Splitting lumps, lumping splits, and other taxonomic shenanigans

18 07 2007

This past March I blogged about a Nature article in the special “Linnaeus issue” involving the problem with determining what actually constitutes a species. In fact, the very same day I also mentioned that a new species of Clouded Leopard (Neofelis diardi)was recognized in Indonesia, on which Darren of Tetrapod Zoology provided a much more thorough history. Now, as Rich at evolgen points out, a new PLoS editorial is suggesting that we take greater care in name (or renaming as the case may be) mammalian species.

Neofelis
Bornean clouded leopard (Neofelis diardi)
Kalimantan (Indonesian Borneo), Indonesia.
CREDIT: (c) WWF-Canon / Alain COMPOST
IMAGE No.: 112939

The authors of the opinion piece, Meiri and Mace, criticize biologists who split species because two or more populations of one species simply do not overlap (either caused by some barrier separating them over a distance or ranges abutting without overlapping). Regarding the caramel-colored clouded leopard, they write;

In resurrecting N. diardi, Kitchener et al. are relying on the phylogenetic species concept whereby species are defined as groups that share at least one uniquely derived character. They distinguish two clouded leopard “species” solely on the basis of pelage (fur color and pattern) characteristics, despite the fact that differences in hair color often reflect minor geographical varieties in many mammals. Borneo and the Malay Peninsula differ in several biotic and abiotic factors. Thus genetic and morphological differences between populations of the 144 mammalian species they share are to be expected, and there could potentially be equivalent evidence to merit specific status for all of these; an outcome that would certainly be unjustified.

Indeed, populations of one species existing in relative isolation from each other is not enough to gain a new species status (if that were true, we’d have many more species of White-Tailed Deer and Cougars throughout the Americas at the moment), but such differences do lead to allopatric speciation events, regional differences showing up over time as local ecologies become more distinct from each other. Such considerations, however, would essentially negate designation of new species by skin/feather/hair color alone, being that the colors or patterns of a particular species can vary without there being any other distinctive features (while perhaps still meeting the requirement of one “derived” character).

Species designation is not all about being objective, however, the designations of species and subspecies inflating or deflating the raw numbers of local biodiversity and having an impact on endangered species status. If, for example, an island is deemed not to have just one large population of a particular species but two populations of two slightly distinct species, then the overall numbers for these organisms fall and may incite groups to try and protect them. A subspecies or local variation is far less likely to gain protection than a distinct species, so splitting is a way in which some people could possibly ramp up the overall biodiversity count (therefore reducing the number of individuals in populations), in turn receiving more aid than others. I have heard this charge made many times, although I have not seen much actual evidence that this is the case (see this opinion piece from the April 2004 edition of Current Science).

So what about the renamed Clouded Leopard Neofelis diardi? What differentiates it from the species to which it previously belonged, Neofelis nebulosa? Fortunately, I was able to access the article “Geographical Variation in the Clouded Leopard, Neofelis nebulosa, Reveals Two Species” (available here)to have a look at the data myself. The researchers, using skins primarily from museums (2 being from private collections) comparing the pelage patterns of 57 clouded leopards (skulls were typically not associated with the skins, if available at all) in order to determine if there was some sort of geographical difference. The primary differences the researchers observed were described this way;

In summary, clouded leopards with large clouds (Neofelis nebulosa) tend to have fewer, often faint, spots within the cloud markings, and they are lighter in color, with a tendency toward tawny-colored fur and a partial double dorsal stripe, whereas clouded leopards with small clouds (Neofelis diardi) tend to have many distinct spots within the cloud markings, greyer fur, and a double dorsal stripe.

