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Associated Press

Scientists in Australia believe they've solved the mystery of when and how animals first appeared on Earth: it was linked to the rise of algae, preceded by 50 million years of huge glaciers pounding entire mountain ranges into powder.

"These large and nutritious organisms at the base of the food web provided the burst of energy required for the evolution of complex ecosystems, where increasingly large and complex animals, including humans, could thrive on Earth," said the lead researcher, Jochan Brocks.

Why it matters: Understanding the conditions that led to complex life here could help to determine whether and how live evolved elsewhere in the universe.

The back story: Scientists have known for awhile when complex forms of life began to show up on Earth, triggering evolutionary processes that culminated in the broad diversity of life we now see across the planet. It generally happened after a time known as "Snowball Earth" (a period when the planet was frozen beginning about 700 million years ago lasting 50 million years). What they didn't know was what triggered the evolution of complex life.

To answer that, a research team crushed ancient sedimentary rocks from central Australia into powder and then extracted molecules from organisms inside them in order to study them more closely.

What they found: Glaciers may have pounded mountain ranges into dust 650 million years ago, releasing nutrients into the oceans and creating perfect conditions for the rapid spread of algae. The researchers think the world's oceans then transitioned from a place dominated by bacteria to one inhabited by algae that served as food for more complex life. Eventually, some of that complex life slithered and crawled onto dry land. The rest is evolutionary history.

Go deeper

Updated 5 hours ago - World

Mexican President López Obrador tests positive for coronavirus

Mexico's President Andrés Manuel López Obrador during a press conference at National Palace in Mexico City, Mexico, on Wednesday. Photo: Ismael Rosas/Eyepix Group/Barcroft Media via Getty Images

Mexican President Andrés Manuel López Obrador announced Sunday evening that he's tested positive for COVID-19.

Driving the news: López Obrador tweeted that he has mild symptoms and is receiving medical treatment. "As always, I am optimistic," he added. "We will all move forward."

6 hours ago - Politics & Policy

Sarah Huckabee Sanders to run for governor of Arkansas

Sarah Huckabee Sanders at FOX News' studios in New York City in 2019. Photo: Steven Ferdman/Getty Images

Former White House press secretary Sarah Huckabee Sanders will announce Monday that she's running for governor of Arkansas.

The big picture: Sanders was touted as a contender after it was announced she was leaving the Trump administration in June 2019. Then-President Trump tweeted he hoped she would run for governor, adding "she would be fantastic." Sanders is "seen as leader in the polls" in the Republican state, notes the Washington Post's Josh Dawsey, who first reported the news.

Coronavirus has inflamed global inequality

Illustration: Aïda Amer/Axios

History will likely remember the pandemic as the "first time since records began that inequality rose in virtually every country on earth at the same time." That's the verdict from Oxfam's inequality report covering the year 2020 — a terrible year that hit the poorest, hardest across the planet.

Why it matters: The world's poorest were already in a race against time, facing down an existential risk in the form of global climate change. The coronavirus pandemic could set global poverty reduction back as much as a full decade, according to the World Bank.