Its Avian Friday: Gavia immer

(Picture used http://www.alaska-in-pictures.com/gavia-immer-4841-pictures.htm)

Now that I live in the great North, and near the ocean, the Common Loon (Gavia immer) is a great deal more common to me. Of course on can see them on any body of water across the US, I see them more now that I did when my excursions into the field were in the Mid-West. It is one of the more evocative and elegant birds to be found in the US. Its haunting call in the evening can make any person's day (birder or not). It seems to encapsulate everything that humans find appealing about the wilderness.

The evolution of loons (Family Gaviidae) has resulted in a group of birds that are more at home in the water than they are either in the air, or on land. Their flight always appears somewhat labored, and on land they can have a great deal of trouble walking. The aspects of their anatomy that make them ooze through the water at great speed, that make them hydrodynamic I suppose, do not make them equally aerodynamic. Increased optimal design for life in the water means trade-offs in other areas. Their feet set back at the end of their heavy tube like bodies, mean great propulsion through water, but make walking on land difficult to say the very least. The costs of these trade-offs must be minimal, which is another way of saying the benefits of life spent almost entirely on the water outweigh the costs of not being able to move well on land, or as effectively through the air.

Right now the The Common Loon is not in its breeding plummage, but they are still elegant. And one can see them with ease at numerous sites around Casco Bay. A good pair of binoculars and they can be seen regularly around Mackworth Island.

Answers Not In Genesis: Where are the uniform genetic bottlenecks predicted by Noah's Flood?

One problem facing the fundamentalist, biblical creationist is the relative tractability of the predictions the Book of Genesis makes when taken literally. The timescales are relatively short, and the events depicted in Genesis, if taken literally, are dramatic enough that evidence for them would not all be washed away in deep time. These predictions form quite easily falsifiable hypotheses. That is to say they are the very kinds of claims that science is most capable of assessing. Also, the predictions are all fairly obvious. So if there really is a Creation Science where is this relatively easy, publishable research on these problems that are so amenable to the scientific method? That is sort of a trick question, because the predictions of a literal reading of the Book of Genesis have already been falsified by science. Of course you would not know this if you only listened to folks like The Institute for Creation Research, or only hung out at the ridiculously unscientific intellectual pride of Kentucky, the Creation Museum. No creationist organization is really very interested in actually doing science. That may seem like a harsh generalization but I invite you to go to their websites, and read their literature and draw your own conclusions. What is called Creation Science is simply a lot of hand waving and special pleading to exempt a cherished dogma from the rules of evidence. They exist to defend the faith even at the expense of the truth. For the creationist this may be good thing. There is simply no research left for them to do.

In the Beginning....God smote genetic diversity
Taken literally, the book of Genesis makes several very specific predictions about the genetic diversity of all life on earth. Here is one very specific prediction that we can derive from Noah's Flood concerning the genetics of all life on earth.

1. All life on earth passed through a very narrow population bottleneck around 4,500 years ago.

2. All species were dramatically reduced to very few in number.

3. All terrestrial, and some semi-aquatic animal species were reduced to either 2 individuals, or 14 individuals.

4. Therefore all terrestrial/semi-aquatic animal populations should demonstrate a very uniform genetics.

5. Variation in this uniform genetics should be able to be traced back to around
4,500 years ago (within a reasonable margin of error).

6. All animal populations should demonstrate the presence of extremely small
populations at the time of the population bottleneck (at least <50).

7. Organisms not deliberately transported on the Ark also would have experienced
a massive population crash, and would also demonstrate marked genetic uniformity
that could be traced back to 4.500 years ago (within a reasonable margin of
error).

I will explain what a population bottleneck is and what consequences it tends to have on a population in a moment, but first....

A brief aside about DNA, genes, and mutation:
I'm going to be using some shorthand in the following paragraphs, and it may help you, if you aren't steeped in biology to have a refresher of your long forgotten high school biology. Genes are stretches of DNA (deoxyribonucleic acid) that code for some cell product, cytochrome-b say, or some other protein. DNA itself is a long two stranded polymer of nucleic acids composed of adenine, guanine, cytosine, and thymine, (A,G,C and T respectively)that forms the classical double helix (think of a ladder that has been spiraled around itself, still linear, but twisted). The nucleic acids form the rungs of the ladder, and every three letters in a gene (a segment of the DNA that codes for some product) is a specific code for a specific amino acid. So in a gene the triplet thynine adenine cytosine (TAC) codes for the amino acid methionine. Other triplets code for other amino acids. Mutations are errors of DNA replication. These errors alter the code, sometimes subtly and sometimes dramatically. The DNA triplets TAC and TCC do not, for instance, instruct a cell to utilize the same amino acid.

When populations diverge, genetic variation between the populations begins to build if there isn't a great deal of interbreeding between them, so their common genes will reveal differences in their sequences of As Ts Gs and Cs (and the triplets they make). No population will have the exact same sequences for the same gene (indeed there may be many different versions of a gene). For instance, different populations of humans may have significant differences in their genes for the manufacture of the structural protein keratin. To establish a reasonable estimate of when these varieties diverged, we need to know the mutation rate for the gene in question (the rate at which the nucleic acid codes are altered and how often those alterations are uncorrected, plus the generation time for the species in question) we need lots of sequence data from numerous populations, and we need powerful modern computers to perform the rather large analysis/comparison of the sequences and their differences.

I am intentionally leaving out the role of RNA (ribonucleic acids) in this, but I don't think we need to wade too deeply into transcription and translation, and protein synthesis. For our purposes what you need to is some knowledge of what a gene is, how it is altered and how examining those genes and their sequences actually gives scientists quite a window into the history of divergence of the genes (and thus the populations) in question.

Population Bottlenecks
A population bottleneck is simply any event that, more or less randomly, and significantly reduces the size of a population. Any such reduction in population size will also result in a reduction in that population's genetic diversity as well. It is also unlikely that the survivors of any such event will be carrying a representative sample of the genetics of the population as a whole. This is why population bottlenecks are also often referred to as genetic bottlenecks. A significant loss in population size will translate to a significant loss of genetic diversity. On one side of the event any sampling would reveal high numbers of individuals and high genetic diversity (as measured in the diversity, and frequency of alleles for given genes) and on the other side of the bottlenecking event sampling would reveal low numbers and low genetic diversity.

Perhaps the best way to illustrate this would be through a simple example (that I think I am stealing from my old Population and Community Ecology professor, Brent Smith at least in part, lets hear if for Earlham College Biology!).

