Any number of factors 50 million years ago could cause an animal to change, but surely CO2 must be the culprit according to these folks. They don’t even have a picture of the darn thing I can find. But read the abstract after this story for a surprise. – Anthony
From a UFL press release:
UF study shows carnivore species shrank during global warming event
GAINESVILLE, Fla. — A new University of Florida study indicates extinct carnivorous mammals shrank in size during a global warming event that occurred 55 million years ago.
The study, scheduled to appear in the December print edition of the Journal of Mammalian Evolution and now available online, describes a new species that evolved to half the size of its ancestors during this period of global warming.
The hyena-like animal, Palaeonictis wingi, evolved from the size of a bear to the size of a coyote during a 200,000-year period when Earth’s average temperature increased about 15 degrees Fahrenheit. Following this global warming event, Earth’s temperature cooled and the animal evolved to a larger size.
“We know that plant-eating mammals got smaller during the earliest Eocene when global warming occurred, possibly associated with elevated levels of carbon dioxide,” said lead author Stephen Chester, a Yale University doctoral student who began the research at UF with Jonathan Bloch, curator of vertebrate paleontology at the Florida Museum of Natural History. “Surprisingly, this study shows that the same thing happened in some carnivores, suggesting that other factors may have played a critical role in their evolution.”
Researchers discovered a nearly complete jaw from the animal in Wyoming’s Big Horn Basin in 2006 during a fossil-collecting expedition, led by Bloch, a co-author on the study. Bloch said the new findings could help scientists better understand the impact of current global warming.
“Documenting the impact of global climate change in the past is one of the only real experiments that can inform us about what the effects global warming might have on mammals in the near future,” said Bloch, who has studied this climate change event for nearly a decade.
Scientists think the Earth experienced increased levels of carbon dioxide and a drier environment during the warmer time period, but they do not completely understand what caused mammals to shrink.
One theory is that carbon dioxide levels reduced plant nutrients, causing herbivorous mammals to shrink. The newly described species primarily consumed meat, meaning plant nutrients couldn’t have been the only factor, Bloch said.
Mammals in warmer climates today tend to be smaller than mammals in colder climates, Chester said. For example, brown bears in Montana are generally smaller than those found in Alaska.
The study’s other authors are Ross Secord, assistant professor at the University of Nebraska, and Doug Boyer, assistant professor at Brooklyn College.
Bloch said a tooth from this animal was described in a paper about 20 years ago, but scientists did not have enough information to name the new species until finding the jaw.
The species was named after Scott Wing, a paleobotanist at the Smithsonian National Museum of Natural History. He studies the impact the global warming event had on forests in the past, and has played an important role in the collaborative research in the Big Horn Basin, Bloch said.
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Only one problem, here’s [the abstract] saying CO2 had nothing to do with it:
A New Small-Bodied Species of Palaeonictis (Creodonta, Oxyaenidae) from the Paleocene-Eocene Thermal Maximum
Abstract
Of course, Real Climate thinks the PETM is “weird” so pretty much anything goes I suppose if you can link anything in that period to CO2 somehow.
A New Small-Bodied Species of Palaeonictis (Creodonta, Oxyaenidae) from the Paleocene-Eocene Thermal Maximum
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According to this article in the New York Times, people in Alaska don’t believe in global warming
http://www.nytimes.com/cwire/2010/08/26/26climatewire-in-alaska-doubts-about-climate-change-rise-w-72310.html
How fickle of them
Since the average size of humans has significantly increased in the last few hundred years, does that mean that we are entering global cooling and responding with evolutionary change?
I’m just sayin…
Dillon Allen says:
“Since the average size of humans has significantly increased in the last few hundred years, does that mean that we are entering global cooling and responding with evolutionary change?”
That size change is mostly due to two causes:
1. Better nutrition
2. Reduced levels of inbreeding
People in general eat a lot better today than a hundred or two hundred years ago, and consequently grow larger. In the West there isn’t much change now (except sidewise), but in countries like Japan and China the young people are very noticeably taller than their parents.
