For a stretch of time that had widely been thought of as an evolutionary non-event, it was always going to be a tough ask to compete with the relative glamour of what came next — the Cambrian period, lauded for its "explosion of life" which took to the land and sea.
Long considered so uneventful in observable developments in life's journey, the span of time dating between 1.8 billion to 800 million years ago was coined the Boring Billion, a term attributed to English palaeontologist Martin Brasier.
Other names for the period include the Dullest Time on Earth and Earth's Middle Ages.
Not according to University of Tasmania Centre for Ore Deposits and Earth Sciences (CODES) PhD student Indrani Mukherjee, who reckons she and her UTAS colleagues can prove it was anything but dull in evolutionary terms.
Rather, it was the birthplace of the first complex cell in evolution at a time of nutrient crisis, new research by Ms Mukherjee has found.
"It's called boring because biological evolution was delayed, but if you actually look into palaeontology papers on evolutionary biology from that time you will find so many examples where you can see evolution was not delayed at all," she said.
"I would say that the Boring Billion in Earth's history has always been known to represent a period of stasis, but our research suggests otherwise."
During this time, there was very little oxygen in the atmosphere and oceans to support life, with only bacteria able to survive.
Scientists looking for signs of evolution in geological samples from this period would only find "non-fluctuating, stable trends", Ms Mukherjee said.
"Macro fossils were not available to us until 540 million years ago, so that's why they felt there might have been a hiatus in evolution."
Unconvinced, Ms Mukherjee set out to "find out why it's boring", all the while aware her research "might say the same", she said.
But she had the advantage of "a very unconventional, novel" method of what she described as the "very, very sensitive" technique of laser-ablation inductively-coupled-plasma mass-spectrometry (LA-ICP-MS).
"My supervisor had this brilliant idea of looking at [the mineral] pyrite, rather than the whole rock. That is the first difference in the conventional and the unconventional method," she explained.
"The other is that we've got the instrument to look closely and get good results."
Ms Mukherjee's method used the technique to measure trace elements absorbed from seawater into the mineral pyrite found in certain rocks, called black shales.
"Importantly, we have been able to prove that trace elements (TE) in pyrite gives you an idea of TE availability in past oceans to primitive organisms."
She said the findings suggested organisms thriving during that time required only minuscule amounts of oxygen — and low concentrations of it did not hinder life.
In fact, it is argued, its scarcity caused stress, leading to the need for organisms to merge, triggering the evolution of complex, multi-celled life.
But having the data is one thing. Understanding its significance is another.
"We've got one of the best labs in the world currently," Ms Mukherjee said. "We are able to process that raw data into something that's meaningful. Not everyone can do that.
"We've got our own inhouse software, and we've got a fantastic laser lab that helps us with all these data reduction processes to actually get something out of the raw data that you've just analysed."
She said the UTAS team was able to show was that the "flat trend" of evolutionary development was "long and high".
"There were fluctuating nutrient element conditions, rather than just this flat trend that other people had identified, possibly due to low sensitivity of their technique."
Less Cambrian, more Proterozoic
Ms Mukherjee said the Boring Billion was, contrary to its reputation, the fertile ground for the Cambrian period of 543 to 490 million years ago that produced most of the major animal groups known today.
In fact, evolutionary biologists and others enamoured with the Cambrian period might do well to turn their attention to the underserved Proterozoic eon, Ms Mukherjee said.
"There's always been a lot of focus on macro evolution and the Cambrian explosion," she said.
"Yet evolution really starts with the transformation of simple cells into complex ones, and it is in the Boring Billion that scientists have previously found the first fossilised evidence of a complex cell.
The UTAS research, The Boring Billion: A Slingshot To Complex Life On Earth, has been published online.
