Blaise Pascal - by Peter Rollins "Five Part Course on Pascal's 'Pensees'"

Blaise Pascal, "Faith without virtue is meaningless"

Introduction - The Child Prodigy, Blaise Pascal

Setting Pascal Ablaze | A Pyrotheological Reading of Pensées

by Peter Rollins

June 14, 2023

JUNE 14 AT 10:52 AM

Setting Pascal Ablaze | A Five-Part Course

Blaise Pascal has earned his place in history as one of the world’s greatest mathematicians and scientists, making important intellectual contributions from the age of 16, including the invention of a calculator as a teenager - just to help his dad work out his taxes. However, Pascal is most famous for his philosophical reflections. Reflections which possess a richness, style and insight that make them feel as fresh and vital today as when they were first written.

His masterpiece was an unfinished work that came to be called the Pensées. Through his endeavor to describe and defend Christianity in a compelling way, Pascal ended up giving the world some of the most profound descriptions of the human condition. Predating both Psychoanalysis and Existentialism, his work describes many of the themes that would become so central to these movements, such as the power of self-deception, the anxiety of freedom and the dizzying experience of feeling both the splendor and insignificance of existence. Basically, it’s a intellectual rollercoaster.

In this five part course, we’ll take a deep dive into Pascal’s Pensées, wrestling with its themes and seeing how they might both illuminate and impact our lives.

Course Schedule:

1. Deception and Distraction - June 25th
2. Without a Compass or a Map - July 16th
3. The Gambler and the Machine - July 23rd
4. Rethinking the God Shaped Hole - July 30th
5. Class Presentations (optional) - August 20th

All classes will commence at 10 am PST (1 pm EDT, 6 pm BST). Recordings of each session will be available, allowing you to watch live or later. I recommend A.J. Krailsheimer’s translation of Pensées (readings will be assigned from that translation).

How to Join:

Go here to join - https://www.patreon.com/peterrollins for $20.00 / month.

This course is open to everyone who supports me at Blaze level on Patreon. By supporting me on Patreon, you not only enable me to dedicate myself fully to this work, but you also get access to hundreds of hours of archived material, along with regular book studies, hangouts, and other events.

Hope you can join me!

The Child Prodigy, Blaise Pascal

Blaise Pascal

French philosopher and scientist

article link

[abridged edits and re-organization of article are mine - re slater]

Written by Jean Orcibal, Lucien Jerphagnon

Fact-checked by The Editors of Encyclopaedia Britannica

Last Updated: Jun 15, 2023 • Article History

Born: June 19, 1623 Clermont-Ferrand, France

Died: August 19, 1662 (aged 39) Paris, France

Inventions

Pascaline

Notable Work

“Essai pour les coniques”

“Les Provinciales”

“Pensées”

“The Physical Treatises of Pascal”

“Traité du triangle arithmétique”...

Subjects Of Study

Pascal’s principle

Pascal’s theorem

Pascal’s triangle

conic section

cycloid

Blaise Pascal, (born June 19, 1623, Clermont-Ferrand, France—died August 19, 1662, Paris), French mathematician, physicist, religious philosopher, and master of prose.

He laid the foundation for the modern theory of probabilities, formulated what came to be known as Pascal’s principle of pressure, and propagated a religious doctrine that taught the experience of God through the heart rather than through reason. 

The establishment of his principle of intuitionism [(feeling? - re slater)] had an impact on such later philosophers as Jean-Jacques Rousseau and Henri Bergson and also on the Existentialists.

Pascal’s life to the Port-Royal years

Pascal’s father, Étienne Pascal, was presiding judge of the tax court at Clermont-Ferrand. His mother died in 1626, and in 1631 the family moved to Paris. Étienne, who was respected as a mathematician, devoted himself henceforth to the education of his children.

While his sister Jacqueline (born in 1625) figured as an infant prodigy in literary circles, Blaise proved himself no less precocious in mathematics. In 1640 he wrote an essay on conic sections, Essai pour les coniques, based on his study of the now classical work of Girard Desargues on synthetic projective geometry.

The young man’s work, which was highly successful in the world of mathematics, aroused the envy of no less a personage than the great French Rationalist and mathematician René Descartes.

Pascaline

Between 1642 and 1644, Pascal conceived and constructed a calculating device, the Pascaline, to help his father—who in 1639 had been appointed intendant (local administrator) at Rouen—in his tax computations. The machine was regarded by Pascal’s contemporaries as his main claim to fame, and with reason, for in a sense it was the first digital calculator since it operated by counting integers. The significance of this contribution explains the youthful pride that appears in his dedication of the machine to the chancellor of France, Pierre Seguier, in 1644.

