Why the Biggest Egg on Earth Beat Every Dinosaur
The News
Scientists at the American Museum of Natural History and Princeton just cracked a puzzle that's stumped researchers for a long time — the biggest known bird eggs (from the extinct elephant bird of Madagascar) are actually bigger than any dinosaur egg ever found, even though many dinosaurs were far larger than any living bird. Their answer, published this week in Royal Society Open Science: bigger brains push animals to make fewer, bigger babies — and bigger babies need bigger eggs.
Professor Pip pushed open the tall doors of the museum's egg hall and adjusted his slightly crooked spectacles. "Ah! Now this is what I've been waiting to show you."
On a wooden pedestal sat an egg the size of a soccer ball. Beside it, a smaller egg the size of Pip's fist. And in a tiny felt-lined box, an egg no bigger than a jellybean.
"Whoa!" Mia's eyes went round. "That big one is HUGE."
"That," said Pip, patting his bulging green pockets, "is an elephant bird egg. Elephant birds lived in Madagascar until about a thousand years ago. They were nine feet tall and weighed two thousand pounds. And this egg? Seven times bigger than an ostrich egg — the biggest bird egg alive today."
Leo squinted. "But… Professor Pip, dinosaurs were WAY bigger than elephant birds. Some were as long as a school bus!"
"Precisely the puzzle!" Pip's tail swished. "Even the biggest dinosaur eggs are smaller than this elephant bird egg. So — why?"
He pulled a small notebook and a bag of dried beans from his pocket. "Here's a game. Pretend you're a parent animal. You have a fixed amount of energy — this bag of beans. You can spread it thin between many babies…" He poured the beans into ten little piles. "…or you can pile it up into fewer, bigger babies." He swept the piles into just two big mounds.
"So the two-mound babies get more food?" asked Mia.
"Exactly right! And here's what scientists just figured out: animals with bigger brains tend to pick the two-mound plan. A big brain needs a LOT of energy to grow. It can't be rushed. So brainy animals — like birds and mammals — invest heaps of energy into each baby. Bigger baby, bigger egg or bigger newborn."
"Oh!" Leo bounced on his toes. "Like how our teacher spends more time on one big project than a hundred tiny worksheets!"
"Curiouser and curiouser — that's exactly the idea!" Pip clapped his paws. "Most dinosaurs had smaller brains for their body size, so they laid lots of smaller eggs and let their babies fend for themselves. Birds took a different path. As bird brains got bigger over millions of years, so did their babies — and their eggs grew right along with them."
Pip gazed up at the elephant bird egg. "Somewhere on this planet, a thousand years ago, a chick that would have grown taller than a grown-up was curled up inside that shell. All because its brain needed a big, cozy, energy-rich place to start."
He pulled a bean from his pocket and pressed it into Mia's palm. "Now — plant this. Give it plenty of sun. And watch what happens when energy goes into one good thing."
Spark a Conversation
- If you could grow up inside an egg, would you want a big one with lots of food, or a small one so you could hatch faster?
- Why do you think growing a big brain takes so much energy?
- Chickens lay many small eggs; elephants have one huge baby at a time. Which strategy do you think is smarter, and why?