Abiogenesis News - Closing Another of Creationism's God-Shaped Gaps - Still No God Found

Formation of polyester protocells under early Earth-like conditions Polyester microdroplets, possible precursors to life, were formed from alpha-hydroxy acids (αHAs) in early Earth-like conditions even at low reaction volume, low reactant concentrations, and/or high NaCl or KCl concentrations.

Credit: Associate Professor Tony Z. Jia

How life’s building blocks took shape on early Earth: the limits of membraneless polyester protocell formation – ELSI｜EARTH-LIFE SCIENCE INSTITUTE

Creationism’ ever-shrinking little god that sits in the abiogenesis gap, just got smaller with the news that researchers led by PhD student Mahendran Sithamparam of the Space Science Center (ANGKASA), Institute of Climate Change, National University of Malaysia, working at the Earth-Life Science Institute (ELSI) in the Institute of Science, Tokyo, Japan, have shown how primitive protocells could have formed under a wide range of realistic probiotic Earth conditions. The research team included scientists from Taiwan and China.

The research showed that membraneless protocells could have formed by polymerization of alpha-hydroxy acids (αHAs) to form polyester microdroplets, not to be confused with the modern plastic polyester. These polymers were polymers of esters - simple organic compounds which are chemically similar to the monomers that make modern polyester fibres.

Tell me all about micro polyester droplets as possible early protocells. Micro polyester droplets have recently been investigated as potential early protocells due to their ability to form spontaneously in prebiotic conditions and exhibit behaviours that mimic some cellular properties. Here’s a detailed breakdown:

1. What Are Micro Polyester Droplets?
   Micro polyester droplets are tiny, membraneless liquid-like structures composed of polyester molecules. Polyesters are a class of polymers that can form via simple condensation reactions between hydroxy acids or polyhydroxy-polycarboxylic acids, which could have been abundant on early Earth.
2. Why Are They of Interest in Protocell Research?
   The origin of life research has long been interested in how early protocells might have formed before the advent of phospholipid membranes. Traditional models include fatty acid vesicles, but recent studies suggest that polymer-based droplets, such as micro polyester droplets, could have played a role. They are particularly interesting because:
   • They **form spontaneously** under plausible prebiotic conditions.
   • They can **sequester biomolecules** like RNA and proteins, potentially aiding primitive metabolism.
   • They exhibit **phase separation**, which allows concentration and compartmentalization of biochemical reactions, a key prerequisite for cellular life.
3. Formation Under Prebiotic Conditions
   Researchers have demonstrated that polyester droplets can form in environments mimicking early Earth. This could occur in:
   • Hydrothermal vents where temperature fluctuations drive condensation reactions.
   • Shallow pools with cycles of wet-dry conditions, which promote polymerization.
   • Areas rich in hydroxy acids, which could be produced abiotically via atmospheric or hydrothermal chemistry.
4. Chemical Properties and Stability
   
   • Polyester droplets are more **chemically robust** than lipid vesicles, which are sensitive to changes in pH and salinity.
   • They are **highly dynamic**, meaning they can fuse, divide, and change size—behaviours reminiscent of primitive cell-like compartments.
   • They can **absorb and concentrate organic molecules**, including amino acids and nucleotides, which could facilitate early biochemical evolution.
5. Relevance to the RNA World Hypothesis
   A major challenge for the RNA world hypothesis is how RNA molecules could have been concentrated and protected from degradation. Micro polyester droplets provide a potential solution:
   • They can **selectively encapsulate RNA**, providing a stable environment for early replication.
   • They offer **compartmentalization**, a crucial step toward molecular evolution and the emergence of self-sustaining reactions.
   • Some studies suggest they could support **primitive metabolic cycles** by allowing localized chemical reactions.
6. Comparison to Other Protocell Models
   
   Feature
   1. Stability
      • Polyester Droplets: High
      • Fatty Acid Vesicles: Moderate
      • Coacervates: High
   2. Formation Ease
      • Polyester Droplets: Simple polymerization
      • Fatty Acid Vesicles: Requires amphiphiles
      • Coacervates: Require charges polymers
   3. RNA Compatibility
      • Polyester Droplets: High
      • Fatty Acids Vesicles: Moderate
      • Coacervates: High
   4. Dynamic Behaviour
      • Polyester Droplets: Yes
      • Fatty Acid Vesicles: Limited
      • Coacervates: Yes
   5. Enclosure of Molecules
      • Polyester Droplets: Strong
      • Fatty Acid Vesicles: Weak
      • Coacervates: Strong
7. Possible Pathways to True Cellular Life
   If micro polyester droplets played a role in early life, they could have eventually given way to more complex protocells by:
   1. Incorporating **primitive catalysts**, such as metal ions or ribozymes, to drive chemical reactions.
   2. Developing **membrane-like structures**, either by merging with lipids or evolving into amphiphilic polymers.
   3. Enabling **genetic material replication**, forming a link between compartmentalization and genetic evolution.
8. Challenges and Open Questions
   
   • How did these droplets transition into more complex cellular structures?
   • Could they catalyse reactions autonomously, or would additional molecules be needed?
   • Were polyester-based protocells widespread, or just one of many competing prebiotic compartments?

Conclusion
Micro polyester droplets present an exciting alternative or complement to traditional lipid-based protocell models. Their ability to encapsulate biomolecules, self-organize, and remain stable under a range of conditions makes them a strong candidate for early protocellular life. Further research into their chemical properties and evolutionary potential could provide deeper insights into life’s origins.

The research findings are published in the American Chemical Society journal ACS Bio & Med Chem Au and are explained in a news release from the Earth Life Science Institute, Tokyo:

How life’s building blocks took shape on early Earth: the limits of membraneless polyester protocell formation

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New research reveals polyester microdroplets, proposed as model membraneless protocells, formed under a wide range of prebiotic conditions, suggesting these molecules were more widespread than previously thought.

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One leading theory on the origins of life on Earth proposes that simple chemical molecules gradually became more complex, ultimately forming protocells—primitive, non-living structures that were precursors of modern cells. A promising candidate for protocells is polyester microdroplets, which form through the simple polymerisation of alpha-hydroxy acids (αHAs), compounds believed to have accumulated on early Earth possibly formed by lightning strikes or delivered via meteorites, into protocells, followed by simple rehydration in aqueous medium. A recent study from the Earth-Life Science Institute (ELSI) at Institute of Science Tokyo provides new evidence supporting the formation of polyester microdroplets under a wider range of realistic prebiotic conditions than previously thought.

Led by PhD student Mahendran Sithamparam of the Space Science Center (ANGKASA), Institute of Climate Change, National University of Malaysia as the first author and co-supervised by ELSI’s Specially Appointed Associate Professor Tony Z. Jia and ANGKASA Research Scientist Kuhan Chandru, the study explored the formation of these microdroplets under conditions more reflective of early Earth. The team found that polyester microdroplets could form even in salt-rich environments, at low αHA concentrations, and in small reaction volumes. This expands on previous research, which primarily considered their formation at high concentrations or in larger bodies of water such as coastal areas of lakes or hot springs. The findings suggest instead that polyester protocells were likely more widespread than previously thought, potentially forming in confined spaces like rock pores or even in high-salt environments such as briny pools or oceanic environments.

In 2019, the research team discovered that polyester microdroplets could form through a simple dehydration process. When gently heated to 80°C, phenyllactic acid (PA), a type of αHA, transitioned into a gel-like substance that subsequently formed membraneless droplets when rehydrated. In their latest study, the researchers investigated whether these microdroplets could form under more dilute or lower volume conditions, similar to those expected on prebiotic Earth.

