Spiked Scorpions and Walking Whales: Modern Animals, Ancient Animals, and Water - Softcover

Claire Eamer is an editor, short-story writer and non-fiction author who has also worked in radio. She is the author of Traitors' Gate and Other Doorways to the Past and Super Crocs & Monster Wings: Modern Animals' Ancient Past. She lives in Whitehorse, Yukon.

Excerpt

It Came from the Sea

WHAT CAME FROM THE SEA? Everything. Everything alive, that is.

Stand on a sandy beach on a hot summer's day and what do you see? Life, everywhere you look.

People build castles in the sand, splash in the waves, and swim in the deeper water. Gulls swoop and scream overhead, shorebirds tiptoe along the water's edge, and insects buzz and flit through the grass above the beach.

It's hard to imagine that the invisible world beneath the water could be more full of life than the beach. But it is. A bucket of water from the top layer of the open ocean can contain as much life, in its way, as the most crowded beach -- whether you measure that life by the number of creatures or by their amazing variety.

Long ago, in fact, life in the sea was the only kind of life on Earth.

And once upon a time, even longer ago, there was no sea on Earth and no life at all.

Nice Weather for Ducks

TODAY, ALMOST THREE-QUARTERS OF EARTH'S SURFACE is covered by ocean. But the water wasn't always there. The oceans were created in the longest rainstorm ever.

When Earth was a newborn planet, more than 4.5 billion years ago, it had no water, no air, no life. It was a spinning ball of glowing, molten rock that boiled and roiled like the inside of a volcano.

A thick layer of water vapor collected around Earth, but the heat pouring off the planet's surface kept it from turning into liquid water. Some of the water vapor was created by chemical reactions within Earth itself. Some may have come from icy comets that collided with Earth.

For half a billion years or more, Earth slowly cooled. The rock on the surface turned solid, and then cracked and buckled and folded as hot rock beneath pushed and stretched it. The water vapor in the atmosphere cooled, too, and did what it does today. It turned into rain.

Rain pelted down onto the cooling rocks year after year after year for thousands or, perhaps, millions of years. Water poured off the mountains and drained through the valleys. Trickles became streams, streams emptied into lakes, and lakes overflowed into great rivers. The water flowed to the lowest parts of Earth, gradually filling them up. By the time the rains slowed, at least three-quarters of the planet was covered with water. The oceans were born.

Life Happens

SOMETIME IN THE NEXT FEW HUNDREDS OF MILLIONS OF YEARS, something strange happened in those oceans. Life appeared.

The earliest fossils of living things date from about 3.5 billion years ago. They're big mounds called stromatolites, made of layers of rocky material alternating with layers of tiny, single-celled life forms called bacteria. Bacteria are so small that 50,000 of them could live in a single drop of water.

Bacteria may have been the largest living things on Earth for quite a long time, but they didn't leave much of a fossil record unless they massed together in a big mound. At some point, larger, single-celled organisms developed and evolved into creatures made up of many cells. But even after the creatures got bigger and more complex, they were still small and soft-bodied. So when they died, they were eaten by other creatures or they simply disintegrated.

When the main fossil record finally picked up again, though, it got really interesting.

Aliens in the Rocks

ABOUT 585 MILLION YEARS AGO, the oceans were home to bizarre life forms that left fossil imprints in rocks as far apart as the dry hills of inland Australia and a layered sea cliff in southern Newfoundland on Canada's east coast.

The life forms that made those imprints look like nothing on Earth today. Or maybe looks are deceiving. It's hard for scientists to tell exactly what a living creature looked like and how it lived when all they have is the faint tracing of a long-vanished body that was flattened beneath millions of years of rock layers.

These fossils all appear to come from soft-bodied life forms with no sign of shells or hard body coverings. Some are shaped like spindles on a spinning wheel, some like feathers, some like disks, and some like plants. One of the larger fossils looks like a long, thin Christmas tree.

Whatever these organisms were, they belong to the past. After them came what is sometimes called the Cambrian explosion -- a sudden burst of life that began in the oceans about 540 million years ago.

And that is where our story begins.

World of Water

SOME OF THE ANIMAL FAMILIES in this book live in water their whole lives, just as their ancestors did. In fact, for some of them, life is much the same as it was hundreds of millions of years ago. Others have been transformed by time and changes on Earth.

Some are land creatures whose ancestors were water dwellers. Some are even water dwellers whose ancestors once lived on land.

Some live between the worlds of land and water. Is the platypus a land creature or a water creature? Or maybe for the platypus, it doesn't matter.

Ducks and geese have gone a step further. They've found a way to live at the place where land, water, and air meet. So what ties them to their ancient Australian relative, nicknamed the Demon Duck of Doom, a giant, flightless bird that lived a very different life?

The thing that ties together all of these animals is their link with water. And that's a link we all share. To find out how, read on!