Why were prehistoric animals so big?
Why were prehistoric animals so big? (Thinkstock)
Why were prehistoric animals so big?
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You asked us, why were prehistoric animals so big?

Though not all ancient critters were huge, a lot of them were and I'm talking 90 ton, 130-foot dinos, 50-foot giant sharks and ground sloths that could go shoulder to shoulder with today's elephants.

It's possible conditions in the environment stimulated this mega-growth at different times in the past, like during the Paleozoic era, when cockroaches as big as house cats may have benefited from the extra oxygen in the atmosphere. Another theory is Cope's Rule, the idea that competition tends to encourage the evolution of bigger animals over time.

Whatever the reason behind their ginormousness is, it made these animals more vulnerable and being super-sized often meant they were slower to adapt to changing conditions, so in the end, most of these behemoths went extinct.

So, yes, at six-foot-seven, it's not looking good for me, folks.

Save me.

For more stories like this, check us out every day at Smithsonian.com.

Critical thinking challenge: Why does competition tend to encourage the evolution of bigger animals?


Source URL: https://www.tweentribune.com/article/teen/why-were-prehistoric-animals-so-big/

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COMMENTS (16)
  • Ashleypatt
    4/06/2015 - 01:53 p.m.

    There are many large animals such as sharks dolphins giraffes and many more! This grows the oxygen over time and the growth of animals over time. It is really cool to see how big animals could get or even how tall they can get. Especially animals in the zoos or on pictures.

  • CassandraHBlue
    4/07/2015 - 02:38 p.m.

    I had no idea that prehistoric sharks were that big Regular dinosaurs I knew were big but sharks that was new but I think that the prehistoric past animals were so big because of the air quality because I am pretty sure that they weren't growing because of competition.

  • albertog-Che
    4/10/2015 - 11:43 a.m.

    I learned that there used to be sharks that were 50 feet, that is very hard to imagine and it must have been a lot more dangerous. There are a different theories to why they used to be so big. One is because of the extra oxygen there was and the other is that competition helps encourage the evolution. The down side to being so big is that it is harder to adapt to the environment which caused them to go extinct.

  • donovanh-Che
    4/10/2015 - 11:52 a.m.

    Everything, or at least almost everything, was larger back then than it they are now. Consider the Jurassic Era (I use Jurassic instead of Triassic because there was an extinction event between the two ears); during this time the CO2 levels were 7 times the levels just before the industrial revolution. The trees were huge and plentiful, Conifers dominated the flora. That in turned increased Oxygen levels to 130% of modern levels. This allowed bugs to be huge because insects don't have lungs they have respiratory holes on the limbs, so the bigger the bug the more oxygen it needs but the holes cant change sizes or the limbs would be weak. Other animals likely got bigger because of the atmospheric conditions, and competition. First, in response to the flora increasing in size, the herbivores would adapt to be larger in size to avoid competition with other herbivores to eat vegetation close to the ground. Then the carnivore would follow suit to be able to prey on the larger herbivores. This was true before and after the Jurassic.

  • ConstanzaCastro
    4/15/2015 - 09:26 p.m.

    Prehistoric animals were big because the conditions of their environment were suitable for their feeding and life styles could adapt and survive, but something had to be changed so that they had extinguished.

  • kealyr-Goo
    5/20/2015 - 11:32 a.m.

    the competition tend to encourage the evolution of bigger animals. The text state that, "a lot of them were and I'm talking 90 ton, 130-foot dinos, 50-foot giant sharks and ground sloths that could go shoulder to shoulder with today's elephants." The text also states that, "Whatever the reason behind their ginormousness is, it made these animals more vulnerable and being super-sized often meant they were slower to adapt to changing conditions, so in the end, most of these behemoths went extinct."

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