Earlier laboratory tests often used high initial concentrations and volumes of αHAs in the hundreds-of-millimolar or microliter range, respectively, which may not reflect the conditions on prebiotic Earth, where such conditions were unlikely; this is why we needed to push the limits of the polymerisation droplet assembly processes to see whether assembly of such protocells would have actually been viable on early Earth.

Associate Professor Tony Z. Jia, co-corresponding author
Earth-Life Science Institute
Institute of Future Science
Institute of Science Tokyo, Japan.

To simulate these more realistic conditions, the researchers reduced the concentration and volume of PA in synthesis and subsequent droplet formation studies. They found that polyesters could be synthesised and droplets could form with as little as 500 µL of 1 mM PA or 5 µL of 500 mM PA. This suggests that polyester microdroplets could have naturally emerged both in confined spaces, such as rock pores, or dilute environments, such as those following flooding or precipitation.

To further test real-world conditions, the team simulated reactions in salinities resembling those in the ancient ocean. They introduced 1M NaCl, KCl, and MgCl2 to the PA reactants, finding that polyester synthesis and microdroplet assembly could proceed in NaCl and KCl but not in MgCl2. This suggests that polyester microdroplets would have been more likely to form in water bodies with specific salt compositions, such as those high in NaCl and KCl but low in MgCl2, favourable to αHA polymerisation and subsequent polyester microdroplet assembly.

The conclusions of this study clearly show that polyester protocells were likely more common on early Earth than previously thought and also informs the next generation of laboratory studies of the system. Thus, a wide range of primitive environments—including oceanic, freshwater, briny, and confined spaces like rock pores—could have ultimately supported the formation of these protocells both on Earth or elsewhere.

Kuhan Chandru, Co-corresponding author
Space Science Center (ANGKASA)
Institute of Climate Change
National University of Malaysia, Selangor, Malaysia.

This research was made possible through the ELSI Visitor Program, which fosters international collaboration involving ELSI researchers; this program supported Sithamparam on two separate visits to ELSI in 2023, as well as a visit during summer 2023 to ELSI for graduate student Ming-Jing He (National Central University) to complete experiments for her master’s thesis. All experiments were conducted at ELSI, and the findings are featured in the ACS Bio & Med Chem Au Special Issue, 2024 Rising Stars in Biological, Medicinal, and Pharmaceutical Chemistry, of which Jia is an awardee.

Reference

Mahendran Sithamparam¹, Rehana Afrin², Navaniswaran Tharumen¹, Ming-Jing He³, Chen Chen⁴, Ruiqin Yi⁵, Po-Hsiang Wang^3,6, Tony Z. Jia^2,7*, and Kuhan Chandru^1,8,9*
Probing the Limits of Reactant Concentration and Volume in Primitive Polyphenyllactate Synthesis and Microdroplet Assembly Processes ACS Bio & Med Chem Au DOI: 10.1021/acsbiomedchemau.4c00082

1. Space Science Center (ANGKASA), Institute of Climate Change, National University of Malaysia, Selangor 43650, Malaysia
2. Earth-Life Science Institute, Institute of Future Science, Institute of Science Tokyo, 2-12-1-IE-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan
3. Department of Chemical Engineering and Materials Engineering, National Central University, No. 300, Zhongda Rd., Zhongli District, Taoyuan 32001, Taiwan (R.O.C.)
4. Biofunctional Catalyst Research Team, RIKEN Center for Sustainable Resource Science (CSRS), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
5. State Key Laboratory of Isotope Geochemistry and CAS Center for Excellence in Deep Earth Science, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
6. Graduate Institute of Environmental Engineering, National Central University, No. 300, Zhongda Road, Zhongli District, Taoyuan City 320, Taiwan
7. Blue Marble Space Institute of Science, 600 first Ave, Floor 1, Seattle, Washington 98104, United States
8. Polymer Research Center (PORCE), Faculty of Science and Technology, National University of Malaysia, Selangor 43600 Malaysia
9. Institute of Physical Chemistry, CENIDE, University of Duisburg-Essen, 45141 Essen, Germany

*Corresponding authors’ email: tzjia@elsi.jp (Tony Z. Jia) and kuhan@ukm.edu.my (Kuhan Chandru)

Abstract

Polyester microdroplets have been investigated as primitive protocell models that can exhibit relevant primitive functions such as biomolecule segregation, coalescence, and salt uptake. Such microdroplets assemble after dehydration synthesis of alpha-hydroxy acid (αHA) monomers, commonly available on early Earth, via heating at mild temperatures, followed by rehydration in aqueous media. αHAs, in particular, are also ubiquitous in biology, participating in a variety of biochemical processes such as metabolism, suggesting the possible strong link between primitive and modern αHA-based processes. Although some primitive αHA polymerization conditions have been probed previously, including monomer chirality and reaction temperature, relevant factors pertaining to early Earth’s local environmental conditions that would likely affect primitive αHA polymerization are yet to be fully investigated. Hence, probing the entire breadth of possible conditions that could promote primitive αHA polymerization is required to understand the plausibility of polyester microdroplet assembly on early Earth at the origin of life. In particular, there are numerous aqueous environments available on early Earth that could have resulted in varying volumes and concentrations of αHA accumulation, which would have affected subsequent αHA polymerization reactions. Similarly, there were likely varying levels of salt in the various aqueous prebiotic solutions, such as in the ocean, lakes, and small pools, that may have affected primitive reactions. Here, we probe the limits of the dehydration synthesis and subsequent membraneless microdroplet (MMD) assembly of phenyllactic acid (PA), a well-studied αHA relevant to both biology and prebiotic chemistry, with respect to reactant concentration and volume and salinity through mass spectrometry- and microscopy-based observations. Our study showed that polymerization and subsequent microdroplet assembly of PA appear robust even at low reactant concentrations, smaller volumes, and higher salinities than those previously tested. This indicates that PA-polyester and its microdroplets are very much viable under a wide variety of conditions, thus more likely participating in prebiotic chemistries at the origins of life.

Sithamparam, Mahendran; Afrin, Rehana; Tharumen, Navaniswaran; He, Ming-Jing; Chen, Chen; Yi, Ruiqin; Wang, Po-Hsiang; Jia, Tony Z.; Chandru, Kuhan
Probing the Limits of Reactant Concentration and Volume in Primitive Polyphenyllactate Synthesis and Microdroplet Assembly Processes ACS Bio & Med Chem Au; doi: 10.1021/acsbiomedchemau.4c00082.

Copyright: © 2025 The authors.
Published by American Chemical Society. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

In addition, the first two paragraphs of the team's introduction to their paper should make grim reading for any creationist still deluded enough to believe the absurd nonsense that biomedical scientists are giving up on the Theory of Evolution and instead turning to magical creationism for answers:

Introduction
Abiogenesis describes the chemical evolution of life on early Earth, i.e., the origins of life (OoL), and involves the formation of simple organic molecules, their polymerization and self-assembly into complex molecules, the emergence of protocells, (1−3) and the development of robust Darwinian evolution before or at the onset of the last universal common ancestor (LUCA). (4) In particular, the synthesis of the primitive chemicals potentially leading to life could have taken place in various settings or by various geological processes on early Earth, including Miller–Urey chemistry, (5) hydrothermal vents, (6,7) shallow pools and lakes, (8,9) panspermia delivery, (10) or wet–dry cycles, (11,12) just to name a few, and likely facilitated possible pathways toward several OoL hypotheses, i.e., the lipid-first world, (13) the metabolism-first world, (14) the RNA world, (15) etc. These primitive environments or processes, combined with energy (i.e., lightning strikes; (16) light, UV-rays, and heat from the young sun; (17) energy from radioactive elements; (18) ionizing radiation; (19) etc.) could have facilitated the formation of many simple biomolecules on early Earth such as amino acids, (20) lipids, (21) nucleotides, (22) simple sugars, (23) or even phosphorus-containing compounds, (24) which could have exhibited important functions or contributions to possibly kick-start the OoL.

