The art of the Roman surveyors emerges from newly discovered pavements in Pompeii

Politecnico di milano

IMAGE: Plan of the house of Orion, Showing the disposition of the newly discovered images (1,2) and of the mosaics (3) view more 

Credit: L. Ferro, G Magli, M. Osanna

The technical skills of the Roman agrimensores - the technicians in charge of the centuriations (division of the lands) and of other surveys such as planning towns and aqueducts - are simply legendary. For instance, extremely accurate projects of centuriations are still visible today in Italy and in other Mediterranean countries. Their work had also religious and symbolic connections being related with the foundation of towns and the Etruscan's tradition.
These technicians were called Gromatics due to their chief working instrument, called Groma. It was based on a cross made of four perpendicular arms each bringing cords with identical weights, acting as plumb-lines. The surveyor could align with extreme precision two opposite, very thin plumb-lines with reference poles held at various distances by assistants or fixed in the terrain, in the same manner as palines (red and white posts) are used in modern theodolite surveying.
Up to now, the unique known example of a Groma was coming from Pompeii excavations, while images illustrating the work of the Gromatics were passed on only by medieval codex's, dating to many centuries after the art of the agrimensores was not practiced any more. It now looks like that again Pompeii is the place where new information about these ancient architects can come out. As part of the Great Pompeii Project indeed, inaugurated in 2014 and co-financed by the European Community, new archaeological investigations unearthed a house with a solemn, ancient facade. Inside, almost intact floors have been found containing two beautiful mosaics probably representing Orion, and a series of enigmatic images.
The interpretation of the images has been recently given in a joint paper by Massimo Osanna, Director of the Pompeii archaeological site, and Luisa Ferro and Giulio Magli, of the School of Architecture at the Politecnico of Milan. Among the images there is, for instance, a square inscribed in a circle. The circle is cut by two perpendicular lines, one of which coincides with the longitudinal axis of the atrium of the house and appears as a sort of rose of the winds that identifies a regular division of the circle in eight equally spaced sectors. The image is strikingly similar to one used in the medieval codex's to illustrate the way in which the Gromatics divided the space. Another, complex image shows a circle with an orthogonal cross inscribed in it, connected by five dots disposed as a sort of small circle to a straight line with a base. The whole appears as the depiction of a Groma.
Was the house used for meetings and/or the owner himself belonged to the gromatic's guild? We do not know it for sure. In any case however, and once again, Pompeii reveals itself as an invaluable source in understanding key aspects of the Roman life and civilization.

Facial deformity in royal dynasty was linked to inbreeding

IMAGE: King Charles II of Spain was the last in the Habsburg line and one of the most afflicted with the facial deformity view more 

