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 and 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 (1)
  • Eugene0808-YYCA
    9/17/2015 - 01:24 a.m.

    I think this is cool to learn because I am interested in prehistoric animals and the environments that they lived in. They would be huge if they were still alive today. A million years is a lot and to us, it seems like a little. Dinosaurs live for more than 100 million years. Imagine living that long. It would be slow and boring.
    Critical thinking challenge: Why does competition tend to encourage the evolution of bigger animals?
    Answer: Competition tend to encourage the evolution of bigger animals because there might be a limited food supply and you want it all.

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