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Monday, 28 July 2014

More Mimetic Evolution

Having blogged a couple of days ago about the role of mimicry in evolution I decided to look more closely at the subject, especially the widespread mimicry found in butterflies. The results are fascinating.

But before I get on to that I just deal quickly with another aspect to evolution - speciation - following on from something I mentioned in the same blog. I pointed out how mimicry involved a two species both of which are prey to the same predator and where at least one of them is toxic or harmful to the predator. I mentioned that the selection pressure for one species to become more and more like the harmful one depends on the presence of the predator in the local environment but the species range may well include areas with different predators, different comimics or indeed the absence of one or both. In this case, and in that part of the range there may be no selection pressure and no particular advantage in adopting the colour pattern of the toxic or harmful species, and there may even be a disadvantage because a different predator my not have any aversion to the mimicked colour.

So, let's take a hypothetical example of a widespread species coexisting in part of its range (we'll call it Area A) with both a toxic comimic and a predator with an aversion to the comimic. In a different part of the range (which we'll call Area B) there may be a different predator and the comimic may be absent. Yet there is nothing to prevent the genes for mimicry flowing from Area A into Area B where they might well act as advertisements rather than deterrents. After all, what's the point of protective mimicry if it isn't conspicuous?

In Area B then, these genes could be being removed from the gene-pool by Natural Selection and there would be a distinct advantage in any mutations which prevented the population in Area B from acquiring genes for mimicry. For example, individuals which selected against potential mates with the mimicry pattern would tend to produce more descendants with that selection preference than those which didn't discriminate, so sex selection and mating displays would come to feature in Area B. These genes would in turn be detrimental as they flowed back to Area A because their carriers would now have genes preventing their offspring acquiring the protective mimicry in Area A.

The environment, together with Natural Selection, would have created the conditions in which it is to both colour varieties' advantage to prevent interbreeding and to evolve barriers to it. In this situation we would expect the two gene-pools to quickly become effectively isolated from one another, or, to put it in taxonomic terms, two new species would have diverged from one original species.

This of course is a simplistic scenario. In reality, and especially with a widespread population, the situation may be far more complex with more than one comimic presenting different levels of risk to predators, more than one predator, overlapping predator ranges, etc, etc., so the result might be a whole range of intermediates, distinct colour forms predominating in different parts of the range and yet not enough environmental pressure for barriers to gene flow to arise.

Creationists tell us that it is impossible for a new species to arise by evolution because they have been fed the lie by creationist pseud-scientists that there is a fundamental difference in the mechanism by which a species changes over time due to changes in its genome, and the mechanism by which gene-pools become effectively isolated with barriers to interbreeding. I would like a creationists therefore to explain to me how the mechanism I have described above by which genes for mimicry are acquired in one part of the range and barriers to the spread of those genes into a different part of the range is fundamentally different and why one is perfectly possible and the other is impossible. During what stage does the mechanism change as the species evolves from allowing full interbreeding to full gene-pool isolation and how does that mechanism then become impossible retrospectively when previously it was perfectly possible? Surely there is a creationist site where this is fully explained, isn't there?

Anyway, on the subject of mimicry in butterflies, scientists have recently discovered that, at least in the Asian swallowtail butterfly, Papilio polytes, wing shape, colouration and pattern are all controlled by a single 'supergene', i.e., a group of genes all physically grouped together on a chromosome making cross linking less likely and so tending to all be inherited together as a single package. Moreover, they have discovered that this supergene is a modified form of another supergene called the doublesex gene which controls sexual dimorphism in butterflies. At some point in their evolutionary history, probably close to the point of divergence of butterflies from the silk moths this gene became doubled so one copy was free to mutate and evolve without being detrimental to the doublesex gene's function.

One of the most striking examples of sexual dimorphism is sex-limited mimicry in butterflies, a phenomenon in which one sex—usually the female—mimics a toxic model species, whereas the other sex displays a different wing pattern. Sex-limited mimicry is phylogenetically widespread in the swallowtail butterfly genus Papilio, in which it is often associated with female mimetic polymorphism. In multiple polymorphic species, the entire wing pattern phenotype is controlled by a single Mendelian 'supergene'. Although theoretical work has explored the evolutionary dynamics of supergene mimicry there are almost no empirical data that address the critical issue of what a mimicry supergene actually is at a functional level. Using an integrative approach combining genetic and association mapping, transcriptome and genome sequencing, and gene expression analyses, we show that a single gene, doublesex, controls supergene mimicry in Papilio polytes. This is in contrast to the long-held view that supergenes are likely to be controlled by a tightly linked cluster of loci. Analysis of gene expression and DNA sequence variation indicates that isoform expression differences contribute to the functional differences between dsx mimicry alleles, and protein sequence evolution may also have a role. Our results combine elements from different hypotheses for the identity of supergenes, showing that a single gene can switch the entire wing pattern among mimicry phenotypes but may require multiple, tightly linked mutations to do so.

K. Kunte, W. Zhang, A. Tenger-Trolander, D. H. Palmer, A. Martin, R. D. Reed, S. P. Mullen and M. R. Kronforst;
doublesex is a mimicry supergene;
Nature 507, 229–232 (13 March 2014) doi:10.1038/nature13112

So, at least in this swallowtail butterfly, a single supergene controls the form of mimicry the carrier will have and, because this is tied in with the gene controlling gender expression, mimicry is limited to females.

Papilio Polytes MorphComimic Species
Morph cyrus. Either male or female.
No comimic species. Sexes are alike.
Morph stichius. Female.
Common rose Pachliopta aristolochiae
Morph romulus. Female.
Crimson rose Pachliopta hector

Distribution of the different morphs of Papilio Polytes females corresponds closely with that of the comimic species of Pachliopta.

From Mimicry in Butterflies by Reginald Crundall Punnett

  1. Heliconius mirus
  2. Heliconius telchinia
  3. Heliconius eucrate
  4. Heliconius pardalinus
  5. Heliconius splendens
  6. Mechanitis elisa
  7. Mechanitis saturata
  8. Mechanitis lysimnia
  9. Mechanitis egaensis
  10. Mechanitis methona

In this group from South America, each species of Heliconius has a corresponding comimic in the Mechanitis genus.

From Mimicry in Butterflies by Reginald Crundall Punnett

  1. Planema macarista (male)
  2. Planema macarista (female)
  3. Planema tellus
  4. Planema paragea
  5. Planema epaea
  6. Pseudacraea eurytus (male)
  7. Pseudacraea eurytus (female)
  8. Pseudacraea eurytus
  9. Elymnias phegea (female)
  10. Papilio cynorta (female)

Note that each of the top three morphs of Pseudacraea eurytus has a mimic, even mimicking the sexual dimorphism seen in the top two. This linkage of sexual dimorphism and mimicry type reflects the fact that the supergenes for both are closely related and controlled in the same way. A female will also inherit the female mimicry supergene and the male will inherit the male one. These supergenes, although in different species have remained relatively stable in the way they are arranged and in how they express since early in the evolutionary history of butterflies. This can also mean that there is not a whole array of genes which need to evolve as mimicry develops but the entire change can be due to a small number of changes or even a single 'switch'.