The reason for the striking difference in coat pattern may be due, the researchers hypothesize, to the Isthmus of Kra acting as a biogeographical barrier, essentially isolating the two groups of clouded leopards from each other. The differences don’t merely reflect inconsequential differences in variation (i.e. the authors of the PloS cite Merriam going overboard splitting bear species based upon the smallest differences), but rather a split that has caused a good amount of differentiation in the appearance of the Indonesian leopards. Hair color is not the only evidence backing up the split, however, mitochondrial DNA analysis (the research appearing in the same issue of Current Biology as the pelage paper) showing that the greatest genetic difference between the clouded leopards is that between the “mainland” species & subspecies and Neofelis diardi. What’s more, the difference between the two different clouded leopard species appears to be equal to or greater than the differences between other cat species, further supporting the differentiation of these leopards. The authors do admit, however, that their sample size was rather small and more study needs to be done, but the results we have as of now strongly suggest that there are two separate species of clouded leopard living in southeast Asia.

While Neofelis diardi is not yet officially recognized as a species (at least to my knowledge), I do side with those who regard it as a distinct species. Suggesting that the authors of the pelage study merely looked at a few coats and said “Gee, these look different” and attempted to create a new species is a bit disingenuous, and the current PLoS editorial does not address the genetic studies of Buckley-Beason, et al. other than to say they were carried out. Their point about taking great care to accurately distinguish species is well-taken, but they did little more than make a caricature of the Neofelis diardi studies, and they probably could have picked a better example (although the overall attention the clouded leopard story got would make it an obvious choice because of its visibility).

Given the complexity and diversity of species concepts, there will likely always be disagreements and arguments. Indeed, if we look at the history of life on earth, it’s probably a good thing the fossil record is fragmentary; if we had all the organisms that ever lived and could line them up according to direct ancestor/descendant relationships from the first life form to us, we’d probably have a hell of a time determining when to make a species division. In essence, we have given ourselves a designation of Homo sapiens, but millions of years ago, billions of years ago, our direct ancestors looked quite different than us and would receive very different names. Indeed, as much as taxonomy is helpful, sometimes I wonder if designations of extant species sometimes conflates the evolution issue, suggesting that “species” are end-products of evolution that do not continue to evolve (and if we have no close ancestors, that they came out of nowhere). How this could be helped/fixed, I do not presently know, at least outside of serious contemplation and study of the history of life on earth.





Beheading Naosaurus

5 06 2007

The AMNH archives really are a rich resource of information about paleontology, and I’ve definitely taken advantage of their availability to learn more about giant crocodilians, “mummified” dinosaurs, curious museum mounts, and the taxonomic confusion created by some early studies of dinosaurs. Continuing in the theme of cranial-confusion surrounding “Brontosaurus”/Apatosaurus that kicked off the last post, today we’ll be looking at a similar case involving Naosaurus, a fin-backed creature that also had to lose its head.

In 1896, Charles Sternberg discovered the most of the vertebrae and ribs of what E.D. Cope called a “sail-backed reptile,” the name stemming from Cope’s suspicion that the long spines had a membrane stretched between them and could be used to catch the wind, just like a sail, the fearsome Dimetrodon being named by Cope some years earlier in 1878. The material Sternberg found in the Texas red beds, however, was different from that of Dimetrodon despite the superficial similarities and so it was given a new name, Naosaurus (or “ship lizard”).

Naosaurus

A Charles R. Knight reconstruction of Naosaurus. Note the horizontal notches along the spine that belie the fossil’s true affinities. [From: The Project Gutenberg EBook of The Human Side of Animals, by Royal Dixon]

In 1907, a reconstruction of Naosaurus was undertaken at the American Museum of Natural History under the supervision of Henry Fairfield Osborn, although most of the material seemed pieced together. The Permian red beds of Texas gave up a lot of material, but it was difficult to figure out what bones belonged to Dimetrodon of various sizes and what belonged to Naosaurus. Despite this, an reconstruction of Naosaurus was attempted, despite warnings from other scientists that the reconstruction may not be accurate. From the 1907 AMNH Bulletin;

Dr. E. C. Case, the chief authority on this group writes his belief that the skull of Dimetrodon cannot be used as a basis for the restoration of the skull of Naosaurus.

The reader will, therefore, thoroughly understand that the assemblage is largely composite. It serves, nevertheless, to give us for the first time an adequate conception of the unique and imposing characters of these great extinct forms.

