Evolutionary Insights by Anthropology.net

For decades, the story of Sumer—the world’s first urban civilization—has been told as one of rivers, irrigation, and ingenuity. It begins with the Tigris and Euphrates winding across a flat Mesopotamian plain, nourishing the fields of early farmers who would one day invent writing, law, and monumental architecture.

But a new study published in PLOS One suggests the reality was far stranger. Southern Mesopotamia, it turns out, was once a tidal world. The ancestors of Sumerian city-builders were not just farmers on a floodplain. They were navigating a restless delta where rivers met the sea and tides surged inland twice a day, pushing freshwater deep into what is now Iraq.

“Sumer was literally and culturally built on the rhythms of water,” said Liviu Giosan, senior scientist emeritus at Woods Hole Oceanographic Institution and lead author of the study. “The cyclical patterns of tides together with delta morphodynamics were deeply woven into the myths, innovations, and daily lives of the Sumerians.”

A World of Shifting Shores

Between 7,000 and 5,000 years ago, the Persian Gulf reached much farther inland. Where later generations would plow dusty fields, early Neolithic farmers lived in a tidal estuary. Short canals connected tidal creeks to plots of land. Twice a day, the incoming tide brought fresh water to irrigate fields and date groves without the need for vast infrastructure.

The tidal rhythm provided stability. Then, slowly, the delta began to build outward as sediment from the Tigris and Euphrates pushed the coastline farther from the interior. The dependable tides receded.

When the tides disappeared, so did the easy irrigation system. Farmers faced a crisis. Maintaining agriculture now required digging extensive canals and embankments, coordinating labor on a scale never before seen. The environmental shift was not just a nuisance—it was the crucible for social transformation.

“We often picture ancient landscapes as static,” said Reed Goodman, co-author and environmental archaeologist at Clemson University. “But the Mesopotamian delta was anything but. Its restless, shifting land demanded ingenuity and cooperation, sparking some of history’s first intensive farming and pioneering bold social experiments.”

The Birth of Cities and the Rise of Inequality

The response to this hydrological upheaval was monumental. Canals stretched across the plains. Temples became managers of water and labor, consolidating political and religious power. From these projects emerged the first true city-states—Uruk, Ur, and Lagash—and with them, the hallmarks of urban civilization: centralized authority, class hierarchies, and written record-keeping.

Flood myths echo these transformations. The water-centered Sumerian pantheon—Enki, god of wisdom and freshwater; Enlil, god of wind and storms—may preserve memories of a world in which tides dictated survival.

“The radical conclusions of this study are clear in what we’re finding at Lagash,” said Holly Pittman, director of the Penn Museum’s Lagash Archaeological Project. “Rapid environmental change fostered inequality, political consolidation, and the ideologies of the world’s first urban society.”

A Lesson for Today

The study underscores an unsettling reality: the first cities were born from an environmental crisis. When the natural irrigation of tides ended, humans had to build an artificial one. The effort produced civilization—but also entrenched inequality and ecological vulnerability.

“Our work highlights both the opportunities and perils of social reinvention in the face of severe environmental crisis,” Giosan noted. “Beyond this modern lesson, it is always surprising to find real history hidden in myth—and truly interdisciplinary research like ours can help uncover it.”

As modern cities confront rising seas and shifting climate zones, the story of Sumer offers both a warning and a paradox. Civilization, it seems, has always been built on unstable ground.

Additional Related Research

Here are closely related studies that complement this research:

* Altaweel, M. (2021). "Water, Society, and Ancient Urbanism: Hydrological Change and Resilience in Mesopotamia." Journal of Archaeological Research, 29(3), 321–359. https://doi.org/10.1007/s10814-021-09154-2

* Pournelle, J. R. (2003). "Marshland of Cities: Deltaic Landscapes and the Evolution of Early Mesopotamian Civilization." PhD Dissertation, University of California, San Diego. [Available via ProQuest]

* Hritz, C. (2010). "Tracing Settlement Patterns and Channel Systems in Southern Mesopotamia Using Remote Sensing." Journal of Field Archaeology, 35(2), 184–203. https://doi.org/10.1179/009346910X12707321358964

* Wilkinson, T. J. (2003). Archaeological Landscapes of the Near East. University of Arizona Press.

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Few fossils in Europe have sparked as much debate as the skull from Petralona Cave in northern Greece. Discovered in 1960, the nearly complete cranium seemed to belong to a hominin that was neither Homo sapiens nor Neanderthal. For decades, its age was anyone’s guess, with estimates ranging from 170,000 to 700,000 years old. A new study narrows that window considerably—and deepens the mystery of who this individual was.

Dating a Skull Without Dating the Bone

Bones alone often refuse to give up their secrets, particularly when it comes to age. In the damp environment of Petralona Cave, the original bone material lacked enough organic content for radiocarbon dating. Previous attempts using indirect methods produced wildly inconsistent results.

This time, researchers turned to uranium-series dating. Rather than the bone itself, they analyzed the calcite crust that had grown over the cranium while it sat in the cave. When water carrying dissolved uranium dripped onto the skull and dried, it left behind tiny layers of mineral deposits. Those deposits act like a clock: as uranium decays into thorium at a known rate, scientists can calculate how long the crust has been forming.

