Discovering the Diet of Early Neolithic Farmers in Scandinavia

 

 

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One of the 14 grindings tones that archeologists found while excavating a 5,500 years old settlement on the Danish island Funen. A new study reveals that the stones were not used to grind cereal grains.

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Credit: Niels H. Andersen, Moesgaard Museum

Water and Gruel – not Bread: Discovering the Diet of Early Neolithic Farmers in Scandinavia

At a Neolithic settlement on the Danish island Funen dating back 5,500 years, archaeologists have discovered both grinding stones and grains from early cereals. However, new research reveals that the inhabitants did not use the stones to grind the cereal grains. Instead of making bread, they likely prepared porridge or gruel from the grains.

A grinding stone, as the name suggests, is a stone with a sufficiently flat surface that allows grinding against it with another, smaller stone.

Archaeologists found fourteen of such stones when they excavated the remains of a settlement from the Early Neolithic Funnel Beaker Culture at Frydenlund, on Strandby Mark southeast of Haarby on Funen (see fact box at the bottom of this text).

You can view 3D images of 11 different grindings stones from the Frydenlund site here (you can rotate and turn them with your mouse). 

They also found over 5,000 charred grain kernels of naked barley, emmer wheat, and durum wheat, amongst others.

One might offhand assume that the inhabitants 5,500 years ago ground their cereals into flour and baked bread with it. That has indeed been the typical interpretation of grinding stones from that time.

But they didn’t.

An international research team from Denmark, Germany and Spain has now analysed both the grains and the stones, concluding that the grinding stones were not used to grind cereals. 

The researchers examined microscopic mineral plant remains (phytoliths) and starch grains in small cavities on the surfaces of the stones. Surprisingly, they did not find any evidence of grinding of cereals.

The researchers found only few phytoliths on the stones, and the starch grains they identified came from wild plants instead of cereals.

“We have not identified the plants the starch grains originate from. We have merely ruled out the most obvious candidates – namely the cereals found at the settlement, which were not ground, as well as various collected species, including hazelnuts,” explains archaeobotanist, PhD Welmoed Out from Moesgaard Museum.

Together with senior researcher, Dr. Phil. Niels H. Andersen, also from Moesgaard Museum, she led the study recently published in the scientific journal Vegetation History and Archaeobotany.

What the grinding stones were used for remains open to interpretation, aside from the fact that they lack clear wear marks from the pushing motions used for grinding grain.

“The trough-shaped querns with traces of pushing movements emerged 500 years later. The grinding stones we studied here were struck with pestles made of stone, like crushing in a mortar. We also found such pestles at the site, resembling rounded, thick stone sausages. However, we have not analysed them for phytoliths or starch,” explains Niels H. Andersen.

This is the first time a state-of-the-art combination of phytolith and starch analyses has been performed on grinding stones from the first farmers in Northern Europe. The results support a hypothesis that archaeobotanists and archaeologists elsewhere in Northern Europe also have proposed after discovering remains of grains cooked into porridge and gruel: that the first farmers did not live on water and bread but rather on water and gruel, alongside berries, nuts, roots, and meat.
And yes, they likely drank water. According to Niels H. Andersen, no definitive traces of beer brewing have been found in Denmark before the Bronze Age.

However, as the two researchers from Moesgaard Museum emphasize: “This study only involves one settlement. While it supports other findings from the Funnel Beaker Culture, we cannot rule out the possibility of different results emerging when this method is applied to finds from other excavations.”

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Facts:

• The Funnel Beaker Culture was an early farming culture in Northern, Central, and Eastern Europe during the period ca. 4000–2800 BCE, marking the introduction of agriculture and cattle farming to Scandinavia. The name refers to the culture's commonly found clay beakers with funnel-shaped necks.
• The discovery on Southern Funen is the most extensive find of grinding stones and grains from the Funnel Beaker Culture in the entire region it encompassed.
• The study was done in collaboration between researchers from Moesgaard Museum and Aarhus University in Denmark, Kiel University in Germany and the Spanish National Research Council (IMF-CSIC) in Barcelona

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Journal

Vegetation History and Archaeobotany

DOI

10.1007/s00334-024-01020-9 

The earliest surviving inscribed tablet of the Ten Commandments

 The Ten Commandments: The earliest surviving inscribed tablet of the Ten Commandments, incised during the late Roman-Byzantine era, The Holy Land, (ca. 300–800 CE)

The Only Complete Example Of A Ten Commandments Tablet From This Early Period. 