Credit: Don Juan Carreño de Miranda

The "Habsburg jaw", a facial condition of the Habsburg dynasty of Spanish and Austrian kings and their wives, can be attributed to inbreeding, according to new results published in the Annals of Human Biology.
The new study combined diagnosis of facial deformities using historical portraits with genetic analysis of the degree of relatedness to determine whether there was a direct link. The researchers also investigated the genetic basis of the relationship.
Generations of intermarriage secured the family's influence across a European empire including Spain and Austria for more than 200 years but led to its demise when the final Habsburg monarch was unable to produce an heir. However, until now no studies have confirmed whether the distinct chin known as "Habsburg jaw" was a result of inbreeding.
"The Habsburg dynasty was one of the most influential in Europe, but became renowned for inbreeding, which was its eventual downfall. We show for the first time that there is a clear positive relationship between inbreeding and appearance of the Habsburg jaw," says lead researcher Professor Roman Vilas from the University of Santiago de Compostela.
The researchers recruited 10 maxillofacial surgeons to diagnose facial deformity in 66 portraits of 15 members of the Habsburg dynasty. Despite differences in artistic style, the portraits are characterised by a realistic approach to the human face. The surgeons were asked to diagnose 11 features of mandibular prognathism, otherwise known as "Habsburg jaw", as well as seven features of maxillary deficiency, the most recognisable of which are a prominent lower lip and an overhanging nasal tip.
The portraits, which can be viewed online, are preserved by some of the most important art museums in the world, including the Kunsthistorisches Museum in Vienna and the Prado Museum in Madrid.
The surgeons gave scores for the degree of mandibular prognathism and maxillary deficiency in each member of the Habsburg family. Mary of Burgundy, who married into the family in 1477, showed the least degree of both traits. Mandibular prognathism was most pronounced in Philip IV, King of Spain and Portugal from 1621 to 1640. Maxillary deficiency was diagnosed to the greatest degree in five members of the family: Maximilian I (regent from 1493), his daughter Margaret of Austria, his nephew Charles I of Spain, Charles' great-grandson Philip IV and the last in the Habsburg line, Charles II.
The study authors detected a correlation between the two conditions, suggesting that "Habsburg jaw" is in fact characterised by them both and that they share a common genetic basis. The extent of inbreeding was calculated from a large-scale family tree, including more than 6,000 individuals belonging to more than 20 generations. Analysis was carried out to determine if it was connected to the degree of facial deformity. The researchers detected a strong relationship between the degree of inbreeding and the degree of mandibular prognathism. The relationship to maxillary deficiency was also positive, but it was only statistically significant in two of the seven features diagnosed.
The causes of the relationship between inbreeding and facial deformity remain unclear, but the authors suggest it's because the main effect of mating between relatives is an increase in the chances of offspring inheriting identical forms of a gene from both parents, known as genetic homozygosity. This reduces people's genetic fitness, so "Habsburg jaw" should be considered a recessive condition.
However, the authors note that the study involves only a small number of individuals so it's possible that the prevalence of Habsburg jaw is due to the chance appearance of traits, or genetic drift. They suggest this scenario is unlikely, but can't rule it out.
"While our study is based on historical figures, inbreeding is still common in some geographical regions and among some religious and ethnic groups, so it's important today to investigate the effects," says Vilas. "The Habsburg dynasty serves as a kind of human laboratory for researchers to do so, because the range of inbreeding is so high."

Justinianic plague not a landmark pandemic?

National Socio-Environmental Synthesis Center

IMAGE: A graphical abstract showing highlights of the research presented in the article: "The Justinanic Plague: An Inconsequential Pandemic? " view more 

Credit: Elizabeth Herzfeldt-Kamprath, SESYNC

Researchers now have a clearer picture of the impact of the first plague pandemic, the Justinianic Plague, which lasted from about 541-750 CE.
Led by researchers at the University of Maryland's National-Socio Environmental Synthesis Center (SESYNC), the international team of scholars found that the plague's effects may have been exaggerated. They examined diverse datasets, but found no concrete effects they could conclusively attribute to the plague. Their paper appears in the December 2 issue of the Proceedings of the National Academy of Sciences (PNAS).
"Our article is the first time such a large body of novel interdisciplinary evidence has been investigated in this context," said lead author Lee Mordechai, a postdoctoral fellow at SESYNC, and co-lead of Princeton's Climate Change and History Research Initiative (CCHRI). He is now a senior lecturer at Hebrew University of Jerusalem. "If this plague was a key moment in human history that killed between a third and half the population of the Mediterranean world in just a few years, as is often claimed, we should have evidence for it but our survey of datasets found none."
The research team, which collaborated through the CCHRI, examined contemporary written sources, inscriptions, coinage, papyrus documents, pollen samples, plague genomes, and mortuary archaeology.
The researchers focused on the period known as Late Antiquity (300-800 CE) that included major events such as the fall of the Western Roman Empire and the rise of Islam--events that have been sometimes attributed to plague, including in history textbooks.
"Our paper rewrites the history of Late Antiquity from an environmental perspective that doesn't assume plague was responsible for changing the world," said Merle Eisenberg, also a SESYNC postdoctoral fellow, member of the CCHRI and a co-author on the paper. "The paper is notable because historians led this PNAS publication, and we asked historical questions that focused on the potential social and economic effects of plague."
The team found that previous scholars have focused on the most evocative written accounts, applying them to other places in the Mediterranean world while ignoring hundreds of contemporary texts that do not mention plague.
"While plague studies is an interdisciplinary, demanding field of study, most plague scholars rely solely on the types of evidence they are trained to use. We are the first team to look for the impacts of the first plague pandemic in very diverse datasets. We found no reason to argue that the plague killed tens of millions of people as many have claimed," said co-author Timothy Newfield, another co-lead of the CCHRI who is now an assistant professor of history and biology at Georgetown University. "Plague is often construed as shifting the course of history. It's an easy explanation, too easy. It's essential to establish a causal connection."
Many of these datasets, such as agricultural production, show that trends that began before the plague outbreak continued without change.
"We used pollen evidence to estimate agricultural production, which shows no decrease associable with plague mortality. If there were fewer people working the land, this should have shown up in pollen, but it has failed to so far," said co-author Adam Izdebski, a member of CCHRI who is now a research group leader at the Max Planck Institute for the Science of Human History and an assistant professor of history at Jagiellonian University.
Even some of the most well-known effects of large epidemics, such as changes in burial traditions, follow existing trends that began centuries earlier.
"We investigated a large dataset of human burials from before and after the plague outbreak, and the plague did not result in a significant change whether people buried the dead alone or with many others," said co-author Janet Kay, a lecturer in the Council of the Humanities and history and the CSLA-Cotsen Postdoctoral Fellow in Late Antiquity in the Society of Fellows at Princeton University. She contrasted that with the Black Death, a plague that took place about 800 years after the Justinianic Plague. "The Black Death killed vast numbers of people and did change how people disposed of corpses," she said.
The researchers also used available plague genomes to trace the origin and evolution of the plague strains responsible for outbreak, which certainly killed people across Eurasia--how many people is the question.
Co-author Hendrik Poinar, a professor of evolutionary biology and director of the Ancient DNA Centre at McMaster University, added: "Although tracing the origins and development of the plague bacterium is crucial, the presence of the pathogen does not in itself mean catastrophe."