Industrialization also cause people to move a lot more than in the past. The parents of a child today are much less likely to be closely related than a few generations ago. Crossing two inbred lines often result in an exceptionally vigorous offspring (that is the concept behind hybrid corn).
Oh dear. I think there has been a misunderstanding. “Only one problem, here’s [the abstract] saying CO2 had nothing to do with it”, you shout gleefully. But the press release accurately reported what the paper said, and neither said that CO2 had “nothing” to do with it.
CO2 and Nutrition
I have been doing a literature search on CO2 and animals. There have been some recent publications on CO2 and “herbivores”–actually herbivore insects.
These said the protein component of plants went down. That would be true–the chief protein of the world is surely rubisco, the lead protein of photosynthesis. Plants need a lot of it to make up for the very low concentration (<.04%) of CO2 in today's atmosphere. Raise the CO2 a little, and plants can use the energy for other things, like carbohydrates and vitamin C.
There is some indication that this is bad for insects but good for us. What an amazing possibility!
CO2 is a blessing, not a pollutant.
jim hogg says:
August 25, 2010 at 9:08 am
When Huxley and Orwell gave form to their dystopian visions they assumed that the future of humanity would be shaped by malevolent intelligence; I read items like this which emanate from our national seats of learning and realise that they never for a moment anticipated the real shaping force: low level immorality and stupidity. How did science get like this?
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How did science get like this? I’d like to know also.
To be really unPC….. It probably doesn’t help, at least in developed countries, that apparently far fewer women who get university degree’s have children than those who don’t – and apparently somewhere between 1/5th to 1/4th of all women with advanced degrees never have children. Of course, then we can get into the whole debate about whether a propensity to higher education is really reflective of intelligence levels or not, but anyhow….
I’m sure that the huge influx into science univ./college programs and graduate programs from folks who were NOT in love with science but trying to avoid the draft didn’t help either – so many of those are now of an age to be in higher level positions throughout academia, not to mention having become professors responsible for the development of students for years and years. I suspect this has had a very large and negative effect on science in general in the USA.
Then add to it the push for ‘post normal science’ which is, as best I can tell, utterly anathema to the very idea of science – as Orwellian a concept as you can get…. I have no idea how widespread ‘post normal science’ is throughout universities in general, and haven’t had anyone in a better position to know volunteer an answer to that question when I’ve asked it a time or two.
Heck, the lack of rigor allow, even encouraged by ideas of post normal science makes doing ‘science’ if one is an adherent far far easier than doing real work. Just make everything match what you want to believe anyhow!
(/sarc)
Sigh. I wonder also (re how did science get like this). I also seriously wonder how much is really problems with ‘science’ and scientists in general or a change within actual scientific research, vs. how much is just appearances from poorly written articles…. Or if what we are seeing is more a function of one off research projects now being able to get almost instantaneous coverage because our communications are so developed and rapid now, where before they’d’ve died from lack of attention from other scientists due to being of poor quality or been quickly debunked by other researchers, long before poor research or sheer speculative pieces made it to the public eye. I have to say it also has always seemed to me that the softer sciences have been afflicted with problems this way far more than the harder sciences – and while there is a lot of ‘hard’ science involved in archeology and paleontology, there is so much that is totally unknown – and it seems that in those fields researchers have always liked to speculate – and state those speculations as if fact – far far more than I’ve ever been comfortable with. Example, how many “largest dinosaur that ever lived just discovered” bits have come out over the years? It ALWAYS should have been ‘largest found to date’ NOT ‘largest ever.’ Again, I hesitate, however, because I don’t know how much of that is the ‘science writer’ who’s doing the story vs. the actual scientists involved. Some of it the latter, however, as you see from their interviews or quotes.