Mimicry is by no means confined for insects or course. The following shows Mülarian mimicry in poisonous South American frogs. The top row are all members of the same species (Dendrobates imitator) which have evolved in different areas to resemble other poisonous species.

Above: regional morphs of Pseudacraea eurytus
Dendrobates variabilisDendrobates fantasticusDendrobates ventrimaculatus

With Mülarian mimicry, two harmful species come to resemble one another as a kind of spread bet. The display is conspicuous and each benefits from a predator's aversion to the other.

Coralsnake and a scarlet kingsnake.
My last example of mimicry, this time Batesian mimicry where a harmless species gains protection from resembling a dangerous one is the coralsnake and scarlet kingsnake. Remember here that not all of the potential predators on the harmless coralsnake will have colour vision and neither snake will always be seen in perfect lighting or for more than a fraction of a second, so any resemblance, no matter how approximate, will give the coralsnake some protection.

There is of course absolutely no way evolved mimicry can be fitted into an intelligent design model because it is entirely dependent on wasteful competition, predation and avoidance. There is no intelligent reason to design a predator to prey on one species (even if we forget the supposed benevolence) and then design the prey to deter the predator from eating it, and without this need for deterrence there is no reason for the prey to be toxic in the first place so no benefit would accrue from mimicking it.

The only rational explanation for mimicry in living things is as the result of a mindless, purposeless, evolution over time directed only by an unemotional natural selection which results in the genes of those which leave the most descendants coming to predominate in the species local gene-pool. In their advocacy of intelligent design, creationists pseudo-scientists betray one of two things: an ignorance of the subject on which they expound with feigned expertise or a disregard for truth, honesty and integrity. As even devout Old Earth Creationist, Francis Collins pointed out in an otherwise thoroughly dishonest book, The Language of God, Young Earth Creationism (i.e, those who advocate ID and try to have it inserted into school science curricula in pursuit of an extremist political agenda) have reached a point of moral and intellectual bankruptcy, both in it's science and in it's theology.

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Sunday, 27 July 2014

Recent Evolution - That Old Chestnut

Horse chestnut leaves infested with Cameraria ohridella lavae.
If you live in Southern England, for an example of very recent evolution you probably only need walk to your nearest horse chestnut tree. I took this photograph near Sunningwell, Oxfordshire earlier on Saturday when we went out for a last distant look at Didcot Power Station, which is probably England's best-loved 'eyesore' but which is due to disappear in a cloud of dust in a few hours time. The chances are that by now your nearest horse chestnut tree will be becoming infested with the leaf-miner caterpillars of a moth which was unknown before 1985 when the first outbreak was recorded in Macedonia, Greece.

Since then, Cameraria ohridella has spread at an average of 60 Km per year across western Europe reaching England in 2002, where it is now widespread, causing the leaves of horse chestnut trees (Aesculus hippocastanum) to turn brown, wither and fall off by late summer. Devastating though this attack appears, the general health of the trees seems not to be unduly affected since they come back into leaf and grown normally the following spring.

Although this moth was a newly-discovered species in 1985, specimens of it were accidentally collected and pressed in botanical specimens as early as 1879 only to be rediscovered when a team of researchers carried out a systematic search of specimens stored in herbaria.

Determining the native geographic range or origin of alien invasive species is crucial to developing invasive species management strategies. However, the necessary historical dimension is often lacking. The origin of the highly invasive horse-chestnut leaf-mining moth Cameraria ohridella has been controversial since the insect was first described in 1986 in Europe. Here, we reveal that herbarium collections across Europe indicate a Balkan origin for C ohridella. We successfully amplified nuclear DNA and mitochondrial DNA barcode fragments from larvae pressed within leaves of herbarium samples collected as early as 1879. These archival sequences confirm an identity of C ohridella and set back its history in Europe by more than a century. The herbarium samples uncovered previously unknown mitochondrial haplotypes and locally undocumented alleles, showing local outbreaks of C ohridella back to at least 1961 and dynamic frequency changes that may be associated with road development. This case history demonstrates that herbaria are greatly underutilized in studies of insect–plant interactions, herbivore biodiversity, and invasive species' origins.

David C Lees, H Walter Lack, Rodolphe Rougerie, Antonio Hernandez-Lopez, Thomas Raus, Nikolaos D Avtzis, Sylvie Augustin, and Carlos Lopez-Vaamonde 2011.
Tracking origins of invasive herbivores through herbaria and archival DNA: the case of the horse-chestnut leaf miner.
Frontiers in Ecology and the Environment 9: 322–328.

Spread of C ohridella from the Balkans.
Examination of the DNA from these preserved specimens shows that there have been two or three significant changes which have almost certainly caused the sudden explosion of this moth from its probable homeland in the Balkans, one of them genetic and two environmental. The interesting thing about the genetic change is that it seems to have been in the mitochondrial DNA.

Of the thirty known mitochondrial haplotypes occurring in the Balkans, only three, known as A, B and C are known to have moved into the rest of Europe of which haplotype A is the dominant form. This probably represents a new haplotype which somehow has enabled C ohridella to colonise new environments, something which may have been aided by a succession of years of above average temperature and below average rainfall across Europe. However, hot dry weather as such does not seem to suit the moth judging by its failure so far to invade the Iberian Peninsula.

The second environmental change which may have facilitated the initial expansion out of the Balkans was increased road building - the moths are known to be transported accidentally by road goods vehicles.

So we have an example of a genetic change, in the presence of fortuitous environmental change, leading to a massive increase in population and range of a species but seemingly restricted to just three of the thirty mitochondrial haplotypes and predominantly just one of them. This illustrates the founder effect, in which a small, and therefore genetically unrepresentative, founder population moves out of its normal range into new territory and then moves quickly out into the new territory by a process which increases the proportion of the alleles which facilitated the expansion in the first place, so, for example, the genetic profile of C ohridella in, say, southern England, may be very different to that in the Balkans.

And so we have an example of evolution in progress as the allele frequency in different parts of the range changes and adapts to environmental change and opportunity, and Britain now faces late summers with an important amenity tree becoming disfigured and unsightly and losing most of its leaves by late August.

However, the explosion of C ohridella into western Europe is also an environmental change which other species can exploit. It is now becoming a major food source for blue tits (Parus caeruleus), great tits (Parus major) and marsh tits (Parus palustris) which are learning to extract them from the leaves and are now believed to account for 2 to 4 percent of lavae.

It has also created a potential new resource for parasitic wasps to exploit. The prediction is that a generalised parasitic wasp will 'discover' this new resource and will become a major predator so bringing about a degree of population control of a species which currently appears to be limited only by the availability of horse chestnut trees.

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Friday, 25 July 2014

Copycat Evolution

Which ones would you pick up?
A friend asked me the other day to explain how mimicry can play a role in evolution. This is my attempt to do so.

