Oldest fossils shed light on life’s beginning

“It’s alive!”: Were Earth’s earliest microbes formed by lightning, or at the bottom of the sea?

Scientists claim to have found the oldest known fossils on Planet Earth. If they are right, the discovery suggests answers to huge questions: How did life begin? and Is it unique?

“This discovery answers the biggest questions mankind has asked itself,” Matthew Dodd told the BBC on Wednesday. “Which are: where do we come from and why we are here?”

Extraordinary claims, you could say, about a bit of old rock from the coast of Canada. Except that it is not any old rock — it is potentially the oldest rock on Earth, at somewhere between 3.77 and 4.28 billion years old. And Dodd is part of a team of scientists who now claim that the rocks also contain the oldest fossils on Earth.

The rocks were discovered above ground. But they once lay at the bottom of an ancient ocean, where they are thought to have been part of hydrothermal vents — fissures at the seams of tectonic plates, which spew out jets of water heated by the planet’s magma.

When studying the rocks, the scientists spotted tiny straw-like shapes, thinner than a strand of hair. They now believe that these are “microfossils”, evidence of ancient microbes which were created by the chaotic chemistry of the ocean floor. If they are right, it would be the oldest known life on Earth.

Many scientists are not yet convinced, calling the findings “dubious” and “speculative”. But others are intrigued. The observations have been “carefully made” and the scientists “may indeed have found something truly remarkable,” said an astrobiologist at NASA.

If they are right, Dodd says the discovery implies that life can appear in extremely hostile conditions — bubbling up amid high temperatures and immense pressures at the bottom of the sea — and therefore may be abundant across the universe. It would also mean that life formed on the planet around 300 million years earlier than scientists previously thought.

What’s more, it contradicts the theory that life first formed in a “primordial soup” of early chemicals on the planet’s surface, which reacted with the primitive atmosphere and was sparked into being by lightning.

How exactly did life on Earth start? And why does it matter?

In the beginning…

There is an element of chance — or perhaps destiny — to the lightning theory, observe some. It requires a delicate balance of chemicals which are then jolted into life to form the amino acids from which early microbes evolved. Earth, in this version of events, is special. What are the chances that such perfect conditions existed at just the right time?

But if life formed due to hydrothermal vents at the bottom of the ocean — geological structures which are thought to have once existed on Mars, and may still exist on Jupiter’s moon Europa — then Earth may not be so special after all. The universe is probably teeming with bacteria. And, says Dodd, we will have a much better idea of where to look for it.

You Decide

  1. Do you think that life on Earth happened by chance? Or is it common across the universe?
  2. Imagine the answer is that life is common. How would this make you feel about Earth’s place in the universe?

Activities

  1. Do you agree with Matthew Dodd’s suggestions for “the biggest questions mankind has asked itself”? Can you think of two more?
  2. Research another theory about how life on Earth began (using the last link under Become An Expert) and create a short presentation explaining it to your class.

Some People Say...

“The origin of life appears at the moment to be almost a miracle.”

Francis Crick, co-discoverer of DNA.

What do you think?

Q & A

Why does it matter how life began billions of years ago?
The answer will not particularly affect your everyday life. But pondering our beginnings has occupied humanity for centuries, and scientists are very slowly piecing together the evidence. Of course, we will never know for certain, because we were not around to see it. But understanding how it may have happened will help us in the search for life elsewhere.
Why are other scientists questioning their findings?
Because the rocks are very, very old, and that means they have been distorted and compressed over time. It is difficult to be certain whether the tiny tubes really are fossils. And as the old scientific mantra goes: “Extraordinary claims require extraordinary evidence.” For some, that does not exist yet in this case.

Word Watch

4.28 billion
Earth itself is thought to be around 4.5 billion years old. If the rocks are as old as 4.28 billion years, it suggests that life developed on Earth extremely quickly.
Hydrothermal vents
These act a bit like chimneys on the ocean floor. When they were discovered in 1977, scientists were amazed to find that they were surrounded by large numbers of previously-unknown organisms. Clearly, they have the conditions to support life.
Microbes
Microorganisms, such as bacteria.
300 million
Until now, scientists thought life existed around 3.4 to 3.5 billion years ago. For context, in the last 300 million (ie, 0.3 billion) years Earth has seen three mass extinctions, including the rise and fall of the dinosaurs.
Primordial soup
The name for the combination of chemicals which led to life’s existence. In 1952, scientists Stanley Miller and Harold Urey recreated these conditions, then simulated lightning with electricity. After a week, the experiment produced 11 of the 20 amino acids now used by life.