Convergent evolution

I was hunting around for some blogging ideas recently when I came across this post by Wintery Knight. It’s basically a copy and paste job because Mr. Knight is not qualified to speak of anything in biology (and he has amply demonstrated as much). However, the person he extensively quotes, Cornelius Hunter, is also 100% unqualified to analyze the world of biology. I’ve written about Hunter in the past.

As in his last post that just barely merited a response, Hunter makes a series of confused remarks about convergent evolution. (For those who don’t know – such as Hunter – convergent evolution is the process by which species of usually distant relatedness will acquire the same trait independent of their last common ancestor.) Let’s take a look at how Hunter mangles this:

The theory of evolution states that the species arose spontaneously, one from another via a pattern of common descent. This means the species should form an evolutionary tree, where species that share a recent common ancestor, such as two frog species, are highly similar, and species that share a distant common ancestor, such as humans and squids, are very different. But the species do not form such an evolutionary tree pattern. In fact this expectation has been violated so many times it is difficult to keep track. These violations are not rare or occasional anomalies, they are the rule.

Hunter is only leading into his mention of convergence here, but he’s already off to an embarrassing start. He’s attempting to claim that we don’t see an expected pattern of descent because that pattern is premised on the idea that similar traits must come from closely related organisms. He is factually incorrect. All he has described here is one method for determining relatedness between species: morphology. And even then, he has grossly over-simplified the process. For instance, take the skull of a dingo versus the skull of a Tasmanian tiger. They resemble each other quite closely, but they aren’t exactly the same. The latter has two holes in the roof of its mouth, a characteristic of marsupials. Go further and one will see that they also have different genetic codings.

Many examples are the repeated designs found in what, according to evolution, must be very distant species. Such evolutionary convergence is biology’s version of lightning striking twice. To explain this evolutionists must say that random mutations just happened to hit upon the same detailed, intricate design at different times, in different parts of the world, in different ecological niches, and so forth.

Were Hunter to take a peak at the genes in a Euphorbia, he might notice that they are markedly different from the genes in a cactus. That’s because, while both plants are prickly desert survivors, one is from the Malpighiales order whereas the other is from the Caryophyllales order. They have significantly different genotypes, but similar phenotypes. In other words, Hunter’s argument that random mutations are always hitting “upon the same detailed, intricate designs at different times, in different parts of the world, in different ecological niches” is not only verbose, but entirely wrong. It would be as though he said home builders have hit upon the same intricate design because some use cellulose insulation while others use spray foam. It’s the same result by a different means.

Everyone has heard of the kangaroo and its pouch. It is a marsupial—mammals that give birth at a relatively early stage in development, and then carry their young in a pouch. There are a great variety of marsupials that are curiously similar to a cousin placental species. The flying squirrel (a placental) and the flying phalanger (a marsupial) are one such example. Because of their reproductive differences evolutionists must say they are distantly related on the evolutionary tree. Yet they have strikingly similar designs which must have been created independently by random mutations. Every mutation leading to the two different species must, according to evolution, have been random (that is, independent of any need). No, natural selection doesn’t help.

First, his mutation argument is still wrong. Second, it isn’t merely reproductive differences that tell us the flying squirrels (which are two independent groups of rodents) are different from the flying phalanger. There is also evidence from their genetic relatedness, not to mention the obvious fact that one is placental and the other a marsupial. Third, of course natural selection is relevant here. That’s the whole reason two species are able to converge on the same solution to similar problems; natural selection has found an efficient solution to one problem faced by two species.

Though evolutionists sometimes deny biological convergence, it is a scientific fact.

I don’t know what Hunter is talking about, but that’s okay because I don’t think he does either.

He goes on to quote from a recent paper:

In mammals, hearing is dependent on three canonical processing stages: (i) an eardrum collecting sound, (ii) a middle ear impedance converter, and (iii) a cochlear frequency analyzer. Here, we show that some insects, such as rainforest katydids, possess equivalent biophysical mechanisms for auditory processing…

Thus, two phylogenetically remote organisms, katydids and mammals, have evolved a series of convergent solutions to common biophysical problems, despite their reliance on very different morphological substrates.

