Pauling, Zuckerkandl and the Molecular Clock


Dr. Emile Zuckerkandl, 1986.

In 1963, a year after first publishing their ideas on the study of molecules as indicators of evolutionary patterns, Emile Zuckerkandl and Linus Pauling continued to explore what they felt to be a very promising thread of inquiry.

Specifically, the two joined in arguing that the molecular clock method – as they had since termed it – might be used to derive phylogenies (or evolutionary trees) from essentially any form of molecular information. This position was further explicated in “Molecules as Documents of Evolutionary History,” an article published in Problems of Evolutionary and Industrial Biochemistry, a volume compiled in 1964 on the occasion of Soviet biochemist Alexander Oparin’s 70th birthday.

Zuckerkandl and Pauling’s most influential work on this subject was first put forth that same year, in a paper that they presented together at the symposium “Evolving Genes and Proteins,” held at the Rutgers University Institute of Microbiology. The talk, formally published a year later and titled, “Evolutionary Divergence and Convergence at the Level of Informational Macromolecules,” classified molecules that occur in living matter into three groups. Each of these groups was identified according to new terms that the pair had developed that were based on the degree to which specific information contained in an organism was reflected in different molecules. These three categories were:

1.Semantophoretic Molecules (or Semantides), which carry genetic information or a transcript of it. DNA, for example, was considered to be composed of primary semantides.

2. Episemantic Molecules, which are synthesized under control of tertiary semantides. All molecules built by enzymes were considered episemantic.

3. Asemantic Molecules, which are not produced by the organism and do not express (directly or indirectly) any of the information that the organism contains. In their discussion, Zuckerkandl and Pauling were quick to point out that certain asemantic molecules may shift form. Viruses, for example, can change form when integrated into the genome of the host; so too can vitamins when used and modified anabolically.

Semantides were considered most relevant to evolutionary history, but the term never caught on in biology, paleontology, or other allied fields relevant to the study of evolution. Nonetheless, whatever the nomenclature, the “semantides” that Zuckerkandl and Pauling wanted to investigate – DNA, RNA, and polypeptides – proved indeed to be precisely the treasure trove of information on evolutionary history that the duo had hoped would be the case.


A figure from the French translation of Zuckerkandl and Pauling’s 1964 paper.

Fundamentally, Zuckerkandl and Pauling aimed to elucidate how one might gain information about the evolutionary history of organisms through comparison of homologous polypeptide chains. In examining these substances, the researchers sought specifically to uncover the approximate point in time at which the last common ancestor between two species disappeared. In essence, it is this approach that we speak of when we use the terms “molecular clock” or “evolutionary clock.”

Zuckerkandl and Pauling argued that, by assessing the overall differences between homologous polypeptide chains and comparing individual amino acid residues at homologous molecular sites, biologists and paleontologists would be better equipped to evaluate the minimum number of mutational events that separated two chains.

With this information in hand, researchers would thus be empowered to exhume the details of evolutionary history between species, as inscribed in the base sequences of nucleic acids. This set of data, they believed, would hold even more useful information than would corresponding polypeptide chain amino acid sequences, since not all substitutions in the nucleotides would be expressed by differences in amino acid sequence.


A table from Zuckerkandl and Pauling’s 1965 Bruges paper.

As their work moved forward, Pauling and Zuckerkandl published another paper, 1965’s “Evolutionary Divergence and Convergence in Proteins.” This publication appeared in Evolving Genes and Proteins, a volume that emerged from a conference that the two had attended in Bruges, Belgium.

By this point, the duo’s idea of the molecular clock, or “chemical paleogenetics,” had elicited opposition from organismal evolutionists and taxonomists, as well as some biochemists. Now referring to their “semantides” simply as informational macromolecules, Zuckerkandl and Pauling used the 1965 meeting to argue strongly against their skeptics. Zuckerkandl chided

Certainly we cannot subscribe to the statement made at this meeting by a renowned biochemist that comparative structural studies of polypeptides can teach us nothing about evolution that we don’t already know.

Pauling likewise added that

Taxonomy tends, ideally, not toward just any type of convenient classification of living forms (in spite of a statement to the contrary made at this meeting).

Directly challenging those present who were attempting to discredit the idea of the molecular clock, the pair insisted that taxonomy tended toward a phyletic classification based on evolutionary history. Since the comparison of the structure of homologous informational macromolecules allowed for the establishment of phylogenetic relationships, the Zuckerkandl-Pauling studies of chemical paleogenetics therefore had earned a place within the study of taxonomy. This, they argued, was true both as a method of reinforcing existing phyletic classifications and also of increasing their accuracy. Specifically, the two claimed that

The evaluation of the amount of differences between two organisms as derived from sequences in structural genes or in their polypeptide translation is likely to lead to quantities different from those obtained on the basis of observations made at any other higher level of biological integration. On the one hand, some differences in the structural genes will not be reflected elsewhere in the organism, and on the other hand some difference noted by the organismal biologist may not be reflected in structural genes.