There are in fact two main types of mimicry recognised by biologists, although the distinction is quite technical and is blurred anyway. For all practical purposes, they can both be regarded as forms of the same thing. They are known to biology as:

  • Batesian mimicry. Named after the English naturalist Henry Walter Bates. This is where a harmless species evolves to resemble a harmful species if it and the harmful species share a common predator.
  • Müllerian mimicry. Named after the German biologist Fritz Müller. This is where two harmful species evolve to resemble one another if they both share a common predator.

The distinction is further complicated by the fact that the mimicry is seen from the point of view of the predator and need not be too readily apparent to a human eye. It is also quite possible for the same species to be a Batesian mimic in respect of one predator and a Müllerian mimic in respect of another. Seeing the mimicry from the predator's point of view is obviously key to understanding how mimicry works. Bear in mind also that a predator might not have colour vision so whatever works in shades of grey will suffice. Some predators may even see in ultraviolet or infrared, so mimicry can be operating outside our own perception altogether.

Key to understanding how it evolves is understanding the fundamental basis of evolution - natural selection incidentally 'favouring' those small variations which produce more descendants so the genes for those small variations increase throughout the population's gene-pool over time and no matter how unlikely the original mutation was, it will become increasingly common in the gene-pool.

You also need to understand the basic economics of the trade off between the risk of being bitten by a poisonous snake, getting badly stung by a wasp or bee, being poisoned by eating a poisonous meal or even being eaten by another predator, and getting a meal. In almost every case the 'cost' to the predator of being killed, injured or made sick is far greater than the cost of missing a meal so the tendency will be for the predator to be highly risk-averse. Where the predator has alternative food, the evolutionary pressure on it to improve its ability to tell the mimic from the comimic might not be that strong so the mimic gets away with only a passing resemblance. This difference is reflected in the different intensity of selection pressure on predator and prey.

Although once thought to be an example of Batesian mimicry, it has recently been discovered that the viceroy butterfly (top) is actually more unpalatable than the monarch butterfly (bottom), making this a case of Müllerian mimicry.
Imagine a situation in which a harmless fly is preyed on by a bird which is also a potential predator on a stinging wasp. The bird will quickly learn to avoid anything that resembles a wasp. Indeed, over time, it may even have evolved a natural reflex avoidance so it doesn't even need to learn by experience.

Imagine now a few flies in the population occasionally having a mutation which, for example, gives them a yellow tip to their abdomen or a yellow stripe across the centre of it, or maybe a yellow thorax - anything which a bird in some situations might mistake for a wasp. This will give the mutant form a slight edge over the normal forms so it will leave more descendants on average than the normal form and the mutation will, over time, become the norm in the population. It's easy to see how even something that works in poor lighting or only on those birds at the lower end of the range of visual acuity for the population - maybe the oldest or the youngest - and the environment will slightly favour the mutant flies.

It's now in the interests of the bird's genes for it to learn to tell this mutation from real wasps, otherwise its former food supply will not be available to it, so natural selection will favour bird genes which enable the bird to tell the difference. Meanwhile, there will now be renewed selection pressure on the fly to overcome this recognition ability by even more closely resembling a wasp. And so we have a classic arms race developing which is driving the fly ever more closely to resemble the wasp and the bird to become ever better at telling the difference. However, the bird may well also have alternative prey species so there is far less selection pressure on it than there is on the fly. The bird only misses a mean and has an alternative; the fly loses its life and fails to pass its genes on.

For another example of this, see Seeing Eye To Eye With A Butterfly, an earlier blog of mine on how the peacock butterfly came to have what look like mammalian eyes on its wings.

Mimicry need not be confined to visual mimicry either. Some bats find the taste of tiger moths distasteful and tiger moths have evolved to produce a sound audible to bats when they hear the bat's echolocatory signals so the bats avoid them. Some other insects have now evolved to mimic these tiger moth sounds. There may be a whole world of auditory mimicry of which we are hardly aware, including in the sea and rivers where dolphins use echolocation extensively.

What we have here of course is the classical situation of a change in the environment of one species being caused by a change in another. In the absence of a predatory bird, yellow stripes on a fly could not have meant, "Avoid me I might be a wasp". In the absence of wasps, they might have meant, "Look! Here I am!", to a predator with no reason to distrust yellowish things, and so would have been quickly removed from the gene-pool. The same mutation with the same information can have entirely different meanings in different environments and the meaning is constantly changing in a dynamic environment.

The same mutation can either be advantageous, detrimental or neutral entirely dependent on environmental context. This could even hold true for the same species with a continuous gene-pool over a wide geographical range, so evolutionary pressures favouring one mutation in one part of the range could be countered by different pressures favouring the normal gene in a different part of the range, so a gradient or 'cline' can develop giving geographical variation in the same species. And of course it's always possible that a species now has a pattern evolved millions of years ago in the presence of a long-extinct predator or a long-extinct comimic. Since colours don't fossilise well we may never know what benefit the species got from a particular pattern when it first evolved it, so it may not be recognised even as evolved mimicry.

It's probably too easy a target to point out how none of this makes any sense as the design of an intelligent designer, since each side of an arms race only makes sense when seen from the narrow perspective of one side or the other, never both, so I'll just challenge creationists to explain how mimicry can be explained in terms of intelligent design by a benevolent designer and how the change in meaning of information by environmental change fits in with the creationist dogma that no new information can arise by mutation.

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Thursday, 24 July 2014

Evolution Arms Race - Moose Spit Detox

Ungulate saliva inhibits a grass–endophyte mutualism

A fascinating example of both evolutionary cooperation and an evolutionary arms race was published in Royal Society Biology Letters yesterday.


Fungal endophytes modify plant–herbivore interactions by producing toxic alkaloids that deter herbivory. However, studies have neglected the direct effects herbivores may have on endophytes. Antifungal properties and signalling effectors in herbivore saliva suggest that evolutionary pressures may select for animals that mitigate the effects of endophyte-produced alkaloids. Here, we tested whether saliva of moose (Alces alces) and European reindeer (Rangifer tarandus) reduced hyphal elongation and production of ergot alkaloids by the foliar endophyte Epichloë festucae associated with the globally distributed red fescue Festuca rubra. Both moose and reindeer saliva reduced the growth of isolated endophyte hyphae when compared with a treatment of distilled water. Induction of the highly toxic alkaloid ergovaline was also inhibited in plants from the core of F. rubra's distribution when treated with moose saliva following simulated grazing. In genotypes from the southern limit of the species' distribution, ergovaline was constitutively expressed, as predicted where growth is environmentally limited. Our results now present the first evidence, to our knowledge, that ungulate saliva can combat plant defences produced by a grass–endophyte mutualism.

Andrew J. Tanentzap, Mark Vicari, and Dawn R. Bazely; Ungulate saliva inhibits a grass–endophyte mutualism
Biol. Lett. July, 2014 10 7 20140460; doi:10.1098/rsbl.2014.0460 1744-957X

The team from the Department of Plant Sciences, University of Cambridge, UK and the Department of Biology, York University, Toronto, Canada were specifically looking for evidence that Moose and Reindeer could counteract the defence mechanism which some grasses have evolved in cooperation with a fungus. The fungus is known to produce the highly toxic alkaloid ergovaline which can cause, amongst other things, hooved animals to lose their hooves.