The innermost layer of calcite on the cranium provided a minimum age of 286,000 years, with a margin of ± 9,000 years. That doesn’t reveal when the individual died, only when the skull began accumulating calcite. It could have been resting there even earlier.

“The calcite tells us the latest possible time the skull was exposed to dripping water,” explains study co-author Christophe Falguères. “It’s a minimum bound. The fossil itself may be older.”

An Ancient Neighbor, Not Quite Us

Stratigraphic clues from elsewhere in the cave add more context. Speleothem layers in the chamber known as the Mausoleum suggest parts of the cave were forming over half a million years ago. That makes it plausible that the Petralona hominin lived during the later Middle Pleistocene—a period when Europe was home to a mosaic of human populations.

The morphology of the Petralona skull remains distinctive. It does not fit neatly with Neanderthals, nor with early Homo sapiens. Instead, researchers see affinities with more archaic hominins, possibly part of a lineage that coexisted alongside early Neanderthals in Europe.

“This fossil shows that human evolution in Europe was not a simple linear progression toward Neanderthals,” notes the team. “It suggests a complex population structure, with groups diverging and perhaps occasionally interacting.”

Why It Matters

Every new date for an old fossil ripples across our evolutionary timeline. If the Petralona skull truly falls between 286,000 and over 400,000 years old, it reinforces the picture of Europe as a patchwork of hominin populations long before modern humans entered the scene. It also underscores how traits we associate with Neanderthals or our own species may have evolved in parallel among different groups.

Further Reading & Related Research

* Hublin, J.-J., & Roebroeks, W. (2009). The prehistory of Neanderthals and modern humans in Eurasia. Science, 326(5949), 1081-1088. https://doi.org/10.1126/science.1181716

* Mounier, A., & Lahr, M. M. (2019). Deciphering African late Middle Pleistocene hominin diversity and the origin of our species. Nature Communications, 10, 3406. https://doi.org/10.1038/s41467-019-11213-w

* Stringer, C. (2012). The status of Homo heidelbergensis (Schoetensack 1908). Evolutionary Anthropology, 21(3), 101-107. https://doi.org/10.1002/evan.21311

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When maize first emerged from its wild ancestor, teosinte, in the valleys of central Mexico some 9,000 years ago, the transformation above ground was dramatic. Kernels once locked in hard, inedible shells swelled into soft, starchy grains. But below the surface, changes were equally crucial, if less visible.

A recent study in New Phytologist suggests that the roots of maize—those unseen structures binding plant to soil—were shaped by both human agricultural practices and natural shifts in climate and soil over thousands of years (Lopez-Valdivia et al. 2025).

“We reconstructed the root phenotypes of corn and teosinte, as well as the environments of the Tehuacán Valley… using a combination of ancient DNA, paleobotany and functional-structural modeling to reconstruct how root traits evolved over time,” said Jonathan Lynch, plant nutrition researcher and senior author of the study.

Roots in Deep Time

The researchers built their analysis around one of the most archaeologically rich regions of Mesoamerica: the Tehuacán Valley. Known for some of the earliest evidence of maize domestication, the valley’s soils and pollen records preserve traces of environmental change over the last 18,000 years.

By combining ancient DNA with computer simulations (the OpenSimRoot model), the team traced how maize roots shifted in step with climate pressures and changing cultivation techniques.

Three key evolutionary changes stood out:

* Fewer nodal roots – the shallow roots sprouting from the stem base declined, giving way to deeper foraging.

* The rise of multiseriate cortical sclerenchyma – a dense tissue that allows roots to penetrate harder, drier soils.

* More seminal roots – early-developing roots that anchor seedlings and extract nutrients in their most vulnerable stage.

These shifts suggest that maize adapted not only to human cultivation but also to fluctuating rainfall, soil degradation, and rising atmospheric CO₂.

Farming, Climate, and Root Evolution

The study identified three distinct phases of root evolution:

* 12,000–8,000 years ago: Rising CO₂ levels encouraged deeper rooting, helping early maize draw water and nutrients from below.

* Around 6,000 years ago: Irrigation spread through the valley, pushing nitrogen deeper into the soil. Maize with tissues designed for deep penetration thrived.

* By 3,500 years ago: Agricultural intensification and soil depletion made early root systems critical. More seminal roots appeared, ensuring seedlings could establish quickly in stressed soils.

“The research suggests that root phenotypes that enhance plant performance under nitrogen stress were important for corn adaptation to changing agricultural practices,” explained lead author Ivan Lopez-Valdivia.

Archaeology Meets Plant Science

For archaeologists, the study adds a subterranean layer to the story of domestication. While charred cobs and grinding stones document maize’s role above ground, roots rarely leave direct traces. Yet, by reconstructing their evolution, the study ties together environmental shifts, human subsistence, and the biology of a crop that now feeds much of the planet.

The findings also highlight how the plant-human relationship was not one-sided. Farmers selected plants for larger kernels, but soils and climate nudged the species in directions that would prove essential for long-term survival.

Looking Forward

As maize remains one of the most widely planted crops today, the ancient dance between roots, soils, and human cultivation may offer lessons for the future. Rising CO₂ and shifting rainfall patterns once again threaten crop stability. Understanding how ancient maize adapted to change could help guide breeding programs today.

