The Age Of Mammals

An advanced dating technique has revealed that the non-avian dinosaurs bit the dust 66 million years ago, which paved the way for the Age of Mammals, aka. the Tertiary, aka. the Cenozoic. The final blow for the dinosaurs came when a large rock hit the Earth, ending the Mesozoic Era, which began about 250 million years ago. The argon-argon technique indicates that the Dinosaurs Went Extinct Almost Immediately After [the] Mexican Asteroid Strike.

Scientists using a new and highly precise dating technique have concluded that the late Cretaceous asteroid strike in Mexico's Yucatan Peninsula coincided almost exactly with the extinction of the dinosaurs — give-or-take a few tens of thousands of years. While it's clear that other factors were contributing to the rapidly deteriorating environmental conditions, it's now obvious that the asteroid was the final coup-de-grace for the dinosaurs.

Indeed, all was not well on Earth when the asteroid struck. Volcanoes in India [resulting in the Deccan Traps] were wreaking havoc to the planet's ecosystems, and earlier asteroid strikes may have contributed to an already fragile environment. Other research shows that Earth experienced six abrupt temperature shifts of two degrees or more in mean temperatures in the one million years before the impact. In one instance, the temperature swung 6-8 degrees...

Researchers Paul Renne, Jan Smit and colleagues determined that the Yucatan impact event happened 66,038,000 years ago — give or take 11,000 years. It's an extraordinarily precise measurement, as it was only a few decades ago that the margins for error were measured in the millions of years.

The scientists also updated the date of dinosaur extinction. It happened about 33,000 years after the asteroid impact, which is a revision from the previous estimate of 300,000 years (which, when considering the cataclysmic effects of the impact, didn't really make a lot of sense). Given the narrow margins of error for the dating technique, it's very likely, therefore, that the asteroid impact coincided almost exactly with the demise of the dinosaurs. Consequently, the researchers are describing the event as the final blow. It was not the only factor, they admit, but it was certainly a major contributor.

The extinction of the big dinosaurs opened the door for the adaptive radiation of the mammals during the Cenozoic. And there is news about that, too, as we learn in Placental mammal diversity exploded after [the] age of dinosaurs.

An international team of researchers has reconstructed the common ancestor of placental mammals—an extremely diverse group including animals ranging from rodents to whales to humans—using the world's largest dataset of both genetic and physical traits...

"Analysis of this massive dataset shows that placental mammals did not originate during the Mesozoic," said lead author Maureen O'Leary, an associate professor in the Department of Anatomical Sciences in the School of Medicine at Stony Brook University and a research associate at the American Museum of Natural History...

[image left, text below, from the Science article Ancestor of All Placental Mammals Revealed — "The ancestor to all placental mammals was a tiny insect-eating creature that evolved soon after the mass extinctions that wiped out the dinosaurs.]

The fossil record has long suggested that even though mammals existed long before dinosaurs died off, most likely at the hands of an asteroid impact, the furry critters didn't really diversify or reach a large size until their reptilian competitors were out of the picture and ecosystems had recovered, says Maureen O'Leary, a paleontologist at Stony Brook University in New York. And even though the earliest placental mammals don't appear in the fossil record until after the dino die-offs, previous genetic analyses of living species have hinted that placental mammals may have evolved as much as 100 million years ago, tens of millions of years before that mass extinction.

To help settle the debate, O'Leary and her colleagues reconstructed the family tree of placental mammals using evidence from a large number of living and extinct species. The team's database included more than 4500 characteristics for each of 86 species...

Results suggest that the ancestor of all placental mammals evolved less than 400,000 years after the mass extinctions that wiped out the dinosaurs, the researchers report online today in Science. The hypothetical creature, not found in the fossil record but inferred from it, probably was a tree-climbing, insect-eating mammal that weighed between 6 and 245 grams—somewhere between a small shrew and a mid-sized rat.

It was furry, had a long tail, gave birth to a single young, and had a complex brain with a large lobe for interpreting smells and a corpus callosum, the bundle of nerve fibers that connects the left and right hemispheres of the brain.

The period following the dinosaur die-offs could be considered a "big bang" of mammalian diversification, with species representing as many as 10 major groups of placentals appearing within a 200,000-year interval [in the Paleocene], O'Leary says.

Long before I started writing about the environment, energy and the economy, I studied paleontology and the history of the Earth. Even today, though I am often busy exposing typical economic or financial fraud and inquality, I try to keep current in those subjects, which is easy to do in so far as describing pressing scientific concerns regarding the Earth and Climate are also part of my daily reporting.

I would never have been able to write this blog the way I do if I hadn't spent all those years developing the perspective which only a prolonged consideration of geological time can offer. According to these latest results, the ancestor of all current mammals, including the primates, including the hominids, and thus including Homo sapiens, was some kind of placental tree shrew which was furry, had a long tail, ate insects, and had a complex but very, very tiny brain.

That this hypothetical animal had an opportunity to be the last common ancestor of all current placental mammals was due only to the fact that a large asteroid impact in what is now the Yucatan wiped out the large non-avian dinosaurs. This random event opened up previously unavailable ecological niches for the mammals, thus spurring the evolution which gave rise to new types (the placentals), and these developments over 66 million years eventually "culminated" in big-brained bipedal primates like us.