Now, remember the crux of Hunter’s opening: Similar morphology is the same thing as intricate design, thus Jesus. Yet here we see a “reliance on very different morphological substrates”. That is, natural selection in some insects has hit upon the same broad method for attaining hearing as it has in mammals, but it goes about the process in a largely different way, relying upon the insect phenotype it has already given itself. So not only is Hunter’s argument wrong from the get-go, but even if we’re generous and grant him his incorrect basis, he still gets blown out of the water. He has managed to somehow be wrong in his wrongness.

It’s one thing when someone branches into biology from time to time, relying upon the insight of others. We see that with Wintery Knight (the reason being that he hasn’t a clue about the field). We can’t expect everyone to be an expert, even if they should know better. However, Cornelius Hunter is another story. This is a guy who fancies himself qualified and reasoned, able to break down complex scientific ideas. Yet what we see is a man unable to even come remotely close to getting much of anything right about a relatively simple idea. And he keeps trying, getting things wrong every. single. time.

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The genius of Charles Darwin

By the time that an animal had reached, after numberless generations, the deepest recesses, disuse will on this view have more or less perfectly obliterated its eyes, and natural selection will often have affected other changes, such as an increase in the length of antennae or palpi, as compensation for blindness.

The above quote comes from On the Origin of Species. It is just one of the numerous instances where Charles Darwin, on the basis of his theory, makes a wonderful prediction that comes true so many years after the fact. In this case, his prediction has been shown to be true over and over; species which have gone millions of years in the dark lose their eyesight again and again. We see this especially in many species of cave fish, but it isn’t limited to the oceans:

With a leg span of only six centimetres and a body size of around twelve millimetres, the spider Sinopoda scurion is certainly not one of the largest representatives of the huntsman spiders, which include more than 1100 species. However, it is the first of its kind in the world without any eyes.

“I found the spider in a cave in Laos, around 100 kilometres away from the famous Xe Bang Fai cave,” reports Peter Jäger, head of the arachnology section at the Senckenberg Research Institute in Frankfurt. “We already knew of spiders of this genus from other caves, but they always had eyes and complete pigmentation. Sinopoda scurion is the first huntsman spider without eyes.”

One prediction the theory of evolution allows us to make today that Darwin couldn’t make in his lifetime is that the genes for vision in these now-blind species should exist but be broken. If they do not exist, then either there is some really funky timeline and divergence activity (that is, these are old lineages that evolved before their sighted brethren) and we should see a lot of other genetic differences or evolution just isn’t true. Neither one of those options is very likely, of course. What we observe instead is that, indeed, the genes for vision are a broken, jumbled mess. That isn’t the case yet for the above spider because, as far as I know, no such studies have been carried out, but it is the case wherever else these sort of species have had their genes analyzed.

One point I think that needs to be made sure with Darwin’s quote here is this: Natural selection is unlikely to be the only factor in the disappearance of eyes among these species*. In fact, it could have little to nothing to do with the process at all. Vision in the dark is a useless thing, so natural selection may obliterate it for the sake of saving energy or preventing potential injury to a sensitive body part, but I believe it is much more likely that it simply did nothing. It neither selected for nor against vision. As a result of the lack of positive selection, mutation and genetic drift took over and vision in these species simply faded away.

*I really have two points here. First is the one I just made in the above paragraph. Second is the fact that Darwin was referencing natural selection in regard to it creating some compensation for blindness, not in regard to it directionally causing the blindness.

Chromosome 2

It has been proposed and well evidenced that human chromosome 2 is the result of a fusion event between two chromosomes in our evolutionary past. Briefly, here is the evidence:

All great apes except humans have 24 pairs of chromosomes. We only have 23. That means we need an explanation for such a difference that dates back only a relatively short period of time (5-7 million years). As it happens, human chromosome 2 shows strong evidence of being two fused chromosomes. The way we know this is that all chromosomes have telomeres and centromeres. Telomeres are repeating units of DNA that serve to protect the ends (and therefore middles) of chromosomes, sort of like a good pair of shoes and a strong helmet. Centromeres are DNA units located somewhere between the telomeres of chromosomes, generally relatively close to the center. Their function is to help assemble the two parts of a chromosome during cellular replication and reproduction. In human chromosome 2, we see that there are actually two telomeres fused together in the center. There are also telomeres on the end, but between each end and the center are centromeres. That means we have three telomeres (one of which is fused) and two centromeres.