New archaeological information on the use of plants in prehistoric northern Europe

University of Helsinki

IMAGE: Charred remains of prehistoric gathered plants: a rose hip, a nutshell fragment, a raspberry seed, a yellow water lily seed and a bird cherry seed. The rose hip, dating back... view more 

Credit: Santeri Vanhanen

In the study, the following questions were explored: Which plants did humans gather in prehistoric times? When did the first cultivated plants make their initial appearance, and where did they come from? How did farming develop after its adoption?
To find answers to these questions, ancient plant remains, such as nutshells, seeds and grains found at archaeological digs were analysed.
Finland was settled roughly 11,000 years ago after the ice cover receded. Today, Finland is covered mostly by coniferous forest, including pine and spruce.
Prior research has focused on the animals that Stone Age people hunted. Based on the recently completed study, a number of plants were also utilised in Stone Age Finland. For example, hazelnuts and water chestnuts were gathered for food, and they in fact grew further north than today. At that time, the average temperature was a couple of degrees higher, and deciduous trees grew in larger numbers in the forests of the region. These days, the northernmost regions where water chestnut grows are approximately 1,000 kilometres further south.
Agriculture was introduced to Europe by populations migrating from the Middle East. During their journeys, farming cultures underwent change. Hunter-gatherers had an impact on the human DNA, while material culture was transformed and the number of cultivated plants decreased the further north humans travelled.
Earliest grains found on Åland In the study, the oldest barley and wheat grains in Finland were found on the Åland Islands, located in the Baltic Sea between Finland and Sweden. Based on radiocarbon dating, these grains proved to be roughly 5,000 years old, making them a thousand years younger than those found in the area surrounding Stockholm and 2,500 years younger than those found in Central Europe. At the time, hunter-gatherers specialised in hunting seals and representing the Pitted Ware culture moved to the islands from the area of today's Stockholm. They appear to have adopted agriculture from farmers who had spread to Scandinavia 6,000 years ago. The finding was a surprise, as hunter-gatherers have very rarely been demonstrated to have adopted the art of cultivating land.
After the first farming wave, there is roughly a thousand-year break in the incidence of crops in Finland, even though the Corded Ware culture, spread through Estonia, did practise animal husbandry.
The cereal grain discoveries indicate that farming became an established practice in the south-west coastal area of Finland only from the beginning of the Bronze Age, approximately 3,500 years ago. Based on the shape of burial sites and material culture, this farming culture arrived from Sweden.
Barley as the key cereal crop Due to its adaptation to colder climates, barley was the most important cereal crop throughout prehistory. In the early Common Era, the plants cultivated in fields also included emmer wheat, rye and common wheat, as well as flux and hemp. Slash-and-burn cultivation has been considered the oldest cultivation method employed in Finland, but on the basis of the weeds found in this study and previously analysed discoveries in ancient fields, it appears that field cultivation was adopted no later than approximately 1,500 years ago.
In addition, plant gathering continued even after the adoption of farming. However, cereal crops seem to have replaced carbohydrate-rich wild plants, such as yellow water lily, the seeds of which contain approximately 80 grams of carbohydrates per 100 grams. The use of wild strawberry, raspberry and juniper, among others, continued, potentially for their taste as well as for their medicinal effects.
The ancient hunter-gatherers of northern Europe adapted to their changing surroundings and took advantage of the plants available to them in many different ways. The introduction and establishment of farming, which took place later, constituted a development of thousands of years affected alternately by migrant waves and local developments.

