{"id":13283,"date":"2022-06-07T00:00:00","date_gmt":"2022-06-06T22:00:00","guid":{"rendered":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/?post_type=purple_issue&p=13283"},"modified":"2022-06-08T10:34:10","modified_gmt":"2022-06-08T08:34:10","slug":"life-as-we-know-it","status":"publish","type":"post","link":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/2022\/06\/07\/life-as-we-know-it\/","title":{"rendered":"Life as we know it"},"content":{"rendered":"\n
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LIFE AS WE KNOW IT<\/span><\/h2>\n\n

When the asteroid smashed into Earth 66 million years ago, it wiped out the fiercest, strongest creatures on Earth: the dinosaurs. So how exactly did our tiny, furtive ancestors thrive in the aftermath of an apocalypse? <\/strong><\/p>\n\n

by PROF STEVE BRUSATTE <\/strong><\/span><\/p>\n\n

D<\/span>uring the Triassic, some 225 million years ago, two types of animals went their separate ways. They were both born on the supercontinent of Pangaea, the single slab of land that stretched from the North Pole to the South. Their fates would be different, but forever intertwined. One group was destined for grandeur, and before long, their aeroplane-sized bodies thundered across the land. Dinosaurs. The other group was relegated to the shadows to bide their time. <\/p>\n\n

Mammals. Us, our distant ancestors. <\/p>\n\n

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The supercontinent Pangaea began to break apart in the early Jurassic, around 200 million years ago <\/figcaption><\/figure><\/div>\n\n

Fast-forward some 160 million years, through the Jurassic and to the end of the Cretaceous. Temperatures spiked and crashed, sea levels rose and fell, and the supercontinent became the many continents of today. Through all of this time, dinosaurs and mammals lived together, but followed their own paths. No mammal ever got larger than a badger, as they were held in check by the dinosaurs. Conversely, the smart and furry little mammals kept dinosaurs from the small-bodied niches, so there never was a miniature T. <\/em>rex <\/em>or Triceratops. <\/em>Like ships passing in the night, the dinosaurs and mammals both diversified, claiming separate realms as their own. Dinosaurs ruled the forests and plains by day, mammals the brush and underground in darkness. <\/p>\n\n

Then, in an instant, everything changed. Sixty-six million years ago, a sudden disaster reshaped the world, and within days, months and years, it upended an evolutionary status quo that had persisted for more than 100,000 millennia. The dinosaurs \u2013 except for a few peculiar species with wings and feathers, which became today\u2019s birds \u2013 couldn\u2019t cope, and they went extinct.<\/span><\/p>\n\n

Many mammals felt the pang of death, too, but some managed to endure. From these plucky survivors, the next great dynasty of Earth history would blossom. <\/p>\n\n

DINOSAURS DIE, MAMMALS SURVIVE <\/span><\/strong><\/h5>\n\n

With no hint of hyperbole, what happened 66 million years ago was probably the worst single day in the history of our planet. <\/p>\n\n

As herds of Triceratops <\/em>awoke and began their breakfast of ferns, they had no idea that an asteroid the size of Mount Everest was on a collision course with Earth. It darted through the heavens faster than a gunshot, and by the dumb luck of the cosmos, smashed into what is now the Yucat\u00e1n Peninsula of Mexico, detonating with the force of over a billion nuclear bombs, punching a hole in the crust over 160 kilometres (100 miles) wide. Earthquakes ravaged the land and tsunamis sliced up the coasts, the atmosphere turned into an oven, forests spontaneously combusted, pellets of molten rock rained down from the sky. The soot and the grime coagulated in the atmosphere, turning the world dark for many years. Then, in a final insult, the carbon dioxide liberated by the impact superheated the Earth for millennia.<\/span><\/p>\n\n

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Illustration of the Chicxulub crater, located off the coast of modern-day Mexico, shortly after impact<\/figcaption><\/figure><\/div>\n\n

The effects of these immediate, medium-term, and long-term catastrophes was nothing short of an apocalypse. Ecosystems collapsed like houses of cards. Three out of every four species died, making this end-Cretaceous disaster one of the five biggest mass extinctions in Earth history. The most famous victims were all of the non-bird dinosaurs; monsters like T. rex <\/em>would never stalk the Earth again. Also departing were the pterosaurs (flying reptiles) and the many reptiles, like plesiosaurs and mosasaurs, which swarmed the oceans.<\/span><\/p>\n\n

\u201cSHOCKINGLY, NEW RESEARCH SHOWS THAT MAMMALS NEARLY WENT THE WAY OF THE DINOSAURS\u201d <\/em><\/strong><\/span><\/p><\/blockquote>\n\n

All mass extinctions \u2013 at least so far \u2013 have had survivors. And this time, they were the mammals. Shockingly, new research shows that mammals nearly went the way of the dinosaurs: only about 7 per cent of species are thought to have made it through the fire and brimstone. Consider a game of asteroid roulette: a gun, with 10 chambers, nine of which hold a bullet. Take your shot: those survival odds are even better than what our ancestors faced at the end of the Cretaceous. <\/p>\n\n

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When the asteroid smashed into Earth some 66 million years ago, as visualised here, it altered the path of evolution for the planet\u2019s species <\/figcaption><\/figure>\n\n

This raises the question: why were some mammals able to endure when the dinosaurs, and most mammals, were not? When comparing mammals to dinosaurs, the answer seems straightforward. Most dinosaurs were large, it took them a long time to grow from baby to adult, and they had highly specialised diets focused on a few particular types of food. These were all liabilities when the world turned to madness. The surviving mammals, however, were drastically different, as shown by the research of Prof Gregory Wilson Mantilla and colleagues. These mammals were smaller than both the dinosaurs and the mammals that died, so they were able to hide easier, and maybe grow and reproduce faster. They had generalist diets, so they were not handicapped by reliance on one particular food source, but could eat whatever was on offer.<\/span><\/p>\n\n

It\u2019s as if survival was a game of poker \u2013 part luck, part skill. The dinosaurs had a terrible hand of cards \u2013 the dead man\u2019s hand. Some mammals did too, particularly early relatives of marsupials (today\u2019s mammals that raise their tiny babies in pouches), which were common in the Cretaceous but then were nearly extinguished by the asteroid. Other mammals, however, had a much stronger hand of cards, and it was their ticket to a new future. The vast majority of these mammals were placentals: species that give birth to live, well-developed young. <\/p>\n\n

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