“That’s not only interesting historically… it also gives some guidance as to what we can do with corn roots in the future to make them better adapted to developing conditions,” Lynch noted.

Related Research

* Piperno, D. R., Ranere, A. J., Holst, I., & Hansell, P. (2000). Starch grains reveal early root crop horticulture in the Panamanian tropical forest. Nature, 407(6806), 894–897. https://doi.org/10.1038/35038055

* Kistler, L., Maezumi, S. Y., de Souza, J. G., Przelomska, N. A., Costa, F. M., Smith, O., & Allaby, R. G. (2018). Multiproxy evidence highlights a complex evolutionary legacy of maize in South America. Science, 362(6420), 1309–1313. https://doi.org/10.1126/science.aav0207

* Wang, H., Studer, A. J., Zhao, Q., Meeley, R., & Doebley, J. F. (2015). Evidence that the origin of naked kernels during maize domestication was caused by a single amino acid substitution in teosinte glume architecture1. Genetics, 200(3), 965–974. https://doi.org/10.1534/genetics.115.176651

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In the foothills of Uzbekistan’s Tien Shan mountains lies a rock shelter that may hold a surprising chapter in human technological history. Excavations at Obi-Rakhmat have revealed stone fragments that researchers argue were likely parts of projectiles, possibly even arrowheads, dating to nearly 80,000 years ago. If confirmed, this would place the origins of bow-and-arrow technology tens of thousands of years earlier than many archaeologists once believed.

The study, published in PLOS ONE, combines microscopic wear analysis and experimental archaeology to assess whether small stone points excavated from the site could have been used as hunting weapons.

“The presence of fractured micropoints in these layers suggests they were mounted on shafts and used as projectiles,” the authors write. “Their size and morphology make them most consistent with arrow-like tips rather than heavy spearheads.”

The site and its layers

Obi-Rakhmat sits in the Paltau valley at the southwestern edge of the Talassky Alatau range. Archaeological deposits at the site span 21 sedimentary levels across ten meters, covering a timeframe between about 90,000 and 40,000 years ago. Layers 20 and 21, the oldest excavated so far, yielded a trove of lithics: nearly 200 small triangular flakes and 194 point specimens, some shaped using Levallois reduction techniques.

Of these, 20 pieces were set aside as possible weapon tips. Researchers began with macroscopic observations of impact-related breakage, then moved to stereoscopic and reflective optical microscopy to examine surface wear.

Experiments with ancient tools

To test their hypotheses, the team replicated the tools using local silicified limestone and mounted them on wooden shafts. Using a 36-pound laminated bow, they shot these experimental armatures at a small ungulate carcass. The results were telling: several of the stone points fractured on impact in ways that matched the archaeological specimens.

The study identified three classes of possible armatures: large retouched points (likely used as spear tips), bladelets that may have served as inserts, and the most intriguing—micropoints, small triangular flakes averaging just 18 millimeters wide and often weighing little more than a gram.

These micropoints showed microscopic impact traces consistent with high-velocity penetration, making them unlikely candidates for thrusting spears. Instead, their lightweight design fits better with arrows.

What this means for human evolution

If the interpretation is correct, Obi-Rakhmat would push the use of arrow-like projectiles back to 80,000 years ago, deep within the Middle Paleolithic. That predates the commonly accepted timeline for bow-and-arrow technology, usually associated with Homo sapiens populations in Africa around 60–70,000 years ago.

This raises the question of who the makers were. Fossils from Obi-Rakhmat include remains with both Homo sapiens and Neanderthal-like traits, fueling debate over whether the occupants were an admixed population. The projectile evidence now adds another layer to the mystery, suggesting that complex weapon systems may have been present in Central Asia earlier than expected.

“Evidence for small, lightweight armatures at Obi-Rakhmat demonstrates the possibility of diverse hunting strategies during the Middle Paleolithic,” the authors note, “challenging assumptions that complex projectile technology only emerged during the Upper Paleolithic.”

For archaeologists and anthropologists, the implications extend beyond weaponry. Projectile technology has long been linked to shifts in social organization, cooperative hunting, and even cognitive planning. If arrows were part of the toolkit this early, the behavioral capacities of hominins in Central Asia may need to be re-evaluated.

Open questions

The evidence is still limited, and the researchers themselves stress the need for larger samples to confirm the findings. It remains unclear whether these tools were widely used for hunting or represent early experiments with new technology. Further excavations may help establish whether such lightweight projectiles persisted in later layers, bridging the Middle to Upper Paleolithic transition.