White marble tablet, approximately 24 ⅞ x 22 ⅛ x 2 ⅜ inches (632 x 562 x 62 mm), weighing approximately 115 pounds (52 kg), neatly chisel-inscribed with the Mosaic Ten Commandments in their Israelite Samaritan version, 20 lines in a Paleo-Hebrew script, each line containing between eleven and fifteen characters, with margins of about 10 cm on either side; the letters have a width of between one and 2 cm and words are separated from one another with one or two dots; a few letters are confused for each other (especially ה and א) and a few characters on the right side of the first two lines are effaced and re-inscribed.

The Ten Commandments are by any measure one of the most widely known and influential texts in the vast canon of the world’s written word, taking primacy in disciplines ranging from religion to literature to philosophy to law to ethics to pedagogy and beyond. Described in their earliest recordings as being spoken directly by God to Moses so that they could be conveyed to the Israelites encamped at Mount Sinai after the Exodus from Egypt, the Ten Commandments—or the Ten Statements, as the Hebrew would be rendered literally—remain fundamental to the adherents of Judaism and Christianity. But the influence of the Decalogue extends far beyond the Judeo-Christian religions, underpinning around the globe the foundational concepts of common law, natural law, formal legal codes, personal conduct, and the social compact. 

THE HISTORY

Dating to the late Roman-Byzantine era, this remarkable artifact is approximately 1,500 years old and is the only complete tablet of the Ten Commandments still extant from this early era. Weighing 115 pounds and measuring approximately two feet in height, it is now called the Yavne Tablet after the city on the coastal plain of the Land of Israel near where it was rediscovered more than a century ago. This monumental, incised marble slab was serendipitously uncovered during excavations for a railroad track running through the Land of Israel to Egypt. The significance of the discovery went unrecognized for many decades, and for thirty years it served as a paving stone in a local home.

In 1947, Jacob Kaplan, the highly regarded municipal archaeologist for Tel Aviv, published an article in the Bulletin of The Jewish Palestine Exploration Society that detailed his acquisition of this Tablet four years previously and provided further information about the Tablet’s origin and provenance. Kaplan described how in 1943, an Arab man from Yavne sold him a white marble Tablet with an inscription engraved upon it. According to the seller, his father found the Tablet in 1913 during the excavation for the railroad and transferred it to his home where he placed it at the threshold of one of the rooms of the inner courtyard.  

In a companion article in the same issue of the Bulletin of the Jewish Palestine Exploration Society, Yitzhak Ben-Zvi, a historian and the second and longest-serving president of Israel, provided an overview of the earlier history of the Yavne Tablet. Based on the Paleo-Hebrew script and on the paleography, Ben-Zvi dated the Tablet to the Byzantine era and ascribed its creation to the Israelite Samaritans, an ethno-religious people who lived in Samaria in the Land of Israel. The Samaritans claim partial descent from the Israelite tribes of Ephraim and Manasseh, but they set themselves apart religiously and ethnically from the Jews.

According to further information received by Jacob Kaplan, the Tablet was discovered buried to the east of the central Jama Mosque in the same spot where a church and a Samaritan synagogue once stood. Historical documents associated with the mosque indicate that it was established in 1292 and/or around 1373 C.E. This places the mosque’s construction after the era of the Christian Crusaders.  Before the mosque's establishment, the site was occupied by a Christian church built by the Crusaders following their conquest of the area in 1142 C.E. During this period, the Crusaders besieged the city of Yavne and conquered the city. However, several decades later, following the Muslim victory over the Crusaders, a large mosque was constructed atop the ruins of this church.

This raises intriguing questions about the site's earlier history. It is likely that an ancient Samaritan synagogue once existed in the same location during the time when Samaritans inhabited Yavne and that the Crusaders destroyed the Samaritan synagogue to erect their church. Following the Crusaders' defeat, it is conceivable that Muslims constructed the new mosque in the 13th century, utilizing the remnants of the church as its foundation. This pattern of religious structures being built atop one another is not uncommon; for instance, remnants of other Samaritan inscriptions have been discovered in the ruins of a small 4th century church on Mount Nebo, suggesting that an ancient Samaritan synagogue had previously stood there as well.

