Science Magazine announced its top pick for "breakthrough of the year" this week — and it's a great choice! CRISPR, the gene-editing technique, definitely dominated the news in 2015. For the uninitiated, scientists use CRISPR to target and alter DNA segments with a high level of accuracy. It’s very cool — and very controversial. So this year, the biggest science story was accompanied by an intense debate over the ethics of a method that could, hypothetically, be used to permanently alter the human gene pool.

But, as this Science Magazine video suggests, CRISPR had some pretty stiff competition this year. In fact, CRISPR lost to Pluto in the magazine's "People's Choice" poll. So here are a few of Science Magazine's biggest stories of the year, as The Verge covered them:

Yeast can now make opiates

In August, scientists made a surprising announcement: a strain of yeast had been engineered in a lab and was now able to transform sugar into a pain-killing drug — called hydrocodone — for the first time. In addition, a second strain could produce thebaine, an opiate precursor that pharmaceutical companies use to make oxycodone. The finding was touted as a potential avenue for making new pain-relieving drugs. But others suggested that the technique might one day be used to "home-brew" heroin.

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New species of ancient human discovered

(Lee Roger Berger / wikimedia commons)

In September, scientists announced the discovery of 15 partial skeletons belonging to what they think was a previously unknown species of ancient human. The bones were collected from Rising Star Cave in South Africa and the species was dubbed Homo naledi. The bones of H. naledi display a mixture of primitive and modern traits, with a small skull that's about the size of a gorilla's, and humanlike extremities.

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A surprising number of psychology studies can’t be reproduced

In August, a very large group of researchers published a study in which they tried to recreate 100 psychology studies that had recently been published in major psychology journals. They found that only 39 of those studies' results could be replicated. The scientists suggested two possible explanations for finding: it could mean that the studies were wrong, or it could mean the difficulty of designing a reproducible study got in the way.

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Ebola vaccine is 100 percent effective in Guinea trial

In July, the World Health Organization proclaimed that a vaccine was "highly effective" against Ebola. Early results from a clinical trial in Guinea demonstrated that the vaccine protected 100 percent of the people who received it. Margaret Chan, director-general of the World Health Organization, said in a press conference at the time that the drug could turn out to be a "game changer."

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Pluto Flyby

On July 14th, NASA’s New Horizons spacecraft zipped past the dwarf planet Pluto — an event that secured its place in history as first man-made object to reach the space rock. Thanks to this mission, scientists learned that Pluto is larger than we thought, that is had a number of icy mountains on its surface, and that it's very colorful. More recently, researchers suggested that it might even be home to an icy volcano.

Pluto storystream

CRISPR

(Caroline Davis2010 / Flickr)

In April, scientists in China revealed what had long been a rumor: they had used CRISPR to edit the genetic code in human embryos — non-viable human embryos, to be precise. The work was an attempt to remove a gene responsible for a potentially fatal blood disorder. The experiment didn't work all that well — only a small number of embryos were successfully edited — but the attempt was enough to convince the public of the technique's importance. It also prompted a debate over the ethics of human gene editing. Earlier this month, an international panel of experts concluded that scientists shouldn't use CRISPR to modify human embryos that might result in a person.