Sixty-six million years ago, an asteroid crashed into Earth with the force of 10 billion atomic bombs. The skies darkened and the plants, no longer able to photosynthesize, died; then the animals that fed on them also died. The food chain collapsed taking more than 90% of all species with it. When the situation stabilized again, very few species remained alive: the dinosaurs were gone.
As the Latins said: "Mors tua, vita mea". This event, while devastating, made human evolution possible. Surviving mammals thrived, including small proto-primates that would evolve to the present day, with or without smartphones.
Now imagine if dinosaurs had survived. Make an effort: what would we have today? The first dinosaur on the moon? Or a dinosaur blogger writing a post about the hypothetical world where mammals didn't go extinct. Or maybe we would somebody else.
It's not bad science fiction, on the contrary: it helps to ask us profound questions about our evolution
Is humanity here only by chance or can evolution to an intelligent and skilful species not be avoided? Brain, tools, language and sociability make us the dominant species on the planet. There are 8 billion Homo sapiens on seven continents. Proportionally, there are more humane than all wild animals.
Our Customers half of the earth turned upside down to feed us. Was it just luck?
In the 80s, the paleontologist Dale Russell proposes a speculative experiment in which a carnivorous dinosaur was imagined that evolved into a "dinosaur habilis", able to use utensils and tools. This "dinosauroid" had a large brain with opposable thumbs and walked upright.
It's not impossible, but it's unlikely. An animal's biology constrains the direction of its evolution. The starting point limits the points of arrival. All comparisons possible and imaginable only confirm the thesis.
Dinosaurs: big shoes, smart brains
Consider the size of the dinosaurs. Starting from the Jurassic the sauropod dinosaurs, the brontosaurs and relatives they evolved into giants of 30-50 tons up to 30 meters long. This happened on different continents, at different times and in different climates, from deserts to rainforests.
But it didn't happen to all kinds of dinosaurs: it happened to sauropods.
Something about the anatomy of sauropods (their lungs, hollow bones with a high strength-to-weight ratio, metabolism, and more) allowed them to grow bigger than any animal before, and like no animal since.
Yet, their brains they didn't grow much. Even in the late Cretaceous, more than 80 million years after their appearance, the T-Rex had a brain weighing just 400 grams. That of a velociraptor weighed 15 grams. (Ours weighs 1,3kg. Yes, even Mister Bean's).
In other words, in the 100 million years of history that we know of, we have little evidence that dinosaurs would have made an exploit and wielded spears and clubs. Or invented the radio. However, they would probably have continued to dominate the planet, strong in their size.
Dinosaurs had no chance.
Mammals, on the other hand, had different constraints than dinosaurs. They have never "produced" supergiant herbivores and carnivores: but they have repeatedly developed large brains. Massive brains (as large or larger than a human's) are found in orcas, sperm whales, whales, elephants, leopard seals, and apes.
Of course, today some descendants of the dinosaurs, birds such as crows and parrots, also have complex brains. They can use some instruments, communicate and even count. But they're pretty basic compared to mammals like monkeys, elephants and dolphins that have evolved bigger brains and more complex behaviors.
Case closed, therefore: if the asteroid takes out the dinosaurs, the mammals automatically develop more intelligence and become people who read blogs and buy an electric car. Or not?
All thanks to the asteroid, then? It's not that easy
Starting points may limit ending points, but they don't guarantee them either. Steve Jobs, Bill Gates, and Mark Zuckerberg all dropped out of college and became billionaires, sure. But if dropping out of college automatically made multimillionaires, we'd have a sea of rich people. Opportunity and luck also play a major role.
The evolutionary history of primates suggests that our evolution was far from inevitable. In Africa, primates evolved into large-brained apes and beyond 7 million years, they produced modern humans. But elsewhere primate evolution has taken very different paths.
When apes reached South America 35 million years ago, they "only" evolved into other ape species. And those that have reached North America (at least three times: 55 millions of years ago , 50 millions of years ago e 20 millions of years ago) have even become extinct, although we still don't know why or how.
In Africa, and in Africa alone, primate evolution has taken a unique direction. Something about the fauna, flora or geography of Africa has guided the evolution of the apes: terrestrial primates, full-bodied, big brains , who use tools. Even without dinosaurs, our evolution needed the right combination of opportunity and luck.
We needed an asteroid, okay. But we have to thank mother Africa if we are here.