I bring this up because I was recently reading yet another excellent post by The A-Unicornist and he was dealing with this stuff:

ID is really nothing but an argument from ignorance – it claims that certain things simply cannot be explained by science, so it must be ‘best explained’ by a designer instead. Take for example this post from The New Creationist. I often point creationists to the Ken Miller video where he explains the Chromosome-2 fusion in humans, because it’s a perfect example of the theory of evolution making a falsifiable prediction that ended up being powerful evidence that evolution is true – something that ID has never done and in principle cannot do, which is why it will never be a science. Now, this “new creationist”, who incidentally sounds just as credulous as the old ones, argues that such a fusion is impossible – that the chromosome should never have been able to fuse at all.

Being that I’m not a biologist, I have no idea how to directly refute what he’s arguing. But it’s conspicuously odd that rather than, I dunno, ask a biologist or two (like, golly I dunno, write a letter to Ken Miller?), he simply frames his argument as though the unanswered question itself creates a major problem for the theory of evolution.

Since I’ve used chromosome 2 as an argument for evolution, I am familiar with the creationist responses. As such, I want to address what the blogger known as The New Creationist is arguing:

If the fused chromosomes in an end-to-end fusion are ripped apart by the centromeres during cell division and cells must divide to produce an embryo then how does an embryo develop with two previously fused but now ripped apart chromosomes? We know that the loss of just one chromosome would be lethal and here we have the loss of both of the two
fused chromosomes. If fused chromosomes do not make it through cell division then how could a fused chromosomal configuration be a result of common descent since there would be no descendants by a biological pathway. Such would be miraculous. Indeed, I believe it is a miracle not only because it can not be explained by any natural pathway but also because it is contradicted by experimental data.

What he is trying to say (and what he later says a little more clearly) is that two centromeres would cause division and assembly to occur in two separate places. This would be an all around mess that would prevent not only mitosis, but meiosis as well. So what could the solution be? Well, he answers it himself:

Now, it has been proposed that the deactivation of one of the centromeres in the fused chromosome would prevent the rupture and subsequent loss of the newly formed fusion…

And that is the case. One of the centromeres has been deactivated. One possible reason for this could relate to the fact that the area near the deteriorated centromere (the pericentromeric sequences) has gone through a large number of duplication events, but this isn’t known and requires certain confirming evidence around other deactivated centromeres. I don’t know if any significant research has been done in this area since the 2006 paper about chromosome 2.

The New Creationist continues:

…but this poses another equally lethal problem during the pairing off of homologous chromosomes.

Let’s say that if C2A fused with C2B forming C2 (which has 2 centromeres) in the paternal germ line, the male’s sperm. Now, that sperm would have to fertilize an egg where both C2A and C2B not having been fused would have to pair off with the paternal C2 BUT if C2 has been prevented from being ripped apart because one of its centromeres has been deactivation then the corresponding maternal C2B (or C2A) will not combine with C2 in the mother’s egg because that centromere would have been deactivated.

In other words, he is saying that if two ancestral primates had offspring with the fused chromosome, then that offspring would have 23 chromosomes whereas the rest of the population still had 24. Mating between the two could not occur as a result, thus the fused chromosome could never make it beyond a single generation.

The most obvious solution to this problem is that several members of a population experienced a fusion event. It could have been a completely chance event, or it could have been due to a particular mutation that had spread down the line. That is, my money is on a mutation existing in a population that caused the fusion between two specific chromosomes. Perhaps all the pericentromeric duplications (which pre-date the fusion event, incidentally) gave rise to a gene that was free to mutate neutrally in the population. After some time, it managed to survive the generations, and made a marked difference. (That’s what has happened, minus the specific duplication events, with Richard Lenski’s E. coli.) Or maybe a mutation popped up just out of completely random chance, as opposed to being connected to any particular type of event. It’s hard to say just how any of this happened, but there are good hypotheses to be had on the question.

