A Blue View: Colonial Animals

Insects today are among the Earth's smallest creatures, but about 300 million years ago, huge bugs were relatively common. The dragonfly-like Meganeura, for example, had the wingspan of a modern-day hawk.

Published April 05, 2016


In contrast, today's largest insects have average wingspans of less than a foot!

So, why the shrinkage in size? The prehistoric atmosphere contained 50 percent more oxygen than our current environment. This extra O2 gave prehistoric creatures more energy per breath, allowing them to power larger bodies.

According to new research by Matthew Clapham, a paleobiologist at the University of California Santa Cruz, suggests we have the evolution of birds to thank for not being constantly attacked by giant insects when we venture outside. 

During the Jurassic period (even as oxygen levels were rising), insects stopped growing larger as birds started to evolve. Clapham's work suggests that birds reversed the evolutionary favoring of large sizes. Large insects quickly became much less maneuverable, making them easy targets for agile birds. 

Like the insect, evolutionary pressure also led to a decrease in the size of sloths. During the Pleistocene period (roughly 2.6 million years ago to 10,000 years ago), the Megatherium roamed South America. This sloth relative weighed in at a whopping 7 tons and was outfitted with foot-long toenails. 


It's believed that the evolution of a superior predator, in this case early humans, caused the extinction of Megatherium and led other sloth species to decrease dramatically in size, making them faster and more able to hide. Today's sloths weigh approximately 15 pounds, about the equivalent of one of those giant claws!

To learn more about other prehistoric giants (including some that are still roaming the Earth), listen to our latest episode of A Blue View: 

Previous Post

Featured Stories

Jellies in petri dish Welcome to the Jelly Jungle

Deep inside the Institute of Marine and Environmental Technology (IMET) building, the National Aquarium runs a little-known lab. Here we carry out the propagation of jellies, many of which later end up on exhibit in Jellies Invasion. Read on for a peek into the process!

Read the full story

Cold stunned turtle Cold Stunning: Where, How and Why?

Picture this: You’ve just spent a wonderful, late summer week on Cape Cod, swimming in the ocean and enjoying the sunshine with friends and family. As fall sets in, you know it’s time to head home. You get on the highway, but something strange happens … despite driving for hours, you end up back where you started. You feel sluggish, confused and exhausted. If you were a turtle, you just might be cold-stunned.

Read the full story

Related Stories

A Blue View: Shark Navigation is All in the Nose

Published June 28, 2016

A Blue View: Oyster Gardens

Published June 21, 2016