Further information about the early Samaritan communities in the Holy Land is provided by Peter the Iberian (ca. 417–491), the son of Bosmarios, king of Georgia (Iberia). Peter traveled to Jerusalem and become a monk, eventually settling in a monastery near Gaza. During the last 3 years of his life, he lived in the town of Yavne and reported that the entire city of Yavne and its coastal areas were settled by the Samaritans. During that time, Yavne served as a vital center for the trade of Samaritan grain. Historical accounts from Greek and Arab sources indicate that a significant population of Samaritans resided in Yavne and its surrounding regions until the end of the 9th century. This is further corroborated by Samaritan sources, including the 12th century Tolidah chronicle, considered to be the oldest Samaritan historical work. This text references a Samaritan settlement in the vicinity of Yavne, offering additional evidence of the area's historical significance to the Samaritan community.

Benjamin of Tudela, the famous 12th century Jewish traveler who provided a colorful and detailed account of the many places he visited, noted in his diaries that Ashkelon (a city not far from Yavne) was home to a large Samaritan community of approximately 300 families. However, following the era of the Crusaders, we do not have any further information regarding a significant Samaritan community in this area and it would therefore stand to reason that this Tablet discovered near Yavneh must have been created for the larger Samaritan community that lived there during the earlier Roman or Byzantine era.

THE SCRIPT

The text of the Ten Commandments on this Tablet is engraved in a Paleo-Hebrew script, an ancient writing system used by the Israelite people during the early stages of their history, specifically from around the 10th century BCE to the 5th century BCE. This early script, known in Hebrew as Ktav Ivri, is characterized by its angular and linear forms. By the 5th century BCE, the Jewish people had largely transitioned from this alphabet to the Aramaic alphabet and adopted a square form that is now known as the Hebrew alphabet (and in Hebrew as Ktav Ashuri). The Samaritans, however, continued to use the early Paleo-Hebrew alphabet, as seen on this Tablet. As a precursor to the modern Hebrew alphabet, Paleo-Hebrew script holds significant importance for the study of the Hebrew Bible.

THE TEXT OF THE YAVNE TABLET

THE TEXT OF THE YAVNE TABLET

Translated from Hebrew, the line-by-line inscription runs as follows:
1. Dedicated in the name of Korach
2. I will call you to remember for goodness forever
3. God spoke
4. all these words
5. saying I am the Lord
6. your God you shall not have
7. for yourself other Gods
8. besides me; you shall not make
9. for yourself a sculptured image or any likeness;
10. for I the Lord
11. your God am an impassioned God;
12. Remember the Sabbath day
13. keep it holy; honor
14. your father and your mother;
15. you shall not murder; you shall not commit adultery;
16. you shall not steal; you shall not bear [false witness] against your neighbor
17. you shall not covet; you shall erect
18. these stones that
19. I am commanding you today
20. on Mount Gerizim rise up to God

The Ten Commandments are most familiar from their inclusion in two of the books of the Pentateuch: Exodus, chapter 20 and Deuteronomy, chapter 5. But there is a significant degree of variation in the enumeration and even the content of the Commandments among the various translations and faith traditions that consider the Five Books of Moses to be sacred texts. Simply put, there are a variety of ways the Commandments can be listed, combined, and separated to get to “Ten.”  Even between the rosters of Commandments presented in Exodus and Deuteronomy, there are several differences, for example, the variant explanations given for the observance of the Sabbath.  

The Yavne Tablet opens with two lines of dedicatory text and for reasons that cannot now be discerned, omits the Third Commandment against taking the name of God in vain. But this omission may not simply be an error or oversight on the part of the stonecutter; it must be noted that the Palestine Museum Tablet also omits this prohibition, and the scholars Bowman and Talmon hypothesize that the Palestine Museum Tablet inscription included in its Second Commandment by implication the Jewish Third Commandment. The same implied inclusion could well pertain to the Yavne Tablet.