To conclude, the first argument presented here was defeated before it was even made. One of the two centromeres was deactivated long ago, as stated in the original paper. Indeed, that very paper even suggested a correlating factor in centromere deactivation that could be useful for future research. As for the second argument, I’m going to give Mike the last word:

[T]he fact that an explanation is either unknown or not immediately apparent would not refute the fact that the theory of evolution made this falsifiable prediction, nor would it suggest that there cannot be a rational explanation at all. Our new creationist seems to think that because he does not know how to explain it that a rational explanation is not merely unknown, but in principle impossible. Ergo, Goddidit. That ain’t how science works, kids.

Evolution, fruit flies, and counting

Don’t let any creationist tell you complex things don’t come from simple precursors:

US and Canadian researchers have evolved a population of fruitflies that can count. The result, presented on 9 July at the First Joint Congress on Evolutionary Biology in Ottawa, Canada, supports the notion that the neural mechanisms underlying basic arithmetic skills first emerged hundreds of millions of years ago. It could also eventually offer a key to understanding why some people have problems with numbers…

During a 20-minute training period, flies were exposed to either two, three or four flashes of light — two and four flashes coincided with a vigorous shake administered by placing a electric toothbrush next to the box containing the flies. After a brief rest, the flies were returned to box and shown the light flashes. Despite a dislike for being shaken, most of the flies were not able to learn to associate the negative stimulus with the number of flashes. But 40 generations later, they could.

The researchers caution that the work is preliminary and that they do yet know what genetic changes are behind the insects’ evolved number sense.

What I find interesting is exactly how this constitutes selection pressure. The flies certainly don’t like being shaken, but that’s entirely irrelevant if there isn’t some sort of reproductive advantage to be had from recognizing when the shaking will occur. Clearly there is, and we could speculate all day long as to why flies that associate the flashes with negative stimulus pass on more of their genes than the other flies, but I would like to see some experimental data showing the details. Does shaking disorient the flies? Does it interrupt the mating process? Does it affect fertility? Perhaps the paper that comes from all this can shed some light.

Now excuse me while I go murder the fruit flies that appear to have evolved to make my kitchen just awful for the past week.

Lynn Margulis, 73, dead

Lynn Margulis was one of those scientists that biology needed. She forged the now universally accepted endosymbiotic theory only about 44 years ago, bringing it to the mainstream 30 years ago. I have heard her work compared to that of Watson & Crick insofar as it marked a significant turning point within the field. She really did have some great ideas and it’s a shame that she died so young.

Garuda wasp

Biogeography and endemic species are two great pieces of evolution. The former refers to the distribution of species across the planet and only evolution adequately explains what we observe. Take for instance Australia. It is filled with marsupial mammals, yet it is off all by its lonesome in the ocean. Clearly mammals did not evolve twice, the second time taking an alternative path to being placental. We need an explanation. The one we have is that this marsupial subset of mammalian life migrated down the Americas, through Antarctica, and into Australia. Fossil and tectonic plate evidence independently confirm this hypothesis – marsupial fossils are found all through South America and into Antarctica (and, of course, Australia), dating back to the time when those continents were still all connected.

Endemic species also constitute a nice bit of evidence for Darwinists. The man himself, Charles Darwin, saw quite an array of species that are only present on the Galapagos Islands, their relatives residing back in South America for the most part. (One of my favorite Galapagos animals is the marine iguana.) But there are far greater islands out there. Madagascar has to be the first to come to mind (and, in turn, its lemurs come to mind next for me). There is also Alejandro Selkrik Island, a place I mention in the first link in this post. And then there is Sulawesi, an Indonesian Island a fair bit north of Australia. It’s a haven for researchers who want to study unique flora and fauna, including many large mammals. It has a lot of protected land and animals (especially its marine life), so it’s a prime location for many biologists. One such biologist is Lynn Kimsey, an entomologist who recently described a pretty striking find:

It sounds like the stuff of nightmares – a wasp that supplements a vicious sting with jaws longer than its front legs.

But this is a very real newly discovered warrior wasp found on the remote Indonesian island of Sulawesi.

