Rosa Rubicondior: Refuting Creationism - LUCA Was An Asgard Archaea

Saturday, 22 March 2025

Refuting Creationism

LUCA Was An Asgard Archaea

An artist’s depiction of an Asgard archaeon, based on cryo-electron tomography data: the cell body and appendages feature thread-like skeletal structures, similar to those found in complex cells with nuclei.

Graphic: Margot Riggi,
Max Planck Institute of Biochemistry

Asgard tubulin.

Origin of Life: How microbes laid the foundation for complex cells | ETH Zurich

Recent research indicates that the last universal common ancestor of complex (eukaryotic) cells, which encompass all multicellular plant and animal life, likely originated from the Asgard group of archaea. This ancestor is believed to have formed a symbiotic relationship with an alphaproteobacterium, which eventually evolved into the mitochondrion.

The initial nature of this symbiotic relationship—whether parasitic or predatory—remains uncertain. However, its establishment was pivotal in setting the evolutionary course that led to the diversity of life on Earth. Compelling evidence supporting the Asgard archaea hypothesis has been uncovered by Professor Martin Pilhofer and his team at the Eidgenössische Technische Hochschule (ETH) Zurich, Switzerland. Their findings have been published in the journal Cell and is explained in an ETH news item by Peter Rüegg:

What can you tell me about the recently-discovered Asgard archaea?

The Asgard archaea are a recently discovered and significant group of microorganisms that are fundamentally reshaping our understanding of how complex (eukaryotic) life evolved. These archaea bridge a critical evolutionary gap, providing insights into the origins of eukaryotes, the domain of life that includes all plants, animals, fungi, and protists.

Here's a concise overview of what is currently known about the Asgard archaea:

Discovery

First discovered: Identified initially through environmental DNA sampling (metagenomics) in deep-sea sediments near hydrothermal vents, published in 2015.
Naming: Named after figures from Norse mythology, reflecting their evolutionary importance and enigmatic nature. Major groups include Lokiarchaeota, Thorarchaeota, Odinarchaeota, and Heimdallarchaeota.

Evolutionary Significance

They represent a critical branch on the tree of life, positioned closely to the ancestors of all eukaryotic cells.
Evidence strongly suggests that the Last Eukaryotic Common Ancestor (LECA) originated from within the Asgard lineage, making Asgard archaea the closest known archaeal relatives of eukaryotes.
They provide substantial genetic and structural clues about how the complex structures of eukaryotic cells, such as the cytoskeleton and membrane-trafficking systems, evolved from simpler ancestors.

Cellular Complexity

Recent research has shown that Asgard archaea have more complex cellular machinery than previously thought. They carry genes coding for proteins previously assumed unique to eukaryotes, such as proteins involved in:

Cytoskeletal structures (e.g., actin-like and tubulin-like proteins).
Membrane remodelling and vesicle transport.
Processes related to cell division and cellular organization.

Symbiotic Origin of Mitochondria

The Asgard archaea are pivotal in the hypothesis that the eukaryotic cell originated from an ancient symbiotic relationship between an archaeal host (an Asgard archaea) and an alphaproteobacterium.
This symbiosis eventually led to the alphaproteobacterium becoming the mitochondrion, the energy-producing organelle in eukaryotic cells.
While the exact nature of the original relationship remains uncertain—possibly parasitic, predatory, or mutually beneficial—it undeniably sparked a profound evolutionary innovation.

Cultivation and Research Breakthroughs

For years, researchers could not isolate these archaea in the lab; however, in 2020, scientists successfully cultured an Asgard archaeon (Prometheoarchaeum syntrophicum) from marine sediments, marking a major breakthrough.
Recent (2025) studies by Professor Martin Pilhofer's team at ETH Zurich, published in Cell, provided strong microscopic and biochemical evidence supporting the relationship between Asgard archaea and eukaryotes.

Ecological Roles

Found primarily in marine sediments, often near hydrothermal vents or methane seeps, indicating they likely have roles in the biogeochemical cycling of carbon and nutrients.
They thrive under extreme conditions, which makes them particularly important in understanding early-Earth environments.