Maybe I’m just getting ‘old’ and suffering from the ‘it used to be better than this’ syndrome.
re: Rich Matarese says: August 25, 2010 at 2:58 pm
–
A number of comments have run along the line of what kernels had posted at 2:30 PM on 25 August, writing:
“So a single jawbone provides insights into 200,000 years of evolutionary history?”
Not really. But that bone fragment can readily provide information on that particular critter – and it’s possible to infer that said critter is a specimen representative of its species – which accurately reflects its stature (size), developmental maturity, nutritional status, and the environment in which it lived and died.
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Ah, but does it really? Recent research is now saying that triceratops doesn’t even actually exist as a separate species, that its the immature version of what was thought to be a different dino altogether. Over time, all sorts of anomalies have been found from what was once thought to be ‘known’ based on various bone fragments. I would think the possibility of error based on a single jaw and tooth would likely be quite high. Look at the controversy over the ‘hobbit’ humans and pigmy mammals recently found – all sorts of questions about whether they were dwarfs/midgets, or actually a very small version of similar species – and those were from within the last 15K to 30K years.
—
At 3:58 PM on 27 August, Rational Debate had written:
“Over time, all sorts of anomalies have been found from what was once thought to be ‘known’ based on various bone fragments. I would think the possibility of error based on a single jaw and tooth would likely be quite high.”
There’s a bit of unintended lucidity. I wasn’t going to bring this up, but I have had to wonder how the authors of this paper establish Palaeonictis wingi as a new species of creodont on the basis of what they’d found in Wyoming in 2006. From the abstract above:
“We describe Palaeonictis wingi sp. nov. from the PETM in the Cabin Fork drainage, southeastern Bighorn Basin, Wyoming, based on associated right and left dentaries with P2-M2. Palaeonictis wingi sp. nov. is substantially smaller than the other North American congeners, making it similar in size to P. gigantea from the earliest Eocene of Europe and the previously described PETM specimen.”
To get the conclusion that P. wingi was a species unto its own, distinct from the other genus Palaeonictis species already identified, I’d think that there would have to be specimens representing more than just one critter.
But I’m not a paleontologist, and – of course! – Springer Verlag (yet another one of those international academic mega-publishers like Wolters Kluwer and Elsevier) has the full article behind a paywall), so I’m not likely ever going to read it. Have the authors of this paper a real basis for asserting that they’ve got themselves evidence of a distinctly different species of hyaenadont?
Rational Debate may not understand this, but a specimen comprising “associated right and left dentaries with P2-M2” is more than enough to tell a paleontologist that he’s got a creodont, which was a family of predators with some damned unusual dentition among the mammalia, and it will tell quite reliably whether or not the generating individual animal was physically mature and therefore at the peak of its growth. It’s also possible to reliably infer size, based upon what is known about other creodont species already documented by way of the fossil record, just as can be done with a similar section of “associated right and left dentaries” drawn from a human corpse.
But is it an entirely new species?
Those of us who were taught Ernst Mayr’s biological or reproductive species concept in Biology 101 tend to accept the “can’t crossbreed” argument as the acid test, but this can’t be applied in evaluating speciation among extinct critters, where the phylogenetic concept has to obtain.
It also gives some difficulty when considering offspring generated by matings between representatives of what are commonly accepted to be very different living species. If specimens of Panthera leo and Panthera tigris can mate to produce viable and fertile hybrid offspring, can we really speak of the lion and the tiger as “genuine” species?
And the day somebody comes up with a way to reliably breed fertile stallion mules (anybody not familiar with Robert A. Heinlein’s novel Time Enough For Love?) and get a majority of mare mules to be fecund, Equus mulus won’t be a half-joke appellation any more.
So how is it that the authors of this paper can assert that their particular critter (and it looks as if they’ve only got the residue of one critter) is in itself evidence of a whole new species of hyaenadont?
I think it might be argued that the animal upon which this paper (and its assertions) are focused could well have been a dwarf adult of another Palaeonictis species. Has anybody reading here considered how the authors of this paper in JME addressed the criteria of the International Code of Phylogenetic Nomenclature (PhyloCode) in claiming P. wingi as a new species of creodont?
