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Water pressure: Ancient aquatic crocs evolved, enlarged to avoid freezing

Water pressure: Ancient aquatic crocs evolved, enlarged to avoid freezing

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Study pinpoints minimum survivable size of Jurassic crocodiles

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Credit: Steve Castillo / Evolution: International Journal of Organic Evolution / Scott Schrage

Taking the evolutionary plunge into water and abandoning land for good, as some crocodilian ancestors did nearly 200 million years ago, is often framed as choosing freedom: from gravity, from territorial boundaries, from dietary constraints.

Water might inflict more pressure in the pounds-per-square-inch sense, the thinking went, but it also probably relieved some — especially the sort that kept crocs from going up a size or 10. If they wanted to enjoy the considerable spoils of considerable size, water seemed the easy way.

A recent study from the University of Nebraska-Lincoln’s Will Gearty, who compiled a database of 264 species stretching back to the Triassic Period, says that freedom was actually compulsion in disguise.

After analyzing the database of crocodyliforms — a lineage of crocodile-like species that share a common ancestor — Gearty found that the average weights of aquatic crocodyliforms did easily surpass their semi-aquatic and landlocked counterparts, sometimes by a factor of 100.

But the study suggests that this disparity represented a response to, not a release from, the pressures of natural selection. Rather than expanding the range of crocodyliform body sizes, as some longstanding theories would predict, taking to the water instead seemed to compress that range by raising the minimum size threshold needed to survive its depths. The maximum size of those aquatic species, by contrast, barely budged over time.

And when Gearty derived a set of equations to estimate the largest feasible body sizes under aquatic, semi-aquatic and terrestrial conditions?

“All three habitats had roughly the same upper limit (on size),” he said. “So even though it seems like you’re released from this pressure, you’re actually squeezed into an even smaller box than before.”

Two major factors — lung capacity and body heat — seem to have helped initiate the squeeze play. Prior research had proposed that aquatic crocodyliforms got big in part because they needed to dive deeply for food, including the choice prey that would sustain a larger size. Upon digging into the literature, though, Gearty learned that lung volume increases more or less in lockstep with body size.

“So you actually don’t have much excess lung volume to spare,” said Gearty, a postdoctoral researcher in biological sciences. “When you get bigger, (lung capacity) is just basically scaling up with your body size to accommodate that extra size. The amount of time you could stay underwater increases a little bit, but not that much.”

At larger sizes, the evolutionary tradeoff between the benefits of longer, deeper dives and the energy demands of finding more food probably also reached a stalemate, he said, that helped cement the aquatic ceiling on size.

As for the higher floor? That’s where the thermal conductivity of water cranked up the evolutionary heat, Gearty said. Unfortunately for the aquatic crocs, water steals heat far faster than air does. The issue was likely compounded by the fact that temperatures in the waters they occupied were lower than the air temperatures enjoyed by their land-dwelling counterparts.

That would have left smaller aquatic crocodyliforms with only bad options: limit the duration and depth of their dives so that they could regularly return to the surface and warm themselves in the sun, or risk freezing to death during deeper hunts for food. Whether by starvation or hypothermia, either would eventually spell doom.

“The easiest way to counteract that is to get bigger,” Gearty said.

Getting bigger was especially appealing because the volume of body tissue, which generates heat, increases faster than the surface area of the skin that surrenders it. But the unforgiving consequences of heat loss still limited the pool of ancestors from which aquatic crocodyliforms could evolve.

“They actually needed to start at a larger size,” Gearty said. “So it’s not like a marine crocodile could have just evolved from anywhere. It had to be evolving from some non-marine crocodile that was already a little larger than normal.”

The fossil records of the crocodyliforms allowed Gearty and Jonathan Payne, his former doctoral adviser at Stanford University, to pinpoint the minimum weight threshold for aquatic survival: 10 kilograms, or about 22 pounds. And when they plotted the relationships of heat loss and lung capacity to body mass, they discovered that the two slopes crossed at almost exactly the same value: 10 kilograms.