Indeed, despite Case’s contrary take on the fossils, the skull of Dimetrodon was used as a model for Naosaurus (see illustration above), the two animals looking exceedingly similar in reconstruction.

Dimetrodon

Reconstruction of Dimetrodon from “DESCRIPTION OF A SKELETON OF DIMETRODON INCISIVUIS COPE. BY E. C. CASE.” (1910)

What is most curious is that Naosaurus was reconstructed as a fanged predator much like Dimetrodon when its spines would have given away a different relationship. Rather than being straight bones that superficially resemble fingers | , the spines of this pelycosaur had horizontal projections when you looked at them straight on + , the tell-tale mark of Edaphosaurus, described by Cope in 1882. Even today Edaphosaurus often gets confused with Dimetrodon (“They’re both sail-backed reptiles, what’s the difference?”), but there is perhaps more to the story here as well. While we could go into detail about the errors in body reconstruction involved in “restoring” the non-existent Naosaurus, the skull, as in so many other cases, is what is most out of place. The year before Osborn published the 1907 Bulletin on Naosaurus, E.C. Case published his own 1906 paper on the skull of Edaphosaurus. The material available to Case, however, was partial and crushed, and while his efforts to reconstruct the skull were admirable, he was a bit off the mark.

Edaphosaurus, Case reconstruction

Interestingly, Case notes in his paper that Edaphosaurus was probably not closely related to Naosaurus, despite Cope’s earlier assertion that the two were related, so even though Case did not believe Dimetrodon would be a good candidate to reconstruct the skull of Naosaurus, Edaphosaurus seemed to be out of the running as well. In fact, it was not until D.M.S. Watson re-evaluated the skull of Edaphosaurus in 1916 based upon a new, un-crushed skull that we got an idea of what the animal’s head really looked like.

Edaphosaurus Watson Reconstruction

Eventually the dubious status of Naosaurus became apparent and faded from memory, although I’m sure if Knight’s reconstruction popped up today those unfamiliar with the story would immediately suggest it was an obscure rendering of Dimetrodon. Doubts seem to be apparent in Case’s 1910 paper on Dimetrodon which provided the skeletal reconstruction above, and the removal of Naosaurus as a valid taxon was probably not long following Case’s work. In the end, however, just as with Phobosuchus, Naosaurus no longer haunts the 4th floor of the AMNH, relegated to little more than a dusty memory.





A fishing dinosaur!

25 04 2007

What a time to be a paleontologist; evidence for a carnivorous dinosaur that waded into the water for its prey has been discovered in St. George, Utah. According to a recent news report from the Discovery Channel, a new Dilophosaurus relative has been found in a lake environment, in addition to a new shark species, at least three new fish species, and three new tree species. This is absolutely wonderful, allowing us a look into the early Jurassic ecology of this area, and I hope the excavations and study of this area continues.

Perhaps more impressive than all these new species, however, are the preserved trackways. According to the report, the tracks seem to show the predatory dinosaur walking out into the water and even scrambling to get back onto dry land, proof that this dinosaur enjoyed fish dinners. Much to my dismay, there are no photographs of any of the skeletons, tracks, or anything else, so I guess I’ll have to keep my eyes peeled for updates and announcements about the discoveries.

Also, some of the paleontologists explain in the report that the new dinosaur has a head/mouth shape seen in spinosaurs, including nostrils moved back on the top of the skull and lots of small, sharp teeth for catching/holding onto fish. This got me wondering; could there be a relationship between Dilophosaurus and its relatives and later dinosaurs like Spinosaurus, Suchomimus, Baryonx, and Irritator? I pulled out my copy of The Dinosauria (2nd ed.) and did a quick search on Wikipedia to check out how things stand. Currently, spinosaurs have been folded into the Superfamily Megalosauroidea and Dilophosaurus and its kin belong to the Superfamily Coelophysoidea, although there seems to be some doubt as to the true affinities of spinosaurs. To get to the point, I’m wondering of these elongated skull shapes adapted for catching fish/holding onto prey evolved at least twice because of environmental pressures in these two different groups or there if there is an ancestor/descendant relationship here between some sort of coelophysid and the impressive spinosaurs. Maybe I’m way off base, but even if I’m wrong it would be worth it to determine if the piscivore skull evolved multiple times or belies an evolutionary relationship.