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Re: Rich Matarese says: August 27, 2010 at 8:00 pm
–
Funny, but I thought it was a bit of intended lucidity myself. 😉
Yes, as I noted, possibility of error from a single jaw and tooth, of long extinct species/family/critter fairly high – on many counts, including speciation as you note.
Bingo. Lots of other bingo’s just waiting in this abstract/article also, from the sounds of it, although as you noted, its behind a paywall and I’ll not likely wind up reading the actual paper either, unfortunately. Some of the various issues may well be addressed, there’s just no way to tell without the full paper.
You went on to write:
Frankly I have no real problem with family identification from a jaw this way, that’s plausible. I wasn’t aware of the unusual dentition, but that’s not a big issue in this case beyond lending credibility to the basic identification of the critter. I have no real problem with the idea of identifying the level of maturity either – with some reservations, depending on how many other examples they have of this family, including both immature and mature samples to generate a spectrum. One of the problems with trying to compare the information that can be drawn from human remains, vs. extinct creatures, however, is that with human remains we have all sorts of living examples and recently deceased examples along with all sorts of samples of our environment all of which allow for exquisite comparisons so we can take very small samples and know quite a few things with a good degree of accuracy – this simply isn’t the case with extinct species.
Look at it this way even… take two living present day human examples such as the basketball star Yao Ming (sp?) as compared to a world class male gymnast, who is likely 5’4″ or less, at full mature height (or any healthy adult male, who’s on the short end of the spectrum). Then extrapolate forward, say a million years, and lets assume that the majority of fossil remains of humans that had been found were of average height men… Now, what is the likely supposition going to be when suddenly Yao Ming’s jaw is discovered? Or what if the outlier happened to be one of those gymnasts? Or what if, because of chance occurrence for where fossils happened to be both created more commonly and happened to be found, if the majority of adult male fossil remains were of dutch and kenyan men, and then a completely healthy, fully mature specimen from a fellow living on a continent (not island) who was all of 5′ tall is found? Is he a ‘new species’ of human? Did his ‘species’ shrink because of too much CO2 (or too little?)?
Or how about a modern day draft horse (or the no longer existent heavy horse of old that carried knights?), compared to a pony, or a typically small sized horse breed such as the Arabian? Same species, radically different sizes.
I know these analogies aren’t perfect for the article, but I believe you get my point. Size variations may have nothing to do with anything other than natural variation within the species. Just look around you – the diversity is incredible both within species and between species. Speciation is difficult enough with present day living things, natural/normal size variations can be huge, vegetation, climate, etc., all contribute – the only reason we can tell so much from present day remains is we have ways to actually check the accuracy or faults of our predictions, our assumptions…. that’s quite different from extrapolating and trying to make accurate predictions of exactly what something was like from a limited number of fossil remains, especially when all too often these declarations are built from assumptions being made which are often based on previous assumptions and so on.
—
At 10:04 PM on 27 August, Rational Debate had written:
“Frankly I have no real problem with family identification from a jaw this way, that’s plausible. I wasn’t aware of the unusual dentition, but that’s not a big issue in this case beyond lending credibility to the basic identification of the critter.”
Er, yeah, it is a “big issue.” Look at it this way. The predator mammal species that largely out-competed the creodonts in their ecological niches are referred to as “fissipedia.” Think canidae and felidae and mustelidae and even hyaenidae. The name emphasizes the fact that their toes are separated, and morphologically we concentrate on their feet. The creodontidae, by contrast, are distinguished principally by virtue of the fact that their carnassials (large teeth designed for shearing soft tissues and bone) are set further back in the jaws than modern-day fissiped predators, whose analogous dentidae are crushing-type molars.
