This year, humanity landed on its first comet, a child was born to a woman with a transplanted womb, and a fossilized sea shell forced us to reconsider our conceptions of human culture. Those are just a taste of the 20 achievements, innovations, and advances we've selected for our roundup of 2014's biggest scientific breakthroughs.

The Oldest Artwork In The World Predates Modern Humans

In 2007, archaeologists examining fossilized seashells in a museum collection stumbled upon a detail other scientists had somehow missed: deliberate engravings of abstract patterns. These shells were dated to over 500,000 years ago, and were found amongst other shells that had been carefully crafted into specialized tools, at the same site where the first fossils of Homo erectus, our hominin ancestor, had been discovered, in 1890. Taken together, these discoveries suggest that Homo erectus was far more sophisticated than previously believed and capable of symbolic thought. This year, these scientists published the fruit of seven years of confirmation that these shells indeed represent the earliest examples of art and tools in the world. While scientists disagree somewhat on the original purpose of these artifacts, the discovery "raises the possibility that the development of human cognition — human culture — was a very long process. It was not a sudden development," says Alison Brooks, a paleoanthropologist from George Washington University.

Evidence For The Big Bang Is Refuted By Interstellar dust

In March, Harvard's servers were brought to their knees dealing with the international demand to watch a press conference about ... gravitational waves. It's no surprise; as physicist Marc Kamionkowski reflected, "It's not everyday you wake up and learn something completely new about the early universe." Scientists had finally observed a particular pattern in the cosmic microwave background radiation, known as B-mode gravitational waves, which cosmological theorists had predicted would peak during the first 10-34 seconds of the primordial universe following the Big Bang. Or so they thought.

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Soon after the announcement, evidence came to light that the study's findings were likely an experimental artifact. In the ensuing months, scientists confirmed that interstellar dust was the likely source of the observed B-mode gravitational waves. As with all science, it takes some time for the dust of a big discovery to settle, and in this case, dust was all that was left. Hopefully scientists will soon use their massive Antarctic telescope, BICEP2, to observe real B-mode gravitational waves through dust-less regions of the Earth's surroundings.

The World's First Birth With A Donated Womb

Above: The newborn baby just after birth, via Brännström et al.

In late September, for the first time ever, a woman gave birth to a baby after receiving a womb transplant. The mother and child offer hope to women the world over with missing or non-functional uteruses, who desire to carry their own children to term.

The unidentified 36-year-old woman was born without a womb (a congenital disorder known as Mayer-Rokitansky-Küster-Hauser – or MRKH – syndrome), and is one of nine Swedish women who received a uterine transplant from live donors between 2012 and 2013. Some of those women received wombs from family members (including their own mothers), but this particular uterus was reportedly donated by a 61-year-old "family friend" who had undergone menopause 7-years prior to the 2013 surgery.

Young Blood Rejuvenates Old Brains

A few years ago, scientists from Stanford discovered that it's possible to reverse cognitive decline in old mice by injecting them with the blood of the young. At the time, researcher Saul Villeda wasn't entirely sure how young blood reversed the effects of cognitive decline. This year, several studies helped elucidate the mechanism responsible for this rejuvenation.

The Orion Spacecraft Proves Doubters Wrong

Orion blasting off on top of a Delta IV Heavy rocket at 7:05 am EST, on Friday December 5, 204. Image credit: NASA/Bill Ingalls

When NASA announced plans for sending humans on deep space exploration, their dream was met with a mix of wistfulness and scorn, as few believed it would ever become a reality. As the Orion spacecraft worked its way through design, development, and systems testing, that same disbelief continued to haunt it. Even those hopeful that it would take shape as a vessel to carry humans beyond the Earth-Moon system were convinced it would be the archetype of a government project: over-budget, behind schedule, and ultimately unfulfilling.

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This December, NASA proved the doubters wrong. For the first and only uncrewed test flight, Orion went through its paces absolutely perfectly, blasting out of Florida, soaring through the Van Allen radiation belts, and splashing down into the Pacific Ocean. On one hand, it was just a test flight. On the other, this was real, undeniable progress in moving from a dream to a reality. The next time Orion heads to space it will be with astronauts on board, and the time after that will be to carry humans to an asteroid. NASA is trying to do something outrageously ambitious on a starvation budget and this could all fall apart, but if it keeps working, Orion's test flight was the first real step on an incredible journey.

The Largest Robotic Swarm In History Takes Shape

In August, researcher Mark Rubenstein and his colleagues reported the most impressive demonstration of robotic swarm activity to date: A group of 1,024 low-cost, inch-wide robots called "Kilobots" that can self assemble into a variety of two-dimensional shapes (two-dimensional in the sense that the shapes are never more than one-Kilobot tall). Speedy they're not, but Kilobots can twitch, scuttle, and jostle around one another to achieve complex global behaviors – and they can do it autonomously. Together, they constitute the largest, most technically impressive robotic swarm ever created.