Further, while Ben-Zvi acknowledges that the Commandment “You shall not take the name of God your Lord in vain” is absent from the Yavne Tablet, he points out that this commandment is carved on the stone in the Green Mosque in Shechem [i.e., Nablus], but another commandment “You shall not make for yourself a sculptured image” is missing.

The Yavne Tablet concludes with the Tenth Commandment that focuses on the imperative to worship exclusively at Mount Gerizim, reflecting the Samaritans' belief that this location is the true and divinely ordained site for worship. The text directs the reader to construct an altar and place inscribed tablets on Mount Gerizim and worship God there.

The text of the Yavne Tablet is succinct, largely due to its format: incising or carving in marble is necessarily a slower process than engrossing with a reed and ink on papyrus or parchment. But by all accounts, with the first two Commandments presented as they were originally intended, and with the concluding Samaritan Commandment regarding Mount Gerizim, the Yavne Tablet is a true Decalogue. 

While a handful of other fragmentary stone tablets of the Decalogue have been documented, crucially, all these other witnesses are partial, and several are weathered to the point of illegibility. They contain only a portion of the Ten Commandments or otherwise cannot be considered complete. Several of them are also from a later period than the Yavne Tablet, and the current locations for some of them are not known. No other is believed to be in private hands and certainly no other is in the United States. Ferdinand Dexinger has published ten other inscriptions of the Samaritan Ten Commandments—in addition to the present, Yavne Decalogue (his g), these can be found in an appendix to this catalogue entry.  

The Yavne Tablet is not simply the earliest surviving complete inscribed stone tablet of the Ten Commandments, but the text it preserves represents the spirit, precision, and concision of the Decalogue in what is believed to be its earliest and original formulation. 

A Comparative Table of the Ten Commandments as Recorded on  the Yavne Tablet and in Exodus and Deuteronomy 

Ten Commandments Comparative Table

PROVENANCE

1913: Tablet was found during excavations for a railroad track near the city of Yavne on the coastal plain of the Land of Israel

1913 to 1943:  Taken home by the local man who found it while working on the railroad and used as a paving stone in his courtyard

1943:  Tablet passed to the finder’s son, and its text now recognized, sold to Mr. Jacob Kaplan, a scholar in Israel.

1995:  Sold by Kaplan’s descendants to the Israeli antiquities dealer Robert Deutsch

2005: Sold to Rabbi Saul Deutsch (no relation to the above dealer), Founder and Director of the Living Torah Museum in Brooklyn, New York

2016: Deaccessioned by the Living Torah Museum and purchased by the Judaica collector Dr. Mitchell Stuart Cappell 

The Israeli Antiquities Authority has provided an export license and agreed to the public or private ownership of the tablet.

The bacteria used to produce Gruyère, Emmental and Sbrinz cheese show signs of ancient domestication

 The domestication of plants and animals has played a key role in the development of human societies. And microbes, too, have been tamed: a study by UNIL, published in the journal Nature Communications, shows that the bacteria used to produce Gruyère, Emmental and Sbrinz cheese show signs of ancient domestication.

The domestication of livestock and plants marked an important stage in the settlement of human populations in the Neolithic period, as they moved from a hunter-gatherer lifestyle to a subsistence model based on animal husbandry and agriculture. Because of the microscopic size and virtual absence of fossils of micro-organisms, their domestication is more difficult to prove than that of flora and fauna. Although several studies have already demonstrated this in the case of yeasts (microscopic, single-celled fungi with nuclei), the case of bacteria (micro-organisms that are mainly single-celled and have no nuclei) has yet to be elucidated. This was the objective of Vincent Somerville, a former doctoral student in Philipp Engel's team at the Department of Fundamental Microbiology (DFM) in the Faculty of Biology and Medicine at UNIL. The results of his latest study, carried out under the co-direction of Florent Mazel and in collaboration with Agroscope, have been published in the journal Nature Communications.

An old process

Domestication consists of artificially selecting - generation after generation - variants of a wild species that have developed interesting characteristics for agriculture or livestock farming, such as the nutritional quality of plants or the size and docility of animals. As human population has grown throughout history, and food demand has increased, long-term storage solutions were needed. ‘This is the case with fermentation, which converts sugars into acids, protects against the proliferation of undesirable microbes and therefore enables food to be preserved for longer,’ explains Philipp Engel, co-director of the study. This technique, which dates back several thousand years, uses micro-organisms such as yeast to make beer or wine, or bacteria to make cheese. The first indirect archaeological evidence of milk fermentation dates back around 10,000 years, to the Neolithic period.

