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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In general, animals shrinking in size in hotter climates makes sense to me. The smallest, the more area exposed per unit of volume, therefore the easier it is to refrigerate. In the same way, colder climates favor bigger bodies.
What I don’t understand is the assumption that getting smaller was a bad thing. Why? Isn’t it the most efficient? Wouldn’t it be great if us humans could keep our same intellect and emotions in a body half the size? That can only be a good thing, from any point of view.
‘One theory is that carbon dioxide levels reduced plant nutrients, causing herbivorous mammals to shrink.’ That’s news to me.
Remember the small people of Flores, isolated by rising seas from global warming, naturally shrank to fit their new environment. I also remember reading there were small elephants there as well and it had nothing to do with CO2.
Unless of course there was a buildup of ‘carbon pollution’ hovering around the island in the good old days, which I doubt.
Well, why do commercial vegetable producers pump a huge amount of extra CO2 into their greenhouses? Crop yields are 4X greater than they would be without the extra CO2. And yet, these alarmists want us to believe that extra CO2 is bad for nutrition and plants.
Surely a smaller body size is advantageous from a species survival perspective – with a smaller body size, fewer resources are required to support a bigger and more diverse population and thus a bigger genetic pool. This bigger genetic pool provides better chances of species survival – so there would be a tendency to reduce in size if possible.
Due to volume vs surface area and its effect on heat loss, a colder climate means a smaller body size is a disadvantage.
Thus a warmer climate provides a species a better opportunity to survive better with a smaller body size – CO2 and poor nutrition don’t need to be blamed.
Blaming species body size decline on poor nutrition smacks of Lysenkoism.
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Particularly in any homoiothermic (warm-blooded) species, a warm environment will tend to stress the individual creature by way of the need to bleed off excess body heat. The inverse-square law operates with regard to the ratio of body mass to body surface area, which latter provides the principal means of radiative cooling.
In very cold climates, it pays to reverse the ratio in order to conserve heat, and so cold-weather species tend (all other factors being equal) to have higher mass, and therefore mass-to-BSA ratios that enable such conservation of metabolic heat.
This is pretty much a no-brainer.
Consider that little kids – who have a lot of body surface area relative to their mass – are much more comfortable than adults in hot weather, and do not tolerate cold as well as adults do. They’re “built” to lose heat into the environment by way of convection, radiation, and conduction.
Any parent is familiar with how rapidly little kids’ lips turn blue – a sign not of cyanosis but of diversion of capillary flow from the skin and exposed mucous membranes to the body’s core circulation – when they’re swimming in relatively warm water. This develops much more quickly in children than in adults. It’s an early warning of developing hypothermia, and since time out of memory has been the sign interpreted by mothers that it’s best to get their kids out of the water and have ’em towel off and sit in the sun for a bit before allowing them further splash-and-swim time.
For the same reason that human beings many generations resident in extremely cold climates (like the Yupik and the Inuit) trend toward compact builds and even endomorphism and those in consistently hot regions become ectomorphic (and even get smaller in stature, as have the ǃKung of the Kalahari Desert), it can be reasonably expected that individuals of various other species in any given region will tend to get more massive as the climate gets colder, and selection pressures will result in smaller critters when temperatures are consistently elevated.
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jorgekafkazar says:
Yes, the Area to Mass ratio is crucial for warm-blooded animals. Larger animals retain heat better; small animals emit heat better.
I always understood that it was surface area to volume (rather than mass) ratio.
Small animals also tend to reach maturity faster than large animals and often produce more offspring.
Using jaw bones? Triceratops would be upset about that.
http://gizmodo.com/5601514/the-triceratops-never-existed-it-was-actually-a-young-version-of-another-dinosaur
Of course, I don’t know what I am trying to prove by linking the use of bones in a study to the disappearance of a make-believe species of dinosaur…
So let me see if I got this right.
At a certain CO2 level you will have 205% more vegetation but only double the nutrition, for example? Is that how this alarmist reduced nutrition meme works?
To my mind all this proves is that to get funding, get published or get your press release noticed you just have to bring CO2 in somewhere, however speculative or confusing.
cheers David
Recent research has shown that plants produce more growth and higher nutrient levels with high atmospheric CO2 levels. Were plants 15ma years age so different to today’s? Also all animals survive warm periods when smaller and survive cold periods when larger. It is about the ratio of mass to surface area and an ability to remain cool. Nothing to do with CO2. These scientists neglect to mention CO2 levels when the climate cooled. I suspect it changed very little.
@Mark: Since density of wet tissue is more or less constant for a species, volume and mass are very highly correlated. Or, simply: volume is mass at constant density.
On islands, species will commonly shrink. The smaller animals need less feed to survive, and when food is scarce from a well grazed or hunted island, the small guy finds enough to live. Oddly, there is also some pressure to larger size if the competition is based on fighting not on feeding.
In warm climate zones there is an upper bound were function starts to fail. I once saw a giant cow on display at a county fair. It was about twice the size of the typical cow. They had to put a load of fans on it and provide periodic water misting to prevent it from dying in the summer heat (not needed for normal sized cows). If it had needed to run from a predator it would have been dead from heat stroke in no time. So there is pressure to smaller size to move fast while still being able to dump the excess heat.