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A 1024-strong horde is still several orders of magnitude shy of the swarms we see in nature (the number of ants in a supercolony, for example, can easily exceed 100-million), but it's a significant step for the field of swarm robotics. As Rubenstein and his colleagues note, their work advances the ambitious goal "of creating artificial swarms with the capabilities of natural ones.

The First Earth-Sized, Habitable Zone Planet

Above: An artist's conception of Kepler-186f Credit: NASA Ames/SETI Institute/JPL-CalTech

In April, scientists announced the discovery of Kepler-186f, a faraway planet that's perhaps the most Earth-like yet discovered. It's the same size as our home world, and at the right distance from its parent star to have liquid water.

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"The ultimate goal of all this searching for exoplanets – the real reason we're doing this – is to answer the question ' are we alone?'" So said Tom Barclay, a research scientist working with NASA's planet-hunting Kepler mission, and co-author of the paper recounting Kepler-186f's discovery.

Barclay says that the answer to that big, ultimate question is almost certainly contained in the answers to a host of smaller ones, starting with: Are there other places out there like Earth? With the discovery of Kepler-186f, Barclay said, it's clearer than ever that "the answer to that question is 'Yes.'"

An Ocean's Worth Of Water Below Earth's Surface?

After a series of experiments, geologists have come to a rather startling conclusion. There may be a ocean-sized amount of water far beneath the Earth, trapped inside the high-pressure mantle zone between our planet's liquid metal core and its outer crust.

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For decades, geologists have speculated about what created Earth's vast oceans of water. One popular theory is that icy comets crashed into the planet, eventually melting into oceans. But another theory, which now seems more plausible, was that Earth was already packed with water when it formed. As the planet coalesced out of dust and rocks, that water became trapped in various rocks below the crust.

Galactic Supercluster Laniakea

Our galactic supercluster is 100 times bigger in volume and mass than previously thought. Using an innovative mapping technique, astronomers have charted an enormous region they're now calling Laniakea. The new study, which better defines the dividing line between superclusters, offers a completely new look at our galaxy's surroundings.

King Richard III's Remains Confirmed To 99.999% Accuracy

The case is officially closed on what's been called the oldest forensic investigation in history. A new genetic analysis is providing incontrovertible evidence that the skeleton found under a parking lot in Leicester belonged to the king, while uncovering new truths about his appearance and lineage.

Enceladus Harbors A Hidden Ocean. Does That Ocean Harbor Life?

In 2005, NASA's Cassini spacecraft beamed back images showing what appeared to be plumes of water vapor spewing from fractures, called "tiger stripes," near the southern pole of Enceladus, an icy moon of Saturn. These images alone could not prove that liquid water existed beneath the moon's surface. But in April, an analysis of gravity measurements taken by Cassini confirmed that a large reservoir of liquid water exists underneath Enceladus's icy exterior. Moreover, they've confirmed that the tiny moon is a differentiated celestial body; it's comprised of two layers — an external icy layer and an internal rocky core made up of silicates. Excitingly, this layer of silicate rock, in conjunction with liquid water, means that Enceladus features a potentially habitable environment — one that could be even more hospitable to life than Europa, a moon of Jupiter.

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Not four months later, the Cassini team presented observations that suggest the moon's geysers may be directly connected to the sea beneath its surface – a monumental discovery. As Carolyn Porco, leader of the Cassini imaging team, put it: "For me, the finding of an easily sampled, habitable environment within Enceladus has been Cassini's most profound discovery. Many of us are now asking whether a second origin of life in our solar system could have occurred on this little moon."

A Skull Discovered In An Underwater Cave Holds Clues To The History Of America's First Settlers

Paleoamericans began exploring the western coasts of the Americas about 15,000 years ago, but never managed to establish the longer-lasting empires (Inca, Maya) that would give rise to Native Americans. Because of the distinct facial features of paleoamericans and Native Americans, scientists thought the two groups had distinct ancestry. However, a skull found underwater off the shore of Mexico proved this year that Native Americans and paleoamericans share common ancestry in the people who lived in Beringia (an enormous stretch of fertile grassland connecting Eurasia and the Americas during the last ice age) and that differences in their facial structure must have come about from differences in lifestyle, not ancestry.

Dreadnoughtus, An "Astoundingly Huge" Supermassive Dinosaur

Dreadnoughtus Schrani – the herbivorous, titanosaurian sauropod described in September by University of Drexel paleontologist Kenneth Lacovara and his team – is estimated to have been 85 feet long. Its tail accounted for roughly 30 of those feet. Its neck, the individual vertebrae of which measure more than three feet across, stretched 37 feet in length. Its scapula, pictured here beside Lacovara's son, stands more than five and a half feet tall – the tallest ever reported for any titanosaur.