Blaise Pascal conducting experiments

Blaise Pascal

Until 1646 the Pascal family held strictly Roman Catholic principles, though they often substituted l’honnêteté (“polite respectability”) for inward religion. 

An illness of his father, however, brought Blaise into contact with a more profound expression of religion, for he met two disciples of the abbé de Saint-Cyran, who, as director of the convent of Port-Royal, had brought the austere moral and theological conceptions of Jansenism into the life and thought of the convent.

Jansenism was a 17th-century form of Augustinianism in the Roman Catholic Church. It repudiated free will, accepted predestination, and taught that divine grace, rather than good works, was the key to salvation. [Of the three, process theology is argues for, and is based upon, freewill, rejects predestination in favor of a divinely open present and future, and elevates divine grace - re slater]

The convent at Port-Royal had become the centre for the dissemination of the doctrine. Pascal himself was the first to feel the necessity of entirely turning away from the world to God, and he won his family over to the spiritual life in 1646. His letters indicate that for several years he was his family’s spiritual adviser, but the conflict within himself—between the world and ascetic life—was not yet resolved. 

Absorbed again in his scientific interests, he tested the theories of Galileo and Evangelista Torricelli (an Italian physicist who discovered the principle of the barometer). To do so, he reproduced and amplified experiments on atmospheric pressure by constructing mercury barometers and measuring air pressure, both in Paris and on the top of a mountain overlooking Clermont-Ferrand.

These tests paved the way for further studies in hydrodynamics and hydrostatics. While experimenting, Pascal invented the syringe and created the hydraulic press, an instrument based upon the principle that became known as Pascal’s principle: pressure applied to a confined liquid is transmitted undiminished through the liquid in all directions regardless of the area to which the pressure is applied. His publications on the problem of the vacuum (1647–48) added to his reputation. 

When he fell ill from overwork, his doctors advised him to seek distractions; but what has been described as Pascal’s “worldly period” (1651–54) was, in fact, primarily a period of intense scientific work, during which he composed treatises on the equilibrium of liquid solutions, on the weight and density of air, and on the arithmetic triangle: Traité de l’équilibre des liqueurs et de la pesanteur de la masse de l’air (Eng. trans., The Physical Treatises of Pascal, 1937) and also his Traité du triangle arithmétique [Treatise of Triangle Arithmatic - re slater]. In [his] last treatise, a fragment of the De Alea Geometriae, [Of Angular Geometry? - re slater], he laid the foundations for the calculus of probabilities.

By the end of 1653, however, he had begun to feel religious scruples; and the “night of fire,” an intense, perhaps mystical “conversion” that he experienced on November 23, 1654, he believed to be the beginning of a new life.

He entered Port-Royal in January 1655, and though he never became one of the solitaires, he thereafter wrote only at their request and never again published in his own name. The two works for which he is chiefly known, Les Provinciales and the Pensées, date from the years of his life spent at Port-Royal.

Les Provinciales of Blaise Pascal

Written in defense of Antoine Arnauld, an opponent of the Jesuits and a defender of Jansenism who was on trial before the faculty of theology in Paris for his controversial religious works, Pascal’s 18 Lettres écrites par Louis de Montalte à un provincial deal with divine grace and the ethical code of the Jesuits. 

They are better known as Les Provinciales (“The Provincial Letters”). They included a blow against the relaxed morality that the Jesuits were said to teach and that was the weak point in their controversy with Port-Royal; Pascal quotes freely Jesuit dialogues and discrediting quotations from their own works, sometimes in a spirit of derision, sometimes with indignation. In the two last letters, dealing with the question of grace, Pascal proposed a conciliatory position that was later to make it possible for Port-Royal to subscribe to the “Peace of the Church,” a temporary cessation of the conflict over Jansenism, in 1668.

The Provinciales were an immediate success, and their popularity has remained undiminished. This they owe primarily to their form, in which for the first time bombast and tedious rhetoric are replaced by variety, brevity, tautness, and precision of style; as Nicolas Boileau, the founder of French literary criticism, recognized, they marked the beginning of modern French prose.

Something of their popularity, moreover, in fashionable, Protestant, or skeptical circles, must be attributed to the violence of their attack on the Jesuits. In England they have been most widely read when Roman Catholicism has seemed a threat to the Church of England.