“We were able to explain, with these physiological equations, exactly why there were no marine crocodiles below a certain size,” Gearty said. “This indicates that these very fundamental physiological constraints and controls … actually may be some of the strongest forces for pushing animals to different body sizes through time. Not whether there’s an asteroid hitting the world, not whether you’re being (hunted) by some other animal — that just these physical and chemical properties of the world we live in are what drive this. And if you want to enter a new habitat, you need to conform to that new set of properties.”

The findings mostly reinforce a 2018 Gearty-led study that found similar trends among nearly 7,000 living and extinct mammal species. An elementary difference between mammals and reptiles, though, initially left the verdict in doubt.

“The whole (premise) of the marine mammal project was that these things are warm-blooded, and they have to keep their temperature up,” Gearty said. “They have to really worry about this heat loss. So the idea was, ‘Well, would the same constraint occur in cold-blooded organisms that are also living in the ocean?’

“There have been a couple papers suggesting that some of these marine crocodiles may have been somewhat warm-blooded, and so they may have been able to kind of reheat their own bodies. But even if that’s the case, they were still going to be losing heat like these marine mammals would. They were still constrained by these thermoregulatory controls.”

GREYHOUNDS AND DOLPHINS

With the help of an undergraduate student at Stanford and funding from the National Science Foundation, Gearty spent most of the summer of 2017 tracking down the fossil records that informed the new study.

“But that was to find the stuff that’s readily available online,” he said. “Then you’ve got, you know, undocumented books that you need to find, and they have to get shipped from Europe or somewhere. So there were a lot of these one-offs. I was still measuring specimen photos and getting records up until I submitted the paper in the middle of last year.”

Gearty said he was mostly spared the time and expense of traveling to museums and physically measuring fossil dimensions, as some of his colleagues have in the name of their own research. But the haphazardness of some older classifications and documentation still had him following false leads and trying to make sense of the nonsensible.

“A lot of the crocodiles that people have described in papers have never actually been documented the way they’re supposed to be,” he said. “Someone might say, ‘Here’s the Nebraska crocodile.’ It’s just a colloquial name. And you’ll be like, ‘I guess I’ve got to go find the Nebraska crocodile.’ You look this up, and you see that there’s this crocodile from Nebraska, and this one, and this one. You don’t know which one is the ‘Nebraska crocodile.’

“You need to follow this trail of breadcrumbs, sometimes, to find these papers that may or may not have ever been published on these crocodiles that may or may not have ever been found. Fortunately, I was able to get most of the specimens just from the literature. But it did take a lot of digging to find the last probably 10% of the crocodiles.”

Many of the terrestrial fossils, in particular, trace body shapes that barely resemble the low-slung profile of the modern crocodile.

“The example I like to give is: Imagine a greyhound, and then put a crocodile skull on it,” Gearty said. “There were things like that running around on land probably 200 million years ago.”

Though their maximum size remained almost constant, marine species did evolve two to three times faster than the semi-aquatic and terrestrial groups, Gearty found. Along with increasing the size of smaller aquatic species, natural selection molded body forms to surmount the challenges presented by water. Scales, plates and other drag-increasing skin deposits disappeared. Heads and tails flattened. Snouts narrowed.

“All of these were probably more dolphin-like than modern crocodiles, with even longer, thinner tails,” he said. “And some of them had very paddle-like feet, almost like flippers.”

Despite the fact that virtually all modern crocodile species are semi-aquatic, Gearty said those adaptations served the aquatic crocodyliforms well — more than 100 million years before mammals ventured into the deep.

“No one has talked about it much, but really, these things were quite successful,” he said. “And some of them weren’t even fazed by some of the big, (cataclysmic) events. When the asteroid hit that killed all the dinosaurs, one of the marine groups just kind of kept going like nothing happened. A lot of the terrestrial species went extinct, but this group just kept ticking along for a long time.”