Update: Zeta was kind enough to bring to my attention a passage from Gregory S. Paul’s famed work Predatory Dinosaurs of the World (1988) which hints at a connection between dinosaurs like Dilophosaurus and the spinosaurids like Baryonx and Spinosaurus. Once again, I find that I am late to the party, but I think a re-evaluation of the relationship of the coelophysids and spinosaurs is needed now, especially given the discoveries made in recent years. Paul writes;

The kinked snouts, crests, and peculiar jaw supports show that coelophysids were an increasingly aberrant side branch that left no descendants. This means they paralleled other advanced theropods and birds in such details as extensive bone ossification and increasingly narrow cannon bones. Crests, peculiar jaw supports, and narrow cannon bones show that dilophosaurs are the most advanced of the bunch, so their reduced hips must be a secondary reversal to a more primitive condition. It may be that the extraordinarily aberrant Baryonx and Spinosaurus are extremely specialized developments of the dilophosaur branch; their deeply kinked snout and other similarities certainly suggest so.

If any of the above genera were new to you, why not check them out on DinoBase!





Tuesday mini-book reviews: “Moa” and “The Dinosaur Heresies”

17 04 2007

Being that classes were canceled yesterday due to local flooding (people were using boats to get around in Edison and Rt. 18 was underwater about a mile away from my apartment) I had the opportunity to read Moa by Richard Wolfe in its entirety, as well as dig into the first 100 pages of Robert T. Bakker’s landmark work, The Dinosaur Heresies. One was so good that it made me nearly euphoric, the other a huge disappointment; can you guess which?

Me & moa

Being that I actually finished Moa, I should probably discuss it first. Although I have never actually seen any remains of the animal (the closest I’ve come are life-sized reconstructions at the Bronx Zoo and Philadelphia’s Academy of Natural Sciences), I am fascinated by the Great Auk, Dodo, Rodrigues Solitaire, and other large extinct birds. How they evolved, lived, and ultimately went extinct are, I believe, important to know and learn from, but unfortunately Wolfe’s book did little to illuminate details about the Moa (which is actually an entire family of extinct birds, not just one species).

Much of Wolfe’s book is about what led to the discovery and early study of the moa, but most of the book revolves around the colonization of New Zealand and the search for more information about the moa. Sir Richard Owen is given copious amount of time in discussion in the book, with the author fawning over the late, great anatomist towards the end of the book (and referring to him as the “Hunterian Professor” and other lofty titles throughout). History is all well and good, but the titular subject of the book seems to be little more than a common theme to tie the book together. Nevertheless, I did learn a few interesting fact, i.e. that Richard Owen had the spine of his long-time rival Gideon Mantell (the man who discovered the first known remains of an Iguanadon) removed and put on display at the Hunterian Museum, as well as part of the spine as geologist William Buckland. I should not blame the author being that in the introduction he mentions he did not intend the work to be primarily about the birds themselves, but alas, I had ordered it before I knew this was the case. It will continue to sit in my collection and perhaps may even come in handy as a resource at some point, but if you’re looking for a book about the extinct, giant birds, it would be best to look elsewhere.