Yet they have also helped Catholicism to rid itself of laxity; and, in 1678, Pope Innocent XI himself condemned half of the propositions that Pascal had denounced earlier. Thus, the Provinciales played a decisive part in promoting a return to inner religion and helped to secure the eventual triumph of the ideas set forth in Antoine Arnauld’s treatise De la fréquente communion (1643), in which he protested against the idea that the profligate could atone for continued sin by frequent communion without repentance, a thesis that thereafter remained almost unchallengeable until the French church felt the repercussion of the revocation of the Edict of Nantes (which had granted religious freedom to French Protestants) in 1685.

Whereas the Jesuits seemed to represent a Counter-Reformation predominantly concerned with orthodoxy and obedience to ecclesiastical authority, the Provinciales advocated a more spiritual approach, emphasizing the soul’s union with the Mystical Body of Christ through charity.

Further, by rejecting any double standard of morality and the distinction between counsel and precept, Pascal aligned himself with those who believe the ideal of evangelical perfection to be inseparable from the Christian life.

Although there was nothing original in these opinions, Pascal nevertheless stamped them with the passionate conviction of a man in love with the absolute, of a man who saw no salvation apart from a heartfelt desire for the truth, together with a love of God that works continually toward destroying all self-love.

For Pascal, morality cannot be separated from spirituality. Moreover, his own spiritual development can be traced in the Provinciales. The religious sense in them becomes progressively refined after the first letters, in which the tone of ridicule is smart rather than charitable.

Pensées

Pascal finally decided to write his work of Christian apologetics, Apologie de la religion chrétienne, as a consequence of his meditations on miracles and other proofs of Christianity. The work remained unfinished at his death. Between the summers of 1657 and 1658, he put together most of the notes and fragments that editors have published under the inappropriate title Pensées (“Thoughts”).

In the Apologie, Pascal shows the man without grace to be an incomprehensible mixture of greatness and abjectness, incapable of truth or of reaching the supreme good to which his nature nevertheless aspires. A religion that accounts for these contradictions, which he believed philosophy and worldliness fail to do, is for that very reason “to be venerated and loved.” 

"The indifference of the skeptic," Pascal wrote, "is to be overcome by means of the “wager”: if God does not exist, the skeptic loses nothing by believing in him; but if he does exist, the skeptic gains eternal life by believing in him." Pascal insists that men must be brought to God through Jesus Christ alone, because a creature could never know the infinite if Jesus had not descended to assume the proportions of man’s fallen state.

The second part of the work applies the Augustinian theory of allegorical interpretation to the biblical types (figuratifs); reviews the rabbinical texts, the persistence of true religion, the work of Moses, and the proofs concerning Jesus Christ’s God-like role; and, finally, gives a picture of the primitive church and the fulfillment of the prophecies. The Apologie (Pensées) is a treatise on spirituality. Pascal was not interested in making converts if they were not going to be saints.

Pascal’s apologetics, though it has stood the test of time, is primarily addressed to individuals of his own acquaintance. To convert his libertine friends, he looked for arguments in their favourite authors: in Michel de Montaigne, in the Skeptic Pierre Charron, in the Epicurean Pierre Gassendi, and in Thomas Hobbes, an English political philosopher. For Pascal, Skepticism was but a stage. Modernist theologians in particular have tried to make use of his main contention, that [i] “man is infinitely more than man,” in isolation from his other contention, that [ii] man’s wretchedness is explicable only as the effect of a Fall, about which a man can learn what he needs to know from history. In so doing, they sacrifice the second part of the Apologie to the first, keeping the philosophy while losing the exegesis. For Pascal, as for St. Paul, Jesus Christ is the second Adam, inconceivable without the first.

Finally, too, Pascal expressly admitted that his psychological analyses were not by themselves sufficient to exclude a “philosophy of the absurd”; to do so, it is necessary to have recourse to the convergence of these analyses with the “lines of fact” concerning revelation, this convergence being too extraordinary not to appear as the work of providence to an anguished seeker after truth (qui cherche en gémissant).

He was next again involved in scientific work:

First, the “Messieurs de Port-Royal” themselves asked for his help in composing the Élements de géométrie; and second, it was suggested that he should publish what he had discovered about cycloid curves, a subject on which the greatest mathematicians of the time had been working.

Once more fame aroused in him feelings of self-esteem; but from February 1659, illness brought him back to his former frame of mind, and he composed the “prayer for conversion” that the English clergymen Charles and John Wesley, who founded the Methodist Church, were later to regard so highly.

