Micro-fossils of one billion-year-old seaweed discovered

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Micro-fossil of one BILLION-year-old seaweed discovered in China could be an ancient relative of the earliest land plants and trees to evolve on Earth, study claims

  • One billion-year-old fossil was found in China and is only 2mm long 
  • It is thought it is an ancestor of the earliest land plants and trees that evolved
  • The fossils are believed to be the oldest green seaweeds ever found 

By Joe Pinkstone For Mailonline

Published: | Updated:

One-billion-year-old seaweed fossils discovered in China are thought to be related to an ancestor of Earth’s earliest land plants and trees that lived 450 million years ago.

The 2mm-long specimens are also believed to be the oldest green algae ever discovered.    

The micro-fossil seaweeds, a form of algae known as Proterocladus antiquus, add support to the theory stating terrestrial life evolved from marine lifeforms.   

The micro-fossil seaweeds, a form of algae known as Proterocladus antiquus, are hardly visible to the naked eye, at just 2mm in length

HOW DID LIFE MOVE FROM WATER TO LAND?  

The current hypothesis is that land plants, including trees, grasses and crops, evolved from green seaweeds, which were aquatic plants. 

Through geological time – millions upon millions of years – they moved out of the water.

The slowly became adapted to dry land and prospered in their new environment.  

Small adaptations like improved strength to combat gravity and the ability to convert atmospheric oxygen into food helped the plants survive. 

They eventually mastered the environment and diverged into the stunning diversity of foliage we see today. 

But some scientists think that green plants started in rivers and lakes, and then conquered the ocean and land later. 

The specimens were imprinted in rock taken from an area of dry land near the city of Dalian in the Liaoning Province of northern China, which was underwater millions of years ago.  

Before the discovery, published in the Nature Ecology and Evolution journal, the earliest convincing fossil records of green seaweeds were found in rock dated at about 800 million years old. 

Examples of red seaweed – more primitive than green algae – have been found dating back 1.047 billion years.

Professor Shuhai Xiao of Virginia Tech, said: ‘These new fossils suggest that green seaweeds were important players in the ocean long before their land-plant descendants moved and took control of dry land. 

‘The entire biosphere is largely dependent on plants and algae for food and oxygen, yet land plants did not evolve until about 450 million years ago.’

But according to the scientists, the seaweeds’ multiple branches, upright growth and specialised cells suggest the fossil is a green seaweed that is about one billion years old. 

‘Our study shows that green seaweeds evolved no later than one billion years ago, pushing back the record of green seaweeds by about 200 million years,’ Professor Xiao adds.

One-billion-year-old seaweed fossils discovered in China are believed to be the oldest green algae discovered. (pictured, an artist's impression of what they may have looked like). They are also thought to be the ancestor of the earliest land plants and trees

One-billion-year-old seaweed fossils discovered in China are believed to be the oldest green algae discovered. (pictured, an artist’s impression of what they may have looked like). They are also thought to be the ancestor of the earliest land plants and trees

The specimens were imprinted in rock taken from an area of dry land near the city of Dalian in the Liaoning Province of northern China, which used to be ocean

The specimens were imprinted in rock taken from an area of dry land near the city of Dalian in the Liaoning Province of northern China, which used to be ocean

According to the researchers, who found the fossil using an electron microscope, say the tiny seaweeds once lived in a shallow ocean.

When the primitive plant died, it became entombed beneath a thick pile of sediment, preserving the organic shapes of the seaweeds as fossils. 

Many millions of years later, the sediment was then lifted up out of the ocean and became the dry land where the fossils were retrieved. 

The current hypothesis for how life travelled onto solid land states that land plants like trees, grasses and food crops, evolved directly from green seaweeds – aquatic plants. 

However, not all geobiologists agree on the origins of green plants, with some suggesting they started in rivers and lakes, before conquering the ocean.   

‘These seaweeds display multiple branches, upright growths, and specialised cells known as akinetes that are very common in this type of fossil,’ Professor Xiao says. 

‘Taken together, these features strongly suggest that the fossil is a green seaweed with complex multicellularity that is circa 1 billion years old. 

‘These likely represent the earliest fossil of green seaweeds. In short, our study tells us that the ubiquitous green plants we see today can be traced back to at least one billion years.’ 

HOW DO SCIENTISTS THINK LIFE ON EARTH BEGAN?

Life on Earth may have started thanks to a modified version of modern-day DNA’s sister molecule, scientists believe.

DNA is the backbone of life and almost all of our planet depends on it but, on primordial Earth, a primitive version of its lesser-known sister – RNA – was the focal point for evolution, experts say.

RNA is structurally similar to DNA, except one of the four fundamental pieces, thymine, is substituted for uracil. 

This changes the shape and structure of the molecule and researchers have long believed this chemical was vital to the development of Earth’s first lifeforms. 

An accidental discovery by Harvard academics published in December 2018 found that a slightly different version of RNA may have been the key ingredient allowing life on Earth to blossom.   

Scientists claim that a chemical called inosine may have been present in place of guanine, allowing for life to develop. 

This slight change to the bases, known as a nucleotides, may provide the first known proof of the ‘RNA World Hypothesis’ – a theory which claims RNA was integral to primitive lifeforms – they say.