Study Suggests Walking May Be Linked to Treetop Foraging

The ancestors of humans may have begun moving on two legs to forage for food among the treetops in open habitat, researchers have suggested, contradicting the idea that the behaviour arose as an adaptation to spending more time on the ground.

The origins of bipedalism in hominins around 7m years ago has long been thought to be linked to a shift in environment, when dense forests began to give way to more open woodland and grassland habitats.

In such conditions, it has been argued, our ancestors would have spent more time on the ground than in the trees, and been able to move more efficiently on two legs.

But now researchers studying chimpanzees in Tanzania say that trait may have different origins. “I think we have long told this very logical story, that at least our data don’t really support,” said Dr Alex Piel, a biological anthropologist at University College London and a co-author of the research.

Writing in the journal Science Advances, the researchers report how they spent 15 months studying 13 chimpanzees living in Issa Valley in western Tanzania, an environment similar to that experienced by our ancient ancestors.

The results reveal that these chimpanzees spent a greater proportion of their time on the ground, and in movement, when in an open environment of woodland and grasses than in densely forested parts of the same area.

However, even in the open environment, the proportion of time the chimpanzees spent on the ground was similar to that previously recorded for other populations of the apes living in densely forested areas, including Gombe and Mahale.

“Even though we have far fewer trees, [the chimps are] no more terrestrial,” said Piel.

The team then combined the data for the different environments in Issa Valley and analysed how often the chimpanzees either stood or moved on two feet.

The results reveal that while bipedal behaviour accounted for less than 1% of recorded postures, only 14% related to chimpanzees on the ground.

“Most of the time that they are on two legs is in the trees,” said Piel, adding that the behaviour, at least amid the branches, appears to be most commonly linked to foraging for food.

Rhianna Drummond-Clarke, first author of the research from the University of Kent, said that open woodland could favour bipedalism in chimpanzees, and by extension early human ancestors, because such environments have more sparsely distributed trees than dense forests.

“[Bipedalism may help them] safely and effectively navigate the flexible branches and access as many fruits as possible when they find them,” she said.

The team says that while the study cannot prove that our human ancestors showed the same patterns of bipedal behaviour, it calls into question common assumptions of how humans ended up walking on two legs, and suggests that trees continued to play a role in our evolutionary story even as the environment shifted.

“Rather than time on the ground stimulating [bipedalism], it may have catalysed it, but it was already there,” said Piel. “And that fits perfectly with the fossil record because all the all these early hominins have both arboreal and terrestrial adaptations.”

11th-Century Settlement Uncovered in Zanzibar’s Stone Town

A UAE-led heritage project is shedding new light on the origins of Zanzibar’s Stone Town. Archaeologists have discovered evidence of an original settlement at the Unesco World Heritage site in Tanzania that dates back to the 11th century.

It proves the town — previously thought to be an 18th century Omani Arab town — was actually established much earlier by local Swahili people, archaeologists believe. During a major dig this summer, they unearthed traces of homes, cooking pits and significant amounts of pottery from this era.

They were then able to pinpoint the settlement’s transition to stone buildings by the 14th century. These stone houses gave the trading centre on the east African coast its unique appearance and were ultimately how it got its name. Stone Town became the powerful capital of the Omani Arab Empire in the 19th century and many major buildings were constructed at this time.

But the Emirati-funded work has shown how the trading centre developed much earlier than previously thought.

“Our excavations found walls of houses, stone architecture and established it was urbanised in a much earlier period than historically thought,” said Prof Tim Power of UAE University.

“We can now say that the town was built centuries before the Omanis arrived.”

The project, which started this year, is a collaboration between UAE University, New York University Abu Dhabi, the Royal Agricultural University in the UK and the Department of Antiquities in Zanzibar.

Archaeologists from Abu Dhabi’s Department of Culture and Tourism and students from State University of Zanzibar also volunteered for the project. Stone Town’s Old Fort, built during the Omani era, was the focus of the dig. The fort could be compared with Abu Dhabi’s Qasr Al Hosn, said Prof Power, as it was the nexus of military and political power and also functioned as a customs house.

A test pit dug in the 1980s unearthed pot sherds suggesting this, but Prof Power said this could be described as a sort of background noise. Another dig led by Prof Power in 2017 also yielded promising results.