However, it is important to recognize that the OoL is not necessarily strictly bound to the canonical biomolecules (i.e., lipids, amino acids, etc.). Other prebiotically available organic molecules could have also played equally essential roles during the emergence of life. (25,26) In particular, we speculate that the properties of α-hydroxy acids (αHAs) lead this category of molecules to be potential key compounds at the OoL due to their active participation of αHAs in chemistries ranging from the prebiotic world all the way to modern biology. For example, citric acid (CA) and malic acid, both αHAs, serve as intermediates in the Krebs cycle. (27−29) Ribosomes, traditionally known for synthesizing proteins, have also been shown to polymerize various αHAs, including lactic acid (LA) and phenyllactic acid (PA), into polyesters, a process that can be directed by mRNA through genetic-code reprogramming. (30) Apart from αHA involvement in biology, αHAs are also essential in biotechnology and biomedicine. (31−38)

Far from being impossible like creationists claim, although they can never explain which laws of chemistry and/or physics makes it so. it seems there are a growing number of ways in which self-replicating systems that evolved into complex cells could have arisen on pre-biotic Earth. Of course, there is no reason to suppose at the pre-DNA stage, that there was only one type of protocell produced by just one set of conditions. There is no reason two or more could not have arisen then either joined forces in symbiosis or one emerged the winner in a competition for resources.

But however it happened, it clearly did not need an unexplained magician suspending the laws of chemistry and physics and making them do thing they couldn't do on their own.

Stand by for the imminent eviction of creationism's little shrinking god from one of its few remaining refuges, as science closes yet another gap where gods used to live in more primitive and unenlightened times.

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Refuting Creationism - First Steps to Abiogenesis

Diagram of the atmospheric evolution of Earth's ancient atmosphere estimated by this study

© Yoshida et al.

Research News - How Life Began on Earth: Modeling Earth's Ancient Atmosphere | Tohoku University Global Site

The fact that living organisms arose on Earth from inorganic sources rather than being made of nothing by magic, is an indisputable fact because there are living organisms on Earth and the chemicals they are composed of all exist on the planet in inorganic minerals and gases. 'Life' contains nothing that 'non-life' doesn't contain.

This much we know, but what we don't yet know and can probably never know with certainty, is precisely how and where that happen. In fact, we don't even know whether it did all start in the same place at the same time because the reason there are two different prokaryote cells - bacteria and archaea - could be because life arose on Earth not once but twice, by two different processes in two different places at two different times.

What we have though is lots of working hypotheses in the process of being validated.

What role would Earth's atmosphere have played in abiogenesis? Earth's early atmosphere was crucial in creating the right conditions for abiogenesis—the process by which life originated from non-living matter. While the exact composition of Earth’s primordial atmosphere is still debated, its unique conditions likely contributed in several essential ways:

1. Provision of Basic Building Blocks
   
   • Earth’s early atmosphere likely contained simple molecules like methane (CH₄), ammonia (NH₃), hydrogen (H₂), carbon dioxide (CO₂), nitrogen (N₂), and water vapor (H₂O). These molecules are rich in carbon, nitrogen, oxygen, and hydrogen—elements that are vital for organic compounds and, ultimately, for life.
   • When exposed to energy sources like ultraviolet (UV) radiation from the Sun or electrical discharges from lightning, these molecules could recombine into more complex organic molecules, such as amino acids and nucleotides, which are the building blocks of proteins and nucleic acids, respectively.
   
   
2. Facilitation of Prebiotic Chemistry
   
   • Experiments like the famous Miller-Urey experiment in 1953 showed that simple gases (methane, ammonia, hydrogen, and water vapor) in an atmosphere subjected to electrical sparks could produce amino acids. This suggests that Earth’s early atmosphere could have been instrumental in initiating chemical reactions that synthesized complex organic molecules.
   • Without a protective ozone layer, the early atmosphere allowed substantial UV radiation to penetrate the Earth’s surface, providing the energy necessary to drive these prebiotic reactions.
   
   
3. Supporting a Reducing Environment
   
   • The presence of reducing gases (such as methane and ammonia) would favor the formation of organic molecules because such conditions prevent the oxidation (and hence destruction) of organic compounds. Oxygen is highly reactive and can break down organic molecules, so the absence of free oxygen in the early atmosphere was likely a key factor that allowed these molecules to accumulate and react.
   • This reducing environment might have helped organic compounds to survive long enough to form stable, self-replicating systems.
   
   
4. Encouraging Geochemical Interactions
   
   • The interaction between the early atmosphere and the oceans, along with geothermal activity like volcanic eruptions and hydrothermal vents, provided a diverse range of chemical environments. In particular, hydrothermal vents may have supplied essential minerals and additional energy sources, further driving complex chemical reactions that are believed to be important in the formation of life.
   • The cycling of materials between the atmosphere and oceans would have contributed to creating localized "hotspots" for prebiotic reactions.
   
   
5. Protection and Concentration Mechanisms
   
   • The atmosphere also played a protective role by preventing the immediate dissipation of important compounds into space. It allowed the concentration of molecules and gases at Earth’s surface, increasing the chances of interactions among the essential precursors to life.
   • Early atmospheres may have helped regulate surface temperatures, preventing extreme fluctuations that would have been hostile to complex chemistry.
   
   
6. Encouraging Self-Organization and Membrane Formation
   
   • Interactions in the early atmosphere could have contributed to the formation of lipid molecules that could aggregate to form primitive cell-like structures or vesicles. These structures would eventually help in containing and protecting reactions necessary for early metabolic pathways.
   • These early "proto-cells" or vesicles would have been necessary to create a boundary for molecular interactions, which is a critical step toward the organization needed for cellular life.

In summary, Earth’s early atmosphere provided a chemically conducive, energetically rich environment that fostered the synthesis and concentration of organic molecules necessary for abiogenesis. This atmosphere also shielded these nascent molecules, allowing them to organize and evolve toward increasingly complex systems, eventually leading to the first living organisms.

One of which is the precise details of the atmosphere on the Early Earth, which is important because it would have had a major impact on the rest of the environment in which life arose. To gain a better understanding of that, a team from Tohoku University, Tokyo University and Hokkaido University, Japan, led by Tatsuya Yoshida have succeeded in modelling that atmosphere, as explained in a Tohoku University press release and published in the journal Astrobiology:

How Life Began on Earth: Modeling Earth's Ancient Atmosphere

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The key to unlocking the secrets of distant planets starts right here on Earth. Researchers at Tohoku University, the University of Tokyo, and Hokkaido University have developed a model considering various atmospheric chemical reactions to estimate how the atmosphere - and the first signs of life - evolved on Earth.

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Ancient Earth was nothing like our current home. It was a much more hostile place; rich in metallic iron with an atmosphere containing hydrogen and methane.

Shungo Koyama, co-author
Graduate School of Science
Tohoku University, Sendai, Japan.

These molecules contain an important clue to how life was initially formed. When exposed to solar ultraviolet (UV) radiation, they undergo a chemical reaction that produces organics (also known as the "building blocks of life"). Part of these organics were precursors to essential biomolecules, such as amino acids and nucleic acids. However, understanding the role of UV radiation is difficult. Firstly, this type of atmosphere is unstable and likely underwent rapid changes due to atmospheric chemical reactions. Secondly, when UV radiation efficiently breaks down water vapour in the atmosphere and forms oxidative molecules, the precise branching ratio and timescale has not been determined. In order to address these issues, a 1D photochemical model was created to make accurate predictions about what the atmosphere was like on Earth long ago.

The calculation reveals that most hydrogen was lost to space and that hydrocarbons like acetylene (produced from methane) shielded UV radiation. This inhibition of UV radiation significantly reduced the breakdown of water vapour and subsequent oxidation of methane, thus enhancing the production of organics. If the initial amount of methane was equivalent to that of the amount of carbon found on the present-day Earth's surface, organic layers several hundred metres thick could have formed.

