Breathing Lessons

Once upon a time, two new animal body plans were invented  - OK, it was during the Triassic, 230 million years or so ago. They were, respectively, the prototypes of the mammals and the dinosaurs.  Because the Triassic was notoriously low on oxygen, with maybe half the concentration of today, breathing was tough, and lots of the less talented perished.  Mammals had an innovation, the diaphragm, which allowed walking and breathing at the same time, an advantage not enjoyed by lizards. Dinosaurs had another, a two cycle lung.

The mammalian lung is a cul-de-sac.  Air comes in and leaves by the same path.  The dino lung, though, is a sort of two cycle lung that separates inhaled and exhaled air except at the ultimate intake and exit.  This lung, subsequently inherited by, among others, birds, is more efficient.  At 5000 feet, the bird lung is about twice as efficient as the mammalian version.  Given that during the Triassic and early Jurassic oxygen levels were more like those now found at 15,000 feet, this was a big advantage.

No animals were able to grow very large during the low O2 level days, but when levels rose later in the Jurassic, dinosaurs went to town, leaving their mammalian cousins in the dust.

By the end of the Jurassic the largest land animals of all time were common: dinosaurs were lords of all creation; tiny primitive birds and tinier primitive mammals hid in the lowest-rent districts in town.

At the beginning the seas were so bare that stromatolites had made a comeback, and the larger fish and predators were few indeed. By its end there was a veritable cornucopia of the most spectacular marine denizens to have ever populated the sea: long-necked reptilian plesiosaurs, dolphin-like ichthyosaurs, and splendid primitive fish—similar to the modern-day gar and sturgeon (both with strange body armor)—schooled among vast coral reefs and an ocean filled to exuberance with all manner of ammonites and their more squid-like relatives, the belemnites.

Ward, Peter. A New History of Life (p. 245). Bloomsbury Publishing. Kindle Edition. 

And rule the roost they did, until they met a asteroid with their names on it.

Comments

Post a Comment

Popular posts from this blog

Anti-Libertarian: re-post

The most pointed critique of social security and liberalism in general is the libertarian critique. The problem with libertarians, for a liberal, is that we have too much in common. We both believe in individual rights, tolerance of individual differences, and dislike government prescription of religion. The basic difference, it seems to me, is the different answers we give to Cain's (with thanks to the Captain - my original version had the corpse asking the question!) famous question: "Am I my brother's keeper?" That's not really my basic bitch against the libertarians though. My real complaint is the same as my complaint against most religion - its premise is a fraud. For those who can't stand to wait for the punchline, I believe that trying to implement libertarian principles leads to tyranny or social disintegration. Demonstrating that takes some historical (and pre-historical) context. For all but the last 15,000 or so of the 100,000 years the human spec...
Read more

Uneasy Lies The Head

Uneasy lies the head that wears a crown ........... Shakespeare Henry IV, Part II. So it is with us and our slightly distant primate cousins , so it seems. A 9-year study of wild baboons in Kenya by Princeton University and the Institute of Primate Research may turn conventional assumptions of alphas males upside down. The study found that alpha males have high testosterone levels, which allows them to dominate other baboons, get access to more food, and attract better mates. This is expected. Surprisingly, though, the alpha males also have high levels of stress hormone glucocorticoid, which scientists measured from their feces samples. In fact, the stress of alpha baboons was on par with low-ranking baboons. The convention wisdom is that access to food and females provides life security and thus less stress for dominant males. Conversely, weak males who are constantly threatened by starvation and physical violence from stronger males are thought to be more stressed. The st...
Read more

We Call it Soccer

The US played its best, and maybe only good game of World Cup, but lost thanks to brilliant goalkeeping by the Swedish keeper and the bizarre method soccer uses to settle ties when three US stars could not put the ball on frame from the 12 yard spot.  At the end it came down to a blocked shot that spun in by maybe a couple of centimeters. Well, that's football - too much like life.   Which brings me to a modest proposal.  Replace the thirty minute overtimes with as many 7-player 15 minute periods as needed to settle it.  Scoring should be much easier with fewer players.
Read more