If these animals continually graze the same plants, then it would be quite beneficial. We are still uncovering novel roles for saliva"

Gary Felton, Penn State University, Pennsylvania, USA
They found evidence that moose saliva not only significantly reduced the concentration of ergovaline by between 41% and 70% but it also inhibited a signalling system whereby grazing the grass stimulates growth of the fungus and so the production of the toxin. This is one of the few example discovered so far of a vertebrate being able to do what some insects are known to do - chemically influence the metabolism of a plant. It has also been shown that sheep saliva can stimulate growth in at least one grass, Leymus chinensis.

The fascinating things here are the example of mutualism, whereby a fungus has formed a mutually beneficial association with a grass to defend the grass against being eaten, and the example of an arms race where the species this defence evolved against has evolved a counter-measure.

First the cooperative, or symbiotic alliance:

Epichloë species and their close relatives, the Neotyphodium species, are systemic and constitutive symbionts of cool-season grasses (Poaceae subfamily Pooideae), and belong to the fungal family Clavicipitaceae. Among the Clavicipitaceae, many species are specialized to form and maintain systemic, constitutive (long-term) symbioses with plants, often with limited or no disease incurred on the host.[1] The best-studied of these symbionts are associated with the grasses and sedges, in which they infect the leaves and other aerial tissues by growing between the plant cells (endophytic growth) or on the surface above or beneath the cuticle (epiphytic growth). An individual infected plant will generally bear only a single genetic individual clavicipitaceous symbiont, so the plant-fungus system constitutes a genetic unit called a symbiotum (pl. symbiota).

The evolution of symbiosis probably goes through a stage of parasitism. In this case a fungal infection of grass. However, if something produced by the parasite benefits the host more than the parasite harms it, the host genes which help ensure the parasite is not attacked will do better than those which attack it, so the host will evolve tolerance rather than resistance. Meanwhile, the parasite genes which increase the benefit and/or reduce the harm will also prosper at the expense of those which do the opposite. Hence, the parasite will also tend to evolve towards cooperation with the host and parasitism will move towards symbiosis.

This is all readily understandable in terms of what benefits the genes of both parties. Cooperation serves the 'selfish' needs of both sets of genes.

Red fescue
The other aspect is the arms race between this mutually evolved defence mechanism which clearly benefits the grass by deterring herbivores from grazing it and both the moose and the reindeer which needs to eat a large volume of vegetation, especially the males which depend on a large size and large antlers to defend their females against other males and which feature in female sex selection, so needing a good supply of nutrients including calcium.

As the authors of this paper point out, the endophytic fungus probably originated some 30-40 million years ago and accompanied the grass as they became the dominant plant type about 10 million years later. This was followed by the evolution of large herbivores which diversified into the new niches provided by grasslands. This in turn would have provided a selective pressure on the fungus to maximise the persistence of their hosts.

Meanwhile, some larger herbivores would have been diversifying yet again to occupy niches found in forests, so leaving the grass-eating herbivores with no alternatives and high selection pressure to evolve counter-measures. The classic conditions for an evolutionary arms race and again fully understandable in terms of 'selfish' genes and a natural selection process which ensures those best able to survive and reproduce are the ones who leave the most descendants.

What is not at all understandable is how either this evolution of mutualism or the evolutionary arms race can be explained in terms of the work of an intelligent designer. Why would an intelligent designer design parasites in the first place, so creating the initial conditions for mutualism to evolve in which the parasite needs to defend its host because if its host get eaten, it gets eaten too? If an intelligent designer wanted to protect grass from being eaten by herbivores, why did it also create herbivores, and it it didn't want the herbivores to eat grass, why did it give them the mechanism for doing so?

Similar arguments apply to the notion of intelligent design and arms races. Ultimately, arms races are about two mutually hostile systems coexisting and needing to run to stand still because each is creating a hostile environment for the other and so selection pressure to overcome it. Arms races are ultimately to neither side's benefit and yet are entirely predictable. As a piece of design, arms races such as that between the grass-fungus complex and the moose, are manifestly stupid, lacking both foresight and ultimate purpose.

Creationist proponents of the notion of intelligent design need to explain parasitism, mutualism and arms races. Evolutionary biologists, on the other hand, have a perfectly rational, easily understood and well-evidenced explanation for them. They are all entirely predicted from the basic principles of evolution by natural selection.

*Copyright © 2014, The Royal Society

'via Blog this'

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Wednesday, 23 July 2014

Around the Bend with Ken Ham

2 January 2013: Astronomers have determined that the Milky Way may contain as many as 400 billion exoplanets, with almost every star hosting at least one planet.
"We'll find a new earth within 20 years" | Around the World with Ken Ham

Signs that Ken Ham may be beginning to panic at the thought that science could soon find evidence of life on another planet emerged recently with this desperate attempt to harness his fundamentalist audience in a bid to stop NASA looking for it, dismissing it as a waste of money which is bound to fail. His panic can be gaged from the horrible muddle he gets into with his argument where he inadvertently 'proves' that there isn't non-human life on Earth either.

He also showed his traditional propensity for making things up, even about the Bible, and relying on his ignorant audience not checking.

I'm shocked at the countless hundreds of millions of dollars that have been spent over the years in the desperate and fruitless search for extraterrestrial life. Even Bill Nye "the Science Guy," in our recent debate, happily gloated about tax dollars being spent toward this effort. And now, secular scientists are at it again.

Of course, secularists are desperate to find life in outer space, as they believe that would provide evidence that life can evolve in different locations and given the supposed right conditions! The search for extraterrestrial life is really driven by man's rebellion against God in a desperate attempt to supposedly prove evolution!

Judging by Hamster's snide swipe at him, it seems too that he may still be smarting at his recent public humiliation at the hands of Bill Nye "the Science Guy" in a widely publicised TV debate, which even many conservative Christians thought Nye had won.

How does Hamster know the search for evidence of life on the ever-expanding number of exoplanets (i.e planets orbiting other suns) will be fruitless? The Bible says so, of course.

The only problem is, he claims the Bible says things it simply doesn't say, even if what the Bronze-Age authors who believed Earth was flat, has a single landmass and a dome over it (Genesis 1:6-10) thought had any relevance. For example:

And I do believe there can't be other intelligent beings in outer space because of the meaning of the gospel. You see, the Bible makes it clear that Adam's sin affected the whole universe. This means that any aliens would also be affected by Adam's sin, but because they are not Adam’s descendants, they can't have salvation.

Er... actually Ken, the Bible says almost exactly the opposite.

Unto the woman he said, I will greatly multiply thy sorrow and thy conception; in sorrow thou shalt bring forth children; and thy desire shall be to thy husband, and he shall rule over thee.

