Scientists thought related species of animals generally got bigger as they evolved: now a team has evidence to back up that assumption. We still don't know why critters usually get bigger, though.
That, and seven "croc" species sharing the same turf in the Amazon Basin — before the Amazon was there — is what I picked for this week's post:
- Diverse "Crocs" of Yesterday's Amazon Basin
- Cope's Rule: Bigger May be Better
I think the universe is billions, not thousands, of years old; Earth isn't flat; Adam and Eve weren't German; poetry isn't science; and thinking is not a sin. (November 21, 2014)
I've been over this before — a lot.
The universe is a place of order and beauty. It isn't perfect, yet: but that's the direction it's going. It's being created by God: constantly upheld and sustained, in a "state of journeying" toward an ultimate perfection. (Catechism of the Catholic Church, 32, 302)
We're human, created in the image of God. We can, using reason, see God's work in the universe. Studying this world is okay. (Catechism, 35-36, 282-289, 301, 303-306, 311, 341, 1704)
Thinking is not a sin. We're expected to use our brains: wisely. Science and technology, learning about the universe and using that knowledge to develop new tools, is part of being human. (Wisdom 7:17; Catechism of the Catholic Church, 307, 1730, 2292-2295, 2415-2418)
Around the mid-19th century, some folks said that because the universe operates by rational, knowable, laws: a rational, orderly Creator can't exist. That oversimplifies the situation, of course.
Some Christians agreed: loudly. We've been dealing with fallout from that craziness ever since.
We've learned quite a bit since the 1860s. Some folks see humanity's expanding knowledge as opportunities for greater admiration of God's greatness. (Catechism, 283)
Others, not so much.
To this day, a remarkable number of folks — including some Christians — are convinced that Christianity is against science and that science threatens our faith.
Then there was Pope Pius VII, who said vaccination was "a precious discovery which ought to be a new motive for human gratitude to Omnipotence." And that's another topic. (February 12, 2014
(From Kevn Montalan-Rivera, the American Museum of Natural History in New York; via Reuters, used w/o permission.)
("A model of a life reconstruction of the head of Gnatusuchus pebasensis, a 13-million-year-old, short-faced crocodile with globular teeth that was thought to use its snout to 'shovel' mud bottoms, digging for clams and other mollusks is shown in this undated handout photo provided by the American Museum of Natural History in New York February 23, 2015. Model by Kevn Montalan-Rivera."
"Chockablock with crocs: Seven species rocked ancient Amazon basin"The "crocs" in this article are, or were, crocodilians: big, predatory, semiaquatic reptiles. The earliest models we know of showed up about 83,500,000 years ago. Today's crocodilians are alligators and alligator-like caimans, crocodiles, and gharials.
Will Dunham, Reuters (February 14, 2015)
"If one croc is reason enough to stay out of the water, how about dipping your toes in a place with seven different croc species including two 26-foot (8-meter) monsters, all living side by side eating just about anything that moves?
"That is what life was like in the lush Peruvian Amazon basin 13 million years ago. It featured Earth's all-time croc bloc: the most crocodilian species dwelling in the same place and time in our planet's history, scientists said on Tuesday.
"The scientists unearthed the croc remains in two small fossil bone beds near the northeastern Peruvian city of Iquitos.
"One of the strangest was Gnatusuchus pebasensis, a 5-foot (1.6-meter) caiman with a shellfish fondness. Its shovel-like snout let it bury its head in muddy wetland bottoms and root around for prey. Its bulbous teeth were perfect for crushing shells of mollusks like clams.
" 'This highly specialized anatomy and lifestyle was previously unknown in any other crocodile,' said paleontologist John Flynn of New York's American Museum of Natural History.
"The discoveries are helping scientists better understand both the origins of modern Amazonian biodiversity and the ancient assortment of life before the Amazon River formed 10.5 million years ago. The region 13 million years ago boasted immense wetlands abounding with lakes, swamps and rivers...."
From a distance, Earth looked pretty much like it does today, back in the Miocene, when these "crocs" lived. The Florida peninsula was under water, and Northern Italy and Turkey were at opposite ends of an island.
The Andes had been around since before something dreadful happened to dinosaurs, but the land bridge between North and South America wasn't here yet.
Earth's climate was nice and warm, but it wasn't our fault. We wouldn't show up until the current ice age started, about 2,500,000 years back. (February 20, 2015; July 11, 2014)
Then, as now, quite a bit of the Amazon basin was under water or distinctly damp: and, as Mr. Dunham's article says, home to seven species of "crocs."
The biggest one there, 13,000,000 years back, was a Purussaurus. Eventually, Purussaurs became the biggest crocodilians ever. That we know of, anyway.
Come to think of it, the Amazon Basin wasn't here yet, not quite. South America and Antarctica had parted ways when the Drake Passage opened.