By contrast, I was excited to receive a copy of The Dinosaur Heresies yesterday, and it certainly has proven to be an enthralling read. While I should perhaps hold my ultimate judgment until the end, Bakker communicates clearly, concisely, and effectively, the lavish illustrations further drawing the reader in. Simply put, it is a pleasure to read, and while I didn’t think I would be in the mood to continue reading after slogging through the 217 pages of Moa, I simply couldn’t put the book down. As important and influential as Bakker’s work may have been, I have to sadly admit that there are still things wrong with our dinosaurs, and I know of at least one case where a paleontologist was chastised for telling a newspaper that the skeletons at his museum were not up-to-date. I found this passage from the opening chapter (“Brontosaurus in the Great Hall at Yale”) to ring especially true;

Generally speaking badges are harmful to science. If a scientist pins one labeled “Reptile” on some extinct species, anyone who sees it will automatically think, “Reptile, hmmm… that means cold-blooded, a lower vertebrate, sluggish when the weather is dark and cool.” There are never enough naturalists around, in any age; so most scientific orthodoxy goes unchallenged. There are just not enough skeptical minds to stare at the badge and ask the embarrassing question, “How do you know the label is right?”

Be kind to colleagues, ruthless with theories, is a good rule. A scientific theory isn’t merely idle speculation, it’s verbal picture of how things might work, how a system in nature might organize things-atoms and molecules, species and ecosystems. But old paleontological theories too often aren’t treated roughly enough. Old theories-like reptilian nature of dinosaurs-are accepted like old friends of the family. You don’t yell at Old Aunt Cecilia. So hundred-year-old dinosaur theories live on without being questioned, and too often they are assumed to be totally correct. Even when such theory is caught in error, it’s likely to be excused.

While I am far from being a scientist as of yet, I’ve found that by poking around a bit and saying “How do you really know that?” you can very quickly get some frustrated (and even angry) responses, but I believe such skepticism is vital to scientific understanding. I don’t believe in “teaching the controversy” when one side of the issue is obviously wrong, but we should question, poke, and prod when it comes to established science; if we don’t do this science becomes more about faith than actual understanding. Even if something is entirely reasonable to infer, I think (especially in paleontology) we should be careful before saying “This is simply the way it is” and a healthy does of skepticism would serve us all well.

Yesterday I received an e-mail from my mother notifying me that she had unearthed some old Time-Life natural history books I fondly remember from my childhood. I am not sure when the books I had were printed, but I can still clearly remember diagrams of embryos (Haeckel-style), nude early hominids hunting deer, monkeys clinging to wire-mesh mothers, and a Brachiosaurus submerged in a large body of water because it could not support its own weight. Such was the conventional wisdom at the time, the same inherited paradigm that had Tyrannosaurus rex dragging its tail in pursuit of prey, but we now know both ideas to be entirely wrong. I can only imagine what new discoveries will change old ideas in my lifetime, or how many of my books may be rendered irrelevant scientifically (but still worthwhile to trace the history of science).

Reading Bakker’s book also got me wondering about the current state of taxonomy/systematics when it comes to dinosaurs and birds. If it is conclusive that birds are derived from dinosaurs, shouldn’t we change the taxonomic labels for these groups? Birds are distinguished at the Class level (Aves) while Dinosaurs are distinguished at the level of the Superorder (Dinosauria). If birds really did evolve from theropod dinosaurs, shouldn’t some taxonomic realignment be warranted? Shouldn’t paleontologists, ornithologists, and others organize some big meeting with the ICZN so that our taxonomy reflects what has been observed? If we continue to keep taxonomy separate from systematics, how will we ever coherently be able to explain or trace the history of life on this planet? Tradition be damned; if scientists don’t work together to make some sense out of this than what are we doing other than stamp collecting?

In any event, I look forward to completing Bakker’s book and I hope that I myself make a good “heretic”, not because I wish to raise the ire of my future colleagues, but because I want to know about the natural world, not believe in one idea or another just because of tradition.





New species of Clouded Leopard recognized!