And unto Adam he said, Because thou hast hearkened unto the voice of thy wife, and hast eaten of the tree, of which I commanded thee, saying, Thou shalt not eat of it: cursed is the ground for thy sake; in sorrow shalt thou eat of it all the days of thy life; Thorns also and thistles shall it bring forth to thee; and thou shalt eat the herb of the field; In the sweat of thy face shalt thou eat bread, till thou return unto the ground; for out of it wast thou taken: for dust thou art, and unto dust shalt thou return.

And Adam called his wife's name Eve; because she was the mother of all living.

Unto Adam also and to his wife did the Lord God make coats of skins, and clothed them. And the Lord God said, Behold, the man is become as one of us, to know good and evil: and now, lest he put forth his hand, and take also of the tree of life, and eat, and live for ever: Therefore the Lord God sent him forth from the garden of Eden, to till the ground from whence he was taken.

Genesis 3:16-23

No mention there that Adam's 'sin' affected the whole Universe or even the whole world. In fact, no awareness that there actually was a Universe. The only other species which seems to have been affected is the 'serpent' which gets a curse. There is only the merest hint even that this 'sin' is to be inherited by Adam's descendents even. It's certainly not spelled out with the certainty that Christian fundamentalists like to imagine.

But even if Ken's private version of his 'Holy Bible' were true, wouldn't this apply equally to non-human life on Earth as he says it does to hypothetical life on other planets? Mind you, even Hamsters carefully cultured ignorance of biology would need to go into overdrive to help him pretend there isn't non-human life on Earth, even if the logic of his own argument says there shouldn't be any.

And who was talking about intelligent life anyway? Is Ken preparing an escape hatch here just incase his prophecy is as phoney as that of Ezekiel when he prophesied the destruction of Egypt (Ezekiel 30:10-11) which history shows never happened? Will we be treated to a future creationist fraud confidently telling his audience that only intelligent life is actually living so the living things on other planets don't count?

Ham hasn't thought this through, has he. He's even forgotten now why he had to pretend the Bible said Adam's 'sin' affected the whole Universe. Now he's explaining why it only affected humans. Here he goes again:

Only descendants of Adam can be saved. God’s Son remains the "Godman" as our Savior. In fact, the Bible makes it clear that we see the Father through the Son (and we see the Son through His Word). To suggest that aliens could respond to the gospel is just totally wrong.

An understanding of the gospel makes it clear that salvation through Christ is only for the Adamic race—human beings who are all descendants of Adam.

So, Jesus isn't the saviour of anything non-human so Ken concludes that it can't exist. Er... Ken! Jesus isn't a "Godelephant" or a "Godbacterium" or even a "Godchimpanzee" either. Should we conclude then that elephants, bacteria and chimpanzees don't exist because Jesus can't save them?

In typical Hamster style, he can't help tell a lie about science and what science's aims are either. Remember, Ham's primary mission is to discredit the science he knows is undermining the very foundations of his wealth faith.

Of course, secularists are desperate to find life in outer space, as they believe that would provide evidence that life can evolve in different locations and given the supposed right conditions!

Many secularists want to discover alien life hoping that aliens can answer the deepest questions of life: "Where did we come from?" and "What is the purpose and meaning of life?"

Secularists = scientists, eh? And how would finding life on another planet answer those questions, anyway? Ken wants his audience to think those questions somehow obsess 'secularists' (scientists) because we don't have his glib platitude to save us the bother of asking.

The Creator has told us where we came from: "In the beginning God created the heavens and the earth" (Genesis 1:1; Nehemiah 9:6). And He told us what life's purpose is: "Fear God and keep His commandments" (Ecclesiastes 12:13).

In fact I know of no branch of biology which concerns itself with 'why' questions. There is no reason to suppose there is any purpose for the Universe, for planets or for life on them. These are the stuff of philosophy, charlatan clerics and creationist pseudo-scientists claiming to be able to answer a non question for an audience not too bothered about truth so long as they get a nice warm glow of smug self-importance.

And we know that life arose on Earth by virtue of the simple observation that there are living things on Earth, just as we know that raindrops form in clouds because we can see them. The only thing we are not yet sure of in both cases is the precise details of how it happened and, quite frankly, if we ever find out it will make not one iota of difference to anything very much, so there is no real reason to devote significant time and resource to it. The discovery of a plausible mechanism for abiogenesis will make even less difference to biology than the discovery of the precise details of how raindrops form in a cloud will make to the science of hydrology.

Ken knows the answers of course, because he has it on the authority of ignorant, pre-wheel Bronze-Age people who believed the highest mountains were about forty-five feet high (Genesis 7:19-20), that the sun and moon were lamps hanging from a dome over the Earth (Genesis 1:16-17), that green plants were made before there was sunlight (Genesis 1:11-19) and Heaven was above the stars directly above the Middle-East and within reach of a manmade tower (Genesis 11:1-9). But then Ken Ham is in the business of selling easy answers to ignorant people who are less concerned with truth than with having simple certainties and an authority figure to give them a gloss of respectability.

At least we can see Ken Ham's real worry here - the thought that if life is found on another planet it will show that, in the right conditions, abiogenesis can occur, and if it can occur on another planet it could have occurred on Earth. And so much of creationism depends on their audience swallowing the lie that this is impossible, so creating an unfillable gap in which to sit their god. Ham's 'faith' looks a little shaky on this point.

But to show that life can arise in the right conditions we don't need to find intelligent life or even multicellular life, though that would be good. We don't even need to discover very complex life. All we need to discover is something capable of replicating and of using energy to maintain a degree of order so overcoming the tendency towards disorder, because at its most fundamental level, this is all that life is.

One thing we can be sure of though is that if a simple replicator has arisen on another planet, and has been replicating for a few billion years, as it has on Earth, it will have evolved and diversified and adapted as its home planet changed because this is the inevitable result of a selective environment inevitably selecting in favour of those minor variations in replicators best able to produce the most descendants.

Ken Ham knows this, hence his rather too transparently desperate attempt to stop us finding it out, even needing to invent 'evidence' from the Bible that simply isn't there.

And people still give him money.

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Monday, 21 July 2014

The Sacred Conclusion

Most theists will deny that they do it but it's usually easy to demonstrate that religious beliefs are not based an objective assessment of the evidence but on a received conclusion which is then protected and reinforced by highly selective cherry-picking of the evidence which is often heavily weighted whilst contradictory evidence is minimised, ignored or dismissed on spurious grounds.

'Evidence' can even include assumed evidence such as that 'list of eyewitnesses of the life of Jesus', 'all those fulfilled prophecies in the Bible which have been independently verified', or, in the case in point, 'all the historical names, places and events' mentioned in the Bible. Nothing wrong with these as examples of evidence, of course, apart from just one thing - they are all false. There are no authenticated eyewitness of the life of Jesus; there are no fulfilled prophecies in the Bible which can be independently verified and there are no historical names, places or events in the Bible which give it an authenticity as a holy book.

