Why do dinosaurs have big heads and tiny arms?

kucuva@lemmy.world to No Stupid Questions@lemmy.world – 120 points –

What evolutional benefit is that?

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People think of evolution as it's needed straight A+ to pass, when C is enough.

Also what's the definition of "passing?" The dinos we are talking about are extinct, they didn't "pass" for long. A+ creatures things like alligators, ants, and crabs. On average a given species survives around a million years before going extinct. How long do you have to exist before you're considered a successful species?

T. rex was around for 20 million years or so, I’d say they passed for long enough to be considered successful. Despite the tiny arms.

I think that's been narrowed down to about 2 million years. But that got cut short by a mass extinction event, so it's hard to say how long they would have lasted otherwise.

If you can’t survive a mass extinction are you even really alive?

A question that's going to be surprisingly easy to answer in the near future.

100+ million years qualifies as right in the middle of "for long" in my book. The fact that an asteroid or comet of biblical proportions wiped them out has nothing to do with evolutionary effectiveness. Most of the animals that did survive either A) lived in water or B) lived underground.

I don’t think science really categorizes species based on how successful they were. “Passing” in this sense refers to the individuals in the species who were able to reproduce, not the population as a whole. Most dinosaurs “passed” until ecological conditions killed them off, they didn’t die because they failed to adapt. A lot of the species that survived mass extinction events were just lucky, rather than having some ideal set of characteristics that allowed them to survive.

I agree that most species surviving mass extinction events were just lucky, but I think that also says something special about the ones that survived MULTIPLE events (ants), or those that effectively re evolved into existence after extinction events (crabs)