CHICKENS SHALL INHERIT THE EARTH
It’s Chicken McNuggets all day, every day, at MacDonald’s. It won’t be that way for long, Bucko. Get ‘em while they last. For by the end of the century, the chickens of the world will rise up and overthrow their mammalian overloads, the Homo sapiens. You know, you and me.
Oh, spare me, brother. That’s nonsense.
Take a deep, deep breath. I will tell you why chickens shall come to rule. It is inevitable.
We need to go far back in time to jump start this story. It’s 235 million years ago and the world’s biota is emerging from a desperate struggle to regain its footing following the Great Dying of the end-Permian event, the greatest mass extinction in the history of multi-cellular life. Fifteen million years earlier, Siberia unzipped, cleaved apart and disgorged millions of cubic miles of molten rock over the course of 100,000 years. Carbon dioxide levels soared to more than five times what they are today. Mammoth quantities of temperature-spiking methane gas were released, as well, and oxygen levels in the atmosphere plunged to as low as 10 to 12 percent by volume, about half the amount it is today.
Okay, the vast flood basalt flows in Siberia are the back-story. The plot has to do with the available oxygen on land and in the oceans. At a level of 10 percent, living organisms on land were forced to get by as if living at 15,000 feet elevation. So low was the oxygen content of the air that for nearly half of the 50 million years that define the Triassic, life on land larger than a big toad was rather sparse and low in diversity. Animals of size had a difficult time thriving in such an atmosphere.
The stresses that animals were under proved to be potent drivers of evolution. By the mid-Triassic, two new dynasties of animals had evolved that had somehow reconfigured their respiratory systems so they could extract more oxygen per breath from the air than any other land-bound creatures on the planet. One of the groups we know well. We call them dinosaurs. A chicken, as you may know, is a living descendant of the first dinosaurs. A dinosaur cousin, the pterosaurs, took to the skies on leathery wings covered with downy hairs.
A chicken and your human toddler do not have a whole lot in common physiologically. One of the most striking differences is lung capacity. Humans have two lungs that inflate and deflate. Chickens and all birds, on the other hand, have lungs that have air sac extensions throughout the body. While most of the volume of air you breathe enters your lungs and is immediately expelled, birds breathe in and the air keeps funneling deep into air sac cavities nested in tissues throughout the torso. It’s almost as though the incoming air has only one direction to go. While we humans extract a fraction of the oxygen we breathe in with each breath, birds extract far more per inhalation.
Because of their unique respiratory system, the early dinosaurs had distinct advantages over other beasts in their environment. Not only could they extract more oxygen from the low oxygen levels of the Triassic, they could use that oxygen to remain more active than the resident reptiles and amphibians on land at the time. Their metabolism was, frankly, superior due to their lung capacity and to emerging endothermy: literally self-heating or warm-bloodedness. To the other denizens of the epoch, the early dinosaurs running around fast on two feet must have been nothing short of nightmarish.
The unique dinosaurian breathing apparatus bestowed one other sizable benefit. The early dinosaurs could withstand the hothouse temperatures of the Triassic far more readily than the proto-mammals of the era. Our hairy ancestors had to burrow underground and adopt a nocturnal life in order to withstand the withering daytime heat of the Triassic. The dinosaurs, on the other hand, could stay out in the sunshine and frolic in the heat.
By the end of the Triassic and the earliest chapter of the Jurassic, the dinosaurs were poised to take over the world’s landscapes as oxygen levels steadily increased. They would assume the role of masters of the realm in fantastic and gigantic, brontosaurian fashion, while we mammals remained the size of rats or smaller for 125 million years and spent our days hidden away in burrows.
Now, let’s have a serious talk about chickens, shall we? Chickens are dinosaurs with wings. All birds lost their teeth and a long tail long ago in a successful bid to shed weight. The lighter you are, the easier it is to get the body off the ground and into the air.
Being dinosaurs/birds, chickens have those nifty lungs with the air sac extensions. They can extract more oxygen from the environment and they can use their extensive air exchange system to shed heat and actually stay cool better than you and I can. We sweat to cool our outer skin surface. Birds can ventilate their entire internal structure. Although chickens actually possess a hotter average body temperature than humans, the birds can dump BTUs more readily than we do. That means they can withstand considerably hotter temperatures than we mammals.
Don’t take my word for it. Let the biggest chickens of all time do the talking. Birds 55 million years ago, some 10 million years after an asteroid the size of Manhattan Island knocked the terrible lizards from their throne, began to evolve great size and tried to fill the big-beast niche left by the vanquished tyrannosaurs. The Phorusrhacids, perfectly nicknamed the terror birds, became the top predators for a short span of time at the end of the Paleocene and early Eocene. In the closing days of the Paleocene, ever hotter temperatures slowly ramped up as CO2 levels rose to the 1,000 ppm level. As temperatures climbed across the globe, the big birds exploded across the continents.
The birds would dominate all land-dwellers until mammalian predators eventually grew large enough and cunning enough to take the birds down a notch. Today, we are the top predator of chickens, judging by the proliferation of fast-food chicken fingers across the planet. Thank goodness today we don’t have to go out and tend chickens that stand 11 feet tall and weigh a ton.
And now for the final act.
It’s the year 2118, one-hundred years from right now. The CO2 level in the atmosphere is again approaching 1,000 ppm, 2.5 times what it is today but identical to that of the time when birds ruled the roost. Average daytime temperatures are now six degrees Celsius (10 degrees Fahrenheit) mean annual temperature hotter than today. At mid-day in the Plains in summer it is so broiling hot that it’s impossible to grow corn, soybeans, wheat, sunflowers – much of anything. Humans cannot work outside in the ferocious temperatures. The Plains states, the Southwest, and portions of the South are being abandoned as people flee for northern latitudes. Nearly a third of the continental United States is becoming uninhabitable to humans and non-burrowing mammals.
But the daytime temps are not too savage for our friendly neighborhood dinosaur, the chicken.
So, as you and I drive off into the sunset to escape the heat, the chicken crosses the road to the other side. Your descendants, on the other hand, will one day travel that same road to a dead end.
Breathe easy, cousins.
