It has long been known that ancient Vikings buried dead slaves with their masters, but new isotopic research of ancient skeletal remains is providing at least one researcher with more evidence of how these people lived their lives - more notably what their diets were like.

Elise Naumann, a PhD candidate in archeology at the University of Oslo in Norway, has made several remarkable discoveries using the skeletons that were exhumed at Flakstad in Lofoten. Her research is based on a total of ten individuals, of which at least three were found in double and triple graves and were headless. Her findings are published in the January 2014 issue of the Journal of Archaeological Science.

The isotope analyses, combined with analyses of ancient DNA, gave suggestive evidence that the headless skeletons were slaves who were decapitated before being buried with their masters.

This discovery says a lot about the great differences between people in the society of the time. "Life was undoubtedly difficult and brutal for the majority of people. Only a very few were privileged," wrote Mari Kildahl, a journalist with the University of Oslo.

Naumann noted, however, that there is nothing new about the fact that slaves during the Viking era were buried with their masters, often bound hand and foot and beheaded before burial.

What is new, Naumann explains, is how the analytical methods used and their results have offered fresh insights into the society and people of the past. The isotopic analyses have given researchers new information about the diet and health of these people who lived more a thousand years ago. Analyses of the ancient DNA also yield knowledge about genealogy and genetics.

Researchers have read strands of ancient DNA teased from the thigh bone of an early human that died 400,000 years ago in what is now northern Spain.

The genetic material was pieced together from a clutch of cells found in bone fragments - the oldest human remains ever to yield their genetic code.

The work deepens understanding of the genetics of human evolution by some 200,000 years, raising hopes that researchers can build a clearer picture of the earliest branches of the human family tree by studying the genetic make-up of fossilised remains dug up elsewhere.

"This is proof of principle that it can be done," said Matthias Meyer at the Max Planck Institute for Evolutionary Anthropology in Leipzig. "We are now very eager to explore other sites of a similar age."

The thigh bone was among the remains of at least 28 early human ancestors found at the bottom of a vertical shaft in a cave complex in the Atapuerca mountains in northern Spain. The Sima de los Huesos, or "pit of bones", lies 30m underground and half a kilometre from the cave system's nearest current entrance.

The oldest stone-tipped projectile weapons date to 280,000 years, study says.

The oldest known stone-tipped projectiles have been discovered in Ethiopia. The javelins are roughly 280,000 years old and predate the earliest known fossils of our species, Homo sapiens, by about 80,000 years.

These javelins are some 200,000 years older than previous examples of similar weapons, suggesting that modern humans and their extinct relatives had the know-how to create these sorts of complex thrown projectiles much earlier than often thought.

Scientists investigated stone tools unearthed at the Gademotta Formation on the flanks of an ancient, large collapsed volcanic crater in central Ethiopia's Rift Valley.

"Today, the area represents a ridge overlooking one of the four lakes in the vicinity, Lake Ziway," said researcher Yonatan Sahle, an archaeologist at the University of California, Berkeley.

During much of the Middle Pleistocene, about 125,000 to 780,000 years ago, "the area was overlooking an even bigger paleolake - a megalake composed of today's four separate lakes." Antelope and hippo remains have been recovered from the grassy, forested site.

The oldest artifacts at the site are roughly 279,000 years old. In comparison, the earliest known fossils of Homo sapiens, previously discovered at sites elsewhere in Ethiopia, are about 200,000 years old.

Pointed artifacts with damage suggesting they were used in spears are common at the site. The researchers focused on 141 such obsidian artifacts.

Archaeologists have found some of the most curious canine burials ever unearthed in Egypt - two well preserved dogs buried in pots some 3,000 years ago.

Nicknamed Houdini and Chewie, the dog pots were discovered at Shunet ez Zebib, a large mud-brick structure located at Abydos - one of Egypt's oldest standing royal monuments. The site was built around 2750 B.C and was dedicated to Khasekhemwy, a second dynasty king.

It is also known for the the thousands of ibis burials in jars that had been recovered in the dunes nearby, and for the interments of other animals, mostly raptors and canines.

"The site provided a very secure structure, with conveniently soft, sandy fill that was easy for quick burials within a sacred space," Salima Ikram, professor of Egyptology at The American University in Cairo, wrote in a recently published Festschrift in honor of Dieter Kessler, a renowned scholar in the field of animal cults and Egyptian religion.

The oldest known human DNA found yet reveals human evolution was even more confusing than thought, researchers say.

The DNA, which dates back some 400,000 years, may belong to an unknown human ancestor, say scientists. These new findings could shed light on a mysterious extinct branch of humanity known as Denisovans, who were close relatives of Neanderthals, scientists added.

Although modern humans are the only surviving human lineage, others once strode the Earth. These included Neanderthals, the closest extinct relatives of modern humans, and the relatively newfound Denisovans, who are thought to have lived in a vast expanse from Siberia to Southeast Asia.