There may have been an accumulation of organics that created what was like an enriched soup of important building blocks. That could have been the source from which living things first emerged on Earth.

Tatsuya Yoshida, lead author
Graduate School of Science
Tohoku University, Sendai, Japan.

The model suggests that the atmosphere on ancient Earth was strikingly similar to what we see on current day neighbouring planets: Venus and Mars. However, despite their proximity, Earth evolved into a completely different environment. Researchers are trying to understand what makes Earth so special. As such, this model allows us to deepen our understanding of whether atmospheric evolution and the origin of life on Earth are unique or share common patterns with other planetary systems.

These findings were published in the journal Astrobiology on October 22, 2024.

Publication Details:

Tatsuya Yoshida, Shungo Koyama, Yuki Nakamura, Naoki Terada and Kiyoshi Kuramoto
Self-Shielding Enhanced Organics Synthesis in an Early Reduced Earth's Atmosphere Astrobiology DOI: 10.1089/ast.2024.0048

Abstract
Earth is expected to have acquired a reduced proto-atmosphere enriched in H₂ and CH₄ through the accretion of building blocks that contain metallic Fe and/or the gravitational trapping of surrounding nebula gas. Such an early, wet, reduced atmosphere that covers a proto-ocean would then ultimately evolve toward oxidized chemical compositions through photochemical processes that involve reactions with H₂O-derived oxidant radicals and the selective escape of hydrogen to space. During this time, atmospheric CH₄ could be photochemically reprocessed to generate not only C-bearing oxides but also organics. However, the branching ratio between organic matter formation and oxidation remains unknown despite its significance on the abiotic chemical evolution of early Earth. Here, we show via numerical analyses that UV absorptions by gaseous hydrocarbons such as C₂H₂ and C₃H₄ significantly suppress H₂O photolysis and subsequent CH₄ oxidation during the photochemical evolution of a wet proto-atmosphere enriched in H₂ and CH₄. As a result, nearly half of the initial CH₄ converted to heavier organics along with the deposition of prebiotically essential molecules such as HCN and H₂CO on the surface of a primordial ocean for a geological timescale order of 10–100 Myr. Our results suggest that the accumulation of organics and prebiotically important molecules in the proto-ocean could produce a soup enriched in various organics, which might have eventually led to the emergence of living organisms.

Yoshida, Tatsuya; Koyama, Shungo; Nakamura, Yuki; Terada, Naoki; Kuramoto, Kiyoshi
Self-Shielding Enhanced Organics Synthesis in an Early Reduced Earth’s Atmosphere Journal of Astrobiology (2024) DOI: 10.1089/ast.2024.0048

© 2024 Mary Ann Liebert, Inc.
Reprinted under the terms of s60 of the Copyright, Designs and Patents Act 1988.

So, by the action if UV radiation from the sun on the inorganic molecules in Earth's early atmosphere for a period of some 10-100 million years, the oceans could have accumulated the basic building blocks for organic organisms to get started, and all th result of chemistry and physics with no magic gods involved at any point.

And, as usual with scientific discoveries, the truth is shown to have little resemblance to the origin myths the parochial Bronze Age pastoralists made up to fill the yawning chasm in their knowledge and understanding of the world around them, with their belief that Earth had only existed for a few thousand years, so were blissfully ignorant of the 99.9975% of its history that occurred before then.

Creationism Refuted - What a Mallorcan Cave Tells Us Of Events Before 'Creation Week'.

Bogdan Onac studies the phreatic overgrowths seen in this photo. They grow exactly at sea level and offer a more accurate reconstruction of past sea level history. He used these to determine the age of the submerged bridge.

Photo: M.À. Perelló

Close-up view of the submerged stone bridge from Genovesa Cave, Mallorca, Spain

Photo: R. Landreth

What a submerged ancient bridge discovered in a Spanish cave reveals about early human settlement

The Spanish Balearic Island of Mallorca (Majorca), a favourite holiday destination for Brits looking for sun, sea and sand, is composed largely of limestone which lends itself to cave formation and limestone caves lend themselves to stalactite formation.

They also provided shelters for early humans, so the evidence of human presence gives us a good picture of the timing of human migration into the area.

Like 99,9975% of Earth's history, the events recorded in these Mallorcan caves happened in the long pre-'Creation Week' history, long before creationists believe Earth was made out of nothing by magic.

Readers may recall my recent blog post concerning what is known of the changes in biodiversity as the Mediterranean dried up, then flooded again about 5.5 million years ago due to plate tectonic movements. These Mallorcan caves formed after those catastrophic events but still well before creationism's 'Creation Week'.

The stalactites in one cave in particular, the Genovesa Cave at the eastern end of the island hold a record of sea-level changes that correlate with known periods of glaciation and interglacial warmer periods. During periods of glaciation, water was locked up in polar ice and glaciers, so sea-levels fell.

What information do you have on the Genovesa Cave in Mallorca, Spain, and what it tells us of sea-level changes? Genovesa Cave, located on the eastern coast of Mallorca, Spain, is a notable site for studying past sea-level changes due to its unique speleothem formations (such as stalactites and stalagmites) and its position relative to current sea levels.

Key Information About Genovesa Cave

1. Geological Context:
   • Genovesa Cave is a partially submerged cave system found on the island of Mallorca, part of the Balearic Islands in the western Mediterranean Sea.
   • The cave has been naturally formed in limestone rock, a type of carbonate rock that is particularly responsive to changes in sea level.
   
   
2. Evidence of Past Sea-Level Changes:
   • Speleothem Growth Stages: The most significant evidence for past sea-level changes comes from speleothems, which are mineral deposits formed in caves by the precipitation of carbonate minerals from dripping water. When sea levels rise, the cave becomes submerged, and speleothem growth ceases due to a lack of contact with air. When sea levels fall, the cave is re-exposed to air, allowing speleothems to grow again.
   • Dating Techniques: Researchers use uranium-thorium (U-Th) dating methods to date these speleothems accurately. The growth and cessation periods can be correlated with known global sea-level fluctuations, such as those associated with glacial and interglacial cycles during the Quaternary period (the last 2.6 million years).
   
   
3. Sea-Level Highstands and Lowstands:
   
   
   • Studies of Genovesa Cave have identified speleothems that formed during several past interglacial periods when sea levels were higher than today. This provides evidence for higher sea levels during warm periods such as the Last Interglacial (about 125,000 years ago).
   • Conversely, periods when the cave was submerged or when speleothem growth was halted correspond to glacial periods when sea levels were much lower, sometimes up to 120 meters lower than the current level.

Implications for Understanding Sea-Level Changes

1. Local and Global Sea-Level Correlation:
   • The data obtained from Genovesa Cave speleothems align well with global records of sea-level changes, such as those derived from coral reefs and marine terraces. This reinforces the idea that the cave provides a reliable local record that reflects broader, global sea-level trends.
   
   
2. Understanding the Mediterranean Sea's Response:
   • The cave's findings contribute to our understanding of how the Mediterranean Sea responded to global climatic events. During periods of rapid deglaciation, for example, meltwater pulses could have caused rapid sea-level rises, which would be recorded in the cave's geological formations.
   
   
3. Insights into Future Sea-Level Rise:
   • Studying past sea levels helps scientists predict future changes, particularly in the context of global warming and potential ice sheet melting. The high-resolution records from Genovesa Cave can help refine models of future sea-level rise, especially in understanding how fast and how much sea levels could change.

In Summary

Genovesa Cave in Mallorca is a critical natural archive for studying past sea-level changes, providing both a local record of changes in the Mediterranean and contributing to the understanding of global sea-level fluctuations. The cave's speleothem formations, when dated, tell us about the timing and extent of past sea levels, helping us predict future changes.