###

Media Contact
Will Gearty
wgearty@unl.edu

Related Journal Article

http://dx.doi.org/10.1111/evo.13901

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February Employment Situation

By Paul Gomme and Peter Rupert The establishment data from the BLS showed a 275,000 increase in payroll employment for February, outpacing the 230,000…

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By Paul Gomme and Peter Rupert

The establishment data from the BLS showed a 275,000 increase in payroll employment for February, outpacing the 230,000 average over the previous 12 months. The payroll data for January and December were revised down by a total of 167,000. The private sector added 223,000 new jobs, the largest gain since May of last year.

Temporary help services employment continues a steep decline after a sharp post-pandemic rise.

Average hours of work increased from 34.2 to 34.3. The increase, along with the 223,000 private employment increase led to a hefty increase in total hours of 5.6% at an annualized rate, also the largest increase since May of last year.

The establishment report, once again, beat “expectations;” the WSJ survey of economists was 198,000. Other than the downward revisions, mentioned above, another bit of negative news was a smallish increase in wage growth, from $34.52 to $34.57.

The household survey shows that the labor force increased 150,000, a drop in employment of 184,000 and an increase in the number of unemployed persons of 334,000. The labor force participation rate held steady at 62.5, the employment to population ratio decreased from 60.2 to 60.1 and the unemployment rate increased from 3.66 to 3.86. Remember that the unemployment rate is the number of unemployed relative to the labor force (the number employed plus the number unemployed). Consequently, the unemployment rate can go up if the number of unemployed rises holding fixed the labor force, or if the labor force shrinks holding the number unemployed unchanged. An increase in the unemployment rate is not necessarily a bad thing: it may reflect a strong labor market drawing “marginally attached” individuals from outside the labor force. Indeed, there was a 96,000 decline in those workers.

Earlier in the week, the BLS announced JOLTS (Job Openings and Labor Turnover Survey) data for January. There isn’t much to report here as the job openings changed little at 8.9 million, the number of hires and total separations were little changed at 5.7 million and 5.3 million, respectively.

As has been the case for the last couple of years, the number of job openings remains higher than the number of unemployed persons.

Also earlier in the week the BLS announced that productivity increased 3.2% in the 4th quarter with output rising 3.5% and hours of work rising 0.3%.

The bottom line is that the labor market continues its surprisingly (to some) strong performance, once again proving stronger than many had expected. This strength makes it difficult to justify any interest rate cuts soon, particularly given the recent inflation spike.

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Mortgage rates fall as labor market normalizes

Jobless claims show an expanding economy. We will only be in a recession once jobless claims exceed 323,000 on a four-week moving average.

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Everyone was waiting to see if this week’s jobs report would send mortgage rates higher, which is what happened last month. Instead, the 10-year yield had a muted response after the headline number beat estimates, but we have negative job revisions from previous months. The Federal Reserve’s fear of wage growth spiraling out of control hasn’t materialized for over two years now and the unemployment rate ticked up to 3.9%. For now, we can say the labor market isn’t tight anymore, but it’s also not breaking.

The key labor data line in this expansion is the weekly jobless claims report. Jobless claims show an expanding economy that has not lost jobs yet. We will only be in a recession once jobless claims exceed 323,000 on a four-week moving average.

From the Fed: In the week ended March 2, initial claims for unemployment insurance benefits were flat, at 217,000. The four-week moving average declined slightly by 750, to 212,250


Below is an explanation of how we got here with the labor market, which all started during COVID-19.

1. I wrote the COVID-19 recovery model on April 7, 2020, and retired it on Dec. 9, 2020. By that time, the upfront recovery phase was done, and I needed to model out when we would get the jobs lost back.

2. Early in the labor market recovery, when we saw weaker job reports, I doubled and tripled down on my assertion that job openings would get to 10 million in this recovery. Job openings rose as high as to 12 million and are currently over 9 million. Even with the massive miss on a job report in May 2021, I didn’t waver.

Currently, the jobs openings, quit percentage and hires data are below pre-COVID-19 levels, which means the labor market isn’t as tight as it once was, and this is why the employment cost index has been slowing data to move along the quits percentage.  