Research shows that the Denisovans shared a common origin with Neanderthals but were genetically distinct, with both apparently descending from a common ancestral group that had diverged earlier from the forerunners of modern humans.

Genetic analysis suggests the ancestors of modern humans interbred with both these extinct lineages. Neanderthal DNA makes up 1 to 4 percent of modern Eurasian genomes, and Denisovan DNA makes up 4 to 6 percent of modern New Guinean and Bougainville Islander genomes in the Melanesian islands.

The world's oldest communal toilet is littered with thousands of ancient droppings, each a window millions of years into the past.

Sometimes packed as tightly as 94 fossils per square meter, the feces belong to the Dinodontosaurus, an herbivore that weighed several hundred pounds and reached about 8 feet long.

"There is no doubt who the culprit was," Lucas Fiorelli, of Crilar-Conicet, who discovered the dung heaps, told the BBC. "Only one species could produce such big lumps - and we found their bones littered everywhere at the site."

The fossils, called coprolites, were uncovered in Argentina and date back to the Triassic period, making the site 220 million years older than the previously oldest known common latrine. They vary from dark brown-violet to whitish grey. Some are "sausage-like with segmented surfaces" while others are smooth, and oval-shaped, according to the study published in the journal Scientific Reports.

Regardless of the size, shape or color, however, each carries a story inside.

"When cracked open they reveal fragments of extinct plants, fungi, and gut parasites," said Martin Hechenleitner, a study co-author. "Each poo is a snapshot of an ancient ecosystem -- the vegetation and the food chain."

Deep under the streets and buildings of Rome is a maze of tunnels and quarries that dates back to the very beginning of this ancient city. Now, geologists are venturing beneath Rome to map these underground passageways, hoping to prevent modern structures from crumbling into the voids below.

In 2011, there were 44 incidents of streets or portions of structures collapsing into the quarries, a number that rose to 77 in 2012 and 83 to date in 2013. To predict and prevent such collapses, George Mason University geoscientists Giuseppina Kysar Mattietti and scientists from the Center for Speleoarchaeological Research (Sotterranei di Roma) are mapping high-risk areas of the quarry system.

The mapping is important, Kysar Mattietti told LiveScience, because through the years, Roman citizens have taken the patching of the quarry systems into their own hands. [Photos: The Secret Passageways of Hadrian's Villa]

"The most common way is to take some big plastic bags and fill them with cement and stick them in the holes," she said.

• Rocks make metallic and wooden sounds, in many different notes

• Monoliths were moved by Stone Age man from Wales to Stonehenge

• Researchers believe their musical make-up could be why they were moved

Stonehenge may have been built by Stone Age man as a prehistoric centre for rock music, a new study has claimed.

According to experts from London's Royal College of Art, some of the stones sound like bells, drums, and gongs when they are 'played' - or hit with hammers.

Archaeologists, who have pondered why stone age man transported Bluestones 200 miles from Mynydd Y Preseli in Pembrokshire, South West Wales to Stonehenge, believe this discovery could hold the key.

The 'sonic rocks' could have been specifically picked because of their 'acoustic energy' which means they can make a variety of noises ranging from metallic to wooden sounding, in a number of notes.

Research published today in the Journal of Time & Mind reveals the surprising new role for the Preseli Bluestones which make up the famous monument, and which were sourced from the Pembrokeshire landscape on and around the Carn Menyn ridge, on Mynydd Preseli, South-West Wales.

Archaeologists in Northwest China's Shaanxi Province said they had excavated over 80 skulls in the ruins of the largest neolithic Chinese city ever discovered.

The skulls were found in groups and their limb bones could not be retrieved elsewhere at the Shimao Ruins in Shenmu County, Yulin City, said Sun Zhouyong, deputy head of the Shaanxi Provincial Institute of Archaeology, on Sunday.

Two groups of skulls were firstly found in two pits, with 24 of the grisly finds in each, in front of the east gate of the city ruin while others were later uncovered along the eastern city wall, Sun said.

For decades, experts puzzled over hundreds of ancient dead bodies found at a remote lake. Were they victims of disease? Mass suicide? War? The answer is weirder than you think.

For one month a year, the icy waters of Roopkund Lake melt enough to reveal scattered skeletal remains of 200 humans who perished in the region 1,200 years ago. Because of the harsh conditions of the remote lake, nestled 15,750 feet in the Himalayan mountains of India bordering Nepal and only accessible via a five-day ascending trek, scientists estimate there could still be 400 undiscovered bodies.

This grisly find was first uncovered by a British forest ranger in 1942, and immediately inspired legends to explain the identities of the mysterious group of dead trekkers. It was first posited that they were Japanese soldiers who had died while crossing the area during World War II. But that was soon debunked by the age of the bones. Others believed them to be the remains of the Kashmir warrior Zogawar Singh and his army, who were lost returning from Tibet. And still others theorized the bodies were a result of a battle, epidemic, landslide, or a ritual suicide.