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. Thats when cockroaches were as big as house cats. They may have benefited from the extra oxygen in the atmosphere.

Another theory is Cope's Rule. That's 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?


Assigned 92 times


COMMENTS (35)
  • John0724-YYCA
    4/02/2015 - 04:55 p.m.

    I never knew that the animals that were in the past were very big like the cockroaches were big as house cats which is very insane to hear because then it would have been a major problem for me because I have this really strong grudge on cockroaches because they are nasty. Also does shark though are very big like the sharks are way bigger then the sharks these days.

  • KeaganB-1
    4/02/2015 - 09:44 p.m.

    Prehistoric animals were very big. There were 90 ton 130 foot dinosaur and 50 foot giant shark. These animals being so big could've been because of the different environment than today. There could've been more oxygen in the air or another theory is copes rule which is the idea that competition tends to incurred the evolution of bigger animals like cockroaches that were the size of house cats. There were even sloth that were the size of elephants. I thought this article was very interesting and I hope that they discover more about ancient animals.

    • ajo-Mag
      4/06/2015 - 11:17 a.m.

      I agree with you.I don't think that there were bugs as big as house cats.I do believe that there were really big dinosaurs because there environment must be different than all of the air.They must had more air than us.I thought that this was very interesting to me but it was also weird but everyone has there thoughts mine are different than others.

  • Declanc-Cla
    4/08/2015 - 04:53 p.m.

    why are dinosaurs so big just think of a cockroach as big as your cat roaming your house

  • obeida-Nim
    4/09/2015 - 03:19 p.m.

    because we can squch people
    and this is a good story

  • santij-Nim
    4/09/2015 - 03:20 p.m.

    Compaction is for animals so they can eat the smaller animals for food like t rex that dinosor is big and mean so he eats the other dinosor

  • lamplj-Nim
    4/09/2015 - 03:20 p.m.

    If i saw a cat sized cock roach i would kill it and run away to my mom and my dad.

  • tayloh-Nim
    4/09/2015 - 03:23 p.m.

    If i saw a cat sized cockroach,i would run home and scream.

  • aaronm-Nim
    4/09/2015 - 03:23 p.m.

    wow that was weird If I saw I a cockroach I will run bcause its weird

  • prairiej-Nim
    4/09/2015 - 03:23 p.m.

    If I saw cat sized cockroach I would run as fast as I could.

Take the Quiz Leave a comment
ADVERTISEMENT