Right around that time, the Isthmus of Panama separated the Atlantic and Pacific Oceans — indirectly starting the ice age we're in — or have just left. (February 20, 2015)
A river once ran from the Purus Arch to the Pacific, before the Andes started growing — but there's nothing left of a lake formed when that river's water backed up, where the Solimões River basin is now.
Compared to the Finke, Kanawha, and Rhine Rivers, the Amazon is a young whippersnapper. It didn't form until a few million years later. No, wait, that's not quite right.
Time was when what we call the Congo river was a lot longer, and included a channel that's now occupied by the Amazon.
I seem to have become fond of the word "whippersnapper," and that's yet another topic.
A few years ago, some scientists found evidence that pegged the Amazon's formation as a continuous, and independent, river at somewhere between 11,800,000 million 11,300,000 years back, taking its present shape about 2.4 million years ago.
Maybe Will Dunham's article got information from a more recent study. Like I've said before, we've learned a lot: and discovered that there's much more to learn.
More about rivers and lakes that aren't there any more:
- "The Late Miocene paleogeography of the Amazon Basin and the evolution of the Amazon River system"
Edgardo M. Latrubesse, Mario Cozzuol, Silane A.F. da Silva-Caminha, Catherine A. Rigsby, Maria Lucia Absy, Carlos Jaramillo; Earth-Science Review (Received February 26, 2009; Accepted February 8, 2010; Available online February 16, 2010) (.pdf)
- "Amazon River Dated to 11 Million Years Old"
Robin Lloyd, LiveScience (July 8, 2009)
- "Late Miocene onset of the Amazon River and the Amazon deep-sea fan: Evidence from the Foz do Amazonas Basin"
J. Figueiredo, C. Hoorn, P. van der Ven, E. Soares; Online First, The Geological Society of America (Received October 27, 2008; Revision received February 18, 2009; Accepted February 25, 2009)
- "Amazon River Once Flowed in Opposite Direction"
Phys.org (October 24, 2006)
Apparently the seven crocodilian species could live in the same territory, because the area "...because they shared an elaborate environment with plenty of food and were not all chasing the same prey...." (Will Dunham, Reuters)
It's sort of like Darwin's finches: which aren't quite finches, it turns out. Anyway, it looks like these birds branched out into 15 different species — each specialized for eating one sort of food.
Gnatusuchus pebasensis is another newly-named critter mentioned in Will Dunham's article. It's a caiman, one of the pseudosuchia — or "false crocodiles" — and featured in the article's photo.
Speaking of birds, those critters — plus alligators, caimans, crocodiles, and gharials — are the only surviving archosaurs. (January 30, 2015)
(From Frans Lanting/SPL, via BBC News, used w/o permission.)
("Whales and other modern sea animals tend to be much larger than Cambrian sea creatures"
"Evolution 'favours bigger sea creatures' "
Jonathan Webb, BBC News (February 19, 2015)
"The animals in the ocean have been getting bigger, on average, since the Cambrian period - and not by chance.
"That is the finding of a huge new survey of marine life past and present, published in the journal Science.
"It describes a pattern of increasing body size that cannot be explained by random 'drift', but suggests bigger animals generally fare better at sea.
"In the past 542 million years, the average size of a marine animal has gone up by a factor of 150.
"It appears that the explosion of different life forms near the start of that time window eventually skewed decisively towards bulkier animals.
"Measured by volume, today's tiniest sea critter is less than 10 times smaller than its Cambrian counterpart; both are minuscule, sub-millimetre crustaceans. But at the other end of the scale, the mighty blue whale is more than 100,000 times the size of the largest animal the Cambrian could offer: a trilobite less than half a metre long.
"It appears that the explosion of different life forms near the start of that time window eventually skewed decisively towards bulkier animals...."
The phrase "cannot be explained by random 'drift' " in that article jumped out at me. I rambled on about randomness, faith, and getting a grip, last month. (January 30, 2015)
Jonathan Webb's article explains that today's smallest sea critter is less than 10 times smaller than it's Cambrian counterpart. They're both submillimeter crustaceans: really tiny things. The biggest living animal, the blue whale, is more than 100,000 times the biggest Cambrian critter: a trilobite that was a third of a meter long.
Big and small, then and now:
- Cambrian genus: Zhenpingella (crustacean), 0.6 millimeters
- Modern genus: Luvula (seed shrimp), 0.3 millimeters
- Cambrian genus: Dikelocephalus (trilobite - pictured), 32 centimeters
- Modern genus: Balaenoptera (whale), 30 meters
Edward Drinker Cope, a 19th-century paleontologist with an impressive mustache, never actually stated Cope's rule, but Charles Depéret did, which is why why it's also called the Cope-Depéret rule.
Mr. Cope, who didn't have much formal scientific training, and Othniel Charles Marsh, who did, were rivals in the Bone Wars.
That's the "Great Dinosaur Rush," not the First and Second war between the Netherlands and the Bone sultanate of Sulawesi.