Scarcely capable of regular work, he henceforth gave himself over to helping the poor and to the ascetic and devotional life. He took part intermittently, however, in the disputes to which the “Formulary”—a document condemning five propositions of Jansenism that, at the demand of the church authorities, had to be signed before a person could receive the sacraments—gave rise. Finally a difference of opinion with the theologians of Port-Royal led him to withdraw from controversy, though he did not sever his relations with them.

Pascal died in 1662 after suffering terrible pain, probably from carcinomatous meningitis [a form of brain cancer - re slater] following a malignant ulcer of the stomach. He was assisted by a non-Jansenist parish priest.

Legacy of Blaise Pascal

At once a physicist, a mathematician, an eloquent publicist in the Provinciales, and an inspired artist in the Apologie and in his private notes, Pascal was embarrassed by the very abundance of his talents.

It has been suggested that it was his too concrete turn-of-mind that prevented his discovering the infinitesimal calculus; and in some of the Provinciales the mysterious relations of human beings with God are treated as if they were a geometrical problem.

But these considerations are far outweighed by the profit that he drew from the multiplicity of his gifts; his religious writings are rigorous because of his scientific training; and his love of the concrete emerges no less from the stream of quotations in the Provinciales than from his determination to reject the vigorous method of attack that he had used so effectively in his Apologie.

Process Philosophy & Science - "We Are as All Is"

Process Philosophy & Science

"We Are as All Is"

by R.E. Slater

"All life-forms are relational processes inhabiting a natural world best understood as “an event that never stops." This is how process works in science. - Merlin Sheldrake, biologist

Looking for process in a universe of inorganic things or organic lifeforms isn't hard once you get use to looking for it. It simply is a series of connected, relational events which become... are for a while... and then are not....

Whitehead described these series of events as:

• prehensive - possible relational events which aren't; which are affected by past events and consequently affecting present events once birthed (and I would submit, affected by, and affecting, future events; that is, the future is affecting the past even as the present births the future); as a  philosophical description, prehensive events are "interactions of a subject with an event or entity which involves perception but not necessarily cognition".

• actualized occassions - the momentary now result of prehensive formation (cf. Jay McDaniel's philosophical description here); and

• concrescence - the coalescence, or growing, together of parts/whole+events which were originally separate. When they do, they become "concrete" or "fully actual" or "actualized". (cf. Whitehead's Idea of Concrescence).

The three terms/ideas when taken together imply that "the one comes into being and is increased by one" in Whiteheadian terms.

"Whether we speak of moments in time or events, every occurring moment comes into being, lives for a moment, then dies and in dying creates a new moment which has been affected by its past-present-and future becoming. Not only affecting itself, but by affecting other recurring moments (both backwards in time and forwards in time), as material events come-and-go, plunging into the future as either (i) generative, value-adding events or, (ii) nongenerative, unbecoming (non-valuative) events. This is the Whiteheadian universe." - R.E. Slater

Additionally, a succinct description of processual organism is that of an ontological form, or (Jungian) Arche-Type, which consists as a panrelational, panexperiential, and panpsychic living organism in its eventuating evolution and becoming (both materially and spiritually). Without a deeply processual and experiential relationality there can be no actualizing of a accreting event. Simply, all is irreducibly atomic, isolated, unaffecting, and unbecoming within each non-moment of a timeless cosmology (or, eco-cosmic non-evolving system).

In non-material terms, this kind of processual ontology is part of a processual metaphysic describing a material multiverse both in its parts and its whole through meaningfully interacting contact across its "processualizing being"... a process metaphysic and ontology which I like to describe as eco-comic-pan/cessualism.

Whitehead in his time called this kind of cosmology a "philosophy of organism," with emphasis on "organism". One which is infinitely connected, dynamically alive, and living-and-breathing across it's esoteric being. An esotericism of a kind not sentient but not not sentient. An alien sentience, if you will, describable in its parts as we come across such unhuman-like events.

Which is also why one might speak to process ontology as inhabited by a kind of process-based panpsychicism... the simplest "elemental" forms lying in the very nature of the quantum forces (gravitation, electromagnetism, the weak and strong interaction of forces).

Essentially, Whitehead gives back to evolutionary cosmology and biology a way to scientifically describe how the multiverse "feels" within and across itself. Which is another way of describing our own human version of esoteric panpsychicism as a unique, singular event we might call consciousness, soul, or spirit. Yet, it is UNsingular in that human sentience was birthed as a processual cosmic event that provided to us our ground of being.