As I’d written earlier, one online writer had assembled some years ago (the URL is not available to me as I write) a pretty good argument to the effect that genetic coding for the creodonts’ carnassials had to have been much more complicated than what’s required to set up the dentition in the fissiped predators, and this might have been conducive to reduced reproductive fitness in the creodont species.
They got out-bred by big litters of puppies and kittens and such. The same thing happens among clades of human immunodeficiency virus (HIV) in clinical medicine. The “default” wild-type clades of HIV are always more vulnerable to antiretroviral agents, but the drug-resistance mechanisms make the refractory clades less capable of replication. Such resistance mutations come at a thermodynamic cost. Discontinue the ARV drugs, and the resistant clade will drop down below the threshold of detection in genotypic and phenotypic identification testing, and – voila! – the wild-type bug will predominate again. Not that the resistant clades go away. Re-introduce the drug(s) against which resistance had developed before, and the resistant clade will proliferate explosively.
But you get the notion of reproductive fitness and how that figures in overall viability, right? The charismatic megafauna are markedly more liable to extinction than are retroviral pathogens. The creodonts went pfft! about eight million years ago, despite having been top-niche predators in their time.
This notwithstanding, consider that the taxonomic focus on the creodonts is on their teeth despite the fact that they had a lot of other differences from mammals in contemporary parallel lines of development. Any modern zoologist, given a glance at a creodont jaw, would spot the distinguishing characteristics instantly. They’re not subtle.
Rational Debate had gone on to observe:
“…that with human remains we have all sorts of living examples and recently deceased examples along with all sorts of samples of our environment all of which allow for exquisite comparisons so we can take very small samples and know quite a few things with a good degree of accuracy – this simply isn’t the case with extinct species.”
With the creodonts as a whole, however, that’s not the case. There are fossilized remains for entire animals of (to the best of my knowledge) all of the identified species except for what the authors of this paper claim to be a new species in and of itself, Palaeonictis wingi, and there’s where I’ve got to look with some skepticism and wonder whether these guys have satisfied the rules established by the International Society for Phylogenetic Nomenclature (ISPN) in their determination that these fragments of one critter provide a reliable basis upon which such a decision can be made.
This isn’t so much a question of error, insofar as I can determine, but rather one of over-reach.
It is certainly possible for a paleontologist or anybody else with comparative anatomical expertise to do an effective and accurate job of “extrapolating and trying to make accurate predictions of exactly what something was like from a limited number of fossil remains.” What part about this is still not yet grasped? How the hell can a country G.P. get this and people with real intelligence keep screwing up their appreciation of how anatomical inferences are reliably drawn from even fragmentary fossilized hard tissue remnants?
Look, this is biology, not quantum physics. This is where those of us with fatal math impairments go when we want to play scientist. This is the easy stuff, honest. How hard can it be for people without an undergraduate degree in this discipline to understand?
—
Ah, Buck. What a boon he would have been to the early pioneers.
Without meaning to be impolite, I suspect that part of the problem here may revolve around context and common knowledge. In particular, in any scientific discipline, there exist widely accepted ideas that may not be known or appreciated by those removed from the science. This is clear from some of the commentary in the present case.
1. The PETM occurred about 55.5 +/- 1.0 million years ago on current time-scales. Although the absolute age has some uncertainty, the relative timing of perturbations before, during and after the interval are known much better. The entire “event”, from start to finish, must have occurred within about 200,000 years; the initiation was probably less than 20,000 years. The onset of the event precisely coincides with the start of the Eocene epoch (in fact, it now defines this point in time).
— None of this has to do with radiocarbon (because the half-life is far too short);
— One must be exceedingly careful correlating “happenings” in time because of a “floating” absolute time-scale (for example, something reported as occurring 57 million years ago in 1990 is now reported as 55.5 million years ago in 2010);
— The PETM predates the warmest time of the Cenozoic, which is called the Early Eocene Climatic Optimum, and occurred ca. 53-51 million years ago (again, on the most current time scales).
