Rosa Rubicondior: Refuting Creationism - How Our Blood Cells Have Evolved From Our Single-Celled Ancestor from 700 Million Years Ago

The origin of blood cells can be traced back approximately 700 million years to when human ancestors were single-celled organisms. When these ancestors evolved into multicellular organisms (animals), macrophages emerged as the first blood cells. Over the course of subsequent evolution, various blood cells, such as mast cells, diversified.

KyotoU / Yosuke Nagahata

The 700-million-year history of our blood cells | EurekAlert!

In a stunning, albeit unwitting, rebuttal of creationist claims, a team of researchers at Kyoto University is due to publish, on 29 May 2026, the results of their investigation into the evolutionary history of animal blood cells in Proceedings of the National Academy of Sciences of the United States of America (PNAS). The paper, entitled "Animals have expanded the evolutionary legacy of unicellular ancestors in blood cells", is unlikely to please those creationists who keep assuring their dupes that biomedical scientists are about to abandon 'Darwinism' and adopt creationism instead.

It will also disappoint those who insist there is no evidence for the evolution of complex multicellular organisms from single-celled ancestors — what they like to caricature as the 'microbes-to-man hypothesis', as though humans, preferably modern Americans, were the preordained end-point of the entire history of life. That, of course, is creationist teleology masquerading as biology: the assumption that evolution must have been aiming at us because Bronze Age religion says humans are the central purpose of creation.

What the Kyoto University team found was not a sudden, magical appearance of blood cells, but a deep evolutionary continuity. They developed a new method for comparing gene-expression profiles across different animal cell lineages and species, and included unicellular organisms in the comparison in order to trace the possible origin of blood cells back to our single-celled animal ancestors.

Among human blood-cell lineages, macrophages showed the closest resemblance to unicellular organisms. This is hardly surprising, since macrophages still behave in a remarkably cell-autonomous way: they move through tissues, detect targets, engulf bacteria, clear dead cells and remove unwanted material — behaviour strongly reminiscent of free-living phagocytic cells.

The team then traced the gene FOS, commonly expressed in blood cells across animal species, back to a single-celled ancestor that lived about 700 million years ago, around the time when the first animals were evolving. The implication is that the earliest animal blood cells did not appear from nowhere. They arose when early multicellular animals repurposed genetic programmes inherited from their unicellular predecessors.

From there, the researchers were able to reconstruct a family tree of blood-cell lineages spanning roughly 700 million years. Their analysis suggests that early blood cells were macrophage-like, that mast cells later branched from that macrophage lineage, and that prototypic T cells and red blood cells subsequently branched from mast cells. Prototypic B cells, meanwhile, appear to have branched from the macrophage lineage after mast cells had already diverged.

In other words, the blood and immune cells circulating in our bodies today are not isolated, specially-created structures with no history. They are modified descendants of ancient cellular systems, inherited, repurposed and diversified during the evolution of animals from unicellular ancestors.

So, far from supporting the creationist claim that there is no evidence for the evolution of complex life from single-celled ancestors, the evidence is literally circulating in our blood. It is also circulating in the blood and immune systems of other animals, carrying with it a molecular and cellular legacy hundreds of millions of years older than the creation myths of the Bronze Age.

And, as usual, the Theory of Evolution provides the only coherent explanation for the observable facts. The research does not point to separate acts of creation, nor to a sudden magical appearance of blood cells fully formed and without ancestry. It shows descent with modification, inherited genetic programmes, divergence of cell lineages, and the repurposing of ancient biological mechanisms — exactly the pattern evolutionary theory predicts, and exactly the pattern creationism cannot explain without special pleading.

The Main Types of Mammalian Blood Cell. Mammalian blood is made up of plasma, the liquid component, and the so-called “formed elements”: red blood cells, white blood cells and platelets. Strictly speaking, in mammals only the white blood cells are complete, nucleated cells. Mature red blood cells have lost their nuclei, and platelets are small cell fragments produced from larger bone-marrow cells called megakaryocytes.

Red blood cells, or erythrocytes, are the oxygen-carrying cells of the blood. In mammals they are flattened, flexible, biconcave discs packed with haemoglobin, the iron-containing protein that binds oxygen in the lungs and helps deliver it to tissues. Their lack of a nucleus gives them more internal space for haemoglobin, but also means they cannot divide or repair themselves in the way most cells can.
Platelets, or thrombocytes, are not true cells in mammals but fragments of cytoplasm released by megakaryocytes in the bone marrow. Their main role is in haemostasis — the prevention of blood loss. They stick to damaged blood-vessel walls, clump together and help trigger the clotting process that seals wounds.
White blood cells, or leukocytes, are the immune cells found in the blood. They are much less numerous than red blood cells, but far more varied. They include cells involved in inflammation, defence against bacteria, viruses and parasites, allergic reactions, antibody production and the coordination of immune responses.
The five main types of white blood cell normally recognised in a blood count are neutrophils, eosinophils, basophils, monocytes and lymphocytes.