Related Research

* Villa, P., & Soriano, S. (2010). Hunting weapons of the Middle Stone Age and the Middle Paleolithic: spear points from Sibudu, South Africa, and comparable assemblages. Journal of Archaeological Science, 37(3), 309–331. https://doi.org/10.1016/j.jas.2009.09.043

* Shea, J. J. (2006). The origins of lithic projectile point technology: evidence from Africa, the Levant, and Europe. Journal of Archaeological Science, 33(6), 823–846. https://doi.org/10.1016/j.jas.2005.10.015

* Sisk, M. L., & Shea, J. J. (2009). Experimental use and quantitative performance analysis of triangular flakes (Levallois points) as projectile weapon tips. Journal of Archaeological Science, 36(9), 2039–2047. https://doi.org/10.1016/j.jas.2009.05.023

* Lombard, M., & Phillipson, L. (2010). Indications of bow and stone-tipped arrow use 64,000 years ago in KwaZulu-Natal, South Africa. Antiquity, 84(325), 635–648. https://doi.org/10.1017/S0003598X00100134

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Almost three decades ago, archaeologists uncovered a prehistoric mining complex in the Krumlov Forest of southern Czechia. The site’s shafts reached depths of eight meters, carved into the earth in search of chert, a fine-grained stone valued for blades, axes, and daggers. For years, the emphasis rested on the mining techniques themselves—until researchers encountered burials sealed within the shafts.

A new study published in Archaeological and Anthropological Sciences describes three individuals interred in one of these mining features: two adult women and a newborn. Their remains provide rare testimony to the lives of prehistoric miners and to the ritual landscapes surrounding resource extraction in the Neolithic and Eneolithic of Central Europe.

“Together with the Mauer burials in Vienna, the Krumlov Forest individuals are the oldest European mine graves known to date,” writes Eva Vaníčková and her colleagues.

Hard Lives Underground

The two adult women, designated H1/2002 and H2a/2002, were between 30 and 40 years old. Their skeletons bore the unmistakable traces of hard labor: vertebrae marked by osteophytes and Schmorl’s nodes, spines bent by hyperkyphosis, and muscle attachments enlarged from years of repetitive strain.

These signs point to lives spent working in forward-bent positions, consistent with mining in narrow shafts. One woman’s ulna showed evidence of a fracture that had never healed properly, suggesting she continued working despite injury.

Stable isotope analysis revealed another layer of detail. Both women were locals and consumed diets richer in animal protein than most Neolithic populations in the region. The researchers suggest that such a diet may have been deliberate—sustenance intended to maintain the physical endurance required for mining work.

Kinship and Separation

DNA analysis revealed that the two women were related, likely siblings. Both bore signs of stress during childhood, visible in Harris lines and enamel defects. Their shared trajectory of hardship seems to have continued into adulthood, ending in a shaft dug for stone rather than a grave prepared for ancestors.

The newborn, by contrast, was not biologically related. Genetic testing showed no direct kinship to the two women. The child had died at full term but for reasons unknown was buried alongside the miners. The placement invites speculation: Was the newborn part of a ritual dedication? Or was the interment symbolic, tying fertility, death, and the subterranean world together in one act?

Stone, Symbol, and Sacrifice

Chert was not a rare resource. In fact, it could often be collected from the surface. Its value, then, may have been less about practicality than symbolism. Chert blades and axes appear in ritual deposits across Neolithic Europe, often linked with prestige and ancestral meaning.

As Vaníčková and colleagues note:

“The practical value of the mined chert was minimal, as it could be collected on the surface. However, it is questionable whether people associated the stone from the depths of the earth with some ancestral legacy, meaning that its value was subjective.”

If chert was seen as a material bound to the underworld or ancestral powers, then miners themselves may have been drawn into that cosmology. The burial of the two women in the shaft may not have been accidental or pragmatic. It may have been a symbolic act—returning the miners, and their labor, to the earth.

Gender and Power in the Eneolithic

Why women? The evidence suggests these individuals did not choose their path. The unhealed fracture hints at coercion. Some scholars propose that as male roles expanded in Eneolithic societies, women may have been forced into arduous labor such as mining. Strength was no longer the main criterion; vulnerability to compulsion may have been.

This interpretation positions the Krumlov Forest burials within broader debates about gender, labor, and inequality in prehistoric Europe. Were women exploited as expendable labor in the mines? Or were they ritual specialists whose work carried symbolic importance? The burial of a newborn alongside them only deepens the enigma.

Questions Still Buried

The Krumlov Forest shaft preserves more than bones and stones. It holds questions that cut to the core of prehistoric life: Who mined the earth’s resources, and under what conditions? How did societies assign meaning to the extraction of stone? And how were miners themselves integrated—or sacrificed—into those beliefs?

As more multidisciplinary analyses are applied to such burials, the silent record of labor, kinship, and ritual carved into bones and isotopes will continue to speak.

Related Research

* Knutsson, H., Knutsson, K., Apel, J., & Glørstad, H. (2018). “Technology of the Sacred: Neolithic Axes and the Materialization of Cosmology in Scandinavia.” Antiquity, 92(364), 1439–1455. https://doi.org/10.15184/aqy.2018.148

* Sørensen, M. L. S. (2013). Gender Archaeology. Polity Press.

* Turek, J. (2015). “Ritualized Practices in the Neolithic Mining of Central Europe.” Documenta Praehistorica, 42, 255–267. https://doi.org/10.4312/dp.42.17

* Borić, D. (2007). “Body Metaphors and Technologies of Transformation in the Neolithic of the Balkans.” Cambridge Archaeological Journal, 17(3), 321–339. https://doi.org/10.1017/S0959774307000412

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The Inca Empire has long been remembered for its roads, terraces, and administrative reach. But at the heart of its bureaucracy was something deceptively simple: knotted cords called khipus. These bundles of string encoded census data, tribute, calendrical cycles, and perhaps even narratives. For centuries, scholars assumed that only trained specialists from noble families, the khipukamayuqs, could construct and interpret them.

