{"id":5202,"date":"2022-12-06T22:00:00","date_gmt":"2022-12-06T22:00:00","guid":{"rendered":"https:\/\/modernsciences.org\/staging\/4414\/?p=5202"},"modified":"2022-11-25T06:23:31","modified_gmt":"2022-11-25T06:23:31","slug":"what-if-the-dinosaurs-hadnt-gone-extinct-why-our-world-might-look-very-different","status":"publish","type":"post","link":"https:\/\/modernsciences.org\/staging\/4414\/what-if-the-dinosaurs-hadnt-gone-extinct-why-our-world-might-look-very-different\/","title":{"rendered":"What if the dinosaurs hadn\u2019t gone extinct? Why our world might look very different"},"content":{"rendered":"\n
\n \n
\n Ajnabia odysseus lived 66 million years ago, making it one of the last dinosaurs on Earth.\n Raul Martin<\/span><\/span>\n <\/figcaption>\n <\/figure>\n\nNicholas R. Longrich<\/a>, University of Bath<\/a><\/em><\/span>\n\n

Sixty-six million years ago, an asteroid hit the Earth with the force of 10 billion atomic bombs<\/a> and changed the course of evolution. The skies darkened<\/a> and plants stopped photosynthesising. The plants died, then the animals that fed on them. The food chain collapsed. Over 90% of all species<\/a> vanished. When the dust settled, all dinosaurs except a handful of birds<\/a> had gone extinct. <\/p>\n\n

But this catastrophic event made human evolution possible. The surviving mammals flourished, including little proto-primates<\/a> that would evolve into us.<\/p>\n\n

\n \"\"\n
\n After the asteroid.<\/span>\n Joschua Knuppe<\/span><\/span>\n <\/figcaption>\n <\/figure>\n\n

Imagine the asteroid had missed, and dinosaurs survived. Picture highly evolved raptors planting their flag on the moon. Dinosaur scientists, discovering relativity, or discussing a hypothetical world in which, incredibly, mammals took over the Earth. <\/p>\n\n

This might sound like bad science fiction, but it gets at some deep, philosophical questions about evolution. Is humanity just here by chance, or is the evolution of intelligent tool-users inevitable?<\/p>\n\n

Brains, tools, language and big social groups make us the planet\u2019s dominant species. There are 8 billion Homo sapiens<\/em> on seven continents. By weight, there are more humans than all wild animals<\/a>.<\/p>\n\n

We\u2019ve modified half of Earth\u2019s land<\/a> to feed ourselves. You could argue creatures like humans were bound to evolve<\/a>.<\/p>\n\n

In the 1980s, palaeontologist Dale Russell<\/a> proposed a thought experiment in which a carnivorous dinosaur evolved into an intelligent tool user<\/a>. This \u201cdinosauroid\u201d was big-brained with opposable thumbs and walked upright.<\/p>\n\n\n\n

It\u2019s not impossible but it\u2019s unlikely. The biology of an animal constrains the direction of its evolution. Your starting point limits your endpoints. <\/p>\n\n

If you drop out of college, you probably won\u2019t be a brain surgeon, lawyer or Nasa rocket scientist. But you might be an artist, actor or entrepreneur. The paths we take in life open some doors and close others. That\u2019s also true in evolution.<\/p>\n\n

\n \"\"\n
\n Giant dinosaurs and mammals through time.<\/span>\n Nick Longrich<\/span><\/span>\n <\/figcaption>\n <\/figure>\n\n

Consider the size of dinosaurs. Beginning in the Jurassic, sauropod dinosaurs, Brontosaurus<\/em> and kin evolved into 30-50 tonne giants<\/a> up to 30 metres long \u2013 ten times the weight of an elephant and as long as a blue whale. This happened in multiple groups, including Diplodocidae<\/a>, Brachiosauridae, Turiasauridae<\/a>, Mamenchisauridae<\/a> and Titanosauria<\/a>. <\/p>\n\n

This happened on different continents, at different times and in different climates, from deserts to rainforests. But other dinosaurs living in these environments didn\u2019t become supergiants. <\/p>\n\n

The common thread linking these animals was that they were sauropods. Something about sauropod anatomy \u2013 lungs<\/a>, hollow bones with a high strength-to-weight ratio<\/a>, metabolism or all these things<\/a> \u2013 unlocked their evolutionary potential. It let them grow big in a way that no land animals had ever before, or have since. <\/p>\n\n

Likewise, the carnivorous dinosaurs repeatedly evolved huge, ten-metre, multi-tonne predators. Over 100 million years, megalosaurids<\/a>, allosaurids<\/a>, carcharodontosaurids<\/a>, neovenatorids<\/a> and finally tyrannosaurs<\/a> evolved giant apex predators. <\/p>\n\n

\n \"\"\n
\n Brain size versus body mass for dinosaurs, mammals, and birds.<\/span>\n Nick Longrich<\/span><\/span>\n <\/figcaption>\n <\/figure>\n\n

Dinosaurs did big bodies well. Big brains not so much<\/a>. Dinosaurs did show a weak trend towards increased brain size over time. Jurassic dinosaurs like Allosaurus<\/em>, Stegosaurus<\/em> and Brachiosaurus<\/em> had small brains<\/a>. <\/p>\n\n