Swiss cheeses as study subjects

Thanks to collaboration with Agroscope, the Swiss centre of competence for agronomic and food research, the Lausanne group had access to a collection of bacterial strains used in the production of three different Swiss cheeses: Gruyère, Emmental and Sbrinz, and stored for 50 years. ‘These cultures, also called “cheese starter cultures” were partially reactivated to create some sort of laboratory mini cheeses’, explains Vincent Somerville, first author of the article. ‘We then analysed the evolution of the genetic and phenotypic characteristics of this collection over time in order to identify markers indicative of domestication. By observing more than 100 bacterial isolates and almost 1,000 samples, the scientists found, respectively, low genetic diversity and high stability of traits specific to the food preservation process (for example, acidification) over this half-century period. Those are indicators of an ancient, or even very ancient, adaptation, which by extrapolation corresponds to the appearance of the first fermented dairy products. ‘The temporal concordance between the dating of the micro-organisms and the archaeological history of this fermented food was quite unexpected’, enthuses researcher Florent Mazel. In other words, it is possible to trace the past of the domestication of bacteria from Swiss cheeses.

Guaranteeing food safety

In the future, cheeses from different parts of the world could be compared in order to generalize the study. In addition, research into the domestication of bacterial communities used to initiate the fermentation of other products, such as kefir, looks promising. ‘A better understanding of bacterial domestication will enable us to optimize the characteristics of these microbiota, improve the use of this process and make it a more sustainable method of food storage’, hopes Florent Mazel.

 

Syphilis had its roots in the Americas

 

Syphilis originated in the Americas prior to the arrival of Columbus, and European colonialism made it globally dominant

Peer-Reviewed Publication

Max Planck Institute for Evolutionary Anthropology

 

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Skeletal element (upper hip) that yielded an ancient syphilis-like genome.

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Credit: © Darío Ramirez

In spring 1495, the Italian campaign of Charles VIII of France was interrupted by an intense outbreak of an apparently unknown illness – a disease of high mortality that quickly engulfed the whole of Europe and left its survivors with life changing impairments to their bodies and minds. This documented epidemic is now interpreted to be the first historical account of syphilis.

The origin of syphilis is the subject of a decades-long debate. The late 15th century outbreak occurred shortly after the return of Columbus and his crew from their early expeditions to the Americas, which led some to believe that contact with new lands and people may have had something to do with the sudden disease onset. Though many communicable diseases made a westward journey from Europe to the Americas during the early colonial period where they imparted devastating consequences on indigenous groups, syphilis is one of the few that possibly made the reverse journey. This “Columbian theory” for syphilis has gained popularity over the years, but still has its critics. Its simple narrative starts to unravel when experts turn their attention to lesions seen in bones from Medieval Europe. Both long-term sufferers and those born with an infection can develop changes in their bones or teeth, and over the past several decades, a number of such skeletons have been found in Europe that predate 1492. Many now believe the history of syphilis in Europe began long before Columbus, and the late 15th century pandemic happened for reasons independent of new contacts. But neither theory has been confirmed.

Analyzing five ancient pathogen genomes

Pathogen DNA retrieved from archaeological bone has the potential to tip the scales in support of one theory over another. It has already told us volumes about the deep history of plague, tuberculosis, leprosy, and smallpox, though unthreading the history of syphilis has proven more challenging. “Several genomes from the syphilis family have been reconstructed from archaeological bone, but these haven’t been able to address core questions related to the pre- or post-Columbian theories surrounding syphilis”, says Kirsten Bos, group leader for molecular paleopathology at the Max Planck Institute for Evolutionary Anthropology.