Implications for Evolutionary Biology

Understanding Asgard archaea is crucial in elucidating the origin of complex cellular life and might help answer fundamental questions regarding the evolution of organelles, cellular complexity, and multicellularity.
They serve as a living bridge to deep evolutionary history, illuminating the transition from simple prokaryotic lifeforms to the complex organisms that eventually dominated the planet.

In short, the discovery and study of the Asgard archaea are among the most exciting and transformative advances in evolutionary biology in recent decades, significantly reshaping our narrative of life's complexity and origins.

When are the first eukaryote cells believed to have evolved?

The earliest eukaryotic cells are widely believed to have evolved roughly between 1.8 and 2.3 billion years ago. Current evidence places their emergence most confidently around 2.0 to 2.1 billion years ago based on fossil records and molecular clock estimates.

Key evidence supporting this timeline:

Microfossils and Geological Record:

Fossils displaying clear eukaryotic characteristics, such as complex morphology and size typically larger than prokaryotes, appear in rocks dating back around 1.6–1.8 billion years.
The Grypania spiralis fossil, at approximately 1.9–2.1 billion years old, is one of the earliest known fossil candidates for a eukaryotic organism.

Geochemical Evidence:

Increased levels of atmospheric oxygen (Great Oxygenation Event, around 2.4–2.0 billion years ago) set environmental conditions favourable for aerobic metabolism and consequently the evolution of eukaryotes.

Molecular Clock Data:

Genetic analyses estimating the divergence of archaea and eukaryotes typically indicate the earliest eukaryotes emerged around 2.0–2.3 billion years ago.
This timing aligns with the geological evidence and the appearance of complex cellular structures like mitochondria.

Importance of the Asgard Archaea discovery:

The discovery of the Asgard archaea has reinforced and refined this timeline, providing compelling evidence that the origin of eukaryotes was likely driven by a symbiotic event between an archaeon (from the Asgard lineage) and a bacterial symbiont, eventually evolving into mitochondria.

Current Scientific Consensus:

While exact dates continue to be refined, the current scientific consensus is:

Eukaryotic emergence: around 2.0–2.1 billion years ago.
Multicellularity (complex organisms): much later, approximately 600–800 million years ago.
In summary, eukaryotes evolved roughly 2 billion years ago, arising from transformative evolutionary events involving archaea (like the Asgard group) and bacteria, setting the stage for all complex life on Earth.

ChatGPT4.5 [Response to user request]
Retrieved from https://chatgpt.com/

Information Continually updated

Origin of Life: How microbes laid the foundation for complex cells
Who were our earliest ancestors? The answer could lie in a special group of single-celled organisms with a cytoskeleton similar to that of complex organisms, such as animals and plants. ETH researchers made these findings in a new study.

In brief

Asgard archaea are a group of microorganisms discovered just ten years ago. They represent a link between bacteria, archaea and complex organisms, such as plants and animals.
ETH researchers have now conducted a detailed examination of one such microbe, Lokiarchaeum ossiferum, and discovered cytoskeletal proteins very similar to those found in complex organisms.
As a result, it appears increasingly clear that Asgard archaea are ancestors of humans, animals and plants.

Ten years ago, nobody knew that Asgard archaea even existed. In 2015, however, researchers examining deep-sea sediments discovered gene fragments that indicated a new and previously undiscovered form of microbes.

With computer assistance, the researchers assembled these fragments like puzzle pieces to compile the entire genome. It was only then that they realised they were dealing with a previously unknown group of archaea.

Like bacteria, archaea are single-celled organisms. Genetically, however, there are significant differences between the two domains, especially regarding their cell envelopes and metabolic processes.

After a further search, microbiologists identified the corresponding organisms, described them and classified them as a separate archaeal sub-group: Asgard archaea. Their name, taken from the heavenly realm in Norse mythology, references their initial discovery close to Loki’s Castle – a black smoker on the mid-Atlantic ridge between Norway and Svalbard.