By the late Cretaceous, 80 million years later, tyrannosaurs<\/a> and duckbills had evolved larger brains. But despite its size, the T. rex<\/em> brain still weighed just 400 grams. A Velociraptor<\/em> brain weighed 15 grams. The average human brain weighs 1.3 kilograms.<\/p>\n\n

Dinosaurs did enter new niches over time. Small herbivores became more common and birds diversified. Long-legged forms evolved later on, suggesting an arms race between fleet-footed predators and their prey. <\/p>\n\n

Dinosaurs seem to have had increasingly complex social lives. They started living in herds<\/a> and evolved elaborate horns<\/a> for fighting and display. Yet dinosaurs mostly seem to repeat themselves, evolving giant herbivores and carnivores with small brains.<\/p>\n\n

There\u2019s little about 100 million years of dinosaur history to hint they\u2019d have done anything radically different if the asteroid hadn\u2019t intervened. We\u2019d likely still have those supergiant, long-necked herbivores and huge tyrannosaur-like predators. <\/p>\n\n

They may have evolved slightly bigger brains, but there\u2019s little evidence they\u2019d have evolved into geniuses. Neither is it likely that mammals would have displaced them. Dinosaurs monopolised their environments to very end, when the asteroid hit. <\/p>\n\n

Mammals, meanwhile, had different constraints. They never evolved supergiant herbivores and carnivores. But they repeatedly evolved big brains. Massive brains (as large or larger than ours) evolved in orcas, sperm whales, baleen whales, elephants, leopard seals and apes.<\/p>\n\n

Today, a few dinosaur descendants \u2013 birds like crows and parrots \u2013 have complex brains<\/a>. They can use tools<\/a>, talk and count. But it\u2019s mammals like apes, elephants and dolphins that evolved the biggest brains and most complex behaviours. <\/p>\n\n

So did eliminating the dinosaurs guarantee mammals would evolve intelligence?<\/p>\n\n

Well, maybe not.<\/p>\n\n

Starting points may limit endpoints, but they don\u2019t guarantee them either. Steve Jobs, Bill Gates and Mark Zuckerberg all dropped out of college<\/a>. But if dropping out automatically made you a multibillionaire, every college dropout would be rich. Even starting in the right place, you need opportunities and luck.<\/p>\n\n

The evolutionary history of primates suggests our evolution was anything but inevitable. In Africa, primates did evolve into big-brained apes and, over 7 million years<\/a>, produced modern humans<\/a>. But elsewhere primate evolution took very different paths. <\/p>\n\n

\n \"\"\n
\n Lion Tamarin, a South American monkey.<\/span>\n Wikipedia<\/span><\/span>\n <\/figcaption>\n <\/figure>\n\n

When monkeys reached South America<\/a> 35 million years ago they just evolved into more monkey species. And primates reached North America at least three separate times, 55 million years ago<\/a>, 50 million years ago<\/a>, and 20 million years ago<\/a>. Yet they didn\u2019t evolve into a species who make nuclear weapons and smartphones. Instead, for reasons we don\u2019t understand, they went extinct.<\/p>\n\n

In Africa, and Africa alone, primate evolution took a unique direction. Something about Africa\u2019s fauna, flora or geography drove the evolution of apes<\/a>: terrestrial, big-bodied, big-brained<\/a>, tool-using<\/a> primates. Even with the dinosaurs gone, our evolution needed the right combination of opportunity and luck.\"The<\/p>\n\n

Nicholas R. Longrich<\/a>, Senior Lecturer in Paleontology and Evolutionary Biology, University of Bath<\/a><\/em><\/span><\/p>\n\n

This article is republished from The Conversation<\/a> under a Creative Commons license. Read the original article<\/a>.<\/p>\n\n","protected":false},"excerpt":{"rendered":"Ajnabia odysseus lived 66 million years ago, making it one of the last dinosaurs on Earth. Raul Martin…\n","protected":false},"author":9,"featured_media":5195,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"nf_dc_page":"","fifu_image_url":"","fifu_image_alt":"","footnotes":""},"categories":[11],"tags":[29,25,474],"class_list":{"0":"post-5202","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-nature","8":"tag-dinosaur","9":"tag-paleontology","10":"tag-the-conversation","11":"cs-entry","12":"cs-video-wrap"},"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/modernsciences.org\/staging\/4414\/wp-json\/wp\/v2\/posts\/5202","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/modernsciences.org\/staging\/4414\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/modernsciences.org\/staging\/4414\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/modernsciences.org\/staging\/4414\/wp-json\/wp\/v2\/users\/9"}],"replies":[{"embeddable":true,"href":"https:\/\/modernsciences.org\/staging\/4414\/wp-json\/wp\/v2\/comments?post=5202"}],"version-history":[{"count":1,"href":"https:\/\/modernsciences.org\/staging\/4414\/wp-json\/wp\/v2\/posts\/5202\/revisions"}],"predecessor-version":[{"id":5203,"href":"https:\/\/modernsciences.org\/staging\/4414\/wp-json\/wp\/v2\/posts\/5202\/revisions\/5203"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/modernsciences.org\/staging\/4414\/wp-json\/wp\/v2\/media\/5195"}],"wp:attachment":[{"href":"https:\/\/modernsciences.org\/staging\/4414\/wp-json\/wp\/v2\/media?parent=5202"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/modernsciences.org\/staging\/4414\/wp-json\/wp\/v2\/categories?post=5202"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/modernsciences.org\/staging\/4414\/wp-json\/wp\/v2\/tags?post=5202"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}