A new study led by Bos and Johannes Krause, director of the Department of Archaeogenetics at the Max Planck Institute for Evolutionary Anthropology in Leipzig, has taken a critical step toward resolving this debate. Working with scientists and archaeologists from several countries in the Americas, the study focused on archaeological bone from these regions, where infections that left lesion patterns similar to syphilis are apparent from deep time periods. “We’ve known for some time that syphilis-like infections occurred in the Americas for millennia, but from the lesions alone it’s impossible to fully characterize the disease”, comments Casey Kirkpatrick, a postdoctoral researcher and paleopathologist who contributed to the current study. Bone pathology also cannot tell us whether the disease originated in the Americas, or if it came from Asia deep in our past and merely accompanied groups during the early peopling events of the Americas some 15,000 years ago. 

Using state of the art techniques, the team was able to recover and analyze five ancient genomes of the syphilis disease family from Mexico, Chile, Peru, and Argentina. Computational microbiologist and postdoctoral researcher Lesley Sitter undertook the task of putting together the ancient molecular puzzles and adds “while preservation posed some analytical challenges, we were able to confidently determine the relationships between these extinct forms and the strains that impact global health today”.

Syphilis family of diseases in the Americas pre-dates “Columbus”

Syphilis is part of a small family of diseases that also includes yaws and bejel, both classified as neglected tropical diseases that are found in equatorial regions across the globe. Postdoctoral researcher Rodrigo Barquera has worked previously with archaeological bone from colonial Mexico, and has confirmed the presence of both syphilis and yaws in Mexico City by the 17th century. Drawing upon the latest ancient genomic data, it is now clear that the Americas were a hub for ancient diversity within this disease group before the arrival of Columbus. “We see extinct sister lineages for all known forms of this disease family, which means syphilis, yaws, and bejel are the modern legacies of pathogens that once circulated in the Americas”, asserts Barquera.

“The data clearly support a root in the Americas for syphilis and its known relatives, and their introduction to Europe starting in the late 15th century is most consistent with the data”, adds Bos. Subsequent to this, an explosion in cases of syphilis and yaws seems to have occurred around AD 1,500. This is likely behind the breadth and intensity of the 16th century outbreak in Europe, whose global spread was facilitated by human trafficking networks and European expansions across the Americas and Africa in the decades and centuries that followed. “While indigenous American groups harboured early forms of these diseases, Europeans were instrumental in spreading them around the world,” she concludes.

With support for an American origin of syphilis, how does the current narrative square up with the evidence of syphilis-like bone lesions that many claim to have identified in pre-1492 Europe?  “The search will continue to define these earlier forms, and ancient DNA will surely be a valuable resource”, comments Krause.  “Who knows what older related diseases made it around the world in humans or other animals before the syphilis family appeared.”

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Journal

Nature

DOI

10.1038/s41586-024-08515-5 

Genomic analysis refines timing of Neandertal admixture – and its impact on modern humans

 

Peer-Reviewed Publication

American Association for the Advancement of Science (AAAS)

A genomic study encompassing more than 300 genomes spanning the last 50,000 years has revealed how a single wave of Neandertal gene flow into early modern humans left an indelible mark on human evolution. Among other findings, the study reports that modern humans acquired several Neanderthal genes that ended up being advantageous to our lineage, including those involved in skin pigmentation, immune response, and metabolism. To date, sequencing of Neanderthal and Denisovan genomes has revealed substantial gene flow between these archaic hominins and modern human ancestors, even as scientists have also reported that Neanderthal ancestry is unevenly distributed across the genome. Moreover, certain regions of the genome – known as archaic deserts – completely lack Neandertal ancestry, while others exhibit high frequencies of Neanderthal variants, potentially due to beneficial adaptive mutations. However, much about the nature of this ancient admixture, including the role evolutionary forces like genetic drift or natural selection played in shaping these patterns, remains unclear. Using genomic data from 334 modern humans, including 59 ancient individuals ranging from 45,000 to 2,200 years old, and 275 present-day individuals from diverse global populations, Leonardo Iasi et al. performed a comprehensive evaluation of Neanderthal ancestry variation in modern humans over the last ~50,000 years. Iasi et al. discovered that the vast majority of Neanderthal gene flow is attributable to a single, shared extended period of gene flow that likely occurred 50,500 to 43,500 years ago, which is consistent with archeological evidence for the overlap of modern humans and Neandertals in Europe. Additionally, the findings demonstrate that Neanderthal ancestry underwent rapid natural selection – both positive and negative – within 100 generations after gene flow, especially on the X chromosome.

