What would dinosaurs look like today if they hadn’t gone extinct?
A question that offers ideas for understanding evolution. They made us mammals smarter.
In an interesting article written by Nicholas R. Longrich, Senior Lecturer in Palaeontology and Evolutionary Biology at the University of Bath, a bit of the history of dinosaurs is explored and ideas are offered to answer a question that also interests us. We know that 66 million years ago the asteroid put a stop to the existence of dinosaurs on earth. The plants died and then the animals that fed on them. Over 90% of all species disappeared. By the time the dust settled, all but a handful of birds of the dinosaurs were extinct.
This is where the evolutionary biology professor‘s analysis starts. This cataclysmic event made human evolution possible. The surviving mammals thrived, including the tiny proto-primates that would eventually evolve into us. Let’s imagine another ending instead.
Imagine dinosaurs as animals continuing their evolutionary process: In the 1980s, paleontologist Dale Russell proposed such a thought experiment, in which a carnivorous dinosaur evolved into an intelligent tool user. This “dinosauroid” had a large brain, opposable thumbs, and walked upright. But it seems that this is not possible.
As stated in Gregory Paul’s article , published in the Annals of Carnegie Museum in 2019 and taken up by Science Alert, the size of dinosaurs must be considered. Since the Jurassic, sauropod dinosaurs, Brontosaurs and their ilk have evolved into giants weighing 30-50 tons, up to 30 meters long, ten times the weight of an elephant and as long as a blue whale.
This happened on different continents, at different times and in different climates, from deserts to rainforests. But other dinosaurs that lived in these environments didn’t become supergiants. The common thread that united these animals lay in their being sauropods. Something about sauropod anatomy – lungs, hollow bones with a high strength-to-weight ratio, metabolism, or all of these together – unlocked their evolutionary potential: it allowed them to grow like no other animal. Similarly, carnivorous dinosaurs have repeatedly evolved into huge predators of ten meters and many tons. Over the course of 100 million years, megalosaurids, allosaurids, carcharodontosaurids, neovenatorids and finally tyrannosaurids evolved into gigantic predators always at the top of the food chain.
Huge bodies, brains more or less
From an evolutionary point of view, large bodies are fine, maybe, but only if the brain grows with it. Dinosaurs showed a weak trend of increasing brain size over time, Longrich suggests. Jurassic dinosaurs, such as Brachiosaurus, had small brains, while in the Late Cretaceous, 80 million years later, tyrannosaurs and platypus evolved larger brains. Then an iconic character is mentioned: despite its size, the T. rex brain weighed only 400 grams. The average human brain weighs 1.3 kilograms. They have continued to evolve physically: long and light legs evidently useful for predators busy following their prey.
However, the brain, over time, allowed dinosaurs to enter new niches and social life became slightly more complex. They started living in herds , they started sprouting horns to fight and show strength to the rival male. This is when, it seems, dinosaurs slowed down their evolutionary rush: They started “repeating” themselves , evolving into giant herbivores and small-brained carnivores. In 100 million years of being on earth, that’s all they’ve managed to become. Scholars say they were unlikely to have continued to evolve significantly, asteroid or not.
Longrich comments that they could have developed slightly larger brains, but there is no evidence that they would have evolved into genes. Nor is it likely that mammals would have supplanted them. Dinosaurs monopolized their environments right up until the asteroid hit.
Mammals, meanwhile, never evolved into supergiant herbivores and carnivores. But they have repeatedly developed large brains . It is true that today, some descendants of dinosaurs – birds such as crows and parrots – have complex brains. They can use tools, talk and count. But it is mammals such as monkeys, elephants and dolphins that have developed the largest brains and the most complex behaviors.
So did the elimination of the dinosaurs ensure the evolution of intelligence for mammals?
“Maybe not”. The Prof. uses a “maybe” along with the final no given to this question
He argues that the evolutionary history of primates suggests that our evolution was far from inevitable . In Africa, primates evolved into large-brained apes and, over the course of 7 million years, produced modern humans. But elsewhere primate evolution has taken very different paths. When apes reached South America 35 million years ago, they evolved into other ape species. Primates reached North America at least three times, 55 million years ago, 50 million years ago and 20 million years ago. “Still, they didn’t evolve into a species that produces nuclear weapons and smartphones,” Longrich comments. On the contrary, for reasons we do not understand, they have become extinct. In Africa, and in Africa alone, primate evolution has taken a unique direction. Something in the fauna, flora, or geography of Africa prompted the evolution of apes : large-bodied, large-brained, tool-using terrestrial primates.
Even without dinosaurs, our evolution needed the right combination of chance and luck . The talent that intercepts the good fortune. Concept difficult to accept by a scientist, that of good luck, for this we accept a “maybe” as an answer. Science, moreover, is a continuous updating and revision of the acquired knowledge and this is how its authority is realized.
- What if the dinosaurs hadn’t gone extinct? Why our world might look very different. (theconversation.com)