2. There is overwhelming evidence that the PETM was characterized by a significant rise in mean annual Earth surface temperature (about 10-11 °F), a massive input of carbon to the ocean and atmosphere, and profound environmental and biotic changes across the globe. The magnitude of the total carbon addition across the event remains fairly uncertain (from about 2500 Gt to >6500 Gt), as does the rise in atmospheric pCO2. Nonetheless, it is virtually certain that atmospheric CO2 did rise by a large amount (>400 ppmv). Moreover, it is certain that the carbon input was highly depleted in 13-C, implying that it derived from oxidation of an organic source (such as methane or peat). The environmental changes included a major turnover in mammalian orders as well as mammalian dwarfish (as an aside, this is why there is a Paleocene-Eocene Boundary). There was nothing else like the PETM in terms of rate and magnitude of temperature rise and carbon addition, at least in the last 90 million years.
— There indeed have been many variations in Earth’s climate and the environment; however, the PETM is an extreme and special case;
— It has become a magnet for scientific investigations because of its general characteristics (extreme global warming, massive CO2 input from oxidized organic carbon at a magnitude similar to that projected for the coming centuries, pronounced environmental change);
— Because huge amounts of 13-C rich carbon entered the ocean and atmosphere, the event can be readily located in different environments and correlated.
So, with this context, one might consider the abstract and the authors in a somewhat different light. The authors are interested in seeing what happens to mammals when temperature and atmospheric pCO2 increase significantly. This is because there is a great deal of speculation as to how Earth operates with massive inputs of CO2, extreme warming, or both. They selected the PETM because it is the obvious time interval in which to examine the hypothesis. They chose the location because there have been numerous previous studies here, which means they have an extensive database in which to compare their mammal fossil findings. In particular, they already knew that jaw bone size relates to body size, and that dwarfism occurred in several herbivore mammal lineages across the PETM. An apparent existing suggestion in the literature was that this established dwarfism was caused by the known rise in atmospheric pCO2. The present authors’ idea was that, if correct, carnivores would not become smaller across the PETM. They found that, interestingly and for the first time, carnivores also became smaller across the PETM.
I’m guessing that this is a more accurate take on the issue than that deduced in many of the previous comments. Of course, this would mean that there was no purposed spin to the articles, and that much of the commentary on this issue has arisen because of pre-conceived ideas – basically jumping to conclusions without the appropriate common knowledge.
I have my own problems with the framework of the manuscript. These arise because other environmental parameters clearly changed across the PETM. Of particular importance to the present discussion is precipitation. There is growing evidence that the hydrological cycle became more intense and more seasonal during the PETM (that is, greater amounts of annual rain but over a shorter duration of the year, which should explain the confusion in some of the comments regarding wet and dry). Almost assuredly, this would impact the type and abundance of plants. So, how would one disentangle what parameter caused the dwarfism of herbivore mammals?
Reply to kyzul (August 29, 2010 at 1:46 pm)
The use of the word “dwarfism” implies an undesirable size compared to “normal” size. The straw-man assumption that small is undesirable leads to incorrect conclusions about whether or not increased temperatures and CO2 are harmful.
Small may be undesirable (and may imply a bad environment) for an individual that is smaller than its peers, but the same does NOT apply for an entire species on an evolutionary time-scale. Confusing the two (an individual symptom vs species evolution) is typical of pseudosciences such as Lysenkoism.
Reply to Candae:
The use of “dwarfism” in the article as well as in my comment implied nothing about desirability. It is simply an observation from examination of rock sequences. When one examines strata spanning the PETM, the size of jaw-bones and teeth representing numerous specimens of different mammal species becomes smaller (and larger after the event by the way). By inference using well-established relationships between jawbones, teeth and body size, this indicates that the average body size of specimens representing multiple mammal species became smaller. We also know that the time when this occurred was when climate changed profoundly. These are verifiable observations and testable inferences. I will definitely agree that the pseudoscience begins when one tries to spin the objective observations into some subjective context.