In fact, Asgard archaea appeared almost heaven-sent for research: they turned out to be a missing link between archaea and eukaryotes – that is, between archaea and organisms whose cells contain a nucleus, such as plants and animals.

Tree of life with one branch fewer

In recent years, researchers have found growing indications of close links between Asgard archaea and eukaryotes, and that the latter may have evolved from the former. The division of all living organisms into the three domains of bacteria, archaea and eukaryotes did not hold up to this surprising discovery.

Some researchers have since proposed regarding eukaryotes as a group within Asgard archaea. This would reduce the number of domains of life from three to two: archaea, including eukaryotes, and bacteria.

Redrawing the tree of life, with eukaryotes descending from Asgard archaea.
Graphic: Florian Wollweber / ETH Zurich
At ETH Zurich, Professor Martin Pilhofer and his team are fascinated by Asgard archaea and have examined the mysterious microbes for several years.

In an article published in Nature two years ago, the ETH researchers explored details of the cellular structure and architecture of Lokiarchaeum ossiferum. Originating in the sediments of a brackish water channel in Slovenia, this Asgard archaeon was isolated by researchers in Christa Schleper’s laboratory at the University of Vienna.

In that study, Pilhofer and his postdoctoral researchers Jingwei Xu and Florian Wollweber demonstrated that Lokiarchaeum ossiferum possesses certain structures also typical of eukaryotes.

We found an actin protein in that species that appears very similar to the protein found in eukaryotes – and occurs in almost all Asgard archaea discovered to date.

Professor Martin Pilhofer, lead author.
Department of Biology
Institute of Molecular Biology & Biophysics
Eidgenössische Technische Hochschule Zürich
Zürich, Switzerland.

In the first study, the researchers combined different microscopy techniques to demonstrate that this protein – called Lokiactin – forms filamentous structures, especially in the microbes’ numerous tentacle-like protrusions.

They appear to form the skeleton for the complex cell architecture of Asgard archaea.

Florian Wollweber, co-first author
Department of Biology
Institute of Molecular Biology & Biophysics
Eidgenössische Technische Hochschule Zürich
Zürich, Switzerland.

In addition to actin filaments, eukaryotes also possess microtubules. These tube-shaped structures are the second key component of the cytoskeleton and are comprised of numerous tubulin proteins. These tiny tubes are important for transport processes within a cell and the segregation of chromosomes during cell division.

The origin of these microtubules has been unclear – until now. In a newly published article in Cell, the ETH researchers discovered related structures in Asgard archaea and describe their structure. These experiments show that Asgard tubulins form very similar microtubules, albeit smaller than those in their eukaryotic relatives.

However, only a few Lokiarchaeum cells form these microtubules. And, unlike actin, these tubulin proteins only appear in very few species of Asgard archaea.

Expansion microscopy, a novel light microscopy technique, shows the cytoskeleton of Asgard archaea: Actin filaments (green) and, in the right-hand image, a microtubule (violet)
Image: from Wollweber F, et al. Cell, 2025.

Scientists do not yet understand why tubulins appear so rarely in Lokiarchaea, or why they are needed by cells. In eukaryotes, microtubules are responsible for transport processes within the cell. In some cases, motor proteins “walk along” these tubes. The ETH researchers have not yet observed such motor proteins in Asgard archaea.

We have shown, however, that the tubes formed from these tubulins grow at one end. We therefore suspect that they perform similar transport functions as the microtubules in eukaryotes.

Jingwei Xu, co-first author.
Department of Biology
Institute of Molecular Biology & Biophysics
Eidgenössische Technische Hochschule Zürich
Zürich, Switzerland.

[Jingwei Xu] produced the tubulins in a cell culture with insect cells and examined their structure.

Researchers from the fields of microbiology, biochemistry, cell biology and structural biology collaborated closely on the study

We would never have progressed so far without this interdisciplinary approach.

Professor Martin Pilhofer.

The structure of an Asgard microtubule, which consists of just five filaments (compared to 13 in eukaryotes).