15 03 2007

It is becoming more and more apparent that if you want to recognize new species, Borneo is the place to be these days (although Malaysian “web footed” sharks don’t count). In this case, it’s not so much that a completely new animal has been found, but that a long suspected need for taxonomic revision has become realized. In the past, the Bornean Clouded Leopard (now known as Neofelis diardi) was assumed to be a subspecies of the Clouded Leopard (Neofelis nebulosa), the Bornean Clouded Leopards inhabiting the Indonesian archipelago and Clouded Leopards inhabiting mainland Asia. I haven’t had the opportunity to see an active Clouded Leopard (the one at the Philadelphia Zoo always seems to be sleeping when I’m around, but that’s what cats do best after all), but this is what they look like;

Clouded Leopard

And now, courtesy of the WWF, is the new Bornean Clouded Leopard;

Bornean Clouded Leopard
Bornean clouded leopard (Neofelis diardi)
Kalimantan (Indonesian Borneo), Indonesia.
CREDIT: (c) WWF-Canon / Alain COMPOST
IMAGE No.: 112939

According to the WWF press release, the new species was recognized by use of DNA testing, indicating about 40 differences between the Bornean cats and their mainland relatives, their estimated time of speciation estimated at 1.4 million years ago. Other than the DNA, it is clear merely by looking at the animals that they are of two different species, the Bornean Clouded Leopards being much darker (they almost have a caramel-like coloring) with a double dorsal stripe (not visible in the picture above) and more distinct spots within the larger spots. As Dr. Andrew Kitchener (one author of the paper that determined that there are two species) said, after comparing pelts of animals from the mainland with those of Borneo;

It’s incredible that no one has ever noticed these differences.

While the actual divergence of the Borneo Clouded Leopard occurred 1.4 million years in the past, it still can give us insight into speciation and if we are lucky enough to be around for the centuries (and hopefully, millenia) to come, perhaps providing some clues as to how animals might change after a speciation event. Unfortunately such studies would take much time and effort over many generations, but I hope that by discovering and keeping track of closely related animals in differening ecologies, we can get a better idea about the “tempo and mode” of evolutionary change. Regardless of what we may learn in the future, I for one am ecstatic to know there is another great cat stalking the Bornean jungles, and I hope it will continue to do so far a long time into the future.





And so it begins…

18 01 2007

Last night I had my first Biology 102 class meeting, kicked off with the usual speech about academic integrity, lab issues, etc. I swear, I could probably give the instructions myself at this point. After all the bureaucratic demands were met, however, the professor began a discussion of classification, reciting the famous “King Philip’s Chef Orders Fresh Green Spinach” for Kingdom-Phylum-Class-Order-Family-Genus-Species (with the alternative “Kinky People Come Over For Great Sex”) and mentioning Linnaeus as the “father” of our binomial nomenclature systems. This was all well and good, but then she attempted to make the differentiation between “classification” and “systematics.” She said that classification does not necessarily reflect evolution while systematics has evolution primarily in mind, but this struck me as rather odd. In classifying organisms, isn’t the evolutionary history at least somewhat inherent in the placement of a living thing at the various levels of classification? This isn’t to say that evolution is necessarily always assumed, but it seems to me that in figuring out how closely related one organism is to another (and lots more of varying degrees of similarity as we move up the “ladder” of classification) evolutionary relationships should become self-evident. Obviously Linnaeus didn’t have evolution in mind when he came up with his system, but that doesn’t change the fact that the way in which he organized life reflected its evolutionary history to greater or lesser extent.

After this the professor moved on to the concept of species, quoting Ernst Mayr for the definition. She did mention that for paleontologists, a definition based upon who breeds with whom does not work and makes it necessary to have “morphospecies”, but I think she really shortchanged the rest of the audience as to the controversy surrounding something as seemingly “obvious” as species. Sometimes species don’t “stay where they’re put” as far as reproduction goes, creating hybrids or variations not otherwise seen such as when a wolf and dog interbreed. This is the most widely cited example, but if we think beyond animals for a moment, plants can more readily hybridize and defining species by reproductive habit doesn’t suit botanists well at all. We can’t even say “Well, if there are less than 5 derived characters that are different, then it’s a different species” because such is an arbitrary judgment and what differentiates a species might be something as subtle as behavior, especially if a speciation event has occurred recently. What if two animals look almost exactly alike and can interbreed but do not because of geographic or behavioral reasons? Are they two different species? I’m sure a whole lecture series could be done on the topic, but that would take far too much time in a fast-paced biology course. Even so, sometimes “keeping-it-simple” can do a disservice to students, I think, and I would have taught the lecture differently.