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Measurements taken from one of Dreadnoughtus' femurs, which stands over six feet tall, have led Lacovara and his team to estimate that the dinosaur, which lived approximately 77 million years ago, weighed about 65 tons in life, making it far and away the largest land animal for which a body mass can be accurately calculated (the previous record holder, another Patagonian titanosaur named Elaltitan, had a calculable weight of 47 tons.) No two ways about it –Dreadnoughtus was, to quote Lacovara, "astoundingly huge."

Evidence of Active Tectonics on Jupiter's Moon, Europa

Above: A false-color image of Europa's trailing northern hemisphere, where subduction zones are hypothesized to exist. Credit: NASA/JPL/University of Arizona.

A recent geological survey of Europa revealed a massive, 20,000 square-kilometer portion of the moon's surface had gone missing. In September, researchers published evidence that suggests a plate tectonic system may be moving old portions of Europa's surface beneath adjacent plates. If confirmed, the finding would make Europa the only known place in the solar system (apart from Earth) whose surface continues to be shaped by active plate tectonics.

Stem Cells Could Hold A Cure To Type 1 Diabetes

Above: human-stem-cell derived beta cells. (Douglas Melton)

β cells are insulin-producing cells found in the pancreas that help keep blood glucose levels in balance. In patients with type 1 diabetes, β cells are targeted and destroyed by the immune system. A possible cure? Replace the destroyed cells with ones grown in a lab. In October, researchers at Harvard University published a method for converting human embryonic stem cells into β cells at quantities large enough to make cell transplantation feasible (though researchers still need to figure out how to protect synthesized cells from the autoimmune attacks that eliminate the body's natural β cells). The cell-derived β cells are currently undergoing trials in animal models, including non-human primates.

A Living Organism With An Expanded Genetic Alphabet

The genetic codes of all living things consist of the same four building blocks: Adenine, Thymine, Guanine, and Cytosine. These building blocks, abbreviated by the letters A, T, G, and C, respectively can be found in untold combinations. But in May of this year, researchers announced they had engineered, for the first time, live E. coli bacteria that incorporate two entirely new letters into their genetic alphabet. An achievement nearly 15 years in the making, the team's reconstituted version of the bacteria boasts two artificial base blocks of DNA – DNA that can be carried and passed on to future generations.

An Artificial Yeast Chromosome Was Built From Scratch

Twelve years ago, scientists created the first artificial virus. Eight years later, the world was introduced to the first synthetic genome for bacteria. By 2012, scientists had created the first complete computer model of a living organism. In March of this year, an international team of scientists reconstructed a synthetic and fully functional yeast chromosome. A breakthrough seven years in the making, the remarkable advance could eventually lead to custom-built organisms (human organisms included).

Scientists Discover the Gynosome, A New Kind of Sexual Organ

When Brazilian scientist Rodrigo Ferreira sent a few insect specimens to a Swiss entomologist named Charles Lienhard, the latter identified the insects as belonging to an entirely new genus, henceforth known as Neotrogla. Lienhard also noticed that the females had an erectile "penis-like structure," which he called a "gynosome." Among this group of cave-dwelling Brazilian insects, the females use their gynosomes to penetrate the males. It's a first in the animal kingdom, and scientists say that the lives of these insects challenge everything we thought we knew about sexual selection.

At Stonehenge, A Pair of Monumental Discoveries

Though archaeologists have long suspected that the huge neolithic stones of Stonehenge once formed a complete circle, evidence in support of the claim has remained elusive. In September, following a dry summer season, archaeologists were able to observe patches of dry grass that appear to confirm the prehistoric monument's circular configuration.

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Not two weeks later, archaeologists, u sing powerful ground-penetrating radar, announced they had detected a trove of previously unknown burial mounds, chapels, shrines, pits — and most remarkable of all — a massive megalithic monument made up of more than 50 giant stones buried along a 1,082-foot-long c-shaped enclosure. The new findings upend previous conceptions of Stonehenge as a desolate and lonely place.

The Philae Lander Successfully Touches Down On a Comet

Over ten years ago, scientists at the European Space Agency bid adieu to a robot lander named Philae, as it set off on a mission with the Rosetta space probe to collect data about comet 67P/Churyumov-Gerasimenko. This November, after Rosetta achieved orbit around the comet, Philae detached from Rosetta and landed on 67P. After two wild bounces and no harpoon strikes to anchor it, Philae settled in the shadow of a cliff. For the first time in human spacefaring history, a robotic probe had been placed on the surface of a comet – and already its findings are reshaping the way we view the universe.