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Have you ever wondered how biologists choose what animal to use in their research?

I mean, we can't do a lot of basic research on people, so scientists study animals to

shed light on human health and genetics and how our brains work and whatever the case

may be, and yet just a couple creatures appear over and over again.

And it raises the question, why the mouse?

Why the fruit fly?

The zebrafish.

Well, each of them has a different appeal depending on what you're studying, but there

is one thing all of these so-called model organisms also have in common.

When we try to choose a model organism, fundamentally we're looking for convenience.

This is Cassandra X-Tivoren, evolutionary biologist at Harvard.

For us to work with it in the lab, it can't be very big, so elephants are mostly out.

Ideally, they reproduce quickly, so there are a lot of generations to study.

So also elephants are mostly out.

We'd like it to not be very expensive to maintain, so maybe not very picky about what it eats

or drinks.

And also doesn't need to be raised in super-specific environmental conditions.

And so because of that, a lot of model organisms that are commonly used like mice or fruit flies,

are organisms that are garbage feeding organisms that will live anywhere on anything that are

often considered pests in the natural world.

Cassandra had her lab work with a number of different organisms, but in recent years,

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