Why were prehistoric animals so big? (Thinkstock)
Why were prehistoric animals so big?
Lexile

You asked us, why were prehistoric animals so big?

Though not all ancient critters were huge, a lot of them were. 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. Being super-sized often meant they were slower to adapt to changing conditions. And 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?


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COMMENTS (132)
  • carterr-And
    4/01/2015 - 08:27 a.m.

    That's amazing how big they got, but l think the healthier Earht helped them for like that and that doesn't look good for us. They had a hard time adapting to the new invioronment so the went extinct.

  • ZH2001blue
    4/01/2015 - 08:42 a.m.

    Competition tends to encourage the evolution of bigger because the prey or hunter want to evole in order to become stronger to adapt in their living.

  • D.F2001Rex
    4/01/2015 - 08:44 a.m.

    I think it is super cool that long ago there were huge dinosaurs that weighed tons and tons walked where we are walking now. It would be amazing to see living creatures that big in person.

  • mm2000
    4/01/2015 - 08:47 a.m.

    competition tends to affect the evolution of other animals because god wants animals to be bigger and better then the one that is bigger and better then the last know what I'm saying

  • chrisr-boo
    4/01/2015 - 10:06 a.m.

    During the Paleozoic era, when cockroaches as big as house cats may have been 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.

  • laurenm-boo
    4/01/2015 - 10:06 a.m.

    During the Paleozoic era, when cockroaches as big as house cats may have been 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.

  • nittayah-boo
    4/01/2015 - 10:07 a.m.

    Extra oxygen made animals grow really big, a lot bigger than normal and the theory Cope's rule was the idea that competition tends to encourage the evolution of bigger animals over time.

  • genesisl-boo
    4/01/2015 - 10:12 a.m.

    The reason why competition would encourage the evolution of other animals or creatures is because if there is competition it would force other animals or creatures to adapt so they could survive.

  • genesisl-boo
    4/01/2015 - 10:13 a.m.

    The reason why competition would encourage the evolution of other animals or creatures is because if there is competition it would force other animals or creatures to adapt so they could survive.

  • serenas-boo
    4/01/2015 - 10:19 a.m.

    Competition tends to encourage the evolution of bigger animals because of the oxygen levels were so high they caused the creatures to grow big and tall.

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