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NNhering / iStock

Researchers at the University of Bristol have proposed a date for the origins of chloroplasts — the cellular engines that make energy from the sun via photosynthesis — that, if correct, could confirm or disprove several theories about the earliest life on Earth.

Why it matters: Scientists debate the origins of chloroplasts and, relatedly, what gave rise to complex life on Earth. This research validates some controversial ancient fossil finds, and gives us a better idea of where and how life arose — and what to look for in the search for it elsewhere in the universe.

Scientists know that the engines that help plants make energy from the sun via photosynthesis used to be their own organisms, until they were swallowed by another type of bacterium and formed a symbiotic relationship with them. Most agreed that organism was some type of cyanobacteria, but the species and the date remained open questions.

What they found: The researchers found the chloroplast lineage split from the rest of the cyanobacteria 2.1 billion years ago. They evolved on their own for roughly 200 million years before symbiosis occurred. According to their analysis, the chloroplast's closest relatives are Gloeomargarita bacteria.

What was known: The oldest commonly accepted eukaryote fossil is Bangiomorpha, a 1.1 billion year old red algae. But fossils described earlier this year were controversially dated to 1.6 billion years old, and appear to have chloroplasts and characteristics of eukaryotes. Those fossils, if they were interpreted correctly, pushed back the potential origin of eukaryotes by several hundred million years. Debashish Bhattacharya, an evolutionary biologist at Rutgers University who is familiar with both this study and the fossils, tells Axios that this research "essentially confirms" both Bangiomorpha and this years' ancient fossil find.

What they did: The researchers looked at the genomes of 49 different cyanobacteria and 70 eukaryotes (organisms that, like humans, have genes in a self-contained nucleus). They looked at 26 genes shared by both groups, and used a molecular clock, which estimates time based on mutations in genes, to create and date how the species are related and when they diverged.

Go deeper

DOJ: Capitol rioter threatened to "assassinate" Alexandria Ocasio-Cortez

Supporters of former President Trump storm the U.S. Captiol on Jan. 6. Photo: Kent Nishimura / Los Angeles Times via Getty Images

A Texas man who has be charged with storming the U.S. Capitol in the deadly Jan. 6 siege posted death threats against Rep. Alexandria Ocasio-Cortez (D-N.Y.), the Department of Justice said.

The big picture: Garret Miller faces five charges in connection to the riot by supporters of former President Trump, including violent entry and disorderly conduct on Capitol grounds and making threats. According to court documents, Miller posted violent threats online the day of the siege, including tweeting “Assassinate AOC.”

Schumer calls for IG probe into alleged plan by Trump, DOJ lawyer to oust acting AG

Jeffrey Clark speaks next to Deputy US Attorney General Jeffrey Rosen at a news conference in October. Photo: Yuri Gripas/AFP via Getty Images.

Senate Majority Leader Chuck Schumer (D-N.Y.) on Saturday called for the Justice Department inspector general to investigate an alleged plan by former President Trump and a DOJ lawyer to remove the acting attorney general and replace him with someone more willing to investigate unfounded claims of election fraud.

Driving the news: The New York Times first reported Friday that the lawyer, Jeffrey Clark, allegedly devised "ways to cast doubt on the election results and to bolster Mr. Trump’s continuing legal battles and the pressure on Georgia politicians. Because Mr. [Jeffrey] Rosen had refused the president’s entreaties to carry out those plans, Mr. Trump was about to decide whether to fire Mr. Rosen and replace him with Mr. Clark."

4 hours ago - World

Brazil begins distributing AstraZeneca coronavirus vaccine

Containers carrying doses of the Oxford/AstraZeneca vaccine arrive in Brazil. Photo: Maurio Pimentel/AFP via Getty Images

Brazil on Saturday began distributing the 2 million doses of the AstraZeneca coronavirus vaccine that arrived from India Friday, Reuters reports.

Why it matters: Brazil has the third highest COVID-19 case-count in the world, according to Johns Hopkins University data. The 2 million doses "only scratch the surface of the shortfall," Brazilian public health experts told the AP.