Image: from Wollweber F, et al. Cell, 2025.

Was the cytoskeleton essential for the development of complex life? While some questions remain unanswered, the researchers are confident that the cytoskeleton was an important step in the evolution of eukaryotes.

This step could have occurred aeons ago, when an Asgard archaeon entwined a bacterium with its appendages. In the course of evolution, this bacterium developed into a mitochondrion, which serves as the powerhouse of modern cells. Over time, the nucleus and other compartments evolved – and the eukaryotic cell was born.

This remarkable cytoskeleton was probably at the beginning of this development. It could have enabled Asgard archaea to form appendages, thereby allowing them to interact with, and then seize and engulf a bacterium.

Professor Martin Pilhofer.

Fishing for Asgard archaea

Pilhofer and his colleagues now plan to turn their attention to the function of actin filaments and archaeal tubulin along with the resulting microtubules.

They also aim to identify the proteins that researchers have discovered on the surface of these microbes. Pilhofer hopes his team will be able to develop antibodies precisely tailored to these proteins. This would enable researchers to “fish” specifically for Asgard archaea in mixed microbe cultures.

We still have a lot of unanswered questions about Asgard archaea, especially regarding their relation to eukaryotes and their unusual cell biology. Tracking down the secrets of these microbes is fascinating.

Professor Martin Pilhofer.

Highlights

Asgard archaea express tubulins related to eukaryotic α/β-tubulin and bacterial BtubA/B
Asgard tubulins (AtubA/B/B2) assemble into canonical and non-canonical heterodimers
Asgard tubulin heterodimers polymerize into 5 or 7 protofilament microtubules
AtubA/B form cytoskeletal structures in Ca. Lokiarchaeum ossiferum

Summary
Microtubules are a hallmark of eukaryotes. Archaeal and bacterial homologs of tubulins typically form homopolymers and non-tubular superstructures. The origin of heterodimeric tubulins assembling into microtubules remains unclear.

Here, we report the discovery of microtubule-forming tubulins in Asgard archaea, the closest known relatives of eukaryotes. These Asgard tubulins (AtubA/B) are closely related to eukaryotic α/β-tubulins and the enigmatic bacterial tubulins BtubA/B. Proteomics of Candidatus Lokiarchaeum ossiferum showed that AtubA/B were highly expressed. Cryoelectron microscopy structures demonstrate that AtubA/B form eukaryote-like heterodimers, which assembled into 5-protofilament bona fide microtubules in vitro. The additional paralog AtubB2 lacks a nucleotide-binding site and competitively displaced AtubB. These AtubA/B2 heterodimers polymerized into 7-protofilament non-canonical microtubules. In a sub-population of Ca. Lokiarchaeum ossiferum cells, cryo-tomography revealed tubular structures, while expansion microscopy identified AtubA/B cytoskeletal assemblies.

Our findings suggest a pre-eukaryotic origin of microtubules and provide a framework for understanding the fundamental principles of microtubule assembly.
Graphical abstract
Graphic abstract

Introduction
The two major components of the eukaryotic cytoskeleton, actin filaments and microtubules, can be traced back to the last eukaryotic common ancestor (LECA). Asgard archaea, the closest known relatives of eukaryotes,^1,2,3,4 possess a plethora of eukaryotic signature proteins, including homologs of actin and actin-regulating proteins.^{1,2,3,4,5,6,7,8,9} We recently showed that the Asgard archaeon Candidatus Lokiarchaeum ossiferum carries an actin-based cytoskeleton.¹⁰ The evolutionary origin of the microtubule cytoskeleton, however, remains enigmatic.

