Author: David Sims

Archaeologists digging in Mexico City have unearthed the long-fabled Huey Tzompantli — a tower of human skulls thought to measure about 200 feet in diameter.

The tower was described in contemporary accounts of the Spanish conquistadores when they captured the Aztec capital of Tenochtitlan, which later became Mexico City.

The tower is located at the edge of the Templo Mayor, an edifice dedicated to the Aztec god of sun, war, and human sacrifice, according to a report by The Atlantic.

In the account of Andres de Tapia, a Spanish follower of Hernan Cortes during his conquest of Mexico in 1521, the tower was constructed of tens of thousands of skulls “placed on a very large theater made of lime and stone, and on the steps of it were many heads of the dead stuck in the lime with the teeth facing outward.”

What the archaeologists did not expect to find were so many skulls belonging to women and children. Researchers previously believed that young male warriors were mostly chosen as sacrificial victims. As a result, the discovery is raising new questions about the Aztec Empire’s culture of human sacrifice.

“We were expecting just men,” said Rodrigo Bolanos, a biological anthropologist working on the dig, in a report by Reuters, adding, “Something is happening that we have no record of, and this is really new, a first in the Huey Tzompantli.”

So far, researchers have discovered more than 650 skulls that were covered in lime to cement them together. Only a quarter of the excavation is completed.

A large scale study on ancient human DNA provides new information on past migration patterns and population shifts of sub-Saharan Africa, new research published in the journal Cell reports.

The findings could help answer different questions about the ancestry of the region, including how hunter-gatherer lifestyle and population distribution changed before farmers and animal herders swept across the continent some 3,000 years ago.

“The last few thousand years were an incredibly rich and formative period that is key to understanding how populations in Africa got to where they are today,” said study co-author David Reich, a professor of genetics at Harvard Medical School, according to Phys.org. “Ancestry during this time period is such an unexplored landscape that everything we learned was new.”

Ancient DNA is a great paleontological tool because it is one of the only ways researchers can look into past genomic diversity. However, Africa has been hard to study because the warm climate rapidly breaks down genetic tissue. Only recently have new technological advancements made such research possible.

In the new study, an team of international researchers used such technology to take DNA from the remains of 15 sub-Saharan Africans that dated back to between 500 to 8,500 years ago. They then compared the genomes against almost 600 present-day people from 59 African populations and 300 people from 142 non-African groups.

This showed a large population diversity existed between 2,000 or 3,000 years ago. It also revealed that hunter-gatherer populations quickly disappeared when farmers reached Malawi. Not only that, but those hunters also have no ties to the people living in the region today.

That suggests there was a complete population replacement, which has not been found anywhere else on Earth. In addition, the research similarly sheds light on the origins of many unique groups across the continent and could give a true glimpse into the humans that lived there.

Little is known about the people of ancient Africa. The team hopes the new findings will encourage more investigation into the past and help scientists get a better idea of the diverse genetic landscape.

“Africa is now going to be fully included in the ancient genomics revolution,” added Reich, according to The New York Times. “We’re going to be able to do a lot of things in Africa that we’ve been able to do in Europe and elsewhere.”

Octopuses are known for leading mostly solitary lives. So, biologists were surprised to find the second of two sites off the eastern coast of Australia where as many as 15 gloomy octopuses, or Octopus tetricus, have congregated.

The discovery is reported in the journal Marine and Freshwater Behaviour and Physiology.

The first gloomy octopus site was discovered and described in 2009 by co-author Matthew Lawrence, an independent scholar. The settlement, dubbed Octopolis, contained several dens and a human-made flat object about a foot (30 centimeters) long.

The second site, called Octlantis, is located close to the first site and has a total of 13 occupied and 10 unoccupied dens.

Taken together, both sites support the notion that octopuses will form communities if conditions are right. When they do, they become true architects of their environment.

“At both sites there were features that we think may have made the congregation possible — namely several seafloor rock outcroppings dotting an otherwise flat and featureless area,” said co-author Stephanie Chancellor, a Ph.D. student in biological sciences at the University of Illinois in Chicago, in a statement. “In addition to the rock outcroppings, octopuses who had been inhabiting the area had built up piles of shells left over from creatures they ate, most notably clams and scallops. These shell piles, or middens, were further sculpted to create dens, making these octopuses true environmental engineers.”

The researchers recorded 10 continuous hours of GoPro camera footage, which showed the octopuses interacting with one another. The animals were frequently close to each other and were observed mating, being aggressive, and signaling through color changes.

“Some of the octopuses were seen evicting other animals from their dens,” said Chancellor. “There were some apparent threat displays where an animal would stretch itself out lengthwise in an ‘upright’ posture and its mantle would darken. Often another animal observing this behavior would quickly swim away.”

More research is needed to understand the significance of octopus settlements and interactions, says Chancellor, because so little is known about octopus behavior.