In cold climates you need to be bigger (or better insulated) to minimize heat loss and food needed per pound. So the pressure is to larger sizes. (No, not all animals must be huge, but each animal tends to be favored if a bit larger than it’s neighbor. In South America there is the worlds largest humming bird. It lives in a cold climate and sits down to eat rather than hover, so as to conserve fuel.)
And yes, none of this has anything to do with CO2. It has a lot to do with heat management in warm blooded animals and with competition via feed and fighting.
It has nothing to do with CO2 diminishing the quality of plants. CO2 promotes growth so provides more total food, not less.
And just to throw in one more ringer: the occasional rock from space tends to kill off those species that are very large as they can not hide from it AND need the most food. Food that is scarce post catastrophe. Little things that can hide in holes in the ground tend to survive and eat the small scraps of stuff left to eat. So periodically we have mass extinctions of large stuff, like Dinosaurs, and then a re-radiation of species from the small things living in holes back into big things (as big things survive and dominate in fights better)… until the next rock from space…
The loss of megafauna from North America probably had more to do with a rock hitting the ice sheet than it did with people hunting them. The Clovis People got mostly wiped out too. We are megafauna…
So I don’t see a lot of news in the idea that species sizes change over time. They always have and they always will.
A Cheetah can put on one short burst, then must rest and cool down for about 30 times that burst interval. We sweat so can run a marathon. Mammal size is very much about heat management. (That is also part of why Hippos and Elephants are seen in the water a lot, and not moving much when out of it on hot days.)
Though it is interesting that insects are oxygen limited. The giant 3 foot dragonflies of past eras can not survive in our low oxygen today. The size of the ‘air ducts’ through their joints is limiting and they distribute the oxygen via such air, not blood. So it would take more O2 and higher density atmosphere to have giant bugs again… burning the O2 to make CO2 will shrink the bugs, and I’m all for that. The leg joint air duct cross section is a ‘square of the linear dimension’ function while the mass needing air is a cube function. That puts the upper bound on bug size. Just bugs hit is as air distribution at smaller sizes than mammals who hit it as heat loss. That is also why people and horses sweat. So we can be very active and not die from overheating, while still being (relatively) large.
All this has been known for a long time, so I don’t see why this paper was ever published. Guess someone needed lunch money…
Oh, and perch will tend to overpopulate a pond and ‘runt’ to very small size unless you have enough bass to keep them in check. Then you get fewer, but larger, perch and bluegill. Same thing for tilapia (I’ve done it). If raised in an overcrowded tank, each generation is smaller than the last (total mass of fish constant at the upper bound of the tank carry capacity) until they are about 3 inches long. If culled and spread out, they will grow to about 8 to 10 inches long. So predator / prey ratios matter a great deal too. Again, nothing to do with CO2.
More freshman biology. Generally speaking as the nutritional level of plant material falls, the animal eating it needs to eat more to gain the same amount of benefit. That means a bigger stomach. Bigger stomachs need bigger bodies to carry them around.
So one would expect herbivores to evolve larger bodies to deal with nutient-poor food, not smaller.
This whole paper is BS
I stopped reading at “increased co2 decreases plant nutrition”
This could be the answer to the problems of overpopulation of humans. If we do a rapid evolution (aided by food scarcity) to a smaller size, then the world resources would be able to support an increase in human population.
Birds are shrinking also.
http://news.bbc.co.uk/earth/hi/earth_news/newsid_8560000/8560694.stm
There is nothing crazy or new or even unusual about this. Animals grow larger in colder climate and smaller in warmer climate. This is a well-known phenomenon that is true both in the present (where animals grow larger at higher latitudes) and in the fossil records. Of course it is not true always and everywhere, but in most cases it holds.
There is of course nothing to suggest that CO2 has anything to do with it.
E M Smith says:
“On islands, species will commonly shrink.”
Only true for large animals. Small animals like birds, insects or rodents instead tend to grow larger on islands, perhaps because of less predation pressure.
I told you not to eat meat and exhale CO2 at the same time. You shrinking fool, you. And please look up at me when I’m talking to you……….hey…hey….. Now where has he disappeared? Damn the heat and CO2……he’s gone.
Nylo says:
August 25, 2010 at 12:00 am
” Wouldn’t it be great if us humans could keep our same intellect and emotions in a body half the size?”
Not if your planning to be a professional basketball player.
Simon says:
August 25, 2010 at 2:26 am
I stopped reading at “increased co2 decreases plant nutrition”
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I stopped reading at the title.
Who ever or whom ever wrote this garbage, and expected it to be relevant is sailing too close to the wind. References to CO2 in this flawed nonsense is a grab for research dollars. Have these people no shame.
Soooooo. a single tooth and a single jaw from a species alive 50 million years ago “proves” shrinkage of the species… I wonder what the alarmists wil think 50 million years from now when they find the remains of a midget.
SSam says:
August 24, 2010 at 11:06 pm
“This still doesn’t explain the immense size of AlGore… unless he’s in a really frigid environment now.”
The Gore effect was well documented, frigid temperatures would affect the locations of his speaking engagements. Evolutionary change was necessary to support natural (parasitic) life cycle.
So the paper may or may not implicate CO2 as a factor, It’s enough that it has been mentioned. Their work in securing another grant has been done. Irrespective of CO2 or temperature rise , we mammals will never shrink, we have Wallmart for heavens sake.