Say we have a population of 10 lemmings moving up a mountain, or at least a really large hill together, perhaps they are migrating, or emigrating to new land with greener grass. Assume five of those lemmings are male and five are female. In the course of their travels up the hill a large rock comes tumbling down the hill (a mini avalanche caused by hikers pushing boulders down the mountain or hill or whatever) and our large rock crushes all five males who were clumped together for some reason peculiar to male lemmings. We can see with out much effort the kind of disaster this has just had on the population. The population went from possessing five Y chromosomes (any male will have XY sex chromosomes) to possessing no Y chromosomes. It is important to note that a Y chromosome isn't a gene. A chromosome is a specific long strand of DNA, that contains genes. In this example the loss of the Y chromosome represents a significant and dramatic loss of genetic diversity (in this case, all the genes contained on the Y chromosome).

We can see that the random sample that survived isn't representative of the original sample (all our survivors are females bearing only XX chromosomes). It will also be unlikely that each of the females that survived will all be pregnant with each of the dead males, so even if one or two females are pregnant and the population isn't doomed out right, it will still be dealing with very low variation along the Y chromosome, and not just there either. Assume one female was pregnant by one of the males that would give the population one Y chromosome and its alleles (an allele is a variant of a gene). Over time genetic variation would be rebuilt in the population through mutation, possibly horizontal gene transfer (don't worry about it) and the process of genetic recombination that occurs when sex cells (sperm and egg) are made. We probably needn't go further than that.

My hypothetical lemmings (or Brent's hypothetical lemmings)illustrates the way in which population/genetic bottlenecks can influence the size and genetic composition of a population, and we now understand that lost genetic diversity would be rebuilt largely by mutation in populations that manage to survive long past the bottlenecking event (in my freakishly simple example, this could only be done if at least one female was pregnant). One more thing to note is that the occurrence of a bottlenecking event would be identifiable to anyone studying our lemmings. Researchers would note a rather homogeneous genetics characterized by very little variation in genes on the Y chromosome certainly and for many other genes as well. It would be possible for our hypothetical researchers, if they knew the mutation rate for certain genes (the rate at which the strand of DNA in the gene is altered), to calculate an estimate of how long ago different versions of our hypothetical lemming genes (alleles) diverged by comparing target genes across the population. That is they could examine and compare the variation in target genes, typically highly conserved genes (which is a technical way of saying genes that change slowly over time due to crucial functioning of their products). A conserved gene is simply a gene that isn't free to alter too much or too rapidly because alterations in its code tend to have have negative effects on the functionality of that gene's products, which translates to negative effects on the organism bearing such mutations.

With that ground covered we are in a better position to ask whether or not science has found evidence of population/genetic bottlenecks, and if so we can ask whether or not the bottlenecks conform to the predictions of Genesis (that all, or almost all, extant organisms will demonstrate a significant bottleneck with a point of origin around 4,500 years ago).

The answer to the first question is yes. There is no shortage of genetic bottlenecks to be found in nature. However they do not indicate any kind of uniform point of origin. Cheetahs for instance passed through a bottle neck around 10,000 years ago, which is around the tail end of the last ice-age (Menotti-Raymond and O'Brian 1993). Though there is some disagreement over the exact time frame, the range of times given isn't supportive of the 4,500 year hypothesis at all.

Humans seem to have passed through a least one severe population bottleneck, perhaps more. While the matter is by no means settled it seems safe to say that the low genetic diversity among humans does little to support any fundamentalist reading of the Genesis story. The whole genesis account is of course further damaged by the fact that whatever the form of the bottleneck humans faced (Toba disater around 70,000 years ago, or long bottleneck, or some odd combination of smaller bottlenecks, we are left with the well documented human population growth at around 50,000 years ago (Ambrose, 1998). There is no sharp and precipitous population crash from which to recover after that, which is predicted by creationists.

Humans and cheetahs are hardly the only species to demonstrate such population bottlenecks, here is a short list with estimates for the time of their respective bottlenecking events:
Albatross (Amsterdam and Wandering)- >840,000 years ago
Northern Elephant Seal- ~121 years ago
Giant Panda- 43,000 years ago
Golden Hamster- 81 years ago
Orangutan- ~170,000 years ago

We needn't go further really. What we can see from these examples is that the Genesis hypothesis fails pretty miserably in its prediction of large scale genetic uniformity across all phyla, originating fairly recently, and within recorded history. I have never seen this rather obvious prediction discussed among creationist authors. I suspect that curious state of affairs stems largely from the fact that creationists tend not to be biologists but theologists, or engineers if they have any science background at all (not entirely of course). A real science minded creationist would certainly see the merit of what I am suggesting here. Where is this research? It will not be forthcoming. I predict what they will produce when confronted by this will be oodles and oodles of hand waving, and magical, supernatural thinking to sweep away the fact that they have no positive evidence for their hypothesis. I can hear it now:
Well God simply touched up the genetic diversity of many species after the flood.
God gave the organisms only the amount of genetic diversity he, in his loving, merciful wisdom, knew they would need.
Genetic diversity isn't really affected by small population sizes, or events that reduce populations to 2-7 pairs of individuals (Genesis states that Noah took either a single pair of critters, or seven pairs).
It is in evasions like that that intellectual suicide is most easily identified.

A mini-glossary

chromosome A chromosome is a particular long strand of DNA (genetic material, comprised of nucleic acids composed of various genes. Different chromosomes have different genes.

gene A unit of heredity. This is actually defined slightly differently by different groups of biologists. For our purposes we will follow the molecular biologists and say that a gene represents any segment of DNA that, as my Penguin Dictionary of Biology puts it, "codes for cell products." So at its simplest, a gene is simply a strand of DNA that creates something in cells. To say that is a gross oversimplification of the state of affairs is to understate the matter considerably.

allele An allele is a variant of a gene. Variation in a gene is built by mutation, which is to say it is built of random changes in the DNA code that are the instructions for building some product (behavior, structure, protein etc). A good way to think of the matter is as follows. The gene may be formally thought of as a specific region of DNA on a specific chromosome, that "creates" some product. Alleles are the various ways in which that product is coded in different bodies of a given species. Maybe iris color is represented by a specific region of the DNA along some chromosome (the gene) and different bodies in a population will have different forms of that gene, green, hazel, brown, blue (the alleles).