If that doesn't put things in perspective, I don't know what would.

Bonus Video — this video has had only 587 views on youtube so far. Why don't you boost that number? If only to further indicate that not all humans are myopic, doomed, irredeemable dimwits. Or, you can be one with the primitives by watching Jon Stewart and Bill O'Reilly.

The choice is yours, assuming you aren't free will-challenged, as almost all humans are.

 

Comments

[Andrew Kirk]

Watched the vid. It is somehow very, very sad. Morpho-Bank, indeed.

[Ben]

Incredible blog entry. There really is a lot to learn here, clicking on all of the links are a must if you're ignorant about this stuff like I am.

[Diogenes]

Dave,

I love you, man - just say'n

It's always about perspectives - EVERYTHING ... it's that matryoshka doll thing. (thanks again for that metaphor) Most stuck in the tiniest, adolescent, narcissistic ones.

Great post - thanks. Takes me back to Koestler and human evolution gone wrong. And, this came to mind...

http://www.youtube.com/watch?v=Mx2GoEV5yf0

As Ever...

[Martin]

Here's my second video suggestion for DOTE:
http://energy-reality.org/

Okay, the site alleges there is some way out away from these images, to some sort of "energy future,"
but there are hundreds of thousands of other photos that could be inserted from vivid energy dumps across the globe, and blueprints for many, many more energy projectsto come that could be the subject of next decade's coffeetable book.
Still, I like the concept.

[Oliver]

Thanks Dave, this post is better than any LSD in opening the mind. That is, of course, if one's mind has evolved beyond the level of some of the commenters on the article you linked to: Ancestor of All Placental Mammals Revealed.

Jeez, why do creationists even bother to visit science sites? I suppose it's the same reason self-appointed moral guardians visit porn sites. ;-)

[JohnWDB]

@Martin, re: the video, it appears even wind farms bother them. As such, the only energy future they could be comfortable with would be one in which we use far less energy...which would be more like a third-world agrarian society. Good luck with raising support for that.

If wind farms are a problem, though, then really anything industrial is a problem, or anything involving concrete and steel. I think most of us would rather live in a world without those things but still benefit from their conveniences. I'd like to live in the garden of eden but still have endless information, entertainment, air-conditioning, and hot water.

The key is obviously consuming less, but humans en masse are not capable of that. Even the indignant hipsters aren't capable of that, using iphones and eating imported quinoa-asparagus wraps while they scoff at polluters. We eventually will consume less, or consume each other, but only because of cruel necessity, not choice.

[Brian]

So, thought experiment...

If the Anthropocene ends in another extinction of the dominant life form on the planet (namely, us), what would be your guess for the next "mother of life forms" in whatever age follows?

Insects are always popular, but my vote might be for yet another small mammal, maybe a vole (based mostly on Murphy's Law and my inability to keep these little creatures from destroying my lawn each winter). Creatures similar to this have survived hotter and colder climates, meteor impacts, the existence of other dominant species, disease, etc. The track record suggests they have staying power.

[Mr. Roboto]

I recall reading a magazine article that said that the common ancestor of all complex multicellular organisms was the sea-sponge. Obviously, that's going rather further back than the common ancestor of all placental mammals.

[Shawntoh]

Great bloggin' as usual, sir. Bravo!

Why do I get the feeling, that is, since it clearly looks like we all came from some ratty lookin' squirrels and, in the 21st Century, when the nuke bombs and radioactive waste finishes off most of the mammals, starting with the humans, that the only thing left, or the last thing to die from the mammal family of creatures on earth, will be some mutated ratty lookin' squirrels or mutated squirrel-like rats?

Not even Samuel Beckett would be so cruel to come up with such irony, methinks, but somehow, rats, ragweed and roaches will be the only thing to survive, if anything at all, on earth from the fatal follies of humans...

[Shawntoh]

Forgive me, here's the reference to the "rats, ragweed and roaches"...

http://articles.philly.com/1991-08-16/news/25807639_1_mass-extinctions-david-jablonski-rain-forests

[Mike Roberts]

I just got round to this blog post. Thanks for updating us, Dave. This is fascinating stuff. It (scientific research) is, perhaps one of the aspects of civilisation that is actually worth preserving and will be missed as the world continues its simplification.

Deep time is certainly a difficult concept to wrap one's head around and, I think is a major problem with those who don't seem to grasp the science of various aspects of our environment and evolution.

On a less serious note, I wonder why video makers like to add irrelevant music to informational videos (not that I like it that much on entertainment videos).

[Martin]

@JohnWMB, you make perfect sense to me.
Wind, though, seems quite evidently full of problems: massive amounts of concrete and fossil fuel in the construction, intermittency, destruction of habitat, small-ball.
The amount of extractive mining that goes in to each of our western lives, from keyboard to screen to road to shoes, makes us beasts of the plains, even the quinoa-wrapped.
These well-intentioned opponents of the corporate extractive order seem to think, hope, plan for "sustainable" resources to replace each and every one of these massive extraction campaigns, as if we'll have cellphones made out of marshmallows and biomimic'd tapioca screens.
Intentional, voluntary, self-managed reduction of global energy demand - yeah, sure, coming right aroudn the bend.