18 August, 2017
Scientists have learned how the first animals on Earth. An Australian National University research team has now published research about the start of complex life on Earth.
Lead researcher and associate professor Jochen Brock said, "We crushed these rocks to powder and extracted molecules of ancient organisms from them".
The Sturtian glaciation - the longest in Earth's history, lasting about 60 million years between 717 million and and 660 millions years ago - is named after geological evidence unearthed from Sturt River Gorge in South Australia.
Those nutrients, along with the period of global cooling that followed, provided ideal conditions for the algae to thrive, Brocks explained in a statement. It is because of the formation of these algae that the food pyramid at the base began to develop rapidly and the higher the pyramid rose, the more complex the nutrients and the organisms became, which eventually led to the arrival of humans on the planet.
Algae first emerged somewhere between 1 and 2 billion years ago, when a large cell known as a eukaryote swallowed a tiny photosynthetic critter called a cyanobacteria and put it to work.
In the research, scientists looked at ancient sedimentary rocks from central Australia associated with the period just after the melting of Snowball Earth. The rebound after the Snowball Earth seems like the kick in the hide that life needed.
Dr Brocks said the extremely high levels of nutrients in the ocean, and cooling of global temperatures to more hospitable levels, created the flawless conditions for the rapid spread of algae. But Brocks wanted to know when algae became abundant, to pinpoint the moment when there were enough of these organisms floating around that they could start to fuel other creatures.
Until the present, why and when animals first showed up on Earth has been a subject of debate.
Dr Amber Jarrett, also of the ANU, said: "In these rocks we discovered striking signals of molecular fossils".
These complex animals at the base of food web helped in the evolution of ecosystems and beginning of complex life on Earth. One group argues that there are internal and non-environmental factors in the evolution of animals, while another believes that something got in the way for animals to evolve more quickly. This would have then created the flawless conditions for the large-scale spreading of algae.
But how? As Brocks puzzled over the problem, he read a paper in the journal Nature linking the snowball periods to a dramatic increase in the global availability of the nutrient phosphate.
Of course, this is quasi-speculating - it's still the best explanation we have for why life took so long to make the big step from tiresome unicellular organisms to a more complex and diverse biosphere which would ultimately lead to humanity's evolution.