A recent study published in Science Advances offers evidence that this assumption may not hold. Within the braids of one particularly fine khipu—radiocarbon dated to around 1498—researchers discovered a 104-centimeter-long strand of human hair. Isotopic analysis of that hair points not to an elite administrator, but to an ordinary Andean highlander.

“It was a complete shock,” said anthropologist Sabine Hyland, one of the study’s authors. “The results pointed to the diet of a commoner.”

A Khipu Like No Other

The khipu in question surfaced in a German auction house with little provenance. Yet its craftsmanship stood out. The cords were tightly spun, with delicate variation in size and braid—features often associated with state administration or elite ritual. Hyland recalled her first impression:

“This is so beautiful, it must be royal.”

But the evidence woven into its fibers told another story. The central cord was formed not from camelid or cotton fibers, as is typical, but from human hair, folded and twisted to reach its length. At 104 centimeters, it represented over eight years of uninterrupted growth.

Tracing a Life in Strands

The team subjected the hair to isotopic analysis, measuring the ratios of carbon, nitrogen, and sulfur along its length. These chemical signatures revealed a diet dominated by potatoes and other tubers, supplemented with greens, but with little maize, meat, or fish.

Such a profile is consistent with life in the Andean highlands, far from coastal trade and the luxury foods enjoyed by elites. Inca nobles typically had access to maize beer (chicha), camelid meat, and preserved fish throughout the year. The absence of these markers suggests the hair came from a person of modest social standing.

Who Could Knot the State’s Knowledge?

Colonial chronicles describe khipu production as the preserve of trained male bureaucrats. These khipukamayuqs were said to be drawn from noble families, entrusted with recording population counts, tribute obligations, and histories of conquest. If so, then the discovery of commoner participation calls for a revision of this rigid model.

There are alternative explanations. The hair might not belong to the khipu’s maker. Yet ethnographic and colonial accounts from the Andes describe hair as a marker of authorship and responsibility, often attached to ritual offerings or records. To give one’s hair was to give one’s essence.

“It must have been something pretty special for the person to sacrifice their hair,” Hyland noted. “My guess is that it was [used for] recording ritual offerings.”

This interpretation suggests that commoners may not only have contributed to the physical making of khipus, but also to the symbolic practices tied to them.

Literacy, Power, and Memory in the Inca World

If commoners did participate in khipu production, it complicates the sharp divide between elite literacy and popular illiteracy often drawn in discussions of pre-Columbian states. Instead, knowledge may have circulated in more layered ways, with ritual and symbolic practices weaving ordinary individuals into the state’s bureaucratic fabric.

For archaeologists and anthropologists, the find raises new questions:

* Who held the authority to inscribe meaning into cords?

* Was participation broader than Spanish chroniclers suggested?

* And how should scholars interpret the relationship between the state’s centralized recordkeeping and the lives of the people whose materials became part of it?

The answers may lie in more than just the knots. They may also reside in the fibers themselves—in the organic traces of lives lived in the shadow of empire.

Related Research

* Urton, G. (2003). Signs of the Inka Khipu: Binary Coding in the Andean Knotted-String Records. University of Texas Press.

* Hyland, S. (2016). “Writing with Twisted Cords: The Inscriptive Capacity of Andean Khipus.” Current Anthropology, 57(3), 278–305. https://doi.org/10.1086/686284

* Urton, G., & Chu, P. (2015). “Narrative Threads: Accounting and Recounting in Andean Khipu.” University of Texas Press.

* Quilter, J., & Urton, G. (Eds.). (2002). Narrative Threads: Accounting and Recounting in Andean Khipu. University of Texas Press.

* Salomon, F. (2004). The Cord Keepers: Khipus and Cultural Life in a Peruvian Village. Duke University Press.

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What makes the human brain so different from that of our closest relatives? The answer is not found in a single gene but in stretches of DNA that regulate when and how other genes turn on. A new study from the University of California San Diego identifies one such region, a molecular “switch” called HAR123, that may have tilted our evolutionary trajectory toward greater flexibility of thought.

The findings, published in Science Advances, suggest that HAR123 influenced how our developing brains balanced the production of neurons and glial cells, two fundamental building blocks of neural circuits. That balance, in turn, may have opened the door to cognitive adaptability, the capacity to revise old information and learn new rules—a trait that sets humans apart from other primates.

“HAR123 is not a gene in itself, but a powerful enhancer that shapes the activity of other genes during brain development,” said senior author Miles Wilkinson, UC San Diego School of Medicine.

A Region That Evolved in the Fast Lane

HAR123 belongs to a class of DNA sequences known as human-accelerated regions (HARs). These are parts of the genome that remained largely unchanged across millions of years of mammalian evolution, only to undergo a burst of rapid mutations after the lineage leading to humans split from that of chimpanzees roughly 5 to 6 million years ago.