Bibliography
Ambrose, S.H. 1998. Late Pleistocene human population
bottlenecks, volcanic winter, and
differentiation of modern humans. Journal of Human Evolution (1998) 34, 623–651

Arora N, Nater A, van Schaik CP, Willems E, van Noordwijk MA, Goossens B, Morf NV, Bastian M, Knott C, Morrogh-Bernard H, Kuze N, Kanamori T, Pamungkas J, Perwitasari-Farajallah D, Warren K, Verschoor E, Krützen M. 2010. The effects of Pleistocene glaciations and rivers on the population structure of Bornean orangutans (Pongo pygmaeus). Proceedings of the National Academy of Sciences, USA 107, 21376-21381.

http://evolution.berkeley.edu/evosite/evo101/IIID3Bottlenecks.shtml

Dawkins, R. 2004. The Ancestor's Tale: A Pilgrimage to the Dawn of Evolution. Houghton Mifflin Company, New York New York.

Menotti-Raymond, M and O'Brien, S.J. 1993. Dating the genetic bottleneck of the African cheetah. PNAS April 15, 1993 vol. 90 no. 8 3172-3176

Milot, E., Weimerskirch, H., Duchesne, P., Bernatchez, L. 2007. Surviving with low genetic diversity: the case of albatrosses.Proc Biol Sci. 2007 March 22; 274(1611): 779–787

http://en.wikipedia.org/wiki/Population_bottleneck, last modified, 13 June 2011 at 20:17

A long response to Twinkledorp

(I was going to post this in the comment section of the last entry of IDGOFB but blogspot claims I used too many characters. So here is my long response to one of Twinkledorp's posts)

Twinkledorp,
I thought it might be fun to address this as well.

"Just consider me a Skeptic. Whilst you may believe your scinetific methods tell you one thing, I am not going to go on 'faith' and believe evolution is all that you believe it to be."

And what are you going to "go on" to reject the Neo-Darwinian Synthesis? It appears at first that we be both believe that faith is an exceedingly bad thing. Do you really have good grounds to reject the findings of nearly 200 years of biology? If you do I think you should publish them, if you don't (and judging by the reasons you give below, we can see you don't) aren't you really just staking out another contradictory faith claim?

"What others 'know as a scientific fact' is of little importance to me. I have yet to be convinced for a few reasons:"

This could be rephrased to I really don't care what the evidence demonstrates because I have this a priori conclusion from which I will not be budged in the slightest.

"1). Though born Atheist, my free thinking process has lead me to the conclusion God exists, though not the Christian or religious God
that you might assume I may be referring to."

Interesting, but essentially content free. Your "free thinking" is meaningless if it isn't backed by some form of verifiable evidence. You could be absolutely, completely, devastatingly correct in every way, and everyone would be absolutely correct to reject your new paradigm if you cannot adduce anything to back it up but your thought, and your, ahem, logic.

"2).
During darwin's time, Science and Religion were at war. Scientists were scratching at the bit to 'give ot to' the Religious folk and there was no way in Hell they were going to have God play any part in the evolutionary process were thus 'intelligence in design' had to be excluded from their conclusions."

Actually this is precisely the opposite of true. Lyell, the great geologist and good friend of Charles Darwin was a more or less orthodox religious man. He, in fact, seemed to hope that Darwin was wrong despite being a very great admirer of Darwin's work. But Lyell also was one of the first to realize how mind-numbingly old the Earth really was. Alfred Russel Wallace, co-discover of natural selection with Darwin, maintained a belief in God (a god of some kind any way) because he simply couldn't think of a way humans could have evolved. I could go in this way for some time. Darwin was probably the only textbook atheist in the bunch (though he was't always so, and his theory of evolution by natural selection probably had less to do with his loss of faith than did the problems of theodicy).

Also while you may say that scientists were "scratching at the bit" (I think you mean tugging at the bit, or chomping at the bit) to, as you so elegantly say, "give ot to" religionists, this seems largely false. Darwin, at least, waited decades to publish because he was sensitive to the injury it would/might do to people's religious sensiblities.

Most of the scientists of Darwin's time would have been believers who didn't take the scriptures literally, they, like many a scientist before them were curious about the true nuts and bolts of God's creation, not what they considered the metaphors of holy books. What is true is that religion has always had an uneasy relationship with an honest pursuit of the truth because it so easily makes canards of holy canon. So, probably as far back as Hypatia (and I would imagine even further) to now, clerics pitch a fit when cherished dogma is challenged by the rigorous findings of any science.

Also there has, as yet, been no need, nor any evidence that would imply an "intelligence in the design" of things. It all just looks like one example after another of "survival of the stable." Which is a great, if simplistic, descriptor (not my coinage) of the natural world.

Also, this is all incredibly irrelevant. Whatever the case was in Darwin's time has no real effect on the science that took place after. The evidence is what the evidence is, and it was compiled by believers, unbelievers and agnostics, and it all seems to support evolutionary biology.

"This poses a massive credibility problem and therefore any conclusions drawn should be taken with a grain of salt. After all, the main objective at the time (which continues today) was winning the war with Religion therefore objectivity was sacrificed in the name of 'Victory'."

There was no war on religion, as I stated above. Scientists just work on their problems, and often unwittingly step on cultural landmines. Scientists are comprised, as I said above, of believers and unbelievers of every stripe. One of the most comprehensive efforts at public understanding of evolutionary biology, and explaining the evidence that supports it was written by a fairly standard god-bothering Christian. The book (excellent by the way) which you should definitely read is Evolution: What the Fossils Say and Why it Matters by Donald Prothero. Its kind of pricey but it will give you one of the best overviews of the state of evo-bio, probably not offend you, and provide plenty of papers for you to track down and read from its literature cited section.

Sorry Max11.

I doubt this very much. Its Max II not, 11.

Evolutionist will need to do a bit of evolving themselves to ensure objectivity and good old common sense in their work unless of course you believe houses are built without blusprints, and people speak 1st and then think, which in your case I could almost be convinced is true.

Objectivity in the pursuit of scientific discovery arises from transparency of experimental design and the replicablity of results. Not from worrying over much about the kinds of thoughts particular researchers have about the status of the universe. Incorrect findings, errors, fraud will be discovered with time and research.

And common sense is useless in science. It leads more often than it does not to rather severe errors. Our common sense fails when it is put to the task of thinking about deep fundamental aspects of nature, human nature included, because nature is vastly weirder than our day to day lives.

Stop by and visit my site anytime.

Do leave a url and I will.

"Twinkledorp Peabody IV."