This year, two trenches made in the fort’s courtyard were dug to a depth of two metres, uncovering rubbish pits, cooking fires, walls, floors, the remains of a Portuguese church, significant amounts of pottery and even evidence of a mosque — structures that show an intensification of human settlement.

The teams were able to date the pieces by comparing the types of pottery unearthed to those found in other excavations.

“We found a lot of imported pottery, especially from China,” said Nour Al Marzooqi, an archaeologist at Abu Dhabi’s Department of Culture and Tourism, who worked at the site over the summer.

“It is similar to what we found in the UAE,” said Ms Al Marzooqi. “But we also found local Swahili pottery such as cookware.”

Archaeologists stumbled upon a carved block from a mosque that once existed at the site but has yet to be found. The project also uncovered one of the walls of a Portuguese church that had been demolished and integrated into the fort. Archaeologists found the wall footings and floor of the church, under which dozens of Christian graves were found dating to the 16th and 17th centuries, when an Augustinian mission stood on the site.

“The excavations go back in time in a focused way,” said Prof Robert Parthesius, who leads NYUAD’s Dhakira Centre for Heritage Studies, the entity funding the project.

“And the ceramics found come from so many different periods. It gives an insight into all those centuries and we now we have come to 11th century.”

Stone Town started as a small fishing village but grew rapidly on the back of trade networks that developed across the Indian Ocean. It came under Portuguese, Omani and European influence but always retained its Swahili identity. It was the capital of the Omani Arab empire in the 19th century and became very wealthy.

“It was like the Venice of East Africa,” said Prof Power. “There was a major trade in ivory, ebony wood and slaves. Omani Arabs also developed clove plantations and it became the leading supplier of cloves in the world.

“This prosperity is reflected in the architecture,” said Prof Power. “There are beautiful merchant houses with carved doors and blocks. They are absolutely gorgeous.”

The project explores the cosmopolitan and multifaceted history of the town and how it plugs into the intricate and vibrant trade networks that existed across the Indian Ocean into the Gulf through the centuries from its foundation.

Gulf to Zanzibar trade

Did Chinese pottery, for example, come direct to Stone Town or through an intermediary?

A lot of trade was conducted on dhows that sailed from the Gulf to Zanzibar and this relationship was important. Stone Town was a market for Arabian goods such as dates and source of labour. Despite the many different ethnicities and differences, a shared culture and way of life also existed.

“This project is bringing to life the Indian Ocean during the Golden Age of Islam,” said Prof Power,” referring to the period between the 8th and 14th centuries, when there was a flourishing of cultural, economic and scientific advancement.

“It was a place where people did amazing things. This diversity and range of characters has been obscured by European colonialism, which split these regions into different territories, and also the post-colonial movement and ethnic nationalism. But there was shared culture across the Indian Ocean at this time.”

Zanzibar’s Minister for Tourism and Heritage Simai Said visited the site of the dig in the summer and said it was an “exciting new discovery” for the archipelago.

“We are happy to host an Emirati-funded archaeology project,” he said. “It will help us in our mission to communicate the island’s rich heritage and culture to tourists and local people alike.”

The work will continue in January when a further expedition is planned. It is also hoped to create a museum at the site to present some of the finds from the excavations to the public.

“This initiative is so important not only for understanding Indian Ocean trade networks but also useful for people living in Stone Town,” said Prof Parthesius, whose work at the centre seeks to forge collaborations with local heritage organisations.

“Our work seeks to bridge the divides. We want to make sure people don’t feel like we have come to teach them. And by working together, more people can be trained in archaeology and we can learn from each other.”

Ancient DNA reveals surprises about how early Africans lived, travelled and interacted

A new analysis of human remains that were buried in African archaeological sites has produced the earliest DNA from the continent, telling a fascinating tale of how early humans lived, travelled and even found their significant others.

An interdisciplinary team of 44 researchers outlined its findings in “Ancient DNA reveals deep population structure in sub-Saharan African foragers.” The paper was published today in Nature and reports findings from ancient DNA from six individuals buried in Malawi, Tanzania and Zambia who lived between 18,000 and 5,000 years ago.

“This more than doubles the antiquity of reported ancient DNA data from sub-Saharan Africa,” said David Reich, a professor at Harvard University and investigator at the Howard Hughes Medical Institute whose lab generated the data in the paper. “The study is particularly exciting as a truly equal collaboration of archaeologists and geneticists.”