Neutrophils are the most abundant white blood cells in many mammals, including humans. They are rapid-response cells, especially important in fighting bacterial and fungal infections. They engulf and destroy microbes and are often abundant in pus at sites of infection.
Eosinophils are involved particularly in responses to parasites, especially worms, and also play a role in allergic inflammation and asthma. Their granules contain toxic proteins that can damage large parasites which are too big to be swallowed whole.
Basophils are rare circulating white blood cells involved in allergic and inflammatory responses. They release substances such as histamine and are functionally related, though not identical, to mast cells, which mostly reside in tissues rather than circulating freely in the blood.
Monocytes are large white blood cells that circulate in the blood before migrating into tissues. Once in tissues, they can develop into macrophages or related cells. Macrophages engulf bacteria, dead cells and debris, and also help alert and organise other parts of the immune system.
Lymphocytes include several major immune-cell lineages. B cells can develop into antibody-producing plasma cells; T cells help coordinate immune responses or kill infected cells; and natural killer cells form part of the innate immune response, especially against virus-infected and abnormal cells.

These categories are useful, but they are simplified. Modern immunology recognises many further subtypes within each broad class — such as helper T cells, cytotoxic T cells, regulatory T cells, memory B cells, dendritic-cell-like monocyte derivatives and many others.

For the purposes of understanding blood evolution, however, the important point is that mammalian blood is not a collection of unrelated, specially-created cell types. It is a diversified system of related cell lineages, many of them traceable back through deep evolutionary history to ancient cell behaviours such as movement, engulfment, signalling and defence against other organisms.

The forthcoming PNAS publication was announced in a Kyoto University news release published by EurekAlert!.

The 700-million-year history of our blood cells
How animals expanded the evolutionary legacy of our unicellular ancestors
Kyoto, Japan -- Almost all animal species -- including humans -- have blood cells, but between different species our blood tells different stories. The lineage and components of blood cells vary widely, and this variety is a testament to how animals have evolved to protect themselves from infectious diseases.

Thanks to advances in hematology and immunology, we now have detailed knowledge of the components and functions of both human and mouse blood cells. However, their evolutionary history has remained largely unknown. This inspired a team of researchers at Kyoto University to investigate when and how blood cells originated, and how they diversified.

The team began by developing a new analytic method to compare gene expression profiles across various cell lineages and animal species. With this they were able to construct phylogenetic trees of cell lineages and estimate the evolutionary history of these lineages in animals. They also included unicellular organisms in their comparison in order to trace the origin of blood cells back to possible single-celled ancestors.

Among the various lineages of human blood cells the team observed, macrophages showed the most striking resemblance to unicellular organisms, suggesting that early blood cells were macrophage-like. They then traced the gene FOS -- commonly expressed in blood cells across animal species -- back to a single-celled ancestor that lived 700 million years ago, suggesting that the first blood cells emerged around the same time as the onset of multicellular animals.

This finding implies that early animals generated the first blood cells by repurposing genetic material inherited from single-celled progenitors. The team's analysis also revealed that mast cells branched off from the macrophages, and that prototypic T cells and red blood cells subsequently branched off from the mast cells. Furthermore, prototypic B cells branched off from the macrophages after the segregation of mast cells.

Ultimately, the scientists were able to reconstruct the family tree of blood cells over the 700-million-year span, revealing that evolutionary history has been imprinted in our bodies as differentiation pathways of these cells. This work illustrates that the blood and immune cells circulating in our bodies can be considered a successful extension of the legacy left to us by our single-celled predecessors.

I feel deeply moved by these findings, which represent the culmination of our work and illustrate that the differentiation pathways of vertebrate blood cells reflect the 700-million-year evolutionary history of these cells.

Hiroshi Kawamoto, lead author.

When I let it sink in that this legacy from so long ago is circulating within my body as blood cells, I feel closer to our distant ancestors.

Yosuke Nagahata, first author
Institute of Evolutionary Biology, Spain.

The researchers expect that the method developed in this study could help unravel the evolutionary origins of diseases such as cancer, leading to a better understanding of mechanisms and the development of new treatments.

Publication:
"Animals have expanded the evolutionary legacy of unicellular ancestors in blood cells" appeared on 29 May 2026 in Proceedings of the National Academy of Sciences of the United States of America, with doi: 10.1073/pnas.2528110123

The Abstract will appear here after publication (29 May 2026).

So yet again, creationists are left with the familiar problem: the evidence is not merely inconsistent with their mythology; it is exactly the kind of evidence that should not exist if their mythology were true. Blood cells should not carry a traceable evolutionary history stretching back hundreds of millions of years to unicellular ancestors if they were created independently, fully formed, and without ancestry just a few thousand years ago.

But they do. Their genes, their behaviours and their relationships to one another make sense as the products of descent with modification. They do not make sense as the products of separate magical acts of creation. The macrophage-like behaviour of some immune cells, the branching relationships between blood-cell lineages, and the repurposing of ancient genetic programmes all point in the same direction: continuity, ancestry and evolutionary tinkering.

This is why modern biomedical science does not need creationism. It explains nothing, predicts nothing and adds nothing to our understanding. Evolution, by contrast, provides a coherent framework in which the origin, diversification and function of blood cells can be understood as part of the wider history of animal life.

And there, circulating quietly in every creationist’s bloodstream, is another awkward little fact they would rather not think about: their own blood cells are carrying the molecular legacy of their single-celled ancestors. Not a trace of special creation; not a hint of magic; just the unmistakable signature of evolution doing what evolution does — modifying what already exists and turning ancient biological machinery to new uses.

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