Fascinating name.

Happy Birthday Richard Dawkins!

Here are some great clips to watch as you tip a glass of something to the great explainer of evolutionary ideas.

Answers Not In Genesis: Biodiversity Dooms the Cruise at the Outset.

(Clicking on the title of this blog will direct you to E.O. Wilson's magnificent, brainchild, the Encyclopedia of Life. There you can see in a clear way, the begining of Noah's problem)

The story of Noah's Ark isn't very charming. But I would be willing to bet that it has been responsible for more than a few rejections of biblical literalism, because even a cursory knowledge of the Earth's biota leads one to the following conclusion. No matter how one interprets the length of a cubit, unless that estimate describes a sphere with an equatorial circumference of 40,075.16 km there would probably not be enough space. It gets worse though when you add all the extant species with all the extinct ones. And this we must do because most biblical literalists think that humans, indeed all organisms, have existed for as long as the earth has. This means that , as the comedian Lewis Black memorably said many fundamentalist Christians believe that “the Flintstones was a documentary.” According to this view all of life as revealed by human observation (and numberless species that we have missed) have all existed together and was created some six to seven thousand years ago. This is a fairly sweeping dismissal of geology and the sweep of natural history that it has revealed.

Imagine this timeline with no lines and calibrate the starting date at 7000-10,000 years ago. That is what the history of the world looks like to Young Earth Creationist (YEC). No epochs or periods, no eons, or eras at least not as a modern geologist understands them.¹

The geology needn’t concern us at the moment as we tackle the immediate problems faced by Noah and his paltry crew of eight. What we need is perspective. How big was the Ark? According to the biblical account the Ark would have been about 450 ft in length, approximately 75 wide, and about 45 ft high. Assuming a simple rectangular box (exactly the kind of thing it couldn’t have been) that gives a volume 1.519 x 10⁶ ft cu. The ship was to be built of something called gopher wood. No one has any real idea what this might be. It could be a mis-translation, odd common name for a common tree, or timber after processing there is no consensus among the literalists. There is also no consensus among the literalists about what the boat would look like. It was to have rooms, apparently a single door and a single opening for light. No doubt translations vary on the details. It was to have rooms. Beyond that….well your guess is as good as mine.ⁱⁱ


But now that we have somewhat established the design space of the Ark we can move on to the second major hurdle he would have to face, namely the biota.

Biodiversity defeats Noah, his Ark and God.

To get an idea of the challenge that faced Noah and his tiny crew we must begin in Genesis where God gives instructions to Noah, though perhaps not very clear ones.

Genesis 6:19 You are to bring into the ark two of all living creatures, male and female, to keep them alive with you. ²⁰ Two of every kind of bird, two of every kind of animal and of every kind of creature that moves along the ground will come to you to be kept alive. ²¹You are to take every kind of food that is to be eaten and store it away as food for you and for them.”

Almost straight forward, but then God adds to the problems in the next chapter.

Genesis 7:2 Take with you seven of every kind of clean animal[ NOTE: According to the New International Version of the bible this seven means seven pairs] , a male and its mate, and two of every kind of unclean animal, a male and its mate, ³and also seven of every kind of bird, male and female, to keep their various kinds alive throughout the earth.

Emphasis added

Noah presumably would have had little trouble identifying clean verses unclean beasts but there appears to be a small discrepancy between Genesis 7 and 6 concerning exactly how many animals he is supposed to have brought on his trip. Is it a pair of birds, clean animals (are birds clean I wonder?) or seven pairs? The difference will not be trivial. There are for instance 9000-10,000 species of extant birds. And Noah must take every kind of food too for himself and for the creatures in his care. Noah might have thought to suggest that God enact a more species specific smiting and save both he and God a lot of odd trouble.

What is a Kind or Why don’t Creationists have a consistent taxonomy?

A problem faced whenever talking to YEC is the fact that what represents a kind consistently waffles as you pin them down. The field of endeavor that is fundamentalist field of pseudo-intellectual endeavor responsible for all this waffling is called Barminology. According Carl Drews (2010), a biblical kind is any of an informal classification of animals and plants but that the term kind most likely refers to something between the genus and species level. The Northwest Creation Network suggests, rather baselessly that kind refers to Family level classification. The fundamentalist pseudo-scientific field of endeavor that is responsible for all this waffling at the apex of bad science and bad philosophy is called Baraminology. The word is derived from two Hebrew words, bara, created, and miyn, kind (Cracraft 1984, Drews 2010).

It would be hard to find a more confused effort than baraminology, just as it would be hard to find a more confused group of researchers than baraminologists. According to the Duane Gish, one of the early, and vocal YEC leaders, a kind can equate to a species, or a it can sometimes equate to the level of the genus. How a kind lines up with modern biological systematics depends on whether a plant or animal (it is always plants or animals with the people no thought given to the microbes) is “truly derived from (presumably by special creation) from a single stock (Gish, 1979).” Joel Cracraft (1983) has stated that YEC is really inconsistent on the whole matter of what constitutes a biblical kind. At times creationists claim that it is the capacity to produce viable offspring is that which constitutes a biblical kind. That would make biblical kind equivalent to the concept of the biological species. A biological species is any phenotypically similar group of interbreeding or potentially interbreeding individuals. Sometimes biblical kind is defined as ability to produce offspring and never mind about viability or reproductive isolating mechanisms. Amusingly, a single barminologist will sometimes contradict themselves by saying both things. Or worse yet they will say something mind numbingly indefensible. Gish (1979) said this of baramins:

We cannot always be sure, however, what constitutes a created kind. The division into kinds is easier the more divergence is observed….within the vertebrates, the fishes, amphibians, reptiles, birds and mammals are all different basic kinds. …Within the mammalian class duckbilled platypus, opossums, bats, hedgehogs, rats, rabbits, dogs, cats, lemurs, monkeys, apes and men are easily assignable to different basic kinds. Among apes, the gibbons, orangutan, chimpanzee, and gorillas would each be included in a different basic kind. (Quoted from Cracraft)

Here, Gish has managed to confuse the issue even more by introducing a strange new construct, the basic kind and essentially says it can be anything he wants it to be. It can be a class, mammals for instance, or it can be something as specific as a hedgehog. Struggle for a moment, if you will, to imagine a more useless theoretical construct than "basic kind."