This is quite different from the typical Christian viewpoint based up Platonic thought that in every way we are a culminating event rather than a proceeding event. If the later, that both the cosmos and the earth birthed us according to its own esotoric kind of panpsychic pancessualism. By logic, we are what lies all around us and are not unique is the cosmic sense but only in the biological sense. And should this be so, then our hubris about ourselves should cease altogether in realizing we are partners with nature which is in us and greater than us in all its entirety.

The Greek/Kantian/Descrates Mind v Body dualsim of material v eternal forms was to remove us from our ground(s) of being. In Whitehead, he returns us to our birthing grounds of sun and star, earth and soil.

In Christian terms, a process theologian says "We are because of what came before to be increased by one and thereby birth a new kind of esoteric pancessual event." - R.E. Slater

And further, all is birthed into a processual God's Imago Dei who took what was , and filled the there there with pancessual possibility (sic, continua creatio NOT creatio ex nihilo....). Why creatio continua? Because the universe always was even as God was and is....

The metaphysical difference is that "the one (creation) is responding to the other (God)" in generatively valuative terms... in this case evolutionary becomingness... thus describing the kind of teleology which pancessually inhabits all ontological entities across all pancessual levels of events.

• Creatio Continua (that which is) - [German Version] "Continuous Creation" aims to express the idea that the created world is dependent at each moment in its temporal existence on the active presence of God for its maintenance and subsistence lest it returns back to its void of unbecoming materiality.

• Creatio ex Nihilo (that which isn't) - According to the Evangelical Dictionary of Theology, creatio ex nihilo 'means God brought the world into existence “out of nothing” through a purposeful act of his free will. In this the Christian doctrine confesses God as the almighty and sovereign Lord of all existence (and by inference, so can the process metaphysician when rewriting classical theism into Whiteheadian forms of panentheism. A panentheism based upon a God of Love and birthing a Theology of Love).

Now, when we read science articles - like the two I've included below as a continuation of my last post on fungi - we can start teaching ourselves how to think in process terms of life.

And to Christians, as they read and study their bible, they might also teach themselves to see a process-based God affecting a process-based world of events in a consistent manner to God's processual nature.

Need Examples?

• The Crucifixion of Christ... which was a result of prehensive events birthing an actualized occasion with deafening concrescencing results.

• Or the salvation of a individual due to the Crucifixion of Christ leading to a re-configuration of one's life identifying with the valuative streams of a generative life.

• Or how the very ground of being we might notice in ourselves we can also see in the Earth's evolutionary process producing sacrificial and redeeming events as a matter of course to it's becomingness when in sync with God's becoming activity of presence, sustainability, and urging across its evolutionary features. Ex: As the Sun activates photosynthesis to give food to creature in life-and-death processes, so too when climate disasters strike the earth responds with greater life forces.

More?

• Observed "spiritual" symbols or "felt" iconographs grounded in the earth and stars above are not isolated metaphysic events in themselves, but symbolize affecting events in a living pancessual universe striving against death to re-birth life everlastingly until it can no longer achieve it's purpose in an entropic universe.

• Though we seemingly exist in a chaotic entropic universe of death (re the Second Law of Thermodynamics) there also inhabits a life-giving force here described as "pancessual (everywhere present) negentropy (non-entropic)" which necessarily reverses death's chaos towards processually valuative birthing events. As example, Christ's atoning resurrection from death aptly illustrates the ying-and-yang between the cycle of life and death.

• This quality of "life from within death" is found pervasively throughout the cosmos having been birthed in the halls of Divine Love which also birthed a freewill universe irresistibly driven towards imagination, novelty, and generative wellbeing. A universe of loving freewill tilted to become more than it is. This then captures Whitehead's idea of something that is which is alway becoming more than it is (being and becoming) as opposed to death's isolating quality of incompleteness and never-becomingness.

Blessings,

R.E. Slater

June 23, 2023

* * * * * * *

These Primordial Organisms May Have Been The First Predators on Earth

article link

by Michelle Starr

NATURE    |   June 9, 2023

Artistic interpretation of organisms in the Protosterol Biota. (Orchestrated in MidJourney by TA 2023)

Traces of molecules found in ancient rocks are revealing a wild ecosystem of early life that hunted and thrived in the world's oceans for nearly a billion years.

Biomarker signatures found in rocks dated to 1.64 billion years ago were left by an entire range of previously unknown organisms that dominated life on Earth, in a low-oxygen world an eon before the emergence of plants, animals, and fungi.

These organisms were unlike anything alive today; their discoverers, led by paleobiogeochemists Jochen Brocks and Benjamin Nettersheim of the Australian National University in Australia, have collectively named them the protosterol biota.