Unique sled dogs helped the inuit thrive in the North American Arctic

UC Davis anthropologists and geneticists traced dog's DNA back 2,000 years

University of California - Davis

IMAGE: A team of Greenland sled dogs are descendants of the Inuit of North American Arctic. view more 

Credit: Article author Tatiana Tatiana Feuerborn

Inuit sled dogs have changed little since people migrated to the North American Arctic across the Bering Strait from Siberia with them, according to researchers who have examined DNA from the dogs from that time span. The legacy of these Inuit dogs survives today in Arctic sled dogs, making them one of the last remaining descendant populations of indigenous, pre-European dog lineages in the Americas.
The latest research is the result of nearly a decade's work by University of California, Davis, researchers in anthropology and veterinary genetics, who analyzed the DNA of hundreds of dogs' ancient skeletal remains to determine that the Inuit dog had significantly different DNA than other Arctic dogs, including malamutes and huskies.
The article, "Specialized sledge dogs accompanied the Inuit dispersal across the North American Arctic," was published Wednesday in the Proceedings of the Royal Society B: Biological Sciences. From UC Davis, authors include Christyann Darwent, professor of anthropology; Ben Sacks, adjunct professor and director of the Mammalian Ecology and Conservation Unit, Veterinary Genetics Laboratory, School of Veterinary Medicine; and Sarah Brown, a postdoctoral researcher. Lead author Carly Ameen is an archaeologist from the University of Exeter; Tatiana Feuerborn is with the Globe Institute in Denmark and Centre for Palaeogenetics in Sweden; and Allowen Evin is at the CNRS, Université de Montpellier, Institut des Sciences de l'Evolution in Montpellier, France. The list of authors includes many others from a large number of collaborating institutions.
Qimmiit (dogs in Inuktitut) were viewed by the Inuit as particularly well-suited to long-distance hauling of people and their goods across the Arctic and consuming local resources, such as sea mammals, for food.
The unique group of dogs helped the Inuit conquer the tough terrain of the North American Arctic 2,000 years ago, researchers said. Inuit dogs are the direct ancestors of modern Arctic sled dogs, and although their appearance has continued to change over time, they continue to play an important role in Arctic communities.
Experts examined the DNA from 921 dogs and wolves who lived during the last 4,500 years. Analysis of the DNA, and the locations and time periods in which they were recovered archaeologically, shows dogs from Inuit sites occupied beginning around 2,000 years ago were genetically different from dogs already in the region.
According to Sacks "the genetic profiles of ancient dogs of the American Arctic dating to 2,000 years ago were nearly identical to those of older dogs from Siberia, but contrasted starkly with those of more ancient dogs in the Americas, providing an unusually clear and definitive picture of the canine replacement event that coincided with the expansion of Thule peoples across the American Arctic two millennia ago."
Preserving an important history
Research confirms that native peoples maintained their own dogs. By analyzing the shape of elements from 391 dogs, the study also shows that the Inuit had larger dogs with a proportionally narrower cranium to earlier dogs belonging to pre-Inuit groups.
The National Science Foundation-funded portion of the research at UC Davis was inspired by Inuit activist and author Sheila Watt-Cloutier, who told Darwent about Inuit sled-dog culling undertaken by Canadian police in the 1950s and asked if there was a way to use scientific methods to tell the history and importance of sled dogs in the Arctic. Preservation of these distinctive Inuit dogs is likely a reflection of the highly specialized role that dogs played in both long-range transportation and daily subsistence practices in Inuit society.

