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Lead author Maayan Lev (right) with colleagues during the excavations on Mount Carmel.
Photo Credit: © Reuven Yeshurun
Scientific Frontline: Extended "At a Glance" Summary: Snake Skin Frictional Properties
The Core Concept: Researchers have discovered that snake skin exhibits varying degrees of friction depending on the direction of movement and the part of the body, allowing for efficient forward motion while preventing backward slipping.
Key Distinction/Mechanism: Unlike typical materials where friction depends on the surface and the object, snake scales are highly structured with microscopic ridges and grooves, creating anisotropic friction. They slide smoothly forward but catch when pushed backward or sideways.
Major Frameworks/Components:
- Anisotropic Friction: Friction that varies depending on the direction of movement.
- Microstructure: The specific arrangement of micro-ornamentations (ridges and grooves) on the scales.
- Scale Variation: The frictional properties differ across the snake's body (ventral vs. dorsal scales) depending on their function in locomotion.
Branch of Science: Biomechanics, Biomimetics, Materials Science, Herpetology
Future Application: The findings could inspire the development of novel materials with directional friction properties for use in robotics, medical devices, or specialized coatings.
Why It Matters: Understanding the precise biomechanics of snake locomotion not only deepens our knowledge of animal movement but also provides a biological blueprint for engineering advanced materials with unique frictional characteristics.
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| A European glass lizard (also known as Sheltopusik). This species was an important part of the diet of the first sedentary humans on Mount Carmel around 15,000 years ago. Photo Credit: © Ryan van Huyssteen via iNaturalist.org (CC BY) |
Around 15,000 years ago, the way of life of human communities in the southern Levant underwent a fundamental change. Groups of hunter-gatherers, who until then had been nomadic, reduced their mobility and established small, permanent settlements for the first time. This culture, called the Natufian, is considered an important stage in the history of human sedentism, even before the development of agriculture. The reduced mobility also had an impact on people’s diets—they could no longer be as selective about their food resources as they had been before.
A new study published in the prestigious journal Proceedings of the National Academy of Sciences (PNAS) provides the first evidence that the people of the Natufian period hunted reptiles. “Lizards and snakes became an important part of their diet during this period,” says Dr. Maayan Lev, lead author of the study and a postdoctoral researcher in the “Kiel Training for Excellence” program (KiTE) at Kiel University (CAU).
Excavations of 15,000-Year-Old Settlements on Mount Carmel The study is based on excavations at the el-Wad Terrace archaeological site in the Nahal Me’arot Nature Reserve on Mount Carmel in Israel, and it includes 20 archaeological layers of repeated settlements over a period of around 3,000 years. Using the radiocarbon dating method, these layers were dated to between 15,000 and 12,000 years ago.
Dr. Lev, along with coauthors Professor Mina Weinstein-Evron and Professor Reuven Yeshurun of the University of Haifa, identified thousands of lizard and snake bones in the settlement layers at el-Wad Terrace.
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| Microscopic image of bone from an large whip snake (Dolichophis jugularis) showing cut marks. Photo Credit: © Maayan Lev |
“Through meticulous microscopic examinations, we were then able to distinguish reptile remains that died naturally at the site or were preyed upon by mammals and birds from those that served as food for humans,” explains Maayan Lev, who also conducts research at the Zinman Institute of Archaeology at the University of Haifa and is an associate member of the ROOTS Cluster of Excellence at Kiel University.
Traces of Flint Knives on Snake Bones For the first time ever, the researchers were able to identify cut marks left by flint knives at consistent locations on the bones of large snakes such as the large whip snake (Dolichophis jugularis) and the eastern Montpellier snake (Malpolon insignitus). In addition, there was indirect evidence of the consumption of the European glass lizard (Pseudopus apodus), whose hard scales required a different method of butchering from that used for snakes.
The team sought to understand why these particular species were chosen as food and why their relative abundance changed over the course of the settlement sequence. “Our hypothesis is that the Natufian people preferred to catch reptiles that were relatively large, relatively slow, and not dangerous. In other words, the glass lizard was an ideal choice, and if none could be found, the hunters would instead catch relatively harmless snakes. Venomous snakes such as vipers, on the other hand, were rarely caught,” explains Dr. Lev.
Fascinating Insights into Prehistoric Diets The high frequency of bones from the “more productive” reptile species, particularly the glass lizard, across all archaeological layers suggests that they constituted a reliable and sustainable food source even during periods of growth and population increase in the Natufian settlement. “These findings shed light on a hitherto little-studied aspect of the relationship between humans and reptiles in prehistory, and they provide a fascinating insight into the diet of humans before the start of the Neolithic period,” summarizes Maayan Lev.
Funding: The study was carried out as part of the sedentism origins research project, led by Professor Reuven Yeshurun and funded by the Israel Science Foundation.
Published in journal: Proceedings of the National Academy of Sciences
Title: Three millennia of lizard and snake consumption by Natufian foragers
Authors: Ma’ayan Lev, Mina Weinstein-Evron, and Reuven Yeshurun
Source/Credit: Kiel University
Edited by: Scientific Frontline
Reference Number: bio082026_01