Dubbed the ‘Komodo dragon’ of the wasp family, the males of the species measure two-and-a-half inches long…

Ms Kimsey, who is also director at the Bohart Museum of Entomology, said: ‘Its jaws are so large that they wrap up either side of the head when closed. When the jaws are open they are actually longer than the male’s front legs. I don’t know how it can walk.’

Luckily the species prefers to dine on insects, but if threatened it could leave a sizeable mark on human flesh too.

It’s a beast.

Whereas this is an insect which not only can fly, but can be carried away by strong winds, it may very well inhabit a number of other nearby islands. However, given its exceptional size, my suspicion is that it is the unique biosphere of Sulawesi itself which has given rise to such a monster. Perhaps the ‘Garuda wasp’, as it is to be known, can survive elsewhere, but my bet is that its currently only known island of habitat is where it can really thrive.

Of course, its current habitat is effectively random and haphazard without the framework of evolution to guide us. It is only with Darwin’s theory that we can really understand anything about the Garuda wasp or any other unique form of life around the globe.

Punching bags

Whenever creationists get hold of a legitimate scientific paper, I groan a little bit for at least two reasons. First, I know whatever they have to say, they’re going to mangle the science. We saw that with Jack Hudson last year (and, actually on literally every post about science he has ever made). And, of course, we also saw that with all the other creationist sites from which Jack stole his material. Second, I know I’m going to have to devote some time to reading and blogging on a paper I would have otherwise missed. It isn’t that I don’t like to read these things – I do. The problem is that it’s a time-suck when the blogging is factored in. You see, unlike creationists I actually research and verify what I have to say on any given piece of science.

Let’s start with the paper in question:

Here we report exceptionally preserved fossil eyes from the Early Cambrian (~515 million years ago) Emu Bay Shale of South Australia, revealing that some of the earliest arthropods possessed highly advanced compound eyes, each with over 3,000 large ommatidial lenses and a specialized ‘bright zone’. These are the oldest non-biomineralized eyes known in such detail, with preservation quality exceeding that found in the Burgess Shale and Chengjiang deposits. Non-biomineralized eyes of similar complexity are otherwise unknown until about 85 million years later6, 7. The arrangement and size of the lenses indicate that these eyes belonged to an active predator that was capable of seeing in low light. The eyes are more complex than those known from contemporaneous trilobites and are as advanced as those of many living forms. They provide further evidence that the Cambrian explosion involved rapid innovation in fine-scale anatomy as well as gross morphology, and are consistent with the concept that the development of advanced vision helped to drive this great evolutionary event8.

The gist of the find is this. Researchers discovered very old fossils of arthropod eyes from the Early Cambrian. They do not predate complex eyes, but they do predate similar non-biomineralized eyes. That is, trilobite eyes are made of calcite, meaning the trilobites produce the minerals for their eyes themselves. In turn, their eyes are hardened (and thus more easily fossilized). So these new fossils show a different way in which eyes could become complex. Furthermore, they showed a tight packing in the lenses, much in the way that a fly’s lenses appear to be tightly packed. They also were curved to form binocular vision, meaning there was a visual overlap in front of the body. This helps for judging distances and discerning complicated backgrounds. This creature was a predator.

But here is where creationists draw issue:

Did you catch that? If you were a high school student who trusted your teachers, you’d think they had evidence for this unbelievably rapid amount of highly complex change. But they merely assume that it evolved, so it “had” to have been a great evolutionary event and another example of “rapid innovation.” [And is thus a tautology.]

This comes from Neil who, like many creationists, was taking his cue from another site. He believes that every paper that mentions evolution must provide a detailed description of why evolution is true.

His quote was a reference to this excerpt from the paper:

[The new fossils] provide further evidence that the Cambrian explosion involved rapid innovation in fine-scale anatomy as well as gross morphology, and are consistent with the concept that the development of advanced vision helped to drive this great evolutionary event.

What this is referencing is the fact that until now advanced eye fossils were almost exclusively restricted to trilobites in the fossil record. These new fossils give evidence that, as suspected, there were other marine creatures swimming around with complex eyes. Furthermore, they show a quantitative change in the number of lenses, not the sudden appearance of these sort of lenses. (But note that we can’t expect to see a perfect fossil record. We can get a good outline, but it’s silly and really very ignorant for creationists to demand to see every intermediate organism. At some point things will have to “suddenly” appear. Of course, this is in geological terms, i.e., over millions of years.) These eyes are evidence that evolution was driven in part by the anatomical changes in vision during the Cambrian.