Quite the contrary, in fact. There are a couple of potential eyewitnesses to the life and acts of Jesus yet none of them mention him. None of the claimed list of authors actually do in ways which have any relevance as a historical source; there are very many demonstrably unfulfilled prophecies in the Bible, and many specific historical events and places mentioned are demonstrably wrong or are simple facts which would have been known to anyone such as the names of major cities and countries, the names of Kings or Roman governors and emperors that anyone writing a story claiming it to be true would have used. Does the name of London and Paris and the historical fact of the French Revolution render the novel A Tale of Two Cities by Charles Dickens a historical source document or the mention of Athens, Sparta, Troy and Macedonia turn Greek myths and gods into historical facts?
This is all, of course, an example of what Peter Boghossian calls 'doxastically closed'. The conclusion comes first and the 'evidence' is filled in later from wherever it can be gleaned without too much attention being paid to its authenticity. It fits the conclusion so it must be right because the conclusion is right. Above all, even the possibility of the conclusion being wrong must not be considered. The conclusion is immune to reason.

This can be easily tested and demonstrated by observing what happens when you show the claimed supporting evidence is false. Just as with a science when the previously accepted evidence for a theory is shown to be false, the intellectually honest - Peter Boghossian's 'doxastically open' - response should be to change the conclusion. In other words, when the evidence changes the honest thing to do is to change one's mind. Is this what we see in religious people?

Take a look at this exchange from Facebook. My original post to the 'Why Atheism?' group was:

Theists! If it's rational to believe the claims in your favourite holy book made by people you've never met, why is it not rational to believe the claims in other holy books made by people you've never met?

The following exchange ensued:

NM: At face value you could be addressing Hindus, asking why Hindus don't believe claims in the Bible... Actually they do. They claim Jesus as their own.

RR: I WAS addressing Hindus. Hindus are theists too. How about you give an honest answer the question instead of avoiding it?

NM: the claims in my "favorite holy book" made by people I've never met contain actual historical names, places and events. The claims in other holy books made by people I've never met do not contain actual historical names, places and events.

Okay, so the Quran does... But it's a plagiarization of my favorite holy book anyway.

RR: Where may we see the verified extra-biblical historical evidence which validates the Bible in ways no other holy book can be validated, please? Hint: the Bible is not evidence of it's own validity.

NM: Name me something historical that's also in the Bible and I'll do a search for you.

RR: Nope. YOU made the claim; YOU prove it. Did you not bother to check first? Do you remember who lied to you?

RR: So you believe the Bible because of all the verified historical facts in it - except you can't think of any and explain how they were verified, by whom and where we can see the evidence, eh?

Now you know the basis for your belief is false, will you be changing your belief or just thinking of some more arguments for it?
MN: I'll ask one last time before I give it up. Name me something historical that's also in the Bible and I'll do a search for you.

RR: Nope. If you can't prove your claim it fails by default. How about answering my question about what you do now your claimed basis for your belief in the Bible has been shown to be baseless? Do you do the intellectually honest thing and change your belief or do you try to think of another reason for it like someone too afraid to change their mind would?

RR: Aaaaand.... no answer.

A confident claim, made on the assumption that it must be true, presumably because he's been told it's true, as evidence that the Bible is unique amongst holy books and the only one to have such roof of authenticity, and yet he can't think of an example nor how it was authenticated. He doesn't actually know what he believes proves his faith; he only thought he knew it. His 'proof' had never even been tested!

And all he has is the desperate demand that I help him with his search or even go look for the evidence for him. The usual excuse to break off the debate quickly follows.

So, does our Christian fundamentalist change his mind, having been forced to confront the fact that his declared 'proof' is false? Of course not. He makes an excuse, assigns blame, guilt and responsibility to me and flounces off. He'll be on another Facebook group soon, offering the same proof and using the same tactic when called on it. It's no different to the insistent claims that there is no evidence for evolution; there is masses of evidence for the existence of God/Allah or that Atheists are rapists and murderers. There is no connection between the belief and reality and given the choice, between belief and reality, reality will be dismissed. It's all a test of faith!

The conclusion is sacred so facts must be ignored.

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Thursday, 17 July 2014

No Bread of Heaven for Creationism

Fiendish wheat genome reveals grain's history : Nature News & Comment

It's been another bad week for the Intelligent Design industry. No wonder their secretive five year 'Wedge Strategy' is now well into it's sixteenth year, during which the number of non-believers in the USA has gone up from about 4% to about 20%, conservative Christianity has become the preserve of the white right fringe and court after court has thrown out their attempts to subvert the Constitution and smuggle fundamentalist Christian extremism into the US public school system disguised as science.

As I explained in a recent blog about the genome of the Norwegian spruce (Christmas tree), one of their lines of attack on Darwinian Evolution is that it always moves from the simple to the more complex - something they imagine they can prove to be impossible with a misrepresentation of the Laws of Thermodynamics. They also habitually misrepresent evolution theory as a theory about the origin of humans. This parody puts humans at the top of some notional 'ladder of evolution' with lesser species arranged on the rungs below and making it look like the TOE says one species (represented by a single animal) spontaneously mutated into another in a single act of speciation (curiously, whilst leaving obligatory fossilised examples of 'transitional forms' as it did so).

So, taking these two together, creationist pseudo-scientists are in effect arguing the the TOE claims that humans are the most complex of all species being the most highly evolved. Evolution theory says nothing of the sort, of course. It's simply that creationists have constructed a ludicrous straw man to attack rather than deal with the real Theory of Evolution. More to the point, the idea that in increasingly complex genome means an increasingly complex organism is nonsensical.

Now, following on from the revelation that the Norwegian spruce has a genome seven times larger than that of humans and a functional (i.e. protein-coding) genome almost twice the size of our 17,000 functional genes, we have news that bread wheat (Triticum aestivum) has a genome more than five times as large as the human one.

Wheat got its large genome by a different route to that of the Christmas tree where the cause was a normally-corrected mistake in the DNA copying mechanism common to most species but in which the error-correction mechanism is broken too. So, over about 120 million years the Christmas tree has been accumulating an ever-expanding genome all to no discernible purpose. Not only would a hypothetical designer have made a fundamental error in the DNA copying mechanism but it would also have designed a broken mechanism for correcting its earlier error.

In the case of wheat, the genome came about by a doubling of the number of chromosomes to give a tetraploid form (i.e., one with four copies of each chromosome instead of the normal two) when two related normal diploid species hybridized to give a new species. This form then hybridized in another rare example of spontaneous speciation by hybridization when the tetraploid form again hybridized with another related diploid form to give a hexaploid genome containing six copies of each of seven chromosomes, giving 42 chromosomes in all divided into six sub-genomes. This is believed to have happened somewhere in the Tigris-Euphrates valley and was the environmental change which probably enabled wheat-based agriculture and urbanization to occur. Bread wheat now feeds 30% of the worlds people and provides 20% of our calories. I've already blogged about this rare example of evolution by hybridization so I'll resist the temptation to upset creationists with is again.

