What if dinosaurs hadn’t died out? Why our world can be very different

Sixty-six million years ago, an asteroid hit the Earth with the force of 10 billion atomic bombs and changed the course of evolution. The sky darkened, the plants stopped photosynthesizing and died. Then, of course, the animals that ate them also died.

The food chain has collapsed. More than 90% of the species have disappeared. By the time the dust settled, all but a handful of birds were extinct.

Yet this seemingly “catastrophic” event made human evolution possible. The surviving mammals flourished, including the small protoprimates that evolved into us.

Without the asteroid, would the dinosaurs have discovered the theory of relativity?

Now imagine that an asteroid flew by and the dinosaurs survived. Can you imagine highly evolved predators planting their flag on the moon? What about dinosaur scientists discovering the theory of relativity or discussing a hypothetical world in which mammals have incredibly taken over the Earth?

The plot may seem like bad science fiction, but it has some deep philosophical questions about evolution. Humanity is here by chance? Is the evolution of intelligent beings using tools inevitable?

Our brains, tools, language, and large social groups make us the dominant species on the planet. There are 8 billion Homo sapiens spread over seven continents. There are more people by weight than wild animals.

We have changed half the earth’s soil to feed ourselves. It can be argued that beings like humans are destined to evolve.

Dinosaurs on two legs? unlikely

In the 1980s, paleontologist Dale Russell proposed a thought experiment in which a carnivorous dinosaur became an intelligent tool user. This “dinosaur” had a big brain, thumbs, and walked upright.

It’s not impossible, but unlikely. The biology of an animal (its starting point) limits the direction of its evolution. If we drop out of college, we probably won’t become NASA neurosurgeons, lawyers, or rocket experts. But we can become artists, actors or entrepreneurs. The paths we walk in life open some doors and close others, and this also happens in evolution.

Pay attention to the sizes of dinosaurs. From the Jurassic period, sauropod dinosaurs, brontosaurus and the like evolved into giants from 30 to 50 tons and up to 30 meters in length. This is ten times the weight of an elephant and the length of a blue whale.

Growth occurred in several groups including Diplodocidae, Brachiosauridae, Turiasauridae, Mamenchisauridae and Titanosauria. And it happened on different continents, at different times and in different climates, from deserts to tropical jungles. But other dinosaurs that lived in the same environment did not become supergiants.

What then did they have in common? That they were sauropods. Something about sauropod anatomy – light, hollow bones with a high strength-to-weight ratio, metabolism or all of the above, who knows – unlocked their evolutionary potential. This allowed them to grow in a way that no other terrestrial animal has been able to, either before or since.

In the same way, carnivorous dinosaurs repeatedly turned into huge thirty-foot multi-ton predators. Over the course of 100 million years, megalosaurids, allosaurids, carcharodontosaurids, neovenaurids, and eventually tyrannosaurids evolved into giant superpredators at the top of the food chain.

Big bodies and small brains

Dinosaurs were good at building big bodies, but not very good at building big brains. Even Jurassic dinosaurs love allosaurus, Stegosaurus and brachiosaurus they had small brains.

At the end of the Cretaceous period, 80 million years later, tyrannosaurs and hadrosaurs finally managed to develop larger brains. But, despite its size, the brain Tirex Weighed only 400 grams. In comparison, the brain velociraptor it weighed 15 grams, while the average human brain weighs 1.3 kilograms.

Over time, dinosaurs occupied new niches. Smaller herbivores have become more common, and birds have become more diverse. Long-legged forms appeared later, indicating an “arms race” between light-footed predators and their prey.

Dinosaurs seem to have led increasingly complex social lives. They began to live in herds and developed elaborate antlers for fighting and display. However, in the end, their paths usually coincide: they always evolve towards giant herbivores and small-brained carnivores. There is nothing in the 100 million year history of the dinosaurs to indicate that they would have done something radically different if an asteroid had not intervened. We’d probably still have those super-giant, long-necked herbivores and huge tyrannosaur-like carnivores.

They may have developed slightly larger brains, but there is little evidence that they evolved into geniuses. It is also unlikely that mammals displaced them. The dinosaurs monopolized the environment until the very end when an asteroid crashed into them.

Mammals, for their part, had other limitations. They never evolved into supergiant herbivores and carnivores. But they repeatedly developed big brains. Killer whales, sperm whales, baleen whales, elephants, leopard seals and great apes all had massive brains the size of ours or even larger.

Today, there are several descendants of dinosaurs—birds like crows and parrots—with complex brains. They can use tools, speak and count. But it was mammals, such as great apes, elephants and dolphins, that developed the largest brains and most complex behaviors.

Did the removal of dinosaurs guarantee the development of intelligence in mammals? Well, maybe not. Starting points can limit final destinations, but they don’t guarantee them either. Steve Jobs, Bill Gates and Mark Zuckerberg dropped out of college. But if dropping out of college automatically made us billionaires, everyone who dropped out would be rich. Even starting from the right place, chances and luck are needed.

The emergence of great apes was not inevitable

The evolutionary history of primates suggests that our evolution was anything but inevitable. In Africa, primates evolved into large-brained apes and gave rise to modern humans over 7 million years. But elsewhere, primate evolution followed very different paths.

When monkeys arrived in South America 35 million years ago, they simply evolved into other types of monkeys. And primates arrived in North America at least three times: 55 million years ago, 50 million years ago, and 20 million years ago. However, they have not evolved into a species producing nuclear weapons and smartphones. On the contrary: for reasons unknown to us, they died out.

In Africa, and only in Africa, primate evolution has taken a unique direction. Something in the fauna, flora or geography of Africa caused the evolution of great apes: large land primates with large brains and large brains. Even with the extinction of the dinosaurs, our evolution required the right mix of chance and luck.

Nicholas R. Longrich, Senior Lecturer in Paleontology and Evolutionary Biology at the University of Bath.

This article was originally published on The Conversation. Read the original.

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