. And even if an abiogenesis event occurred today, despite inhibiting factors like oxygen-rich atmosphere, the exisiting, nearly ubiquitous life forms (which even exit kilometers down in the earth's crust) would probably gobble up the new life forms almost instantly as just another clump of nutrients. So you can tell your grandad that it is essentially impossible to observe another origin of life on earth today.