That burst of change suggests selective pressures were at play. Instead of drifting randomly, HARs likely carried alterations that offered advantages in cognition, development, or adaptation. In the case of HAR123, the research team found that its human-specific sequence drove stronger activity than the chimpanzee version when tested in neural progenitor cells.

These progenitor cells are the stem-like precursors that generate both neurons, responsible for processing information, and glia, which support and regulate neural networks. By tweaking how many of each type are produced, HAR123 may have fine-tuned the architecture of the human brain.

Cognitive Flexibility and the Human Condition

The study suggests HAR123 promoted an especially human trait: cognitive flexibility. This is the ability to discard outdated knowledge, adopt new strategies, and switch between modes of thinking. Archaeological records, from the appearance of new stone tool traditions to shifts in symbolic expression, reflect the importance of this trait throughout human prehistory.

“Our data suggest HAR123 may have contributed to the neural substrate that makes cognitive flexibility possible,” said co-author Kun Tan.

When the human and chimpanzee versions of HAR123 were compared in lab-grown stem cells, the enhancer shaped gene activity differently in each case. The human version promoted more dynamic regulation of neural progenitors, potentially granting our brains a broader repertoire of cell types and connections.

From Evolution to Disorder

The same molecular pathways that fueled the rise of human cognition may also underlie certain vulnerabilities. The authors note that HAR123, and HARs more broadly, are linked to neurodevelopmental conditions such as autism. While HAR123’s human-specific changes may have facilitated adaptability, they may also have introduced susceptibilities that our species continues to live with today.

Why This Matters for Human Origins

For anthropologists and archaeologists, HAR123 provides a molecular foothold for one of the most elusive questions in human evolution: how small tweaks in DNA rewired the brain. Unlike fossils or artifacts, enhancers such as HAR123 do not leave visible traces in the ground. Yet they may explain why our ancestors were capable of innovation, from Acheulean handaxes to Upper Paleolithic cave art.

In this sense, HAR123 bridges the molecular and the cultural, linking mutations in a regulatory sequence to the behaviors that define our lineage.

Related Research

* Pollard, K. S., et al. (2006). “An RNA gene expressed during cortical development evolved rapidly in humans.” Nature, 443(7108), 167–172. https://doi.org/10.1038/nature05113

* Hubisz, M. J., & Pollard, K. S. (2014). “Exploring the genesis and functions of Human Accelerated Regions sheds light on their role in human evolution.” Current Opinion in Genetics & Development, 29, 15–21. https://doi.org/10.1016/j.gde.2014.07.005

* Doan, R. N., et al. (2016). “Mutations in human accelerated regions disrupt cognition and social behavior.” Cell, 167(2), 341–354.e12. https://doi.org/10.1016/j.cell.2016.08.071

* Capra, J. A., et al. (2013). “Many human accelerated regions are developmental enhancers.” Philosophical Transactions of the Royal Society B, 368(1632), 20130025. https://doi.org/10.1098/rstb.2013.0025

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In a shallow gully on Kenya’s Homa Peninsula, scattered among ancient sediments, lie clues to a behavior that would eventually become distinctly human: carrying the right tools to the right place, even if that meant hauling them across many miles.

A recent study in Science Advances reports that early Oldowan toolmakers at Nyayanga, active at least 2.6 million years ago, selectively transported large, durable cobbles from sources up to 13 kilometers away. These stones—quartzite, rhyolite, and other tough rock types—were brought to a site where hominins processed plants, butchered hippopotamuses, and performed heavy pounding tasks. The research pushes back the earliest known evidence of such long-distance raw material transport by more than half a million years.

“The knowledge and intent to bring stone material to rich food sources was apparently an integral part of toolmaking behavior at the outset of the Oldowan,” said Rick Potts, co-author and head of the Smithsonian’s Human Origins Program.

A Landscape Without the Right Stones

The Homa Peninsula’s local geology posed a problem for toolmakers. Nearby rocks, altered by ancient volcanic processes, were softer and prone to shattering. For pounding through bone or slicing meat, they dulled too quickly. Instead, the Nyayanga hominins sought tougher material from river systems in the eastern highlands—stone that never naturally reached the peninsula.

Geochemical analysis revealed that more than 70 percent of the Nyayanga tools were made from nonlocal stone, much of it traceable to the Oboro region of the Awach Tende river basin, about 13 kilometers away. These cobbles were large, often exceeding 10 centimeters, and ideal for producing sharp-edged flakes or enduring repeated pounding.

“Nyayanga hominins were selective,” said lead author Emma Finestone of the Cleveland Museum of Natural History. “They bypassed smaller, poorer-quality stones in favor of bigger, better raw materials from far afield.”

Not Just Tools—Mental Maps

The distance alone is telling. While chimpanzees and other primates occasionally move stones, their transport distances rarely exceed a few kilometers. The Nyayanga toolmakers went far beyond that. The pattern of raw material use does not match the gradual “distance decay” seen when animals pick up and discard tools opportunistically. Instead, it suggests purposeful transport with minimal use en route—stones were carried intact to the site, where they were worked and discarded.

The behavior implies something important: a mental map of the landscape that linked distant raw material sources with predictable food-processing locations.

Whose Hands Held the Tools?