2-US_Job_Quits_Rate-1-2

3. I wrote that we should get back all the jobs lost to COVID-19 by September of 2022. At the time this would be a speedy labor market recovery, and it happened on schedule, too

Total employment data

4. This is the key one for right now: If COVID-19 hadn’t happened, we would have between 157 million and 159 million jobs today, which would have been in line with the job growth rate in February 2020. Today, we are at 157,808,000. This is important because job growth should be cooling down now. We are more in line with where the labor market should be when averaging 140K-165K monthly. So for now, the fact that we aren’t trending between 140K-165K means we still have a bit more recovery kick left before we get down to those levels. 




From BLS: Total nonfarm payroll employment rose by 275,000 in February, and the unemployment rate increased to 3.9 percent, the U.S. Bureau of Labor Statistics reported today. Job gains occurred in health care, in government, in food services and drinking places, in social assistance, and in transportation and warehousing.

Here are the jobs that were created and lost in the previous month:

IMG_5092

In this jobs report, the unemployment rate for education levels looks like this:

  • Less than a high school diploma: 6.1%
  • High school graduate and no college: 4.2%
  • Some college or associate degree: 3.1%
  • Bachelor’s degree or higher: 2.2%
IMG_5093_320f22

Today’s report has continued the trend of the labor data beating my expectations, only because I am looking for the jobs data to slow down to a level of 140K-165K, which hasn’t happened yet. I wouldn’t categorize the labor market as being tight anymore because of the quits ratio and the hires data in the job openings report. This also shows itself in the employment cost index as well. These are key data lines for the Fed and the reason we are going to see three rate cuts this year.

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Inside The Most Ridiculous Jobs Report In History: Record 1.2 Million Immigrant Jobs Added In One Month

Inside The Most Ridiculous Jobs Report In History: Record 1.2 Million Immigrant Jobs Added In One Month

Last month we though that the January…

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Inside The Most Ridiculous Jobs Report In History: Record 1.2 Million Immigrant Jobs Added In One Month

Last month we though that the January jobs report was the "most ridiculous in recent history" but, boy, were we wrong because this morning the Biden department of goalseeked propaganda (aka BLS) published the February jobs report, and holy crap was that something else. Even Goebbels would blush. 

What happened? Let's take a closer look.

On the surface, it was (almost) another blockbuster jobs report, certainly one which nobody expected, or rather just one bank out of 76 expected. Starting at the top, the BLS reported that in February the US unexpectedly added 275K jobs, with just one research analyst (from Dai-Ichi Research) expecting a higher number.

Some context: after last month's record 4-sigma beat, today's print was "only" 3 sigma higher than estimates. Needless to say, two multiple sigma beats in a row used to only happen in the USSR... and now in the US, apparently.

Before we go any further, a quick note on what last month we said was "the most ridiculous jobs report in recent history": it appears the BLS read our comments and decided to stop beclowing itself. It did that by slashing last month's ridiculous print by over a third, and revising what was originally reported as a massive 353K beat to just 229K,  a 124K revision, which was the biggest one-month negative revision in two years!

Of course, that does not mean that this month's jobs print won't be revised lower: it will be, and not just that month but every other month until the November election because that's the only tool left in the Biden admin's box: pretend the economic and jobs are strong, then revise them sharply lower the next month, something we pointed out first last summer and which has not failed to disappoint once.

To be fair, not every aspect of the jobs report was stellar (after all, the BLS had to give it some vague credibility). Take the unemployment rate, after flatlining between 3.4% and 3.8% for two years - and thus denying expectations from Sahm's Rule that a recession may have already started - in February the unemployment rate unexpectedly jumped to 3.9%, the highest since February 2022 (with Black unemployment spiking by 0.3% to 5.6%, an indicator which the Biden admin will quickly slam as widespread economic racism or something).