The discipline has not really advanced since the heady days of Duane Gish and his 1970s ilk. As evidenced by the recent papers published by the Baraminology Study Group in their journal Occasional Papers of the BSG they, like all YEC, are not really interested in an honest examination of nature, but rather on imposing their world view on it. Sanders (2010) has worked very hard to ignore modern biological systematics while appealing to human intuition to create a new system for organizing kinds (he examined five groups of plants) based on pre-cladisitic, pre-molecular authorities. His method did not alter the traditional groupings by much and hinges on a fairly arbitrary metric, and the baseless assertion that it is preferrable to evolutionary analysis. From his conclusion:

It is thought that the cognitum is biologically significant because God created organisms to be perceived by humans who were created to recognize and
sort easily by “gestalt.”

Whatever that reasoning maybe it certainly isn’t scientific (it suggests any grouping is simply the way it is because God arranged it that way and has nothing to do with evolutionary processes-ignore whatever trends you see folks). But that really should not surprise us, because all vocal claims to the contrary, YEC and its pretentious sister Intelligent Design (ID) are not scientific endeavors. All of these specific YEC organizations BSG, The Discovery Institute, and Answers in Genesis all have statements of faith that employees must adhere to and that guide their research (such that it is). They all already back an a priori conclusion and their work can only support that. That they incapable of entertaining evidence contrary to their position almost goes without saying. But more about that later (though if you are interested you can click on the links and see these statements of faith).

All this fundamentalist hand waving about kinds does little to reduce the actual number of animals Noah would have had to wrangle, and it also tends to flout a general quirk that appears to be universal to human psychology. The American paleontologist Stephen J. Gould memorably wrote about the phenomena in an essay titled “A quahog is a quahog.” In it he describes the definitions, the limits of the definition of a species, and notes that almost all humans recognize species whether they are of the Western scientific tradition or organize their classification along indigenous or intuitive lines. Gould probably wasn’t the first to notice, and he certainly won’t be the last, that indigenous peoples classifications of organisms match almost exactly modern biological species level classification. Jared Diamond and Ernst Mayr, experiencing the phenomena through their ornithological expeditions, have both written about their firsthand experience of this during their work with the indigenous peoples of New Guinea. The number of species identified by modern biology and the people of New Guinea differed by only one (owing to the certain techniques of biological specialists). Humans are natural species identifiers and the vast literature on the subject of ethno-biology demonstrates this fact again and again (much to the consternation of many a post-modernist and creationist alike). Cultures from all over the world recognize the same criteria, and base their categories on things like ability to breed, and morphology. Everyone's folk biology is similar (Pinker, 2007), thus it is likely that people who told the stories of Noah certainly recognized the same "kinds" as we do today.

So at root the ambiguity in which the creationist deals is likely a subterfuge (either conscious or unconscious). The subterfuge represents an unwillingness to deal with the large number of species/kinds Noah would have certainly recognized. Even the phrasing in the relevant passage s doesn’t admit of all the vagueness creationists present, which suggests (by the emphasis on bring male and females) something very like the biological species concept. Noah then was faced with one more impossible task, wrangling at least more than a million species, perhaps as many as 50 onto a single boat. The good news for him, apparently is that many of these animals would come to him.

While reading that last paragraph many of you probably thought of animals that would have posed serious problems for Noah. Koala (Phascolarctos cinereus) always spring to my mind. They have a very restrictive diet (the bulk of their calories come from eucalyptus leaves) are nocturnal and largely sedentary. I am unsure how hardy this species is, but their diet of course would have been impossible for Noah to imitate, the biology of the animals themselves precludes them traveling to him as well as the intervening geography? Polar Bear, Ursus maritimus is at least an equal zoo keeping problem, though they are at least used to surviving long periods without food. Polar bear diets are also hyper carnivore diets so Noah had better have had some meat. Housing an animal that can easily over heat even in cold temperatures on an overcrowded ship seems an unlikely feat without serious climate control technology. In these two examples Noah faces some pretty dramatic problems posed by two specialist species. The problem is imitating the diet and climate of ecological specialists. I bet you just thought of some more troubling species for Noah and his hapless crew. How about American Bison, Bison bison? Or Capybara Hydrochaeris hydrochaeris?

Seismosaurus, African Elephant, and the American Mammoth: A damning thought experiment.

This is going to seem ridiculous but creationists think all these animals co-existed (still co-exist in fact) so this is entirely necessary. I have no idea whether or not these creatures would be considered clean or unclean by Noah, but in single pairs or seven pairs it is all going to get a bit funny.


TheAfrican Elephant, Loxodonta Africana is an enormous animal. Weighing five to six tons (10,000-12,000 lbs) and standing three to four meters at the shoulder (males average around 3.75 m and females 3 m), an African elephant takes up a great deal of room (and two of them take up twice as much space as that). It has been estimated that an African elephant consumes about 661.38 lbs of food a day in the wild and 100-300 l of water. You have to see where this is going right? Sure you do, but I’ve done the math for you. Two elephants would require about 52,910.4 lbs (~26.5 tons) of food for their trip. A lot of this food will, of course, have to be off-loaded over the course of their time at sea as it will present itself at the other end. To give Noah a break let’s assume that he could have gotten by with 200 liters of water per elephant, that would mean he still had to bring 16,000 liters of water on board for the African Elephants alone. The amount of space required for the food and water to sustain these animals is several times that of holding the animals themselves. This is the case even if we assume some great packing efficiency of the elephant foodstuffs (think hay bales). Tangentially, but more interestingly, this is the reason Elephants, who travel in herds, migrate around Africa. Their ecological foot print is large and they quickly exhaust local resources and have to move on to greener pastures.

The Columbian Mammoth, Mammuthus columbi, another kind of elephant wandered the Ice Age wilds of North America and remains one of the most evocative of the late Cenozoic megafauna. It was quite a bit more robust than its African cousins, trending larger and heavier, and carrying much more massive tusks. While these animals trended larger than their African cousins, lets conservatively assume they could have gotten by for the trip on the same amount of food. That means we are adding another ~26.5 tons of food to the ship’s cargo hold for the forty day/forty night trip.

(Picture taken from planetdinosaur.com.)