I'll simply point out how the example of bread wheat with its hugely complex genome not only represents all the problems for creationism that I outlined with the Christmas tree example but also gives the lie to another of their lines of attack - the idiotic claim that mutations are always harmful and so Natural Selection will never have an advantageous mutation to 'favour'. Given that bread wheat has six copies of every gene without even considering any gene duplication within each sub-genome, all these spare copies are free to mutate without having any detrimental effect whatsoever. If, however, one of these mutations gives a significant advantage, Natural Selection will ensure it spreads throughout the genepool.

Yes, it's been another bad week for creationism. They must pray for the day when scientists stop producing all this evidence against their daft notion.

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Clearing Up the Unintelligent Designer's Mistakes

Hamilton O. Smith. (Photo: Jane Gitschier ©PLoS Genetics)
I'm homing in on the genetic essence of life - opinion - 14 July 2014 - New Scientist

In an interview published in New Scientist a few days ago, 1978 Nobel Laureate and synthetic biologist Hamilton O. Smith said:

The other thing we want to know is... how much can we rearrange the genes? Evolution has sloppily put them together. A lot of the cell's processes are scattered around. We're putting them together into one neat form.

He was explaining how his synthetic and bioengineering group at the J. Craig Venter Institute in La Jolla, California, USA is using the genome of a bacterium Mycoplasma mycoides to investigate the minimum number of genes needed to function as a viable, living organism.

Their greatest challenge is to work out exactly what DNA is junk, i.e., which has been included over billions of years but which now doesn't serve any purpose. Hamilton Smith estimates that it only needs 400-450 genes to make an organism viable. The other task is to rearrange these genes more efficiently instead of being scattered around the genome in the haphazard and 'sloppy' way they are in M. mycoides.

The aim is to strip the genome down to its bare essentials so it can be used experimentally by adding sequences that allow the organism to live in a different environment, make new substances or use something like photosynthesis. An incidental benefit is that we will discover more about what particular genes do. There are currently some 100 genes in M. mycoides whose function is not understood. Stripping the genome down and then adding or removing these could tell us what they do.

The only reason this is necessary, of course, is because evolution, unlike the design process, is such an unintelligent, utilitarian designer. Just so long as it works and gives the organism some sort of advantage it'll be retained and gradually spread throughout the organism's genepool. It matters not if a gene or group of genes for a specific function is scattered about throughout the genome and it matters not if occasionally chunks of DNA have been accidentally doubled to give two or more copies of the same gene, one of which can then mutate without being eliminated by making its carrier non-viable.

The only thing that matters is that it works. It's a bit like starting with a car to design a boat and retaining the wheels but reducing the drag by making them too small to function as wheels any more, but keeping them anyway because there is no particular benefit in getting rid of them. Another motoring analogy would be to design a sophisticated engine management system but continuing to fit a distributor and a choke cable. Not the act of an intelligent designer.

The J. Craig Venter Institute is a commercial organisation researching into, amongst other things, biofuels. It's objective is to make money. It's not difficult to see why they are using the knowledge they acquired from the study of Darwinian Evolution and have not opted for the idea currently fashionable amongst the religious right in America - so-called Intelligent Design, in other words, fundamentalist Christian biblical literalism. Quite simply, it isn't a scientific theory with any useful application because it's not based on scientific reality but fundamentalist religious dogma with a hidden political agenda.

It almost beggars belief that politically motivated organisations like the Discovery Institute and the Institute for Creation Research continue to get away with their nonsensical 'Intelligent Design' idea when one only needs to scratch the surface to see how much evidence there is against it. It takes profound ignorance, willfully maintained in the face of such an abundance of freely available information, to avoid seeing this evidence. It's almost as though creationists inhabit a different world to the rest of us - one in which the evidence of the world around them is of no importance.

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Wednesday, 16 July 2014

Altruism and Tits

Long-tailed Tit (Aegithalos caudatus)
Browsing through my Royal Society for the Protection of Birds (RSPB) magazine, Nature's Home, just now I came across a reader's letter asking about something he had seen with nesting long-tailed tits recently. He had noticed that several adults were helping to feed the young in addition to the parents and wondered if this was normal.

It is. It is a lovely case of altruism in one of my favourite birds.

The so-called long-tailed tit - it's actually closer to the warbler family than the tits - is one of the UK's smallest bird. Were it not for it's long tail it would actually equal the size of our smallest two, the goldcrest and the firecrest - also, as it happens, members of the warbler family. Both male and female cooperate in building one of the most remarkable of all bird nests made almost entirely out of cobwebs and lichen, lined with about 1,500 small feathers, and suspended in the small branches of, usually, thorny bushes. The nest is domed and has a small entrance hole in one side. It is elastic and remarkably strong. It needs to be because it will expand as the brood of 8-12, sometime more, grows.

Long-tailed tit's nest. Cobwebs and lichen.
I still remember finding my first long-tailed tits nest and taking one of the eggs for my collection when this was still legal in the UK in about 1957. I carried the miniscule egg home using an old egg-collector's trick when climbing back down a tree - placing it carefully under my tongue and keeping the tip of my tongue pressed against my lower teeth while riding home on my bike. I even succeeded in blowing it! I have even taken an incubating bird out of the nest and put it back in again and it continued to sit tight.

All this is thankfully illegal now but we really weren't aware of conservation issues then and, as a ten year-old inveterate collector of everything from birds eggs, to skulls, fossils, pressed leaves, and bird wings (taken from road and rail kills), adding another egg to my collection was probably uppermost in my mind. It's now illegal to disturb a nesting bird or to take wild bird eggs in the UK.

Anyway I digress.

Part of a winter flock (Japan)
What we have in the long-tailed tit is a lovely example of evolved altruism - something that creationists purport not to be able to understand, even claiming it's impossible for 'selfish' Darwinian evolution to create altruistic behaviour. This is either because they genuinely don't understand evolution or more probably because they are playing to an ignorant audience who like to imagine the only reason for altruism is because of the rewards their imaginary magic friend will give them later.

The obvious fact that altruistic and cooperative behaviour frequently evolved simply because that gives greater success than non-cooperation and selfishness, seem incomprehensible to them, but then the do earn their living selling lies, misinformation and spurious confirmation of their bias to ignorant and self-important people for money. Their failure, feigned or otherwise, to comprehend anything good being done if not for a reward, speaks volumes of creationist pseudo-scientists.


Due to high predation, there is a high nest failure rate. If nest failure occurs after the beginning of May, failed breeders will not try to re-nest, but may become helpers at a nest of another, usually related, pair. In one study, around 50% of nests had one or more helpers. By helping close relatives, helpers gain indirect fitness benefits by increasing the survivability of related offspring. Helpers may also gain greater access to mates and territories in the future. Helpers also gain experience raising young and therefore their future offspring have greater survivability rates.

