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What would dinosaurs look like today if they never became extinct?  : ScienceAlert

What would dinosaurs look like today if they never became extinct? : ScienceAlert

Sixty-six million years ago, a asteroid Hit the ground hard 10 billion atomic bombs And changed the course of development.

The The sky darkened And the plants stopped photosynthesizing. The plants died, and then the animals that fed on them died. The food chain collapsed. on me 90 percent of all types disappeared. When the dust settled, that’s it dinosaurs Except bunch of birds Extinct.

But this cataclysmic event made human evolution possible. The rest of the mammals, including a few, thrived primary primates It would evolve to us.

Imagine the asteroid missed, and the dinosaurs survived. Imagine highly evolved birds of prey flying their flag the moon. dinosaur Scientists, with the discovery of relativity, or discuss a hypothetical world, where mammals have taken over the land in an incredible way.

This may sound like bad science fiction, but it raises some deep philosophical questions about evolution. Is humanity only here by chance, or is the evolution of intelligent tool users inevitable?

Brains, tools, language, and large social groups make us the dominant species on planet Earth. There are 8 billion Homo sapiens on seven continents. By weight, there More humans than all wild animals.

we’ve got Half-land modification to feed ourselves. You can argue with creatures like humans It is bound to evolve.

In the 80s, paleontologist Dale Russell Suggest a thought experiment in which a Carnivorous dinosaurs have evolved into a clever tool. This “tyrannosaurus” had large brains with opposite thumbs and walked upright.

dinosaur model. (Dale Russell & Ron Seguin/Canadian Museum of Nature via Naish & Tattersdill, Available here). Canadian Journal of Geosciences2021)

This is not impossible, but it is not likely. An animal’s biology determines the direction of its development. Your starting point limits your end points.

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If you dropped out of college, you probably wouldn’t be a brain surgeon, or a lawyer, or a rocket scientist at NASA. But you may be an artist, an actor or an entrepreneur. The paths we take in life open some doors and close others. This is also true of evolution.

Dinosaurs and giant mammals across the timeline
Dinosaurs and giant mammals through time. (Nick Longrich)

Consider the size of dinosaurs. Starting from the Jurassic period, sauropod dinosaurs, Brontosaurus and relatives They evolved into 30-50 ton giants Its length reaches 30 meters – ten times the weight of an elephant and the length of a blue whale.

This happened in multiple groups, incl DiplodoxidesBrachiosauridae TuriasauridaeAnd the Mamenchisauridae And the Titanosauria.

This happened on different continents, at different times, and in different climates, from deserts to rainforests. But the other dinosaurs that lived in these environments didn’t become super giants.

The common thread connecting these animals was that they were sauropods. Something about sauropod anatomy – lungshollow bones with a High strength-to-weight ratioor metabolism All of these things – Unleash their evolutionary potential. He allowed them to grow in a way never before seen in a wild animal, or not since.

Likewise, carnivorous dinosaurs have evolved over and over again as massive predators, ten meters long and multiple tons. more than 100 million years, megalosaursAnd the allosaurusAnd the carcharodontosauridsAnd the neovenatorids, Finally tyrannosaurs Giant evolved predators.

Diagram of brain size versus body mass for dinosaurs, mammals, and birds
Brain size versus body mass for dinosaurs, mammals, and birds. (Nick Longrich)

Dinosaurs did well with large bodies. Big brains Not much. Dinosaurs showed a weak trend toward increasing brain size over time. Jurassic dinosaurs like AllosaurusAnd the stegosaurus, And the Brachiosaurus He had small brains.

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By the late Cretaceous period, 80 million years later, tyrannosaurs Duck birds have evolved larger brains. But despite its size, the t-rex The brain still weighs only 400 grams. a Velociraptor Brain weight 15 grams. The average human brain weighs 1.3 kilograms.

Dinosaurs entered new domains over time. Small herbivores became more common and birds diversified. Long-legged forms evolved later, suggesting an arms race between fleet-footed predators and their prey.

Dinosaurs seem to have an increasingly complex social life. They began to live herds and evolved elaborate horns to fight and show. However, dinosaurs seem to mostly repeat themselves, evolving into giant herbivores and small-brained carnivores.

There are nearly 100 million years of dinosaur history to suggest that they would have done anything radically different if the asteroid hadn’t intervened. We probably still have those giant, long-necked herbivores and tyrannosaurus-like predators.

They may have evolved slightly larger brains, but there is little evidence that they evolved into geniuses. It is also unlikely that mammals displaced them. Dinosaurs monopolized their habitats until the end, when the asteroid struck.

Meanwhile, mammals had various limitations. They never evolved giant herbivores and carnivores. But they have developed big brains over and over again. Megabrains (larger or larger than our own) evolved in orcas, sperm whales, baleen whales, elephants, leopard seals, and monkeys.

Today, few of the descendants of dinosaurs — birds like crows and parrots — have them complex minds. They can use it ToolsAnd speaking and counting. But it is mammals such as monkeys, elephants, and dolphins that have evolved the largest brains and the most complex behaviours.

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Does the elimination of dinosaurs guarantee the evolution of mammalian intelligence?

Well, maybe not.

Starting points may limit endpoints, but they do not guarantee them either. Steve Jobs, Bill Gates, and Mark Zuckerberg They all dropped out of college. But if dropping out automatically made you a billionaire, every college dropout would be rich. Even if you start in the right place, you need chances and luck.

The evolutionary history of monkeys indicates that our evolution was not deterministic at all. In Africa, primates have already evolved into big-brained apes, and more 7 million yearsproduced modern humans. But primate evolution elsewhere has taken very different paths.

When Monkeys reached South America 35 million years ago they just evolved into more species of monkeys. Primates have arrived in North America at least three separate times. 55 million years agoAnd the 50 million years agoAnd the 20 million years ago.

However, they did not evolve into a species that makes nuclear weapons and smartphones. Instead, for reasons we don’t understand, they went extinct.

In Africa, and Africa alone, primate evolution has taken a unique direction. Something about the animals, plants and geography of Africa led the evolution of apes: terrestrial, big body, big brainsAnd the Use of tools primates.

Even with the dinosaurs gone, our evolution needed the right mix of chance and luck.Conversation

Nicholas RSenior Lecturer in Paleontology and Evolutionary Biology, Bath University

This article has been republished from Conversation Under Creative Commons Licence. Read the The original article.