 

Nature is publishing a related paper, “Earliest modern human genomes constrain timing of Neanderthal admixture,

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Journal

Science

DOI

10.1126/science.adq3010 

New timeline for Neandertal gene flow event

Scientists unravel timing and impact of Neandertal gene flow into early modern humans

Peer-Reviewed Publication

Max Planck Institute for Evolutionary Anthropology

 

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The researchers identified regions with Neandertal ancestry in over 300 individuals. They assessed sharing of segments, inferred gene flow, and looked at variation to identify candidates for positive and negative selection.

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Credit: © Leonardo Iasi et al., Science (2024)

The study of ancient DNA has greatly advanced our knowledge of human evolution, including the discovery of gene flow from Neandertals into the common ancestors of modern humans. Neandertals and modern humans diverged about 500,000 years ago, with Neandertals living in Eurasia for the past 300,000 years. Then, sometime around 40,000 to 60,000 years ago, modern human groups left Africa and spread across Eurasia, encountering Neandertals along the way. As a result, most non-Africans harbor one to two percent Neandertal ancestry today. However, the precise timing and functional legacy of Neandertals remains elusive.

In a new study, researchers from the Max Planck Institute for Evolutionary Anthropology, Leipzig, and the University of California, Berkeley, examined the genomes of 300 present-day and ancient modern humans, including 59 individuals who lived between 2,000 and 45,000 years ago. "We set out to determine the timing and duration of Neandertal gene flow and the resulting impact on modern humans. To do this, we created a catalog of Neandertal ancestry segments. By comparing the segments among individuals from different time periods and geographic locations, we were able to show that the vast majority of Neandertal ancestry can be traced to a single, shared, extended period of gene flow into the common ancestors of all non-African individuals today," says Priya Moorjani from the University of California, Berkeley.

Neandertal ancestry revisited

By observing the length of the Neandertal DNA segments, which is related to the number of generations since the gene flow, the researchers inferred that the gene flow began about 50,000 years ago and continued for about 7,000 years. "This timeline closely matches the archaeological evidence for the overlap of Neandertals and modern humans in Europe. Some early modern humans - Oase, Ust'-Ishim, Zlatý kůň, and Bacho Kiro - possess substantial unique Neandertal ancestry that is not shared with modern humans after 40,000 years," says first author Leonardo Iasi from the Max Planck Institute for Evolutionary Anthropology.

These dates have several implications for human dispersal after the Out-of-Africa event, as they provide a lower bound on the timing of migration and the settlement of regions outside of Africa. For example, this suggests that the major migration out of Africa occurred no later than 43,500 years ago. Moreover, the population receiving Neandertal ancestry may have been highly structured during the gene flow event. "Diversification of humans outside of Africa may have begun during or soon after the Neandertal gene flow, which could partially explain the different levels of Neandertal ancestry among non-African populations and also reconcile our dates with archaeological evidence for the presence of modern humans in Southeast Asia and Oceania by about 47,000 years,“ says Benjamin Peter from the Max Planck Institute for Evolutionary Anthropology and the University of Rochester. "Studying more ancient genomes from Eurasia and Oceania could further our understanding of when humans spread to these regions.“

Functional impact of Neandertal ancestry

To understand the functional legacy of Neandertal ancestry, the researchers examined changes in Neandertal ancestry across the genome and over time. They identified some Neandertal regions that are present at high frequency, possibly because they were beneficial as early modern humans began to explore new environments outside of Africa. "These include genes related to immune function, skin pigmentation and metabolism," says Manjusha Chintalapati from the University of California, Berkeley. "On the other hand, there are also large regions of the genome that are completely devoid of Neandertal ancestry. These regions formed rapidly after the gene flow and were also absent from the earliest modern human genomes, 30,000 to 45,000-year-old individuals. Many Neandertal sequences may have been deleterious to humans and were therefore actively and rapidly selected against by evolution.“

This study sheds light on the complex history of gene flow from Neandertals into modern humans. It also highlights the power of genomic data to elucidate the legacy of human migrations and gene flow.

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Journal

Science

DOI

10.1126/science.adq3010