Diplodocus hallorum, (also referred to as Seismosaurus) is a large species of long-necked sauropod dinosaur, that roamed the Earth in the Jurassic period would have posed an even bigger problem for Noah. D. hallorum, one of the largest of what are referred to as the diplocine sauropods, likely tipped the scales at around forty tons. Forty. Tons.. I’ve come up with a conservative estimate for what their dietary demands might be for such a trip. A pair of D. hallorum would require about 169 tons of food to see them through the cruise. Seven pairs of D. hallorum, if for some reason Noah held them to be clean beasts, would require 1,185.1 tons of food. And let’s keep in mind that D. hallorum wasn’t the largest of the sauropod dinosaurs with Noah would have to find room for on his boat. Looking at the image below (clicking on it will enlarge it)will help you to understand that for all of its size, D. hallorum wasn’t even the biggest sauropod Noah would have had to deal with. Hint, Diplodocus isn't the red dinosaur.
(image taken from Wikipedia)

To recap, and to be conservative, just three species, an African elephant, a new world Mammoth, and a Jurassic sauropod, will not only occupy space with their rather large bodies, but they will also take up enough space for, at the very least, 196 tons of food. Noah probably would have had all the water he needed given the alleged precipitation he was receiving. However that 196 tons only gets Noah and his intrepid explorers through the only forty days (and only for three pairs of gigantic megafauna). Multiply the problem by several million to account for all the other animals and you get a sense the ridiculous problem the Biblical literalists have created.

If the flood happened, the deluge described would have resulted in an ecological collapse worse than any extinction event that preceded it. This means that the amount of time Noah would have to care for the animals would extend well beyond the cruise, and into years of care, if not actually becoming a project of generations. So the question of course becomes this. How much food can the boat carry in addition to space it must necessarily dedicate to the animals it has to house? I don’t think I am pushing my luck when I suggest that the answer is obvious, and damning for any literal interpretation of the Flood story. There is simply no way that Noah could have carried enough food to sustain the animals for decades to centuries.

Worse still for creationists is the fact many facets of their “hypothesis” are utterly and easily tractable. A massive collapse of ecosystems four to ten thousand years ago? Easy. Massive dispersal of species from a single point four to ten thousand years ago? Easily tractable, and amenable to scientific analysis. Where is the universal genetic bottlenecking that we should see demonstrating extreme population crashes four to ten thousand years ago? This is a subject to which we will return in later installments.

Literature cited:
Cracraft, Joel. 1984. Godfrey, L.R. Ed. Scientists Confront Creationism: Systematics, Comparative Biology and Creationism. W. W. Norton, New York.

Diamond, J. 1992. The Third Chimpanzee: The Evolution and Future of the Human Animal. Harper Perennial, New York, New York.

Diamond J. 1997. Guns, Germs and Steel: The Fates of Human Societies. Norton, New York, New York.

Drews, Carl. 23 February 2010. Biblical Kinds. http://www.theistic-evolution.com/kind.html

Lectures in Biology, 2007. Geological Timetable…Pre-cambrian Era. http://biology-g10p.blogspot.com/2007/01/geologic-timetable.html

Pinker, S. 2002. The Blank Slate: The Modern Denial of Human Nature. Viking, New York, New York.

Sanders, Roger W. 2010. A Quick Method for Developing a Cognitum
System Exemplified Using Flowering Plants. Occasional Papers of the BSG. 16:1-63

Wikipedia. 3 December 2010. Young Earth Creationism. http://en.wikipedia.org/wiki/Young_Earth_creationism#cite_note-0

Endnotes
1 YEC isn’t precise where estimates of the age of the Earth, or the Cosmos are concerned. Much hinges on how begats are tallied and added, or on whether one accepts the Jewish date for Creation (set at 3670 BC), or, perhaps more absurdly, by adding the ages of some of the long lived patriarchs found in the Bible, and combining those calculations with those of the begats. It is all obscure and none of it is scientific. But the ages range from the mid-5,000 BCs to 10,000 BC. The most common figures I have heard give an average age of about 7,000 years. What is never adduced in support of these figures are facts from nature.

2 Establishing a reasonable estimate of the size of the Ark isn’t too tricky. It was said to be 300 cubits long, 50 cubits wide, and 30 cubits tall. A cubit is apparently 45.7 cm (about 18 in). From there is all a matter of lwh to determine the volume. At first glance this gives an enormous amount of room. Some creationists will, doubtless marvel at the amount of volume such measurements provide. It shouldn’t because the Ark wasn’t a box, but a ship. If you are a creationist, contain your enthusiasm because I am about to dowse it. Most of this space would have been consumed by superstructure. Struts, cross support, rope, rooms, decks (my copy of the Bible suggests there were three decks), all would have very quickly used up vast amounts of this internal space. However well before that, we must consider that the largest wooden ships ever built were 350 ft long, were manned by large crews, needed massive amounts of metal work to support the wood, and leaked. These ships needed to be pumped constantly to keep them afloat. The Ark had only a crew of eight, and if we are to believe the literalists, millions of species for which they had to care in addition to all the ship maintenance to perform. Of course there is the engineering problem of eight people building such ship to contend with even before we have starting pumping out the water.

3 Calculating Mammoth and Diplodocus food needs.
I used the modern elephant’s dietary needs and extrapolated from there. I am assuming that the modern picture of the dinosaurs (that they were “warm-blooded” animals) is the correct one. I conservatively assumed they would have similar, just larger daily food intake requirements. A diplodocus (Seismosaur) is about 640 % larger than an elephant, so I simply increased their requirements by that amount. To say that is a simplified extrapolation would be correct. Simple or not, I think it is a fair and conservative one. I used the same technique to derive an estimate for the mammoths.

Dog lovers can gloat...

A new paper in the Proceedings of the National Academy of Sciences, (S. Shultz, R. Dunbar, 2010) appears to demonstrate something that has long been suspected. The debate about the evolution of brain size, and thus intelligence and consciousness has been over the question of whether or not encephalization was universal (that is to say most lineages exhibited it) or whether the evolution of brain size affected groups differently and was correlated with certain biological and ecological factors. What Shultz and Dunbar demonstrat in their paper is that highly social species tend to have larger brains than solitary species.

This isn't entirely earth shattering of course. Because on one level it has been rather obvious that evolutionary encephalization (increases in brain size relative to body mass) hasn't been exactly uniform across the mammals. Predators have larger brains than their prey. Social species tend to have larger brains than non-social species. Omnivores tend to have larger brains than specialists. However researchers have, up to this point, drawn their conclusions by comparing extant species. What is unique about the current research is that it examines encephalization within evolutionary lineages rather than between extant species.

Click on the link to read the Sciencenet Daily summary. Also you can, and should read the abstract.