Sulawesi is what used to be called Celebes, not to be confused with Max Ernst's The Elephant Celebes.
Theodor Eimer; who had a beard, had said pretty much the same thing about critters getting bigger before either Cope or Depéret did. These days, he's chiefly known for "Eimer's organs," something moles have — and having Eimeria, a genus of parasitic protozoa, named after him.
I'm forgetting something. Give me a minute. Drinker, beards, paleontology. Got it.
Cope's rule, or the Cope-Depéret rule, or what Theodor Eimer said, is that as critters evolve, they tend to get bigger. Or, for folks who like sophisticated erudition, Cope's rule "postulates that population lineages tend to increase in body size over evolutionary time." (Wikipedia)
Not all animals get bigger. One branch of archosaurs kept getting smaller over a span of about 50,000,000 years, sprouted wings, and survived whatever happened some 66,000,000 years back. (August 8, 2014)
Most critters seem to get bigger, though. Assuming that's true, and backing up the assumption with evidence, aren't the same thing. That's why Stanford University's Dr Noel Heim tested Cope's rule: with the help of professors, undergraduates, and high school interns.
They pulled together information about over 17,000 genera — groups of species. They eventually had data about more than 60% of all animal genera that ever lived.
Sometimes a group of critters got smaller as they evolved, like birds. Most kept getting bigger, though. Branches of the family tree where the critters were bigger generally divided: a lot. By now, Earth's ocean has a great many big animals.
(From Jaime Chirinos/SPL, via BBC News, used w/o permission.)
("Breathing air helped marine reptiles to maintain their extra body size"
"...The team also wanted to work out whether this bigness bias was really driven by evolutionary advantage, or was simply a matter of chance.Dr. Heim says that "degrees of increase in both mean and maximum body size just aren't well explained by neutral drift." (Jonathan Webb, BBC News))
"To this end, they put their size data from the oldest animals into a computer model and ran multiple simulations of how the family tree might evolve. Each species could die out, stay the same, or get bigger or smaller.
"In some simulations, the scientists allowed the animals' size to drift randomly without affecting each species' success; in others, they tweaked the rules so that bigger animals were more likely to survive and flourish.
"The version that best matched the real fossil history was one with a genuine size advantage.
" 'The degrees of increase in both mean and maximum body size just aren't well explained by neutral drift,' said Dr Heim. 'It appears that you actually need some active evolutionary process that promotes larger sizes.'
"As for what those benefits of extra bulk might be, the researchers cannot be sure - but larger species likely took advantage of being able to move faster, burrow better in sediment, or eat larger prey.
"The changing chemistry of the ocean, including an increase in oxygen, may also have played a role, Dr Heim suggested...."
(Jonathan Webb, BBC News))
In other words, the pattern of animal genera getting bigger, the longer they're around, isn't random.
This is a step forward, from simply noticing that animals get bigger: but scientists still aren't sure why they get bigger.
Maybe it's because big animals can move faster, eat bigger prey, or dig in faster, than their smaller counterparts. Or maybe something else is going on: like more oxygen being around these days.
Air-breathing animals get a lot bigger when they return to the ocean: like shonisaurs, mosasaurs, and whales.
Geologists from Mount Holyoke College, Mark McMenamin and Dianna Schulte McMenamin, suggested that an odd pattern of shonisaur bones was the self-portrait of a squid-like animal they dubbed a Triassic kraken.
There's no evidence of the Triassic cephalopod artist, apart from the Holyoke College scientists' imaginative explanation tale: but some scientists though the platypus was a hoax, when they first heard of that unlikely animal.
I can't say that I blame them. An egg-laying, beaver-tailed, duck-billed animal with feet like an otter's — and venomous spurs — must have seemed unlikely, back around 1800.
My opinion about the Triassic kraken is that it makes a good story, and might have actually existed. I also think Brian Switek, quoted on the Shonisaurus Wikipedia page, made a good point:
"The Giant, Prehistoric Squid That Ate Common Sense"And yes, I know that tales of the kraken may have their origins in sightings of (real) giant squid. They're good stories, though, some of them.
Brian Switek, Wired Science Blogs (October 10, 2011)
"...Whether you think the 'kraken' story should have been reported or ignored due to lack of evidence, the fact remains that journalists should have actually done their jobs rather than act as facilitators of hype. You don't have to be a paleontologist to realize that there’s something fishy about claims that there was a giant, ichthyosaur-crunching squid when there is no body to be seen...."
- "Precision-Grip Thumbs and a 'New' Archosaur"
(January 30, 2015)
- "Beauty, Order, and Pterosaurs"
(November 21, 2014)
- "Dinosaur Arms, and Ust'-Ishim Man's DNA"
(October 31, 2014)
- "Strange Critters, a Dinosaur, and Early Permian Night Hunters"
(September 12, 2014)
- "Volcanoes and Fossilized Brains: Studying Earth's Past"
(July 25, 2014)