Why were prehistoric animals so big?
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.
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Critical thinking challenge: Why does competition tend to encourage the evolution of bigger animals?