Another thing that irks me is the nearly ubiquitous (at least during my own education) need to put ecology and evolution at the end of the course. These are two important concepts that could be better understood by keeping track of relationships throughout the course, but instead they are relegated to about 3 weeks worth of lectures at the end as their own separate topics. I think they really should be bookends, the basics introduced at the beginning and then used at the end to tie everything together, as how can you hope to understand biology if you can’t understand the ecology and evolution? I’m sure many in the class are going to move on to be doctors and aren’t as concerned with more “abstract” principles or relationships, but this is partially why there is such controversy involving evolution today; it is not taught correctly, even at the college level.





There’s no way I can back this up at all

14 01 2007

Lately I’ve been enthralled by all things large and mammalian that live(d) in Africa, indulging myself with the Alan Turner/Mauricio Anton books Evolving Eden, Big Cats and Their Fossil Relatives, and Relentless Enemies by Derek & Beverly Joubert. The “charismatic megafauna” of Africa is so interesting to me, especially given the variation in behavior and appearance across the continent. Relentless Enemies is a wonderful example of this, showing lions that have specialized in eating the dangerous Cape Buffalo and have learned to cope with the swampy Okovango Delta habitat. Lions normally aren’t big fans of water, but these lions quickly take to it, only really getting upset when their whiskers touch the surface (I assume because, other than perhaps wanting to keep their whiskers dry, this means they’re in water too deep to feel the bottom).

In any event, although there have been big cats, giraffes, antelope, elephant, hippos, and other extant varieties present for millions of years, they took some rather odd forms and were generally more “pointy” (more horns, teeth, etc) than their living counterparts. This got me wondering about evolution in general and convergence; if you have two animals that have arrived at the same form via two different lineages how different are they going to be genetically? The example that came to my mind first involved flight, bats having their wing made from membrane between their fingers and the extinct pterosaurs having their wings made of a membrane stretched from an elongated 4th digit to their body. Would both these groups have similar genes for making the membranes that allow them to fly? Perhaps not, the actual membrane differing in the way its attached and probably composition, but alas, there is likely no way to tell being we won’t ever be able to faithfull reconstruct a pterosaur genome for lack of material.

Even so, it makes me wonder. I thought about the oft cited similarity between chimpanzees and humans as well (the estimate of similarity going from 98% to 95% recently, if I remember correctly), but I think this implies a flase ancestor/descendant relationship at times. Surely, we are most closely related to chimpanzees out of the extant great apes, but we didn’t evolve from them; at best we shared a recent common ancestor and we’ve both evolved along seperate lineages for at least 2 million years. During the divergance of lineages later leading to humans and then to chimpanzees, what was the ancestor like? What adaptations or novel structures/functions/behaviors have chimps picked up since the split? Since we are related, if we both independantly evolved similar features how would these features be expressed in the genome; would it essentially show up as a “false positive” suggesting that we both inherited a feature that was evolved independantly by both groups?

Unfortunately for me, the areas in which I excel are the more “traditional” areas associated with zoology, mostly being anatomy, behavior, etc. and microbiology/genetics often makes my head spin (as much as I would love to have a natural aptitude for it). Still, I can’t help but wonder if some of the results of phylogenetic studies that don’t match up with the fossil record are because of convergence. In the Big Cats book, it’s mentioned that as a result of phylogenetic study that extant lions were suggested to be descendants of saber-toothed cats, but we know this not to be true (they are sister groups, both on different “brances” of the Tree of Life [or bush, or coral, if you prefer], sharing a common ancestor) because of fossil evidence. Is it possible that because both animals developed similar features independantly, resulting in convergent evolution, they appear to share more genetic material than they actually do? This problem may not be anything new to those who specialize in genetics, but they will have to forgive me for being slow. What if we could genetically figure out the results of convergent evolution, being able to better pinpoint relationships and what occurred during the history of life? If no one has tackled it yet, perhaps I’ll have to buy some genetics books and get cracking.