Males and females are equally likely to become helpers. Parents may allow the care of helpers to be additive to their own efforts, or on the other extreme, they may reduce their efforts with the care of the helpers. Juvenile males have a higher survivability than juvenile females, although the survival rate for adults of the two sexes is the same. Offspring that were raised with helpers have a higher survivability than offspring raised without. Failed breeders that became helpers have a higher survivability than failed breeders who did not. This may be because of the reduced energy expenditure from sharing a nest. This is similar to Acorn Woodpeckers and Green Wood Hoopoes. However, failed breeders that did not help are more likely to breed successfully in subsequent years, so there may be a cost of helping. This may be due to helpers having relatively poorer body conditions at the end of the breeding season, similar to Pied Kingfisher and White-winged Chough. Successful breeders have a survivability rate around the survivability of failed breeders who became helpers1.

  1. Mcgowan, Andrew, Ben J. Hatchwell, and Richard J. W. Woodburn (2003). "The Effect of Helping Behaviour on the Survival of Juvenile and Adult Long-tailed Tits Aegithalos Caudatus". Journal of Animal Ecology 72 (3): 41-99

Next season's altruistic gene carriers
The only requirement for altruistic behaviour to evolve is that it results in more copies of the genes for it than alleles of those same genes which do not support it. In the case of the long-tailed tit, the 'helpers' are almost always the siblings of the parents which have either not bred or have lost their brood to a predator. Long-tailed tits are extremely gregarious and sociable animals with family groups normally banding together into small flocks in the winter. Walk through any UK woodland in winter and you will frequently become aware of a lot of small birds around you, keeping in touch with high-pitched tweets and foraging for small insects.

Because these flocks still stay in contact during the spring and summer, those helping to rear another pair's young will have a high probability of carrying the same genes as the young they are helping to rear. It has been shown that broods reared with helpers will be larger and more successful than those reared without help. There is no mystery to it because one thing follows inevitably from the other. Altruistic behaviour produces more copies of the genes for altruistic behaviour than non-altruistic behaviour produces copies of those genes for non-altruistic behaviour. There is no morality involved and no conscious decision to be kind. The genes for altruism are no less 'selfish' than they ever were.

Selfish genes produce altruistic behaviour if this results in more copies of themselves and in an otherwise weak and vulnerable, highly predated species like the long-tailed tit and humans evolving in leopard and lion country, this is usually the case. An example of evolved moral behaviour.

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Tuesday, 15 July 2014

A Message From 270 Million Years Ago

Amphibians' swim stroke has lasted 270 million years - life - 15 July 2014 - New Scientist

Fascinating pictures of 270 million year-old fossils tracks from the Alps were published today, sadly most of them behind a paywall. They show the tracks laid down, probably by a salamander, as it paddled across a shelving patch of mud from shallow into deeper water and eventually taking to swimming. This is the first recorded instance of the transition from walking to swimming.

Exceptionally preserved Early Permian tetrapod trackways from the Orobic Basin (Central–Western Southern Alps) offer a unique opportunity to investigate in detail locomotion in fossil vertebrates that lived on continental European landmasses. Herein are reported the results of a study on several tetrapod trackways that display a large variety of behavioral, gait and substrate related extramorphologies. They clearly document the transition from terrestrial–underwater walking to swimming and are assigned to the compound ichnotaxon Batrachichnus C Lunichnium. The use of the “C” symbol is here introduced for the first time as nomenclatural indication of a Compound trace. Producers were probably small-sized temnospondyl or lepospondyl (microsaurs) amphibians. Comparisons with living urodelan anatomy and mechanics provide evidence for conservatism of locomotor mechanics in evolutionary history among amphibians. The derived model for locomotor kinematics in Early Permian amphibians provides a reference for interpreting transitional land-to-water trackways. The shift from walking to swimming behavior in early tetrapods, as in extant urodelan amphibians, is described as a complex balance between different dynamics.

Fabio M. Pettia, Massimo Bernardia, Miriam A. Ashley-Rossc, Fabrizio Berrad, Andrea Tessarollod, Marco Avanzinia;
Transition between terrestrial-submerged walking and swimming revealed by Early Permian amphibian trackways and a new proposal for the nomenclature of compound trace fossils;
Journal of Palaeogeography, Palaeoclimatology, Palaeoecology, P. 278-289 DOI: 10.1016/j.palaeo.2014.05.032

To begin with, the salamander was dragging its tail, showing the typical wiggling gait of salamanders and most tetrapodal reptiles which causes their tail to describe a series of curves. As it transitions to swimming all we have is the marks of the claws and the swirls left in the mud by the swimming motions.

This calls to mind something I was discussing only yesterday - how humans may well be the only species which can look at tracks like this and 'read' the information and build a narrative from it. We can see what I've described above, for example, how the salamander moved from shallow to deeper water and transitioned to swimming as it entered deeper water. So we know it could both walk and swim and was very probably semi-aquatic.

We can tell how big it was, that it had a long tail and that it walked with the typical wiggling gait typical of salamanders and lizards. This means we can begin to build an image of its basic body plan and especially how its limbs were attached to the rest of its skeleton.

Unlike mammals, dinosaurs and birds and the small mammal-like reptiles that survived the dinosaur mass extinction and evolved into mammals, the limbs of amphibians and lizards stick straight out from their body, then bend downwards at the elbow or knee joint. In birds, mammals and dinosaurs, the bend occurs at the joint with the pelvic or shoulder girdle. This means the spine can be kept in a straight line when walking, running or swimming and the weight of the body is supported on (normally) four limb with little muscular effort. Reptiles and amphibians need to use energy just to lift their body off the ground.


In typical early tetrapod posture, the upper arm and upper leg extended nearly straight horizontal from its body, and the forearm and the lower leg extended downward from the upper segment at a near right angle. The body weight was not centered over the limbs, but was rather transferred 90 degrees outward and down through the lower limbs, which touched the ground. Most of the animal's strength was used to just lift its body off the ground for walking, which was probably slow and difficult. With this sort of posture, it could only make short broad strides. This has been confirmed by fossilized footprints found in Carboniferous rocks.

So, we also know from that wiggly tail trace that the maker of those tracks belonged to a clade which may have been ancestral to our own but was not a member of our clade. A clade being a group that share a unique common feature. If we arrange species according to the features they have in common we end up with an evolutionary tree showing how we are related. It's fascinating to think that a little newt wrote all that information in the mud 270 million years ago and we can now read it. Our highly developed pattern-recognising ability and our deep-seated desire to tell the story allows us to read and understand that message and build a picture of its author.

These basic abilities have probably made us what we are today and created conditions in which evolving a brain capable of processing and interpreting this information and even relating it to others, especially our children who so can inherit our knowledge and stories, gave us a significant advantage over other evolving hominids in African and possibly Euro-Asia and allowed us to become the dominant and ultimately the only hominid.

Unfortunately, our ability to see patterns frequently where there are none and to invent stories to explain them, probably caused us to invent religions as simple narratives to explain what we did not understand. Some people are still unable to let go of the simplistic certainties that these simplistic explanations give them and accept that the real story was far more complicated and far more magnificent than pre-wheel Bronze-Age hunter-gatherers and nomadic goat-herders could ever have guessed.

So important is it to cling to these simple certainties that some people even go out and kill people who have a slightly different version of the same invented story.

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