Barbequed clams on the menu for ancient Puerto Ricans

Analysis of fossilized shells reveals cooking habits of Caribbean civilizations over 2500 years ago

Cardiff University

IMAGE: Photographs of all shells analyzed in this study. view more 

Credit: Cardiff University

Scientists have reconstructed the cooking techniques of the early inhabitants of Puerto Rico by analysing the remains of clams.
Led by Philip Staudigel, who conducted the analysis as a graduate student at the University of Miami Rosenstiel School and is now a postdoctoral researcher at Cardiff University, the team has used new chemical analysis techniques to identify the exact cooking temperatures at which clams were cooked over 2500 years ago.
With cooking temperatures getting up to around 200oC according to the new analysis, the team believe the early Puerto Ricans were partial to a barbeque rather than boiling their food as a soup.
The study, which also involved academics from the University of Miami and Valencia College, has been published today in the journal Science Advances.
Whilst the results throw new light on the cultural practices of the first communities to arrive on the island of Puerto Rico, they also provide at least circumstantial evidence that ceramic pottery technology was not widespread during this period of history - it's likely that this would be the only way in which the clams could have been boiled.
Lead author of the study Dr Philip Staudigel, currently at Cardiff University's School of Earth and Ocean Sciences, said: "Much of peoples' identity draws upon on where they came from, one of the most profound expressions of this is in cooking. We learn to cook from our parents, who learned from their parents.
"In many parts of the world, written records extend back thousands of years, which often includes recipes. This is not the case in the Caribbean, as there were no written texts, except for petroglyphs. By learning more about how ancient Puerto Rican natives cooked their meals, we can relate to these long-gone peoples through their food."
In their study, the team analysed over 20kg of fossilised clam shells at the University of Miami's Rosenstiel School of Marine and Atmospheric Sciences Stable Isotope Lab, which were collected from an archaeological site in Cabo Rojo, Puerto Rico.
The pre-Arawak population of Puerto Rico were the first inhabitants of the island, arriving sometime before 3000 BC, and came from Central and/or South America. They existed primarily from fishing, hunting, and gathering near the mangrove swamps and coastal areas where they had settled.
The fossilised shells, dating back to around 700 BC, were cleaned and turned into a powder, which was then analysed to determine its mineralogy, as well as the abundance of specific chemical bonds in the sample.
When certain minerals are heated, the bonds between atoms in the mineral can rearrange themselves, which can then be measured in the lab. The amount of rearrangement is proportional to the temperature the mineral is heated.
This technique, known as clumped isotope geochemistry, is often used to determine the temperature an organism formed at but in this instance was used to reconstruct the temperature at which the clams were cooked.
The abundance of bonds in the powdered fossils was then compared to clams which were cooked at known temperatures, as well as uncooked modern clams collected from a nearby beach.
Results showed that that the majority of clams were heated to temperatures greater than 100°C - the boiling point of water - but no greater than 200°C. The results also revealed a disparity between the cooking temperature of different clams, which the researchers believe could be associated with a grilling technique in which the clams are heated from below, meaning the ones at the bottom were heated more than the ones at the top.
"The clams from the archaeological site appeared to be most similar to clams which had been barbequed," continued Dr Staudigel.
"Ancient Puerto Ricans didn't use cookbooks, at least none that lasted to the present day. The only way we have of knowing how our ancestors cooked is to study what they left behind. Here, we demonstrated that a relatively new technique can be used to learn what temperature they cooked at, which is one important detail of the cooking process."

