Mollusk | Chapter 2 | Origins

Life on earth is an ancient dance 3.8 billion years in the making.

Survival of the fittest does not always mean survival of the strongest, or the biggest. When times change, it often means death for all but the luckiest, the strangest. Mollusks are strange. So are monkeys. We’ve been through a lot together.

Let’s build a scene:

440 million years ago, an era of rain and sparkling seas.

A jawless, armored fish, our ancestor cowers in the shallow sands. Humanity is just a twinkle in its eye as it hides from the passing shadow of the ruling mollusk: the giant predatory nautiloid Cameroceras.

As long as a shipping container, Cameroceras sucks great jets of water into the chambered cone of its eighteen-foot long shell. It is hunting us.

Beneath the giant, our ancestor wiggles through beds of coral teeming with mollusks. The sea floor bustles with snails. Bivalves open hinged shells to feed on the algae rich waters. Nautiloids ride the water columns.

The world above the waters is all but empty of life, covered in sweeping storms. Vast supercontinents drift across the oceans. Spores and cells are just beginning to gather on their barren shores.

Then it begins. The sea levels drop. An ice age opens. The planet’s first mass extinction wipes out 85 percent of life on earth.

But the jawless fish survives. And so does the nautilus.

How do we, the children of fish, know all this?

The mollusks left us clues.

In 1909, a mile above the modern sea level in the Canadian Rockies, a paleontologist named Charles Doolittle Walcott and his family discovered one of the richest historical archives on the planet: 65,000 fossils pressed onto the rocky pages of the Burgess Shale. From terrifying armored beasts to animals that look like tiny dancers, many of the fossils they found belong to mollusks.

Doolittle Walcott and family in the Burgess Shale, 1915

Doolittle Walcott and family in the Burgess Shale, 1915

This discovery provided the first evidence of the Cambrian Explosion 550 million years ago, when life underwater began to transform from simple single celled mush into complex animals like the giant Cameroceras.

Millions of years can pass where nothing appears in the fossil record, but when we do manage to find fossils, the stories they tell are invaluable. By examining the fossils we learn about our own past, and our possible futures. We see the mountains rise up from the sea. We realize that, unlike us, nautiluses have barely changed in shape down through the ages.

Once upon a time, the nautiluses preyed on our cowering jawless ancestors, forcing us to evolve. Today, we are driving them to the edge of extinction. In the Philippines, populations of the famous chambered nautilus have declined by 80 percent since 1980, hunted for their shells.

From apex predator to mantle-piece decoration, history has taken a strange turn for the nautilus.

We’re all waiting to see what the future will hold.

More Origins

The man who wrote the book on natural selection, Charles Darwin, had this to say about our limited fossil record: “Of this [book], only here and there a short chapter has been preserved; and of each page, only here and there a few lines.”
The biggest mass extinction, the Permian-Triassic, occurred 251 million years ago. It wiped out more than 90 percent of species on earth. We think a volcanic explosion released massive amounts of sulphur and carbon dioxide into the atmosphere, blocking out the sun and freezing the planet for thousands of years. When the particles blocking the sun dissipated, greenhouse gases baked the earth.
The dinosaurs evolved after the Permian-Triassic extinction. The mollusk fossils from the Walcotts’ discovery in the Burgess Shale are twice as old as the dinosaurs.
Mollusks continue to help us understand the mysteries of being human. The gene that determines which way snail shells spiral also plays a role in determining which side of the body our hearts sit on.
Once upon a time, the nautiluses preyed on our cowering jawless ancestors, forcing us to evolve.  Lee R. Berger

Once upon a time, the nautiluses preyed on our cowering jawless ancestors, forcing us to evolve. Lee R. Berger