A Brunch Film Review: Avatar Part II: A biologist examines Pandora

If Avatar is a film that works for the viewer, a large part of that will be because of the convincing ecology found on Pandora (easily the most stunning creation in science fiction cinema to date). Unlike many sci-fi world creators, it is hard not to think of George Lucas here, Cameron, and his partners at Weta Workshops, ILM and Stan Winston studios (to name just the three large effects houses involved) have put in the time to properly attempt the creation of an entire ecosystem, as well as a convincing anthropology of its native intelligent lifeform. There is certainly a great deal of biological mystery on Pandora (I don't understand its ecosystem fully for instance) however Pandoran ecology all seems so plausible -no surfeit of ecologically inexplicable giants here thank you very much- that even a well trained biologist shouldn't be required to suspend her disbelief in the service of a rewarding two and half hours. And a film that leaves a biologist (like myself) wondering about the evolutionary history of a make believe world without needing to make allowances, and giving passes, is a film going reward in itself.

Pandora is an Earthlike world, though not so Earthlike that humans can breath without aid. (For a detailed account of why this is click here) It is a warm world, or at least the part dominated by the story is and it orbits a gas giant very much like our own Jupiter. The gas giant is probably too much like our own Jupiter, but I will leave all non-biological observations for the astronomically inclined. Pandora is not quite as large as Earth, but large enough to hold an atmosphere capable of trapping heat.

Avatar takes place in what appears to be forests of high photosynthetic productivity. Pandora may have arctic and temperate biomes, but our story takes place in something very like a rainforest. There is a vertical structure to the system, massive canopy trees, and then below a massive complexity to the understory producers. No doubt the books that discuss the planet for other fans will dwell on the film's spectacular fauna, but the structure of that forest is the first step of anchoring the film in reality. Because the makers gave the forest a convincing and diverse understory, as well as the majestic canaopy for its wide shots the world created has a believeable biological depth. It is the brief, or undetailed glimpses of the epiphytes, and ephemerals, of the small game and the creatures of the undergrowth and detritus that will be the unsung heroes of Avatar.

Another compelling detail is the day, night switch in forest ecology that appears to occur on Pandora. Pandora isn't earth, but like Earth, its ecology is not dominated by the same players at all hours of the day and night. But that is probably where the similarities between the two worlds end. The change in players and signals among the players seems more like a pelagic switch on Pandora. Bioluminescence dominates the Pandoran biota. Does this make much sense biologically? At first, I thought it might be a bit of Weta, or ILM or some effects house demonstrating their coolness (and as such it works magnificently) but upon reflection I've come to a different conclusion. Bioluminesence makes some sense considering Pandora does not orbit its solar system's star like Earth. It orbits a gas giant on an outer orbital track. This would mean somewhat reduced exposure to sunlight, and maybe selective pressures pushed toward more intense visual signalling apparatus. Stephen Jay Gould would probably say I am crafting 'just so stories' but regrettably I'm unable to go to Pandora and prove my hypothesis, so just you quiet down ghost of Stephen Jay Gould. The point is that this weird morphological trait, shared by much of the biota (notably absent in at least two of its alpha predators) makes plausible evolutionary sense. We could probably infer from the prevelance among the biota, that bioluminescence is evolutionarily ancient. I suspect that if Grace Augustine's (Sigourney Weaver) research lab had its own Genome Project it would reveal that bioluminescence was actually lost in the alpha predators but that the ghosts of those genes still exist hidden in their genomes. Here the creators have crafted a scientifically believable ecological backdrop. The time and effort that this must have taken is extreme, and it is richly rewarded on screen.



Taxonomy is important and Cameron and his team have given this some thought as well. The plants are not dwelled on enough to examine their taxonomy, but among the land based vertebrate type animals we see at least two major evolutionary families, tetrapods and hexapods, that is four and six limbed types. Hexapods enjoy greater representation in the Pandoran biota (at least in the region where the film takes place). Is this a split similar to the marsupial/placental split in mammals? It isn't discussed. From an evolutionary perspective this would be a fascinating development (oh the research we could do!). On Earth only one major body plan emerged among big land animals, it has been greatly elaborated on, but all vertebrates are basicaly tetrapods. Not so Pandora. The Na'vi, the indigenous people of Pandora, are notably tetrapods. While potentially very interesting, Pandoran morphology is not discussed in any detail in the film, but remains an interesting point of mystery for the serious science fiction fan. There are substantial differences in morphology among the tetrapods and hexapods though both share at least one organ, even if they differ in limb number. I don't want to go to deeply into detail about what is shared, and what is not, because to do so would be to violate spoiler protocols. I will say that there are no evolutionary barriers to plausiblity to this state of affairs. What is clear is that Pandora is a planet that has produced a fascinating biota, that has had a different evolutionary history than our own.

It probably goes without saying that the ethology of the organisms is also meticulously and plausibly created. I will dwell on only one example, the megafaunal predator called a thanator. This intimidating, hexapod, alpha predator, resembles in many ways the big cats of our own planet, except of course for the extra limbs, and the ten senosry quills, attached to flat chitinous plates. There is something insect-like in the quality of its body. It's teeth and claws resemble material found in the chelicerae of spiders, or the stinger of a scorpian. The color of a thanator, an inky blue-black, also hints at some insect like evolutioanry roots. When we see it for the first time it attempts to attack a young Hammerhead Titanothere. Through this vinette we see more of its behaviors (it is a surprise predator, and has an impressive threat display of rattling plates and quills, pulled back lip flaps that reveal a strange set of gums, and a toothy maw). Also terribly crucial to establishing biological reality, we don't see many of these alpha predators in the landscape (this was probably the crucial ecological "flaw" of Peter Jackson's excellent King Kong). Big predators sit atop an energetic knife edge. That is to say consumers (animals that eat stuff and do not produce their own food like plants) are not terribly efficient at aquiring nutrients from their food stuffs. From the base of the food chain, the plants and other producers, to the top of the food chain, the alpha predators, lots of energy is lost by animals as they consume food. If plant consumer X has only managed to acquire 10% of the energy available it becomes immediately apparent that any animal that eats consumer X will need to be eating a lot of X to stay alive. An ecosystem can only support a few such predators (especially if they are "warm-blooded") in a given area.


All of this behavior has the feel of things I've seen in the field. If you have ever watched a bird in your back yard, a coyote in the wild, or had to have a face to face with a big black bear, found fresh mountain lion scat on the trail you use, or nearly been run down by elk, watching the thanotar, or indeed any of the nature in Avatar will seem like authentic nature watching. From climate, to taxonomy, to evolutioanry history Avatar works as a very convincing bit of science fiction.

