Oct 16, 2026 · 32 min · 16 segments
Some animals lay eggs, and their young hatch out of them. Other animals give birth to live young. But which strategy is best? That’s the question that’s been bothering CrowdScience listener Sameer in…
So why do some animals, like chickens, lay eggs, while other animals, like us, give birth to live young? How did these different strategies evolve, and which came first? Before we get cracking with all of that, let's get back to Stu and his chicks, which are so fresh that they've still got bits of shell on.
At the moment, there are eight chicks in there, and we have another eight eggs.
Hopefully will, will hatch soon.
Could you describe what the hatching process actually looks like from start to finish?
Yeah, so what happens is, um, you start to hear the chirping from inside, which is, is really exciting, and then, um, generally, we call it the pip, and there's like a, a little tiny, tiny little hole, y- you know, beak-shaped hole appears, and then it, it just starts to grow, and, and they, they sort of eat around the membrane and, and the shell and, and break out.
It's really noisy in there for them.
They just start to play, and it's almost as if they kick the other eggs around to sort of, um-
... go, "Come on.
Wake up.
Come out."
"It's, it's great out here."
Yeah, what time do you call this?" [laughs] And what do they look like when they first...
Yeah, some of them really struggle to get out, and you, you, you kind of want to get in there and help them, but you don't.
You know, it's 'cause, um, the, it, it, it, it's down to them to do it, and, um, they just, they, they're all squashed and t- you know, really small, and it, it just looks like a little, really like a furball.
And then they just sort of open out, and then they, they kick out, and then they sort of get up, and they fall down, and get up, and then they, they dry, and
andIt's, yeah, it's, it's impr- it's brilliant.
It's pretty amazing to think that these cheeping furballs that are now running around and causing mayhem were tightly packed up inside an egg just hours ago.
Now, at this point, we should say, to answer Samir's question about eggs versus live birth, we're going to focus on vertebrates, animals with a backbone, like mammals, reptiles, and birds.
So why do some animals, like chickens, lay eggs, while other animals, like us, give birth to live young? How did these different strategies evolve, and which came first? Before we get cracking with all of that, let's get back to Stu and his chicks, which are so fresh that they've still got bits of shell on.
At the moment, there are eight chicks in there, and we have another eight eggs.
Hopefully will, will hatch soon.
Could you describe what the hatching process actually looks like from start to finish?
Yeah, so what happens is, um, you start to hear the chirping from inside, which is, is really exciting, and then, um, generally, we call it the pip, and there's like a, a little tiny, tiny little hole, y- you know, beak-shaped hole appears, and then it, it just starts to grow, and, and they, they sort of eat around the membrane and, and the shell and, and break out.
It's really noisy in there for them.
They just start to play, and it's almost as if they kick the other eggs around to sort of, um-
... go, "Come on.
Wake up.
Come out."
"It's, it's great out here."
Yeah, what time do you call this?" [laughs] And what do they look like when they first...
Yeah, some of them really struggle to get out, and you, you, you kind of want to get in there and help them, but you don't.
You know, it's 'cause, um, the, it, it, it, it's down to them to do it, and, um, they just, they, they're all squashed and t- you know, really small, and it, it just looks like a little, really like a furball.
And then they just sort of open out, and then they, they kick out, and then they sort of get up, and they fall down, and get up, and then they, they dry, and
andIt's, yeah, it's, it's impr- it's brilliant.
It's pretty amazing to think that these cheeping furballs that are now running around and causing mayhem were tightly packed up inside an egg just hours ago.
Now, at this point, we should say, to answer Samir's question about eggs versus live birth, we're going to focus on vertebrates, animals with a backbone, like mammals, reptiles, and birds.
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