Did the cave exist during the Messinian Salinity Crisis and the following Zanclean flood?

Genovesa Cave, like many other karstic cave systems on Mallorca, likely did not exist in its current form during the Messinian Salinity Crisis (MSC) and the subsequent Zanclean flood. However, understanding its formation requires a bit of geological context about these events and the development of the cave.

Geological Context of the Messinian Salinity Crisis and Zanclean Flood

1. Messinian Salinity Crisis (MSC) (5.96 to 5.33 million years ago):
   • The MSC was a period when the Mediterranean Sea was largely cut off from the Atlantic Ocean due to tectonic movements, leading to extreme evaporation and a significant drop in sea level. During this time, the Mediterranean became partially or fully desiccated, creating vast salt deposits and deep erosional features (like canyons and river systems) that extended below the current sea level.
   • Sea levels were drastically lower, estimated to have dropped by as much as 1,500 meters. The drop exposed large portions of the continental shelf and caused significant erosion of the landscape, including the areas around Mallorca.
   
   
2. Zanclean Flood (5.33 million years ago):
   • The Zanclean flood marked the end of the MSC, when the Strait of Gibraltar reopened, and Atlantic waters rapidly refilled the Mediterranean basin. This event is thought to have raised sea levels in the Mediterranean by up to 1,500 meters over a short period, flooding the previously exposed and desiccated areas.

Did Genovesa Cave Exist During These Events?

1. Formation of Genovesa Cave:
   • Genovesa Cave, like many karst caves, formed much later than the Messinian Salinity Crisis and the Zanclean flood. The formation of such caves typically occurs over long periods through the dissolution of limestone by slightly acidic groundwater. This process, known as karstification, is generally linked to periods when the sea level is relatively stable and when the water table is at an appropriate level to facilitate cave development.
   • Given that the MSC was a period of extreme environmental conditions (both in terms of erosion during the desiccation and rapid flooding during the Zanclean flood), the specific geological setting that would allow for the gradual formation of karstic caves like Genovesa likely did not exist until after these events.
   
   
2. Post-MSC Karst Development:
   • After the Mediterranean was refilled and the sea level stabilized following the Zanclean flood, conditions would have been more suitable for the formation of karst systems like Genovesa Cave. The Quaternary period, which began about 2.6 million years ago, saw multiple cycles of glacial and interglacial periods, during which fluctuations in sea levels, combined with periods of stability, promoted the development of karst caves in the limestone regions of Mallorca.
   
   
3. Timing of Cave Formation:
   • The specific timing of the formation of Genovesa Cave is not precisely known, but it is generally accepted that most of the karst caves in Mallorca formed during the Pleistocene epoch (2.6 million to 11,700 years ago) or even more recently. The cave's features and deposits suggest that it has undergone several phases of exposure and submersion due to sea-level changes throughout this period, well after the MSC and Zanclean flood.

Conclusion

Genovesa Cave, in its current form, did not exist during the Messinian Salinity Crisis or the subsequent Zanclean flood. The cave likely formed much later, during the Quaternary period, as conditions became suitable for karstification following the stabilization of Mediterranean sea levels after these dramatic geological events. The MSC and the Zanclean flood were important in shaping the broader landscape of the Mediterranean region, but the specific conditions necessary for the formation of caves like Genovesa developed much later.

What are phreatic overgrowths on Speleothems (POS)?

Phreatic overgrowths on speleothems (POS) are unique mineral deposits that form in coastal cave environments at the interface between freshwater and seawater. These overgrowths are specifically associated with periods when the cave is partially submerged in a mix of fresh and saline water, typically at or near sea level. They provide important clues about past sea-level positions and climate conditions.

Key Characteristics of Phreatic Overgrowths on Speleothems

1. Definition:
   • Phreatic overgrowths on speleothems are secondary carbonate deposits, typically composed of minerals like calcite or aragonite. They form on existing speleothems (such as stalactites, stalagmites, or flowstones) when the cave environment is inundated by a fluctuating water table that is influenced by sea level.
2. Formation Environment:
   • These overgrowths develop in the "phreatic zone" of caves— the zone that is below the water table and is saturated with water. In coastal caves, this zone is directly affected by sea-level changes. When sea level is stable or fluctuates within a certain range, the mixing zone between freshwater and saline water can lead to mineral precipitation on submerged speleothems.
3. Mechanism of Formation:
   • Phreatic overgrowths form due to a process known as "degassing" or "precipitation" when carbon dioxide (CO₂) dissolved in water escapes into the cave air. This loss of CO₂ from water that is saturated with calcium carbonate (CaCO₃) promotes the deposition of calcite or aragonite on existing cave formations.
   • In coastal caves, the mixing of fresh and saltwater enhances this process. Freshwater entering the cave mixes with seawater, creating conditions where minerals precipitate more readily due to changes in water chemistry, such as shifts in pH, temperature, and CO₂ concentration.
4. Morphology and Appearance:
   • Phreatic overgrowths typically form flat or gently sloping horizontal crusts, rims, or coatings on existing cave formations. Their horizontal nature reflects the stable water table level at which they formed.
   • These deposits can vary in thickness and are often found at multiple levels within the cave, corresponding to different sea levels over time.

Importance of Phreatic Overgrowths on Speleothems

1. Indicators of Past Sea Levels:
   • POS are valuable indicators of past sea levels because they form at specific elevations related to the water table, which in coastal environments is closely linked to sea level. By dating these formations using techniques such as uranium-thorium (U-Th) dating, scientists can reconstruct past sea-level positions and determine the timing and magnitude of sea-level changes over thousands to hundreds of thousands of years.
2. Understanding Paleoclimatic Conditions:
   • Beyond sea levels, POS can provide insights into broader paleoclimatic conditions. The chemical composition of these overgrowths (e.g., stable isotopes of oxygen and carbon) can offer information about past temperature, rainfall patterns, and even water source characteristics.
3. Calibrating Sea-Level Rise Models:
   • The precise dating of phreatic overgrowths helps in calibrating models of sea-level rise, particularly when cross-referenced with other geological and paleoclimatic data, such as coral reefs, marine terraces, and ice cores. This is particularly important for understanding the rate of sea-level rise in response to past climate events, such as glacial and interglacial periods.

Examples of POS Studies

• Mediterranean Caves (Mallorca, Spain): In Mallorca, POS have been extensively studied in caves like Genovesa Cave and others along the coast. These formations have been used to map out the history of Mediterranean sea-level changes over the last several hundred thousand years, including periods such as the Last Interglacial (about 125,000 years ago).
• Caribbean and Other Coastal Regions: Similar studies have been conducted in coastal caves in the Caribbean and other regions, where POS help reconstruct sea-level fluctuations and regional climate changes.

Summary

Phreatic overgrowths on speleothems are carbonate deposits formed in caves at the interface between freshwater and seawater, directly reflecting past sea levels. They serve as crucial archives for understanding past sea-level changes, climate conditions, and the complex interplay between global climate and regional environmental changes.

In the context of dating caves, what does the following mean?

'A ²³²Th/²³⁸U-²³⁴U/²³⁸U-²³⁰Th/²³⁸U (plotted as a Rosholt A type) isochron age of 5479 ± 120 years B.P.'