At Nyayanga, the tools were found alongside fossilized teeth from Paranthropus—a robust-jawed hominin traditionally not viewed as a habitual toolmaker. Whether these teeth belonged to the toolmakers remains uncertain, but their presence complicates the once neat division between Homo as the toolmaker and other hominins as tool users.

“Unless you find a hominin fossil actually holding a tool, you can’t be certain,” said Finestone. “But Nyayanga suggests a greater diversity of hominins making early stone tools than previously thought.”

Why It Matters

By at least 2.6 million years ago, hominins were integrating tool transport into their foraging strategies. This was not a matter of picking up whatever was at hand—it was deliberate provisioning, anticipating future needs, and linking separate parts of a landscape into a single behavioral system. The same strategy appears again 600,000 years later at another Homa Peninsula site, Kanjera South, suggesting it was a persistent feature of local hominin life.

In the words of Potts, “The mental maps of the oldest known hominins to persistently make stone tools well surpassed their immediate surroundings, even surpassing a few miles.”

Related Research

* Braun, D. R., et al. (2008). “Oldowan behavior and raw material transport: Perspectives from the Kanjera Formation.” Journal of Human Evolution, 55(3), 409–430. https://doi.org/10.1016/j.jhevol.2008.05.004

* Harmand, S., et al. (2015). “3.3-million-year-old stone tools from Lomekwi 3, West Turkana, Kenya.” Nature, 521, 310–315. https://doi.org/10.1038/nature14464

* Panger, M., et al. (2002). “Older than the Oldowan? Rethinking the emergence of hominin tool use.” Evolutionary Anthropology, 11(6), 235–245. https://doi.org/10.1002/evan.10094

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The magnificent pyramids and sprawling plazas of the Maya Terminal Classic period stand today as monuments to a complex, ingenious civilization. Yet, for all their architectural splendor, many of these centers were abandoned between the eighth and tenth centuries C.E., their societies faltering in a decline that has puzzled scholars for generations. The reasons behind this societal unraveling are a mosaic of competing theories, from warfare and disease to shifting trade routes. But among the many explanations, a picture of a civilization at the mercy of its own climate has become increasingly clear.

New research, published in Science Advances, adds a stunning layer of detail to this picture by providing a month-by-month look at rainfall during the last centuries of the Classic period. By studying a stalagmite from a cave in Mexico's Yucatán Peninsula, a team of researchers has mapped out a series of brutal, prolonged droughts that may have tipped the balance for an already stressed civilization. The stalagmite, in essence, is a stone diary of the region’s ancient climate, recording years of extreme dryness that align with archaeological evidence of societal turmoil.

A New Way to Read the Past

Like the concentric circles of a tree stump, stalagmites grow in layers, each one a record of a specific time. They form when water drips from a cave ceiling, carrying dissolved minerals that precipitate over time. By meticulously analyzing the oxygen isotopes trapped within these mineral layers, scientists can reconstruct the environment in which the stalagmite grew. Heavier oxygen isotopes indicate drier conditions, as more of the lighter isotopes would have evaporated from the surface water before it could seep through the ground.

While previous studies have used lake sediments and other speleothems to establish a link between drought and the Maya collapse, this new research offers a more granular perspective. The thick annual layers of the stalagmite allowed researchers to differentiate between wet and dry seasons, a crucial distinction for understanding an agrarian society.

"Knowing the average annual rainfall doesn’t tell us as much as knowing what each rainy season was like. Being able to isolate the rainy season allows us to accurately track the duration of the drought from the rainy season, which is what determines the success or failure of crops."

This detailed seasonal data revealed that between 870 and 1100 C.E., the Yucatán experienced at least eight multiyear droughts, one of which stretched for an unprecedented 13 consecutive years. This was far more than a simple dry spell. Maize, the staple crop of the Maya, is particularly sensitive to changes in the rainy season. A short drought might cause supply issues, but the extreme droughts documented in this study could have dropped crop yields to a tenth of their normal levels.

A Civilization's Response to Climatic Stress

The climatic data from the stalagmite aligns with a wealth of archaeological evidence. Inscriptions on commemorative stone monuments—a key form of public record for the Maya—stopped at various sites during these periods of severe climate stress. The construction of new buildings also ceased, suggesting that society's focus had shifted from monumental public works to more immediate matters of survival.

Yet, not all cities were affected equally. While Uxmal appears to have been abandoned at the end of this period, another major city, Chichén Itzá, continued to prosper for a time. This divergence suggests different social responses to the same climatic pressures.

"The differences between sites reflect different social responses to drought. Chichén Itzá had a wide range of trade networks and was highly centralized, which would have allowed for the accumulation or importation of resources in times of scarcity."

The resilience of some cities over others highlights the fact that climate was not the sole cause of the collapse. Rather, it was a critical factor that exacerbated existing social, political, and economic vulnerabilities. A society dependent on rain-fed agriculture simply could not sustain a large population through years of chronic drought.

However, some scholars argue that this perspective places too much emphasis on annual crops like maize, beans, and squash. They suggest that the Maya were more resourceful and resilient than this.

"There is a marked difference between the food plants available during moderate and extreme drought. While most annual species will not produce enough, a wide variety of nutritious perennial food plants would."