Eukaryotic microtubules are formed by heterodimers of α- and β-tubulins. Their assembly into higher-order structures, typically 13-protofilament microtubules, is mediated via M-loop (microtubule loop)-mediated lateral interactions¹¹ and often aided by nucleating structures ensuring a homogeneous protofilament number.^12,13 Importantly, the protofilament number is variable across the eukaryotic domain of life and even across cell types,¹⁴ ranging from 11 in nematodes^15,16 to 40 in mantidfly sperm cells.¹⁷

Archaea and bacteria show a large number of tubulin homologs,¹⁸ most prominently FtsZ, which mediates cell division.^19,20,21,22 In contrast to microtubules, archaeal and bacterial tubulins typically assemble into homo-oligomeric protofilaments, which do not laterally assemble into microtubule-like structures. This is also true for “Odintubulin,” the only in vitro-characterized Asgard archaeal homolog of tubulin.²³ Even though the cellular function of archaeal and bacterial tubulin homologs is highly diverse,¹⁸ each protein typically possesses a single unique function in either cell division, DNA segregation, or cell shaping, which is in stark contrast to the multifunctional nature of eukaryotic microtubules,²⁴ which, among other roles, mediate long-range transport, form the structural core of cilia, and segregate chromosomes. Although tubulin homologs with close similarities to eukaryotic tubulins exist in Nitrososphaerota (formerly Thaumarchaeota),²⁵ the closest non-eukaryotic relatives of microtubule-forming tubulins have been found in Verrucomicrobia,^26,27,28 bacteria of the Planctomycetes-Verrucomicrobia-Chlamydiae (PVC) superphylum.^29,30

These bacterial tubulins, termed BtubA/B, can form heterodimers^31,32,33 and further polymerize into protofilaments and mini-microtubules consisting of 5 protofilaments in vivo³⁴ and 4 protofilaments in vitro.³⁵ Although their function is unknown, they display eukaryote-like behavior in vitro, such as dynamic instability and treadmilling,^35,36 and they may be linked to membranes.³⁷ Interestingly, BtubA/B do not require the complex eukaryotic tubulin assembly chaperones and can be heterologously expressed in bacteria.^31,33,34,38 Their isolated occurrence in a small number of Prosthecobacter species led to speculations about their horizontal gene transfer from a modern eukaryote,³¹ even though the chimeric nature and biochemical properties of BtubA/B support the origin from a pre-eukaryotic tubulin ancestor.^34,38,39 In the absence of close archaeal relatives of α- and β-tubulins, the evolutionary trajectory of tubulins to form heterodimers and assemble into microtubules remains unclear.

Wollweber, Florian; Xu, Jingwei; Ponce-Toledo, Rafael I.; Marxer, Florina; Rodrigues-Oliveira, Thiago; Pössnecker, Anja; Luo, Zhen-Hao; Malit, Jessie James Limlingan; Kokhanovska, Anastasiia; Wieczorek, Michal; Schleper, Christa; Pilhofer, Martin
Microtubules in Asgard archaea Cell (2025) DOI: 10.1016/j.cell.2025.02.027

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

This discovery not only enhances our understanding of life's evolutionary past but also fatally undermines key creationist assertions. Creationists frequently argue that life forms appeared suddenly, fully formed, and distinctly separate from one another — a perspective fundamentally incompatible with the gradual, branching tree of life supported by this recent research.

The Asgard archaea demonstrate precisely what creationists often insist cannot exist: transitional forms and evidence of incremental complexity. By identifying an organism that sits directly at the evolutionary bridge between simple prokaryotes and complex eukaryotic cells, researchers have uncovered tangible evidence of life's gradual evolution — exactly the type of "missing link" creationists deny. Furthermore, this discovery substantiates the widely accepted scientific timeline, firmly placing the origins of complex cellular life around two billion years ago, vastly earlier than the mere few thousand years proposed by Young Earth Creationism.

Ultimately, the findings at ETH Zurich vividly illustrate the predictive power and verifiability inherent in evolutionary theory, starkly contrasting with the static, untestable assertions of creationism. In bringing us closer to understanding life's true evolutionary trajectory, the Asgard archaea remind us that science, unlike dogma, thrives on inquiry, evidence, and discovery.

And of course, it almost goes without saying nowadays, there is no evidence whatsoever that the scientists found any reason to abandon the Theory of Evolution in favour of magical creationism to explain their findings.

Advertisement

Amazon