The phrase describes the result of a specific type of uranium-thorium dating method used to determine the age of materials, such as carbonate deposits in caves. Let's break down what each part of this phrase means:

Uranium-Thorium (U-Th) Dating Overview

Uranium-Thorium (U-Th) dating also known as Thorium-230 dating is a radiometric dating technique used to determine the age of calcium carbonate materials like speleothems (stalactites, stalagmites, and other cave formations). The method relies on the radioactive decay of uranium isotopes to thorium isotopes. Here's a breakdown of the isotopes involved:

• ²³⁸U (Uranium-238): The parent isotope, which decays over time into various intermediate daughter isotopes, including ²³⁴U (Uranium-234) and ²³⁰Th (Thorium-230).
• ²³²Th (Thorium-232): A stable, non-radioactive isotope of thorium that is not involved in the decay chain but can be present in the sample as a contaminant or from initial conditions.

Explanation of the Phrase

1. "²³²Th/²³⁸U-²³⁴U/²³⁸U-²³⁰Th/²³⁸U":
   • These ratios represent the proportions of different isotopes present in the sample.
     • ²³²Th/²³⁸U: Indicates the ratio of thorium-232 to uranium-238 in the sample.
     • ²³⁴U/²³⁸U: Indicates the ratio of uranium-234 (an intermediate decay product) to uranium-238.
     • ²³⁰Th/²³⁸U: Indicates the ratio of thorium-230 (the target daughter isotope) to uranium-238.
   
   
2. "Plotted as a Rosholt A type isochron":
   • An isochron is a graphical method used to determine the age of a sample by plotting the ratios of isotopes against each other. The slope of the line (the isochron) represents the time that has passed since the sample's formation.
   • "Rosholt A type" refers to a specific type of isochron plot developed by John Rosholt, which plots the ratios of these isotopes in a way that accounts for initial thorium contamination (²³²Th). This method provides a more accurate age by correcting for the presence of any initial, non-radiogenic thorium in the sample.
   
   
3. "Isochron age of 5479 ± 120 years B.P.":
   • This is the calculated age of the sample, determined by the U-Th dating method using the isochron plot.
   • 5479 years B.P.: This means "5479 years Before Present," where "Before Present" is typically defined as before the year 1950. The sample is estimated to have formed 5479 years ago.
   • ± 120 years: This represents the margin of error or uncertainty in the dating. The true age is likely within the range of 5479 years plus or minus 120 years (i.e., between 5359 and 5599 years ago).

Summary

The phrase refers to a method of dating a cave sample using uranium-thorium dating and an isochron plot (Rosholt A type) to determine that the sample is approximately 5479 years old, with an uncertainty of ±120 years. The use of multiple isotope ratios and the isochron method helps correct for initial contamination and provides a more accurate age estimate.

This allowed stalactites to grow as water containing dissolved minerals seeped through the cave roof and dripped down, evaporating as it did so, and leaving a record of rainfall. During interglacial period, sea-levels rose, submerging the caves and preventing the growth of stalactites, leaving a record of these sea-level rises.

But, apart from these records of climate and sea-level changes, the Genovesa Cave contains a more tangible record - that of human habitation on the island and so of colonisation of the Western Mediterranean and the Iberian peninsula in particular.

It is a submerged stone bridge, built when the sea-levels were lower at the height of the last ice age. The bridge was used to cross a now submerged small lake at a low point in the cave system and must have been deliberately constructed.

Scientists these days rarely, if ever, set out to refute creationist mythology but all do so incidentally, simply by doing what good science does and discovering the facts, and this discovery, by speleogeologists from the University of South Florida, does just that. It is the subject of a recent open access paper in Communications Earth & Environment and a recent news release from the University of South Florida:

What a submerged ancient bridge discovered in a Spanish cave reveals about early human settlement

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A new study led by the University of South Florida has shed light on the human colonization of the western Mediterranean, revealing that humans settled there much earlier than previously believed. This research, detailed in a recent issue of the journal, Communications Earth & Environment, challenges long-held assumptions and narrows the gap between the settlement timelines of islands throughout the Mediterranean region.

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Reconstructing early human colonization on Mediterranean islands is challenging due to limited archaeological evidence. By studying a 25-foot submerged bridge, an interdisciplinary research team – led by USF geology Professor Bogdan Onac – was able to provide compelling evidence of earlier human activity inside Genovesa Cave, located in the Spanish island of Mallorca.

The presence of this submerged bridge and other artifacts indicates a sophisticated level of activity, implying that early settlers recognized the cave's water resources and strategically built infrastructure to navigate it.

Professor Bogdan P. Onac, Lead author
Karst Research Group
School of Geosciences
University of South Florida, Tampa, FL, USA.

The cave, located near Mallorca’s coast, has passages now flooded due to rising sea levels, with distinct calcite encrustations forming during periods of high sea level. These formations, along with a light-colored band on the submerged bridge, serve as proxies for precisely tracking historical sea-level changes and dating the bridge's construction.

Mallorca, despite being the sixth largest island in the Mediterranean, was among the last to be colonized. Previous research suggested human presence as far back as 9,000 years, but inconsistencies and poor preservation of the radiocarbon dated material, such as nearby bones and pottery, led to doubts about these findings. Newer studies have used charcoal, ash and bones found on the island to create a timeline of human settlement about 4,400 years ago. This aligns the timeline of human presence with significant environmental events, such as the extinction of the goat-antelope genus Myotragus balearicus.

By analyzing overgrowths of minerals on the bridge and the elevation of a coloration band on the bridge, Onac and the team discovered the bridge was constructed nearly 6,000 years ago, more than two-thousand years older than the previous estimation – narrowing the timeline gap between eastern and western Mediterranean settlements.

This research underscores the importance of interdisciplinary collaboration in uncovering historical truths and advancing our understanding of human history.

Professor Bogdan P. Onac.

This study was supported by several National Science Foundation grants and involved extensive fieldwork, including underwater exploration and precise dating techniques. Onac will continue exploring cave systems, some of which have deposits that formed millions of years ago, so he can identify preindustrial sea levels and examine the impact of modern greenhouse warming on sea-level rise.

This research was done in collaboration with Harvard University, the University of New Mexico and the University of Balearic Islands.

Abstract
Reconstructing early human colonization of the Balearic Islands in the western Mediterranean is challenging due to limited archaeological evidence. Current understanding places human arrival ~4400 years ago. Here, U-series data from phreatic overgrowth on speleothems are combined with the discovery of a submerged bridge in Genovesa Cave that exhibits a distinctive coloration band near its top. The band is at the same depth as the phreatic overgrowth on speleothems (−1.1 meters), both of which indicate a sea-level stillstand between ~6000 and ~5400 years ago. Integrating the bridge depth with a high-resolution Holocene sea-level curve for Mallorca and the dated phreatic overgrowth on speleothems level constrains the construction of the bridge between ~6000 and ~5600 years ago. Subsequent sea-level rise flooded the archeological structure, ruling out later construction dates. This provides evidence for early human presence on the island dating at least 5600 and possibly beyond ~6000 years ago.

Introduction
Mallorca, the main island of the Balearic Archipelago, is the sixth largest in the Mediterranean Sea, yet it was among the last to be colonized¹. An in-depth discussion concerning the earliest colonization of various Mediterranean islands, including Mallorca, may be found in Cherry and Leppard1, Dawson², and Simmons³. Despite extensive research on this topic, there has been considerable disagreement about the timing of the earliest colonization of Mallorca. Radiocarbon dating of bone material excavated from Cova (Cave) de Moleta indicate human presence on the island as early as 7000 calibrated years before present (cal B.P.)⁴. Subsequent age determinations from findings in Cova de Canet, further extended the timeline, suggesting human occupation dating back to approximately 9000 cal B.P.⁵. A series of publications^{6,7,8,9,10,11} revealed inconsistencies regarding the exact stratigraphic position and context of the dated bone (sample KBN-640d12) in Cova de Moleta. Due to the overall poor preservation of the samples and the lack of clear and specific information on this particular radiocarbon-dated sample, Ramis and Alcover⁷ suggested that the bone fragment, initially identified as human, might actually belong to M. balearicus, an endemic bovid. Consequently, this sample was considered not relevant for determining the timing of the island’s colonization. Similarly, the radiocarbon dates from Cova de Canet were considered highly controversial because they originate from a charcoal layer that lacks clear evidence of human activity^7,8. Furthermore, in neither of these caves do the M. balearicus bones show butchery marks, making it difficult to establish a clear link to contemporary human presence2. Due to the aforementioned issues these early results were deemed unreliable^1,8,13.