They could be the world's earliest predators, feasting on microbes abundant in the oceans at that time; and they also appear to be the ancestors of all eukaryotic life on Earth. That's all the plants, animals and fungi that are around now – including us.

"Molecular remains of the protosterol biota detected in 1.6-billion-year-old rocks appear to be the oldest remnants of our own lineage – they lived even before the Last Eukaryotic Common Ancestor (1.2 billion years ago)," says Nettersheim, who is now at the University of Bremen in Germany.

"These ancient creatures were abundant in marine ecosystems across the world and probably shaped ecosystems for much of Earth's history."

Artistic interpretation of a group of early eukaryotes hanging out over a microbial mat. (Orchestrated in MidJourney by TA 2023)

Because eukaryotic life – organisms whose cells contain a nucleus – is so dominant today, scientists think that it must have emerged more than a billion years ago.

Paleobiologists have been on the lookout for these early eukaryotes for a long time, but identification of ancient organisms is challenging at best. Since it's been more than a billion years since they lived, any traces they may have left behind are likely to be extremely degraded, and difficult to confidently diagnose.

The discovery was made analyzing rocks from waterways around the world, the oldest of which were from the Barney Creek Formation in Australia, dating to 1.64 billion years ago.

They were specifically looking for steroids, a biomarker of early eukaryotes first predicted by Nobel laureate biochemist Konrad Bloch in 1994, as nearly all eukaryotes can synthesize steroids, such as cholesterol.

Artistic interpretation of early eukaryotes on the ocean floor. (Orchestrated in MidJourney by TA 2023)

"We employed a combination of techniques to first convert various modern steroids to their fossilized equivalent; otherwise, we wouldn't have even known what to look for," Brocks explains.

He adds, "Scientists had overlooked these molecules for decades because they do not conform to typical molecular search images. Once we knew our target, we discovered that dozens of other rocks, taken from billion-year-old waterways across the world, were oozing with similar fossil molecules."

The discovery shows that these eukaryote biomarkers had been hiding in plain sight all along, although what the creatures that produced them were like remains unknown, since fossils of the creatures themselves have not been found.

However, the researchers believe that the organisms of the protosterol biota were larger and more complex than bacteria, and thrived on them as the next chain up in the food web. "We believe they may have been the first predators on Earth, hunting and devouring bacteria," Brocks says.

Artistic interpretation of stem eukaryotes feeding on a microbial mat. (Orchestrated in MidJourney by TA 2023)

Interestingly, the traces left behind by these creatures stopped appearing in the fossil record around 800 million years ago. After this point, algae and fungi begin to appear; the first animals are thought to have emerged about 700 or 600 million years ago.

The decline of the protosterol biota and the emergence of other organisms is known as the Tonian Transformation, and it's one of the most profound alterations Earth's ecology has undergone, allowing for the rise of modern eukaryotes.

The discovery of sterols very similar to those our bodies produce today, in a very different set of organisms, allows us to trace our history back to a time much farther than ever before.

"The highlight of this finding is not just the extension of the current molecular record of eukaryotes," says paleobiogeochemist Christian Hallmann of the German Research Center for Geosciences in Germany.

"Given that the last common ancestor of all modern eukaryotes, including us humans, was likely capable of producing 'regular' modern sterols, chances are high that the eukaryotes responsible for these rare signatures belonged to the stem of the phylogenetic tree."

* * * * * * *

Parasites May Be Hijacking

Evolution on Planet Earth

article link

by Michelle Starr

NATURE    |    08 June 2023

Felines are the definitive host of famous parasite Toxoplasma gondii, thought
to influence the behavior of its hosts. (Martin Harvey/The Image Bank/Getty)

Life is not always straightforward about the business of living.

A food web, for instance, consists of chains upon chains of organisms stealing other organisms' energy-processing abilities.

We can't process sunlight into the sugars we need for energy; we wait for plants to do it, and eat them. Carnivores can't properly digest plants; they wait for other animals to eat plants, then eat those animals.

In other words, most of us piggyback off other organisms in some way – but parasites take the notion to its ultimate conclusion. Why go about the hard work of living when you can get some other creature to do it for you? Or, even better, make them do it for you.

This is the wild west of parasitology: when a parasite doesn't just hitch a ride, but hijacks the body of their host in some way, driving it to behaviors that benefit the parasite – often to their own great, even fatal, detriment.

"In the scientific literature, the name for that is adaptive host manipulation hypothesis," parasitologist Alex Maier of the Australian National University told ScienceAlert.

