Scroll down for a quick list of key resources in our Teachers’ Toolkit.
- According to the good folks at MIT, the earliest sea sponges probably predated the Cambrian explosion. What is the Cambrian explosion?
- Did the MIT researchers excavate fossils of ancient sponges? Cue the video to about :44 for some help.
- No. According to the video, “very few fossils exist from before the Cambrian explosion.”
- So, scientists studied “molecular fossils.” What are molecular fossils?
- According to the video, “molecular fossils are trace amounts of molecules that have survived in ancient rock long after the actual animal has decayed.”
- How did MIT researchers use molecular fossils to identify sponges that existed before the Cambrian explosion?
- Scientists analyzed rocks containing 24-IPC, a lipid molecule related to cholesterol. 24-IPC is produced by both sponges and algae today, but research shows that sponges developed the ability to produce 24-IPC long before algae. In fact, they developed the ability about 640 million years ago—the same age as the rocks studied.
- Does the suggestion of sea sponges being the first animals on Earth come as a surprise to scientists?
- No, most biologists thought sponges were one of the likeliest candidates for oldest type of animal on Earth. What comes as a delightful surprise is the apparent date of their appearance, much earlier than the fossil record alone suggests. (Take that, stromatolites.)
The Independent: Sea sponges were the first animals on Earth, scientists discover
Nat Geo: Coral Reef Food Web