Several studies have reevaluated most of the previously dated materials and supplemented them with new radiocarbon dates obtained from charcoal, ash, and bones^6,7,9,10. Based on these new results, there is now a consensus that the timeframe for earliest human settlement on the island is between 4600 and 4200 cal B.P.¹⁴.

Dawson2 presents a synthesis of the various lines of argument regarding arrival models in the Balearic islands that includes: (1) Early (~9000 cal B.P.), (2) Intermediate (~7600 cal B.P.), and (3) Late (~5000 cal B.P.) arrival phases. The last two models suggest the existence of stable settlements, yet only the third one has been deemed plausible in the local archeological literature^7,8,14.

While there has been a growing body of evidence revealing progressively earlier human settlements on many islands in the Mediterranean basin, the timeline for the initial human colonization in Mallorca has seen relatively minor adjustments over the past decades^8,15,16. The latest research suggests that this colonization occurred approximately 4400 cal B.P., coinciding with the human-mediated extinction of Myotragus balearicus¹⁴. This conclusion is based on two radiocarbon ages, which provide a relatively narrow time window of 350 years (p > 90%) between the last documented Myotragus bone (4581–4417 cal B.P.) and the first dated sheep bone (4417–4231 cal B.P.). However, it remains challenging to confirm whether the ages of these paleontological remains represent the latest or the earliest such occurrences on the island. Subsequent field work may shed light on this matter.

Our study site is a submerged archeological structure in the Genovesa Cave (also known as Cova de’n Bessó; 39°31’32” N, 3°19’2” E), situated in the eastern part of Mallorca (Fig. 1a, b). The cave hosts ceramic sherds and stone constructions. The latter includes a stone-paved path that connects the cave entrance to the first underground lake (Fig. 1d), a cyclopean stone wall running parallel to the path, and an 8.62 m long¹⁷ and 0.5 m high stone walkway (hereafter referred as to bridge) oriented NE–SW (Fig. 1c, e, Supplementary Fig. 1, Supplementary Table 1). This last structure was built across a lake by stacking large limestone breakdown blocks on top of each other, without the use of mortar or cement. The uppermost layer comprises flat boulders of considerable size (Supplementary Fig. 1b). The largest stone measures 1.63 m in length and 0.6 m in width. Relative to the preindustrial (pre-1900 CE) sea level, the bridge is submerged by 1.05 ± 0.1 m of water at its upper part (Figs. 1e, 2). However, at the time of its construction, it served as an access path to the only other dry chamber in the cave (Sala de les Rates-pinyades, i.e., Bats Room), where pottery, tentatively attributed to the Naviform period (ca. 3550–3000 cal B.P.) was discovered^18,19. The bridge structure was inferred to have been built around the same period²⁰.

Fig. 1: Cave and sample locations.

a Map showing Mallorca in the western Mediterranean (black square). b Location of Genovesa and Drac caves; CCG: Closos de Can Gaià archeological site. c Plan of Genovesa Cave showing the location of the phreatic overgrowth on speleothems samples (yellow circles) and the survey station (red dot). d Photograph of the stone-paved path leading to the bridge (person height = 167 cm). e Cross-section (x–x’) indicating the location of the submerged bridge relative to the cave entrance and the present sea level. Maps (a, b) are available under CC Public Domain License from https://pixabay.com/illustrations/map-europe-world-earth-continent-2672639/ and https://pixabay.com/illustrations/mallorca-map-land-country-europe-968363/, respectively.

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Fig. 2: Positional relationship between the bridge, preindustrial sea level, and analyzed samples.

The cross sections depict the spatial relationship between the submerged bridge and the U-series dated samples (phreatic overgrowth on speleothems: orange/yellow spindle; soda straw tips: red circle) from Genovesa and Drac caves. The vertical scale applies uniformly to all samples from both caves. All ages are reported as thousands of years (kyr) before present, where present is defined as 1950 CE.

Here, we integrate uranium-series (U-series) age data acquired from phreatic overgrowth on speleothems and stalactite tips in Genovesa and Drac caves, along with Late Holocene relative sea level (RSL) information available for Mallorca²¹. Additionally, we consider the presence of the bridge, the coloration mark on its upper part, and the depths at which these respective features occur. This combined evidence contributes valuable insights to the ongoing debate surrounding the timing of human colonization on Mallorca.

Because Creationists love to find fault with the geochronology in these records of pre-'Creation Week' events, I've included sections on geochronology here:

Results and discussion
Speleothems and sea level
Proxies for cave-based sea-level reconstructions include mineralogical (sediments, speleothems)^22,23, archeological (fish tanks, saltpans, submerged structures, etc.)²⁴, and biological (borings, worm tubes, etc.)²⁴ records. In the case of Genovesa Cave, a typical coastal karst feature situated <450 m from the shoreline, both mineralogical and archeological records are present. Many of its well-decorated passages, galleries, and chambers are now flooded due to rising sea levels²⁰. Because of the cave’s proximity to the coast and the high permeability of the Upper Miocene host rock²⁵, the hydraulic gradient is negligible (9 × 10^-5 m /m) for such short distances (see Methods), and thus the water table in the cave is, and was in the past, coincident with sea ^26,27. During times of high sea level stillstands, when the cave was partly flooded, distinct encrustations of calcite and aragonite accumulated over preexisting stalactites, forming the so-called phreatic overgrowths on speleothems²⁸ (POS). This is a particularly useful proxy for precisely and accurately reconstructing sea-level changes across various timescales^21,29. Furthermore, ordinary stalactites, which form in cave passages above the water table and later become submerged as sea-levels rise are also valuable in this process since they document the moment when the cave shifted from being air- to water-filled²².

A distinct light-colored band (~15 cm wide) is visible along the entire bridge at its upper part (Fig. 2, Supplementary Fig. 1a). This coloration mark bears a resemblance to a “bathtub ring” and its presence is likely related to a relatively short-lived stable water table that allowed the precipitation of a sub-millimeter calcite crust at the water/air interface. When the water level increased, the calcite did not disappear since the water below the water table remained somewhat saturated with respect to calcium carbonate. As discussed later, this feature along with the new POS ages and their elevation play a crucial role in determining when this bridge, now submerged, was constructed.

Geochronology
The U-series ages (n = 34; 28 for POS and 6 from stalactites) are given in Supplementary Table 2 and are all reported as years before present (BP), where present is 1950 CE. Ten of these ages are from POS samples GE-D8 (Genovesa Cave; Supplementary Fig. 2) and DR-D15 dated as part of a prior study²¹. The latter was collected in Drac Cave (39°32’9” N, 3°19’49” E), located 1.6 km to the north-east of Genovesa Cave (Fig. 1c, Supplementary Figs. S3–S4).