The study also reanalyzed published data from 28 individuals buried at sites across the continent, generating new and improved data for 15 of them. The result was an unprecedented dataset of DNA from ancient African foragers — people who hunted, gathered or fished.

Their genetic legacy is difficult to reconstruct from present-day people because of the many population movements and mixtures that have occurred in the last few thousand years.

Thanks to this data, the researchers were able to outline major demographic shifts that took place between about 80,000 and 20,000 years ago. As far back as about 50,000 years ago, people from different regions of the continent moved and settled in other areas and developed alliances and networks over longer distances to trade, share information and even find reproductive partners. This social network helped them survive and thrive, the researchers wrote.

Elizabeth Sawchuk, an author of the study who is a Banting Postdoctoral Fellow at the University of Alberta and a research assistant professor at Stony Brook University, said a dramatic cultural change took place during this timeframe, as beads, pigments and other symbolic art became common across Africa. Researchers long assumed that major changes in the archaeological record about 50,000 years ago reflected a shift in social networks and maybe even changes in population size. However, such hypotheses have remained difficult to test.

“We’ve never been able to directly explore these proposed demographic shifts, until now,” she said. “It has been difficult to reconstruct events in our deeper past using the DNA of people living today, and artefacts like stone tools and beads can’t tell us the whole story. Ancient DNA provides direct insight into the people themselves, which was the missing part of the puzzle.”

Mary Prendergast, an author of the paper and associate professor of anthropology at Rice University, said there are arguments that the development and expansion of long-distance trade networks around this time helped humans weather the last Ice Age.

“Humans began relying on each other in new ways,” she said. “And this creativity and innovation might be what allowed people to thrive.”

The researchers were also able to demonstrate that by about 20,000 years ago, people had stopped moving around so much.

“Maybe it was because by that point, previously established social networks allowed for the flow of information and technologies without people having to move,” Sawchuk said.

Prendergast said the study provides a better understanding of how people moved and mingled in this part of Africa. Previously, the earliest African DNA came from what is now Morocco — but the individuals in this study lived as far from there as Bangladesh is from Norway, she noted.

“Our genetic study confirms an archaeological pattern of more local behaviour in eastern Africa over time,” said Jessica Thompson, an assistant professor of anthropology at Yale University, and author of the study and one of the researchers who uncovered the remains. “At first people found reproductive partners from wide geographic and cultural pools. Later, they prioritized partners who lived closer, and who were potentially more culturally similar.”

The research team included scholars from Canada, Kenya, Malawi, Tanzania, the United States, Zambia and many other countries. Critical contributions to the study came from curators and co-authors at African museums who are responsible for protecting and preserving the remains.

Potiphar Kaliba, director of research at the Malawi Department of Museums and Monuments and an author of the study, noted that some of the skeletons sampled for the study were excavated a half-century ago, yet their DNA is preserved despite hot and humid climates in the tropics.

“This work shows why it’s so important to invest in the stewardship of human remains and archaeological artefacts in African museums,” Kaliba said.

The work also helps address global imbalances in research, Prendergast said.

“There are around 30 times more published ancient DNA sequences from Europe than from Africa,” she said. “Given that Africa harbours the greatest human genetic diversity on the planet, we have much more to learn.”

“By associating archaeological artefacts with ancient DNA, the researchers have created a remarkable framework for exploring the prehistory of humans in Africa,” said Archaeology and Archaeometry program director John Yellen of the U.S. National Science Foundation, one of the funders behind this project. “This insight is charting a new way forward to understanding humanity and our complex shared history.”

What Did Human Ancestors Eat?

Quintessential human traits such as large brains first appear in Homo erectus nearly 2 million years ago. This evolutionary transition towards human-like traits is often linked to a major dietary shift involving greater meat consumption.

A new study published today in the Proceedings of the National Academy of Sciences, however, calls into question the primacy of meat-eating in early human evolution.

While the archaeological evidence for meat-eating increases dramatically after the appearance of Homo erectus, the study authors argue that this increase can largely be explained by greater research attention on this time period, effectively skewing the evidence in favour of the “meat made us human” hypothesis.

“Generations of paleoanthropologists have gone to famously well-preserved sites in places like Olduvai Gorge looking for — and finding — breathtaking direct evidence of early humans eating meat, furthering this viewpoint that there was an explosion of meat-eating after 2 million years ago,” W. Andrew Barr, an assistant professor of anthropology at the George Washington University and lead author on the study, said.