So it is clear that none of this is a tautology. This fossil find is further evidence of the nature of evolution and the role vision played in its creation of arms races. What we see from the creationist world, however, is an immature understanding of the science. There is no doubt that Neil never bothered to read the paper from Nature, nor have many of his creationist brethren. If any of these sort of non-academics bothered to look into the literature (or even take formal courses), they would see their obvious errors. Further, even if we are to understand this paper as Neil purports it to be, he’s still in error. That is, he believes the paper is a tautology because it assumes evolution without giving evidence for why evolution is true. This is like drawing issue with physics papers because they assume gravity is true without explaining general relativity. It’s a silly complaint to make and it only demonstrates how wildly over the head of creationists most scientific papers are.

Re: Origins of vision

I’m doing another repost, this time taking from an article I did about the origins of vision. Note that the quote coloring is reversed from how it normally appears.

Vision likely originated as simple eyespots in simple organisms. It also is traced back to jellyfish and their own simplistic eyespots, which are actually still present in some manner today. That is, jellyfish have areas of photoreceptor cells which don’t allow vision as we know it (they don’t even have brains), but they do allow a sensation of particular wavelengths of light to be perceived. These wavelengths often indicate depth (and maybe predators), which in turn may indicate food source (pelagic jellyfish don’t tend to get to plump).

Recent research has discovered the genetic pathway involved in light sensitivity in a close relative of the jellyfish.

“We determined which genetic ‘gateway,’ or ion channel, in the hydra is involved in light sensitivity,” said senior author Todd H. Oakley, assistant professor in UCSB’s Department of Ecology, Evolution and Marine Biology. “This is the same gateway that is used in human vision.”

This allows for a prediction using evolution: all organisms alive today which share a common ancestry with hydras will share this same genetic gateway. Organisms like flies, as the article points out, do not share this ancestry with vertebrates and as such do not share this genetic gateway. If they did share it, then wow. Creationists could actually trot out their improbability arguments.

“This work picks up on earlier studies of the hydra in my lab, and continues to challenge the misunderstanding that evolution represents a ladder-like march of progress, with humans at the pinnacle,” said Oakley. “Instead, it illustrates how all organisms — humans included — are a complex mix of ancient and new characteristics.”

(End different quote coloring.)

I looked this post up because I recently ran across a creationist who actually trotted out that old “the eye is irreducibly complex” bull and I was searching for some other links. But what’s interesting is what a different creationist was saying in the comment section:

You premised your claim of cnidarian relationship to vertebrates and humans on a gene they share in common. You said specifically, “This allows for a prediction using evolution: all organisms alive today which share a common ancestry with hydras will share this same genetic gateway.” I pointed out that certain beetles share certain genes with vertebrates and humans that other insects do not – and by your logic, that would mean these beetles share an ancestry with humans other insects do not.

As I pointed out at the time (and as the creationist failed to even come close to grasping), my claim was not based upon the sharing of individual genes, but rather on the sharing of complex genetic pathways. It is these pathways that ultimately allow for such a prediction. The creationist then confused the discussion on pathways with the article focus of a gateway. (I pointed out his error to him, but to no avail.) It is these pathways, by and large, which first get us to the point of where we can say that hydra and humans share a common ancestry in terms of vision. From that point we can look at the particular gateway in question and make the prediction I originally made. (One caveat: organisms which have lost their ability to see may not share the gateway.)

Neil Shubin inducted into NAS

This is satisfying:

The National Academy of Sciences today announced the election of 72 new members and 18 foreign associates from 15 countries in recognition of their distinguished and continuing achievements in original research…

Shubin, Neil H.; Robert R. Bensley Professor and associate dean, department of organismal biology and anatomy, University of Chicago, Chicago

Shubin is most famous for his evolution-utilizing research into Tiktaalik. I’m glad to see him inducted.

And congratulations to everyone else who was deemed worthy to be a member of such a prestigious institute.