"That means that the parasites actually induce modification in the host, that could maximize the parasite sickness. So that the parasite is distributed more often, and there are more parasites out there."

You may have heard of this before. One of the most well-known examples is Toxoplasma gondii, which causes a disease called toxoplasmosis.

Studies have found that animals infected with T. gondii exhibit behavioral changes, taking more risks, and behaving in ways that may make them more likely to encounter cats – the only host in which the parasite can reproduce.

Whether or not T. gondii does actually manipulate hosts is still under investigation, but T. gondii is just one parasite. There are many parasites out there tweaking their hosts in different ways… and the fascinating thing is that often we have no idea how they actually do it.

Let's get physical

Parasites live a very complicated and circuitous life, but it seems to be incredibly effective. While some parasites stick to one host for their whole life cycle, others require multiple hosts to complete their biological journeys.

Here's how the more complex life cycles tend to work. A parasite reproduces and lays eggs in what is known as the definitive host. Those eggs are shed into the environment, usually in feces; the eggs or larvae are then taken up by the first intermediate host.

There, the parasite continues to develop, and from here can either continue to grow to maturity, or make its way to a second intermediate host to complete its growth.

Once it is fully grown and ready to reproduce, it needs to make its way back to the definitive host – often a specific type of animal, like T. gondii and cats.

Which is where adaptive host manipulation comes into play.

The most obvious way a parasite can manipulate a host is by changing its body in some way. Some of these are spectacularly weird.

Ribeiroia ondatrae, the frog-mutating flatworm, is a flatworm that, like its name indicates, mutates frogs. Specifically, it seems to target the frogs' hind legs. Frogs infected with this parasite grow additional, useless limbs – sometimes lots of them.

Another flatworm, called Leucochloridium paradoxum (the green-banded broodsac), enters the eyestalks of snails, where it swells and pulsates, creating an eye-catching display of movement and color.

In both of these cases, the ultimate target of the parasites is not the frogs, or the snails. Both R. ondatrae and L. paradoxum live and grow in the bodies of their intermediate hosts, but they can only reproduce in the bodies of birds (or also mammals for R. ondatrae).

Their ultimate aim, therefore, is increasing the likelihood that the frogs and snails (or their eyestalks, anyway) will get eaten up, taking the parasites with them.

In the case of the frogs, the parasite reduces its mobility, and ability to flee. In the case of the snails, the colorful display is like a neon sign saying to birds "SNACKS THIS WAY. (Interestingly, Maier notes, the snails' eyestalks regenerate after being eaten by a bird, so the same snail can provide many snacks for birds.)

In these cases, researchers have an understanding of how the parasites are doing what they do.

The larvae of R. ontradae are attracted to the limb buds of their second intermediate amphibian hosts; they encyst themselves around this region, where they influence the growth of limbs. L. paradoxum puts itself where it will be most visible and attractive to predators.

It's not always that simple though.

It's all in the mind

L. paradoxum has another trick up its sleeve, and this one is a little more difficult to figure out. Snails infected with the parasite also behave differently from uninfected snails.

"Green banded broodsac also alter their behavior, not only the morphology," Maier explains.

"So that's the swelling of the eyestalks and this pulsating behavior in the eyestalks. Similarly, they move out into the open so that the birds come in, and then they can pick off those eye stalks."

A whole plethora of parasite species have been linked with similar behaviors. Pomphorhynchus laevis, the thorny-headed worm, inverts its shrimp intermediate host's reaction to light, which makes them more vulnerable to predation by the carp that are the definitive host.

Pacific chorus frog (Pseudacris regilla) infected with R. ondatrae.
(Goodman & Johnson, PLOS ONE, 2011)

Cane toads infected with the lungworm Rhabdias pseudosphaerocephala seek out warmer temperatures and moister environments, which increase the growth and survivability of the parasites, respectively.A 

One particularly fascinating example is Dicrocoelium dendriticum, the lancet liver fluke, which targets sheep and cattle as its definitive host – but how it gets to sheep and cattle is truly devious.

Once the fluke has reproduced, the eggs are shed with the feces of the host, and subsequently eaten by snails, where they hatch and develop. At this point, they make their exit through the snails' slime, which contains a sugary substance that is very delicious to ants.

Inside the ant, the parasite develops to maturity… and from there, the ant is eaten by cattle and sheep, where it can begin the life cycle all over again.

"The logical flaw is the cow is vegetarian. Why should they eat ants?" Maier says.