“However, when you quantitatively synthesize the data from numerous sites across eastern Africa to test this hypothesis, as we did here, that ‘meat made us human’ evolutionary narrative starts to unravel.”

Barr and his colleagues compiled published data from nine major research areas in eastern Africa, including 59 site levels dating between 2.6 and 1.2 million years ago.

They used several metrics to track hominin carnivory: the number of zooarchaeological sites preserving animal bones that have cut marks made by stone tools, the total count of animal bones with cut marks across sites, and the number of separately reported stratigraphic levels.

The researchers found that, when accounting for variation in sampling effort over time, there is no sustained increase in the relative amount of evidence for carnivory after the appearance of H. Erectus.

They note that while the raw abundance of modified bones and the number of zooarchaeological sites and levels all demonstrably increased after the appearance of H. Erectus, the increases were mirrored by a corresponding rise in sampling intensity, suggesting that intensive sampling – rather than changes in human behaviour – could be the cause.

“I’ve excavated and studied cut marked fossils for over 20 years, and our findings were still a big surprise to me,” Briana Pobiner, a research scientist in the Human Origins Program at the Smithsonian’s National Museum of Natural History and co-author on the study, said.

“This study changes our understanding of what the zooarchaeological record tells us about the earliest prehistoric meat-eating. It also shows how important it is that we continue to ask big questions about our evolution, while we also continue to uncover and analyze new evidence about our past.”

In the future, the researchers stressed the need for alternative explanations for why certain anatomical and behavioural traits associated with modern humans emerged.

Possible alternative theories include the provisioning of plant foods by grandmothers and the development of controlled fire for increasing nutrient availability through cooking.

The researchers caution that none of these possible explanations currently have a strong grounding in the archaeological record, so much work remains to be done.

“I would think this study and its findings would be of interest not just to the paleoanthropology community but to all the people currently basing their dieting decisions around some version of this meat-eating narrative,” Barr said. “Our study undermines the idea that eating large quantities of meat drove evolutionary changes in our early ancestors.”

In addition to Barr and Pobiner, the research team included John Rowan, an assistant professor of anthropology at the University of Albany; Andrew Du, an assistant professor of anthropology and geography at Colorado State University; and J. Tyler Faith, an associate professor of anthropology at the University of Utah.

Tanzanian rock art reveals trios of mysterious anthropomorphic figures

It was recently discovered that the rock art was located at the Amak’hee rock shelter site in the Dodoma Region of central Tanzania found in June 2018. Most of the paintings were made with a reddish dye; there are also five white images.

Dr. Maciej Grzelczyk, a researcher at the Jagiellonian University in Cracow, Poland, says, “Most are in good condition, mainly due to a rock overhang that protects them from flowing water and exposure to excessive sunlight,” 

The Amak’hee 4 paintings include depictions of humans, domesticated cattle, and giraffes.

“Particularly noteworthy among the Amak’hee 4 paintings is a scene that centers around three images,” the scientist said.

“In this trio, the figures seem to feature stylized buffalo heads. These shapes recall the central dip in the profile of the buffalo head from where the two horns rise and then curve outward away from the head, as well as the downturned ears.”

“Even though in the present religion of the Sandawe people — who are descendants of those who created the paintings — we find no elements of anthropomorphization of buffaloes, nor belief in the possibility of transformation of people into these animals, there are some ritual aspects that offer parallels,” he added.

“The Sandawe still practice the simbó ritual, the main element of which is entering trance states.” The paintings are estimated to have been made several hundred years ago.

“As there is currently no absolute dating of rock art from central Tanzania, it is difficult to specify the approximate age of the Amak’hee 4 paintings,” the researcher said.

“Due to degradation of the dye and a lack of, for example, motifs depicting domesticated cattle, it can, however, be assumed that they belong to the hunter-gatherer period, so they are at least several hundred years old.”

Motifs featuring trios of human figures are also observed at other rock art sites in central Tanzania.

“The paintings at the Amak’hee 4 rock shelter provide one example of the many rock art sites in the Swaga Swaga area that are locally known but unpublished,” Dr. Grzelczyk said.

“Further fieldwork surveys in this area will be carried out to add to the growing body of published data recording rock art sites in this region.”