Human migration out of Africa may have followed monsoons in the Middle East U

Last year, scientists announced that a human jawbone and prehistoric tools found in 2002 in Misliya Cave, on the western edge of Israel, were between 177,000 and 194,000 years old.
The finding suggested that modern humans, who originated in Africa, began migrating out of the continent at least 40,000 years earlier than scientists previously thought.
But the story of how and when modern humans originated and spread throughout the world is still in draft form. That's because science hasn't settled how many times modern humans left Africa, or just how many routes they may have taken.
A new study published this week [Nov. 25, 2019] in the Proceedings of the National Academy of Sciences by American and Israeli geoscientists and climatologists provides evidence that summer monsoons from Asia and Africa may have reached into the Middle East for periods of time going back at least 125,000 years, providing suitable corridors for human migration.
The likely timing of these northward monsoon expansions corresponds with cyclical changes in Earth's orbit that would have brought the Northern Hemisphere closer to the sun and led to increased summer precipitation. With increased summer precipitation there may have been increased vegetation, supporting animal and human migration into the region.
"It could be important context for experts studying how, why, and when early modern humans were migrating out of Africa," says lead author Ian Orland, a University of Wisconsin-Madison geoscientist now at the Wisconsin Geological and Natural History Survey, in the Division of Extension. "The Eastern Mediterranean was a critical bottleneck for that route out of Africa and if our suggestion is right, at 125,000 years ago and potentially at other periods, there may have been more consistent rainfall on a year-round basis that might enhance the ability of humans to migrate."
For as long as humans have kept records, winters have been wet and summers have been hot and dry in the Levant, a region that includes Israel, Syria, Lebanon, Jordan and Palestine. Before modern times, those hot, dry summers would have presented a significant barrier to people trying to move across the landscape.
Scientists, though, have found it difficult to determine what kinds of precipitation patterns might have existed in the prehistoric Levant. Some studies examining a variety of evidence, including pollen records, ancient lake beds, and Dead Sea sediments, along with some climate modeling studies, indicate summers in the region may have, on occasion, been wet.
To try to better understand this seasonality, Orland and colleagues looked at cave formations called speleothems in Israel's Soreq Cave. Speleothems, such as stalactites and stalagmites, form when water drips into a cave and deposits a hard mineral called calcite. The water contains chemical fingerprints called isotopes that keep a record, like an archive, of the timing and environmental conditions under which speleothems have grown.
Among these isotopes are different forms of oxygen molecules -- a light form called O16 and a heavy form called O18. Today, the water contributing to speleothem growth throughout much of the year has both heavy and light oxygen, with the light oxygen predominantly delivered by rainstorms during the winter wet season.
Orland and his colleagues hypothesized they might be able to discern from speleothems whether two rainy seasons had contributed to their growth at times in the past because they might show a similar signature of light oxygen in both winter and summer growth.
But to make this comparison, the scientists had to make isotope measurements across single growth bands, which are narrower than a human hair. Using a sensitive instrument in the UW-Madison Department of Geoscience called an ion microprobe, the team measured the relative amounts of light and heavy oxygen at seasonal increments across the growth bands of two 125,000-year-old speleothems from Soreq Cave.
This was the first time that seasonal changes were directly measured in a speleothem this old.
At the same time that Orland was in pursuit of geologic answers, his UW-Madison colleague in the Nelson Institute for Environmental Studies Center for Climatic Research, Feng He, was independently using climate models to examine how vegetation on the planet has changed with seasonal fluctuations over the last 800,000 years. Colleagues since graduate school, He and Orland teamed up to combine their respective approaches after learning their studies were complementary.
A previous study in 2014 from UW-Madison climatologist and Professor Emeritus John Kutzbach showed that the Middle East may have been warmer and wetter than usual during two periods of time corresponding roughly to 125,000 years ago and 105,000 years ago. Meanwhile, at a point in between, 115,000 years ago, conditions there were more similar to today.
The wetter time periods corresponded to peak summer insolation in the Northern Hemisphere, when Earth passes closer to the sun due to subtle changes in its orbit. The drier time period corresponded to one of its farthest orbits from the sun. Monsoon seasons tend to be stronger during peak insolation.
This provided He an opportunity to study high and low insolation rainfall during summer seasons in the Middle East and to study its isotopic signatures.
The climate model "fueled the summer monsoon hypothesis" because it suggested that "under these conditions, the monsoons could have reached the Middle East and would have a low O18 signature," He, a study co-author, says. "It's a very intriguing period in terms of climate and human evolution."
His model showed that northward expansion of the African and Asian summer monsoons was possible during this time period, would have brought significant rainfall to the Levant in the summer months, would have nearly doubled annual precipitation in the region, and would have left an oxygen isotope signature similar to winter rains.
At the same time, Orland's speleothem isotype analysis also suggested summers were rainier during peak insolation at 125,000 and 105,000 years ago.
For similar reasons, the Middle East may have also been warm and humid around 176,000 years ago, the researchers say -- about when the jawbone made its way to Misliya Cave. And before the jawbone, the previous oldest modern human fossils found outside of Africa were at Israel's Skh?l Cave, dating back between 80,000 and 120,000 years ago.
Overall, the study suggests that during a period of time when humans and their ancestors were exploring beyond the African continent, conditions may have been favorable for them to traverse the Levant.
"Human migration out of Africa occurred in pulses, which is definitely consistent with our idea that every time the Earth is closer to the sun, the summer monsoon is stronger and that's the climatic window that opened and provided opportunities for human migration out of Africa," says He.