This alternative view holds that the Maya had a diverse diet that included numerous drought-resistant perennial species, which would have continued to provide food even during a moderate drought.

Ultimately, the new research provides a powerful tool for understanding this complex history. By offering a detailed, chronological record of ancient rainfall, it allows scholars to compare climate data with archaeological records and human responses on an unprecedented scale, moving the conversation forward from a simple explanation to a nuanced understanding of a civilization's long, hard winter.

Additional Research

* Fedick, S. L., & Santiago, L. S. (2021). Large variation in availability of Maya food plant sources during ancient droughts. Proceedings of the National Academy of Sciences, 118(50), e2115657118. This study counters the maize-centric view, arguing that the Maya had a diverse array of drought-resistant food plants that would have provided sustenance during dry periods. DOI: 10.1073/pnas.2115657118

* Hodell, D. A., Curtis, J. H., & Brenner, M. (1995). Possible role of climate in the collapse of Classic Maya civilization. Nature, 375(6526), 39-42. This is a foundational paleoclimate study that used lake sediment cores from Lake Chichancanab to provide early evidence of a major drought coinciding with the Classic Maya collapse. DOI: 10.1038/375039a0

* Gill, R. B. (2000). The Great Maya Droughts: Water, Life, and Death. University of New Mexico Press. This book provides a comprehensive review of the evidence for drought as a major factor in the Maya collapse, drawing on a wide range of paleoclimatic, archaeological, and historical data. ISBN: 978-0826327774

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The badlands of Ethiopia’s Afar region are a place where deep time lies close to the surface. Here, in a landscape scarred by faults and volcanic ash, a team from the Ledi-Geraru Research Project has recovered fossils that place two early human relatives—one belonging to the genus Homo and another to a previously unknown species of Australopithecus—side by side, between 2.6 and 2.8 million years ago.

It is a period when rivers meandered through grasslands, shallow lakes filled and receded, and volcanoes periodically blanketed the terrain in ash. That ash would become the clock by which these fossils could be dated.

“Human evolution is not linear — it's a bushy tree; there are life forms that go extinct,” said Kaye Reed, paleoecologist at Arizona State University and co-director of the project.

Fossils in the Ash

The discovery consists of 13 teeth—each small, but packed with information. By comparing their shapes and sizes, the team concluded that some belonged to early Homo, while others fit no known species of Australopithecus. Notably absent were any fossils of Australopithecus afarensis, the species of the famous “Lucy,” supporting the idea that her kind had already disappeared by 2.95 million years ago.’’

This same site yielded the oldest known Homo jaw in 2013, also dated to 2.8 million years ago. The teeth strengthen the case that our genus had already emerged by this time, living alongside other hominins.

“The new finds of Homo teeth from 2.6–2.8 million years ago confirm the antiquity of our lineage,” said Brian Villmoare, the study’s lead author.

Dating the Ancient Landscape

In Afar, the dating method is as much geological as it is archaeological. Volcanic eruptions scattered ash layers rich in feldspar crystals. By measuring isotopes in these crystals, scientists can pinpoint when the eruptions occurred, then bracket the fossils between layers above and below.

“We know that these fossils are interbed between those eruptions, so we can date units above and below the fossils,” explained Christopher Campisano, a geologist on the team.

This precise dating is critical, not only for placing the fossils in time but also for reconstructing the environment in which these hominins lived—a mosaic of wetlands, riverbanks, and open grasslands.

Parallel Lives

If early Homo and this new Australopithecus species shared the same landscape, questions follow. Did they compete for food or shelter? Did they interact? Was one more adaptable than the other, and did that difference determine which lineage endured?

To begin answering these questions, the team is analyzing the enamel of the teeth to reconstruct diet. Were they both eating tough, fibrous vegetation, or did one species favor meat or softer plant foods?

The answers may illuminate how multiple hominin species could coexist—a pattern repeated later with Homo sapiens and Neanderthals.

The Search Continues

No species name has yet been proposed for the new Australopithecus; teeth alone are not enough. More fossils will be needed—especially skulls or limb bones—to reveal how this species moved, fed, and perhaps thought.

“More fossils will help us tell the story of what happened to our ancestors a long time ago,” Reed said.

For now, the Ledi-Geraru finds remind us that the path to modern humans was never a straight line. It was a braided stream of lives and lineages, some of which merged into our story, and others that vanished, leaving only traces in the dust.

Related Research

* Haile-Selassie, Y., Melillo, S. M., & Su, D. F. (2016). Two new early Australopithecus afarensis fossils from the Dikika Research Area, Ethiopia. Journal of Human Evolution, 99, 1–17. https://doi.org/10.1016/j.jhevol.2016.06.006

* Villmoare, B., Kimbel, W. H., Seyoum, C., Campisano, C. J., DiMaggio, E. N., Rowan, J., ... & Reed, K. E. (2015). Early Homo at 2.8 Ma from Ledi-Geraru, Afar, Ethiopia. Science, 347(6228), 1352–1355. https://doi.org/10.1126/science.aaa1343

* Antón, S. C., Potts, R., & Aiello, L. C. (2014). Evolution of early Homo: An integrated biological perspective. Science, 345(6192), 1236828. https://doi.org/10.1126/science.1236828

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