"Actually, infected ants climb up grass in the evenings. During the day they show normal behavior. In the evenings when the temperature drops, normally the ants go back into their nest. But those infected ones climb up the grass. And then when the temperature drops further, they spasm in their mandibles, and they actually lock themself to that grass.

"So they spent the night on that grass; in the morning the cow comes along, eats the grass, and picks up those infected ants."

Somehow, the parasite hijacks the ant and drives it to fatal behavior to get back to the fluke sex party happening in cows.

Or is it in the mind?

We do know, a little, about how D. dendriticum might be pulling this off. A few years ago, a team of researchers conducted CT scans of parasitized ants, and found that, while the majority of the parasites were clustered in the abdomen, there was almost always one lone parasite situated right next to the ant's brain.

False-color CT scan of an ant, showing encysted parasites in the abdomen (emc) and
one non-encysted parasite in the brain (nmc). (Martin-Vega et al., Sci. Rep., 2018)

We still don't know what exactly that pilot fluke does, but it could be manipulating the ant's brain, either chemically or physically.

In many cases, though, we don't know the actual strings being pulled, especially for human parasites. The reason for this is that we're usually relying on behavioral data, and behavior is a complex thing with countless possible drivers, including personality. And there can be bias in the way we select behavioral data for inclusion in research.

A birth-cohort study published in 2016, for example, found little evidence to support the notion that Toxoplasma gondii leads to increased risk of psychiatric disorders or increased impulsivity in humans, as had previously been asserted.

In fact, it's not definitively clear that T. gondii manipulates rodents, either. A 2013 study found the evidence unconvincing. It can be extremely difficult to conclusively link such changes to parasite manipulation.

Perhaps the host is simply behaving differently because they feel ill… you know, because they have a parasitic infection.

The case for rabies is more compelling. Behavioral symptoms include hyperactivity, insomnia, and an extreme fear of water and fresh air, which scientists have linked to a toxin-like neuroinhibitor released by the virus Rabies lyssavirus.

By the time symptoms appear in rabies, it's too late to do anything about it; such cases are almost always fatal. And we have no way to diagnose rabies prior to symptom onset.

Although relatively few parasites are known to alter human behavior, though, adaptive host manipulation is a field that warrants further investigation. These tiny hitch-hikers actually have a huge impact on the larger world.

Driving evolution

The battle between parasite and host is a sort of evolutionary arms race. The parasite wants to maximize its chances of arriving at its definitive host; the host wants to minimize its chances of parasite sickness.

So parasites will develop adaptations that help it infect its hosts, and the hosts increase resistance and tolerance to the parasites in response.

This can have some pretty interesting consequences. One psychologist even theoretically explored the notion that the evolution of the human brain could have, at least in part, been driven by parasites.

While purely speculative, the idea has some interesting implications, such as mimicking a parasite attack to stimulate the brain's defense mechanisms.

It's not that strange an idea. Recent research has shown promise in treating irritable bowel conditions such as coeliac disease and Crohn's disease with parasitic worms that live in the gut, known as helminth therapy.

The rat tapeworm (Hymenolepis diminuta), commonly used for self-treatment
of inflammatory disorders. (William Parker, CC BY-NC SA)

Patients with coeliac disease showed a massive increase in gluten tolerance after being infected with hookworms, and Crohn's disease patients treated with whipworms often enter remission.

These are autoimmune conditions, and the response to parasite infection suggests one potential reason for it, Maier says.

"In the last 50 years, some parts of the human race have grown up in a hygienic environment – that's the hygiene hypothesis," he explains.

"And the part of our immune system that normally used to deal with those wormy parasites is now sitting idle. It has nothing to do. And in some individuals, it starts attacking their own tissue."

Parasitism forces both hosts and parasites to diversify, to enter new ecological niches, to adapt. Populations of animals with parasites have greater genetic diversity, because that limits parasite success.

If we can link parasite behavior to our own evolutionary adaptations, that could have some implications for how we treat, or even prevent, some forms of disease.

Beyond that, however, parasites that are able to manipulate their hosts give us clues to understanding their biology. Altering a neurotransmitter, for example, as rabies does, helps us learn how that neurotransmitter works.

We have a tendency to think of parasites with disgust and revulsion, but there's a lot more going on with these mooching organisms than pulsating eyestalks, no matter how vivid and eye-catching they are.

Maybe the idea of adaptive host manipulation opens up all sorts of philosophical questions about the malleability of our own identities, but perhaps our tiny passengers are also driving us all onward and upward to greater things.