Sixty-six million years in the past, an asteroid hit the Earth with the pressure of 10 billion atomic bombs and altered the course of evolution. The skies darkened and vegetation stopped photosynthesizing. The vegetation died, then the animals that consumed them. The meals chain collapsed. Over 90 % of all species vanished. When the mud settled, all dinosaurs besides a handful of birds had gone extinct.
However this catastrophic occasion made human evolution potential. The surviving mammals flourished, together with little proto-primates that might evolve into us.
Think about the asteroid had missed, and dinosaurs survived. Image highly-evolved raptors planting their flag on the moon. Dinosaur scientists, discovering relativity, or discussing a hypothetical world wherein, extremely, mammals took over the Earth.
This may sound like dangerous science fiction, nevertheless it will get at some deep philosophical questions on evolution. Is humanity simply right here by probability, or is the evolution of clever tool-users inevitable?
Brains, instruments, language, and massive social teams make us the planet’s dominant species. There are eight billion Homo sapiens on seven continents. By weight, there are extra people than all wild animals.
We’ve modified half of Earth’s land to feed ourselves. You possibly can argue creatures like people had been sure to evolve.
Within the Eighties, palaeontologist Dale Russell proposed a thought experiment wherein a carnivorous dinosaur developed into an clever device consumer. This “dinosauroid” was big-brained with opposable thumbs and walked upright.
It’s not unimaginable nevertheless it’s unlikely. The biology of an animal constrains the course of its evolution. Your start line limits your endpoints.
Should you drop out of school, you most likely received’t be a mind surgeon, lawyer, or Nasa rocket scientist. However you may be an artist, actor, or entrepreneur. The paths we absorb life open some doorways and shut others. That’s additionally true in evolution.
Think about the scale of dinosaurs. Starting within the Jurassic, sauropod dinosaurs, Brontosaurus, and kin developed into 30-50 ton giants as much as 30 meters lengthy—ten instances the burden of an elephant and so long as a blue whale. This occurred in a number of teams, together with Diplodocidae, Brachiosauridae, Turiasauridae, Mamenchisauridae, and Titanosauria.
This occurred on completely different continents, at completely different instances, and in numerous climates, from deserts to rainforests. However different dinosaurs residing in these environments didn’t change into supergiants.
The widespread thread linking these animals was that they had been sauropods. One thing about sauropod anatomy—lungs, hole bones with a excessive strength-to-weight ratio, metabolism, or all these items—unlocked their evolutionary potential. It allow them to develop massive in a means that no land animals had ever earlier than, or have since.
Likewise, the carnivorous dinosaurs repeatedly developed big, ten-meter, multi-ton predators. Over 100 million years, megalosaurids, allosaurids, carcharodontosaurids, neovenatorids, and eventually tyrannosaurs developed large apex predators.
Dinosaurs did massive our bodies nicely. Massive brains not a lot. Dinosaurs did present a weak development in the direction of elevated mind measurement over time. Jurassic dinosaurs like Allosaurus, Stegosaurus, and Brachiosaurus had small brains.
By the late Cretaceous, 80 million years later, tyrannosaurs and duckbills had developed bigger brains. However regardless of its measurement, the T. rex mind nonetheless weighed simply 400 grams. A Velociraptor mind weighed 15 grams. The typical human mind weighs 1.3 kilograms.
Dinosaurs did enter new niches over time. Small herbivores turned extra widespread and birds diversified. Lengthy-legged varieties developed in a while, suggesting an arms race between fleet-footed predators and their prey.
Dinosaurs appear to have had more and more advanced social lives. They began residing in herds and developed elaborate horns for combating and show. But dinosaurs largely appear to repeat themselves, evolving large herbivores and carnivores with small brains.
There’s little about 100 million years of dinosaur historical past to trace they’d have performed something radically completely different if the asteroid hadn’t intervened. We’d seemingly nonetheless have these supergiant, long-necked herbivores and large tyrannosaur-like predators.
They could have developed barely larger brains, however there’s little proof they’d have developed into geniuses. Neither is it seemingly that mammals would have displaced them. Dinosaurs monopolized their environments to the very finish, when the asteroid hit.
Mammals, in the meantime, had completely different constraints. They by no means developed supergiant herbivores and carnivores. However they repeatedly developed massive brains. Huge brains (as giant or bigger than ours) developed in orcas, sperm whales, baleen whales, elephants, leopard seals, and apes.
As we speak, a couple of dinosaur descendants—birds like crows and parrots—have advanced brains. They will use instruments, discuss, and depend. Nevertheless it’s mammals like apes, elephants, and dolphins that developed the largest brains and most advanced behaviors.
So did eliminating the dinosaurs assure mammals would evolve intelligence?
Effectively, perhaps not.
Beginning factors could restrict endpoints, however they don’t assure them both. Steve Jobs, Invoice Gates, and Mark Zuckerberg all dropped out of school. But when dropping out routinely made you a multibillionaire, each faculty dropout can be wealthy. Even beginning in the suitable place, you want alternatives and luck.
The evolutionary historical past of primates suggests our evolution was something however inevitable. In Africa, primates did evolve into big-brained apes and, over 7 million years, produced trendy people. However elsewhere primate evolution took very completely different paths.
When monkeys reached South America 35 million years in the past, they only developed into extra monkey species. And primates reached North America no less than three separate instances, 55 million years in the past, 50 million years in the past, and 20 million years in the past. But they didn’t evolve right into a species who make nuclear weapons and smartphones. As an alternative, for causes we don’t perceive, they went extinct.
In Africa, and Africa alone, primate evolution took a novel course. One thing about Africa’s fauna, flora, or geography drove the evolution of apes: terrestrial, big-bodied, big-brained, tool-using primates. Even with the dinosaurs gone, our evolution wanted the suitable mixture of alternative and luck.
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