And then there were average hourly earnings, which after surging 0.6% MoM in January (since revised to 0.5%) and spooking markets that wage growth is so hot, the Fed will have no choice but to delay cuts, in February the number tumbled to just 0.1%, the lowest in two years...

... for one simple reason: last month's average wage surge had nothing to do with actual wages, and everything to do with the BLS estimate of hours worked (which is the denominator in the average wage calculation) which last month tumbled to just 34.1 (we were led to believe) the lowest since the covid pandemic...

... but has since been revised higher while the February print rose even more, to 34.3, hence why the latest average wage data was once again a product not of wages going up, but of how long Americans worked in any weekly period, in this case higher from 34.1 to 34.3, an increase which has a major impact on the average calculation.

While the above data points were examples of some latent weakness in the latest report, perhaps meant to give it a sheen of veracity, it was everything else in the report that was a problem starting with the BLS's latest choice of seasonal adjustments (after last month's wholesale revision), which have gone from merely laughable to full clownshow, as the following comparison between the monthly change in BLS and ADP payrolls shows. The trend is clear: the Biden admin numbers are now clearly rising even as the impartial ADP (which directly logs employment numbers at the company level and is far more accurate), shows an accelerating slowdown.

But it's more than just the Biden admin hanging its "success" on seasonal adjustments: when one digs deeper inside the jobs report, all sorts of ugly things emerge... such as the growing unprecedented divergence between the Establishment (payrolls) survey and much more accurate Household (actual employment) survey. To wit, while in January the BLS claims 275K payrolls were added, the Household survey found that the number of actually employed workers dropped for the third straight month (and 4 in the past 5), this time by 184K (from 161.152K to 160.968K).

This means that while the Payrolls series hits new all time highs every month since December 2020 (when according to the BLS the US had its last month of payrolls losses), the level of Employment has not budged in the past year. Worse, as shown in the chart below, such a gaping divergence has opened between the two series in the past 4 years, that the number of Employed workers would need to soar by 9 million (!) to catch up to what Payrolls claims is the employment situation.

There's more: shifting from a quantitative to a qualitative assessment, reveals just how ugly the composition of "new jobs" has been. Consider this: the BLS reports that in February 2024, the US had 132.9 million full-time jobs and 27.9 million part-time jobs. Well, that's great... until you look back one year and find that in February 2023 the US had 133.2 million full-time jobs, or more than it does one year later! And yes, all the job growth since then has been in part-time jobs, which have increased by 921K since February 2023 (from 27.020 million to 27.941 million).

Here is a summary of the labor composition in the past year: all the new jobs have been part-time jobs!

But wait there's even more, because now that the primary season is over and we enter the heart of election season and political talking points will be thrown around left and right, especially in the context of the immigration crisis created intentionally by the Biden administration which is hoping to import millions of new Democratic voters (maybe the US can hold the presidential election in Honduras or Guatemala, after all it is their citizens that will be illegally casting the key votes in November), what we find is that in February, the number of native-born workers tumbled again, sliding by a massive 560K to just 129.807 million. Add to this the December data, and we get a near-record 2.4 million plunge in native-born workers in just the past 3 months (only the covid crash was worse)!

The offset? A record 1.2 million foreign-born (read immigrants, both legal and illegal but mostly illegal) workers added in February!

Said otherwise, not only has all job creation in the past 6 years has been exclusively for foreign-born workers...

Source: St Louis Fed FRED Native Born and Foreign Born

... but there has been zero job-creation for native born workers since June 2018!

This is a huge issue - especially at a time of an illegal alien flood at the southwest border...

... and is about to become a huge political scandal, because once the inevitable recession finally hits, there will be millions of furious unemployed Americans demanding a more accurate explanation for what happened - i.e., the illegal immigration floodgates that were opened by the Biden admin.

Which is also why Biden's handlers will do everything in their power to insure there is no official recession before November... and why after the election is over, all economic hell will finally break loose. Until then, however, expect the jobs numbers to get even more ridiculous.

Tyler Durden Fri, 03/08/2024 - 13:30

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