Regardless of the sampling depth, all the vadose stalactites on which the POS formed in both caves, produced ages older than 8200 years B.P. (Fig. 2, Supplementary Fig. 5). The phreatic overgrowth samples GE-D6, GE-D7, and DR-D23 (Supplementary Figs. S6–S8), precipitated at ~1.10 ± 0.1 m below the preindustrial sea level (mbpsl). A ²³²Th/²³⁸U-²³⁴U/²³⁸U-²³⁰Th/²³⁸U (plotted as a Rosholt A type) isochron age of 5479 ± 120 years B.P. (n = 3 of 4; hereafter, ± refers to 2 σ uncertainty) was measured for GE-D6 (Supplemental Table 2, Supplementary Fig. 9a). GE-D7, in the same room and at the same elevation as GE-D6, yielded a weighted average age of 5510 ± 549 years B.P. using the same correction (initial ²³⁰Th/²³²Th atomic ratio = 5.1 ± 0.4 ppm) generated by the GE-D6 isochron age. Onac et al.²¹. used a slightly higher initial for GE-D8 (8 ppm) that was located at a higher elevation than GE-D6 & -D7. For DR-D23, we obtained a ²³²Th/²³⁸U-²³⁴U/²³⁸U-²³⁰Th/²³⁸U (plotted as a Rosholt A type) isochron age of 5824 ± 140 years B.P. (n = 6) (Supplementary Table 2, Supplementary Fig. 9b). This isochron shows an exceptionally high initial ²³⁰Th/²³²Th atomic ratio = 527.5 ± 22.1 ppm, more than 10x higher than used for DR-D15 (44 ppm) from the same cave but at a different elevation²¹. The fluffy fibrous cotton-candy texture of the two sub-samples with high U component of DR-D23 may have something to do with the high initial ²³⁰Th/²³²Th. The isochron ages were necessary to produce accurate ages with smaller uncertainties.

Collectively, the POS data from Genovesa and the nearby Drac, reveal three distinct periods of relative sea-level stability (Fig. 2). One occurred at 0 ± 0.04 m from 2720 ± 11 to 296 ± 18 years B.P. The second period lasting from 3703 ± 14 to 3368 ± 8 years B.P., corresponds to a sea level of 0.25 mbpsl. Lastly, a third period at ~1.1 ± 0.1 mbpsl is documented between 5820 ± 140 and 5479 ± 120 years B.P. (Figs. 2, 3). By adding the uncertainty to the older age and subtracting the uncertainty from the younger age, the maximum time span of POS growth at 1.1 mbpsl ranges from 5964 – 5359 years B.P. During this interval, both the POS and the coloration mark formed. For the latter to develop, the bridge must have been submerged, at least to its upper surface, allowing calcite to precipitate during the sea-level stillstand. Therefore, this period is of particular interest because it may aid in providing the timeline of the bridge construction as detailed below.

Timing of bridge construction
The assembly date of the bridge in Genovesa Cave remains uncertain due to the absence of written records or a robust time-stratigraphic context. In order to constrain the building time of this archeological structure, we rely on a well-defined Late Holocene sea-level curve generated by Onac et al.²¹. for Mallorca (depicted by the solid blue line in Fig. 3) and the ages and depths at which POS grew and coloration mark formed. First, we assess previous assumptions regarding the timing of the submerged bridge construction using this curve. Then, we examine our new sea-level data in conjunction with the timing of the earliest human arrival model proposed by Bover et al.¹⁴.

The prehistoric pottery discovered in Sala de les Rates-pinyades of the Genovesa Cave has been linked to the Naviform period (3550–3000 cal B.P.). This attribution is based on typological similarities between the ceramics found in Genovesa and those documented at the Closos de Can Gaià, a Bronze Age site located ~10 km south of our cave (Fig. 1b). The archeological horizon in which comparable pottery was discovered at the latter site was dated to ~3600 cal B.P30. However, Costa and Guerrero31 argue that Closos de Can Gaià excavation required a reassessment of the chronological framework, due to issues with the radiocarbon dates. Despite this, adopting the previously reported radiocarbon age, Gràcia et al.²⁰ suggested that the construction of the bridge likely occurred toward the end of the Naviform period.

However, the RSL curve (Fig. 3) indicates that sea level was ~0.25 ± 0.1 m below the preindustrial baseline ~3500 years ago²¹, implying a total water depth of ~1.3 m in the cave lake. The vertical height of the bridge is 0.5 m, and thus it was submerged by 0.8 m of water at this time (Fig. 3). The construction of the bridge around 4400 years ago, the time suggested by Bover et al.¹⁴ to be the earliest evidence of human presence on the island, is also improbable. At that time, relative sea level in Mallorca was ~0.35 ± 0.1 m below preindustrial level, and the bridge would have been submerged by 0.7 m. Building a bridge below water level is a highly unlikely scenario, and thus it was likely built at an earlier time, when sea level was lower. The predicted relative sea-level curve for Mallorca (Fig. 3) indicates that the top of the bridge would have been close to water level no earlier than 5600 years ago and this provides an approximate lower bound on the age of the feature. The distinct coloration mark on the bridge also provides strong evidence of an age greater than the ages estimated by Gràcia et al.²⁰ and Bover et al.¹⁴. As discussed earlier and according to the POS-based relative sea-level record, this mark would not have developed if the top of the bridge was well below the water level, i.e., at times more recent than ~5500 years ago. However, an age older than 6000 years for the feature can be ruled out since sea level was even lower (Fig. 3), and the construction of a bridge at its current height would have been unnecessary.

Fig. 3: Proposed timing for bridge construction.

Comparison between the position of the submerged bridge, phreatic overgrowth on speleothems (POS), coloration mark, and the RSL prediction (blue curve)²¹ based on a Glacial Isostatic Adjustment model that uses the ICE-6G (VM 5) ice history with an upper mantle viscosity of 1.3 × 1020 Pa s. Solid symbols with age and depth uncertainties represent POS elevations. The brown rectangle depicts the bridge with its coloration band in the upper part. The insets show an underwater image of the bridge (Photo courtesy of R. Landreth) and a close-up view on the RSL position of samples GE-D6, GE-D7, and DR-D23 that grew at 1.1 mbpsl. The uncertainties for GE-D6, GE-D7, and DR-D23 are absolute 2 σ error bars based on three dimensional isochron ages or weighted average (GE-D7). The dotted blue line is a sea-level rise scenario that includes the brief stillstand inferred from the POS growth.

The phreatic overgrowths GE-D6, GE-D7, and DR-D23 from Genovesa and Drac caves formed at a relative sea level of 1.1 mbpsl, which is 5 cm below the upper part of the bridge. The two more precise isochron ages suggest sea-level remained relatively constant for a few hundreds of years between ~5964 and 5359 years B.P. The relative brevity of this time frame might explain why the morphology and size of the POS are somehow atypical and smaller compared to those POS that developed when the sea level was stable at 0 m for over 2000 years. Furthermore, this <600 year period of nearly constant sea level was sufficient to develop the coloration mark. Given that the occurrence of this feature correlates directly with the previously mentioned sea-level stillstand position, it suggests that the bridge was already in place. In fact, its construction could have commenced as early as ~6000 years ago when the water depth in the lake was ~0.25 m. However, it had to be completed before ~5600 years ago when the sea-level rose to the top surface of the bridge.

Onac, B.P., Polyak, V.J., Mitrovica, J.X. et al.
Submerged bridge constructed at least 5600 years ago indicates early human arrival in Mallorca, Spain. Commun Earth Environ 5, 457 (2024). https://doi.org/10.1038/s43247-024-01584-4

Copyright: © 2024 The authors.
Published by Springer Nature Ltd. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

Lots of stuff for creationists to lie about there. Firstly, there is the record of sea-level changes reflecting the advance and retreat of ice sheets over the past few tens of thousands of years.

Then there is the record of human habitation and construction of the bridge when creationist mythology says the world was subject to a genocidal flood in which all life was extinguished save a small handful of survivors that then repopulated the planet in just a few thousand years.

What a creationist now needs to do is explain why all the dating methods, which converge on these dates, are all wrong and should be converging on a much more recent date compatible with creation of Earth from nothing just 10,000 years ago and all human life originating from 8 related individuals just 4,000 years ago.

Sadly, because the authors of these myths knew nothing of the real history of the Western Mediterranean, the book they wrote, and which creationists think is a real history book, is entirely silent on the matter.