There are some animals in Avatar that will seem too much like analogues of Earth creatures, the Direhorse will seem too much like our own horses, the Viperwolves to obviously like wild dogs found on Earth and so on through much of Pandora's fauna and flora. I suspect that would be one of the major objections for the avid science fiction fan. It is an echo of the old complaint, "Why so many humanoids?" that science fiction fans have been offering for decades. It is an important objection but one that I think evolutionary theory allows us to dispense with, at least in the broad strokes, as we watch Avatar.

Stephen Jay Gould rather famously put the problem as follows,

"But if I could rerun the tape of life from the origin of unicellular organisms, what odds would you give me on the reevolution of this complex and contingent insect-flower system? Would we see anything like either insects or flowers in the rerun? Would terrestrial life originate at all? Would we get mobile creatures that we could call animals? Fine-scale predictability only arises when you are already 99 percent of the way toward a particular result -- and the establishment of this 99 percent lies firmly in the domain of unrepeatable contingency."

The notion of historical contingency set ideas about progress in evolution on their ears. There was a tendency among both lay people and many working biologists to think of evolutionary processes as an inexorable march toward humanity. It was a kind of recapitulation, in natural terms, of the idea of the Scala Naturae but without all the angels, or a god. Gould thought his ideas about contingency were fairly radical, but his ideas were often not quite as revolutionary as he made them out to be in his less reserved moments. That isn't to say that contingency is unimportant, clearly accidents of history play huge roles in evolutionary history. Allow me to point out an obvious accident that was a massive biotic regime changer. If, Sixty-five million years ago, a large astroid had managed to slide by Earth, you and I are not here to have this little electronic exchange of ideas. No earth shaking astroid impact in the Yucatan Peninsula, means no age of mammals, and no age of mammals means no humans. Likely it would mean 65 million more years of dinosaurs engaging in the business of being dinosaurs. Contingency is important.

But so is convergence, which Gould simply neglected in his analysis (as does Michael Shermer, Gould's most staunch defender on the point of contingency). The philosopher of evolutionary biology/psychology Dan Dennett, and the evolutionary biologist Richard Dawkins have been most articulate in their (mild) critique of Gould's Radical Contingency. But what is convergence in evolutionary biology? Or to put the question as it may be framed in the reader's mind, "what is convergent evolution and how, Mr. Blogger Fanboy, can it help us see the creatures of Pandora as plausible products of evolutionary processes?"

Convergent evolution is a process whereby organisms only distantly related, in evolutionary terms, exhibit similar morphology, or behaviors because their lineages have been exposed to similar selective pressures. That is to say organisms take on similar traits and come to look like one another because they evolved in either similar environments or engaged in a similar ecology. Below is perhaps my favorite example of evolutionary convergence. This looks like a wild dog. It is not.

This is a marsupial, now very likely extinct, that not only looks like a dog but acts like a dog. The similarities between old world canids and the thylacine exist only because they are the products of similar selective pressures. Evolutionary convergence is not at all uncommon. Another text book example is the form of fish, ichtyosaurs and dolphins. All are only distantly related, but all have converged on a similar form because they evolved in a similar environment. Convergent features are something Dan Dennett has referred to as a "good move" or "forced move" in animal evolution. That is to say certain strategies, forms and structures evolve again and again (not precisely copied mind you and bearing the stamp of contingency) because selective processes favor their discovery. Even the rudimentary stages, it appears, of these evolutionary "good moves" offer such advantages, that selection favors elaboration of the trait, strategy, or behavior.

Eyes have evolved independently on Earth at least forty times. They are not identical, but certainly they are identifiably "eyes." Fin like structures have also evolved dozens of times independently. Insulation, endothermy, parental care, pack hunting, complex problem solving intelligence, chemical warfare have all evolved independently several times on Earth. It is the phenomena of convergence in evolutionary processes that makes the flora and fauna of Pandora more than mildly plausible. The animals have the stamp of their evolutionary history all over them. They are not identical to their earthly analogs, but represent another iteration of a "good evolutionary move." Both contingency and convergence are satisfied.

To return to Gould's famous question, would we be here if we could rewind the tape of life to its unicellular beginnings? If by we Gould means big brained mammalian primates, with opposable thumbs, limited body hair, and a penchant for sweets, then the answer is an obvious no. But if by we he means an intelligent, technology using species then the answer is-given enough time- probably yes. Intelligence, like fins, insulation, and wings, is a good evolutionary move that has been hit upon again, and again by evolutionary processes. So if the presence of horse like things bothers you as you watch Avatar think about contingency, but also convergence and maybe that will resolve your dilema.

The AVATAR program hinges on the genetic hybrid avatar bodies, which are clones of their human "drivers," mixed with DNA of the Na'vi. There is an implication here, wholly unexplored by the film, of quite a bit of extreme genetic similarity between Earth and Pandoran life forms. This is harder to explain. Two hypotheses come to mind, and I will leave it you to essay others.

The first is that our genetic code isn't particularly difficult to make. That is to say, given the right chemical environment, early self-replicating molecules will hit upon nucleic acids regularly. DNA/RNA are simply the most stable of the alternatives. If this is so, we can expect this mechanism of heredity (DNA, RNA)commonly wherever we find life- given a certain set of evironmental conditions.

The second hypothesis belongs to Sir Fred Hoyle and Chandra Wickramasinghe, and is referred to as panspermia. This hypothesis predicts that the origin of life is exceedingly rare, but several forms of that life (unicellular) will be extremely hardy and able to survive interstellar travel (provided it is suitably sheltered) in astroids or comets. These bacteria like organisms find themselves blasted out into space during extreme volcanic eruptions, or impact events and then go on to seed other worlds with life. If this is the case the DNA/RNA mechanism might also be somewhat common in our galaxy as these unicellular space travelers would make planet fall and seed evolutionary processes on different worlds. If you think this is far fetched, there are chunks of Mars that have landed on Earth after being ejected by some phenomena. There is even some evidence that at least one of those Martian bits experienced ancient Martian life. So the mechanism isn't implausible. However there is little evidence for it.

As for the great biological mystery (I will not spoil) at the heart of Pandora, I have no explanation. Is it plausible? I don't know. Possible, but contingency would predict the Pandoran system to be rare I think. But I am not bothered. I will remember Orgel's Second Rule (remember to place tongue in cheek) when thinking about it...."Evolution is cleverer than you are."