Indeed, it was these early observations, coupled with additional work conducted by those scientists who took their ideas seriously, that allowed for the development of a successful measure of rates of evolutionary change over time. Without these data, modern paleontologists, physical anthropologists, and geneticists would not be able to accurately determine evolutionary histories. Today, this technique has been systematized and specialized in the field of bioinformatics, which is now foundational to many studies in both biology and medicine.

The taxonomic purpose of the molecular clock, however, was only a byproduct of Zuckerkandl and Pauling’s main ambitions in studying paleogenetics: to better understand the modes of macromolecular transformations retained by evolution; to elucidate the types of changes discernible in information content; and – most importantly for Pauling – to identify the consequences of these changes for a given organism.


Linus Pauling, 1992.

Despite its considerable potential, the work of Zuckerkandl and Pauling, though conducted at such a critical juncture in a nascent field, was largely forgotten as recently as the early 1990s. In fact, in Allan Wilson and Rebecca Cann’s 1992 article, “The Recent African Genesis of Humans,” it was implied that the concept of the molecular or evolutionary clock was first developed and employed by a Berkeley anthropologist, Vincent Sarich. Sarich had collaborated with Wilson in 1967 to estimate the divergence between humans and apes as occurring between four to five millions years ago.

Pauling was still alive in 1992, and seeing this article he duly wrote to the editor of its publisher, Scientific American, pointing out that that, in fact, he and Zuckerkandl had, in 1962, issued their own estimate of the disappearance of the last common ancestor of gorilla and man. Zuckerkandl and Pauling’s calculations had yielded a divergence at about 7.6 million years before present, which Pauling pointed out was much closer than Sarich’s figure to the more recent estimates of divergence determined by Sibley and Ahlquist in 1984 and 1987. Notably, Pauling and Zuckerkandl’s estimate continues to remain closer to more contemporary notions of 8 to 10 million years.

Today, Emile Zuckerkandl and Linus Pauling are remembered as having first championed the notion of the molecular clock, even if many of the details now deemed as fundamental still needed to be ironed out by an array of scientists who followed. Regardless, as in so many other areas of science, Pauling proved once more to be on the ground floor of a new discipline. This was an academic venture that continued also to serve the younger Zuckerkandl well, as he continued on through a prolific career in science that concluded with his passing in 2013.

Molecules as Documents of Evolutionary History


Linus Pauling and Emile Zuckerkandl, 1986.

[Part 1 of 2]

“Of all natural systems, living matter is the one which, in the face of great transformations, preserves inscribed in its organization the largest amount of its own past history. We may ask the question: Where in the now living systems has the greatest amount of their past history survived, and how it can be extracted?”

-Linus Pauling and Emile Zuckerkandl, 1964

Austria-born Emile Zuckerkandl fled to Paris with his parents to escape the Nazi occupation of his homeland when he was only sixteen. Twenty years Linus Pauling’s junior, this extraordinary scientific mind was nurtured through the study of the biological sciences at the University of Illinois in the United States, and the Paris-Sorbonne University in France. During the course of these studies, Zuckerkandl developed a particularly keen interest in the molecular aspects of physiology and biology, and is now regarded to have been a major contributor to both fields.

Zuckerkandl first met Linus Pauling in 1957, a time period during Pauling himself was spearheading the new study of molecular disease, following his earlier, groundbreaking discovery of the genetic basis of sickle cell anemia. Two years later, Zuckerkandl joined Pauling as a post-doc in the Chemistry and Chemical Engineering Division at the California Institute of Technology. Once arrived, Zuckerkandl was encouraged by Pauling to study the evolution of hemoglobin, a research project that was informed by a basic and crucial assumption that the rate of mutational change in the genome is effectively constant over time.

This assumption was something of a hard sell for biologists at the time, due to the prevailing belief within the discipline that mutations were effectively random. Undaunted, Pauling and Zuckerkandl moved forward with their project and ultimately created a model that, over time, ushered in major changes to the conventional wisdom.

The Pauling-Zuckerkandl project was first revealed to the world in a co-authored paper that appeared in 1962’s Horizons in Biochemistry, a volume of works written and dedicated to the Nobel winning physiologist Albert Szent-Györgyi. The paper, titled “Molecular Disease, Evolution, and Genic Heterogeneity,” is regarded today as a foundational work in its application of molecular and genetic techniques to the study of evolution.

At the time that Pauling and Zuckerkandl wrote this first joint paper, Pauling was, as the title of the work might suggest, very interested in molecular disease; so much so that he was thinking about molecular disease and evolution as occupying two sides of the same coin. Defining life as “a relationship between molecules, not a property of any one molecule,” Pauling believed that disease, insofar as it was molecular in basis, could be defined in exactly the same way. Since both evolution and molecular disease were merely expressions of relationships between molecules, the distinction between the two became blurred for Pauling, who felt that the mechanism of molecular disease represented one element of the mechanism of evolution.

In their paper, Pauling and Zuckerkandl outlined their point of view as follows:

Subjectively, to evolve must most often have amounted to suffering from a disease. And these diseases were of course molecular. …[T]he notion of molecular disease relates exclusively to the inheritance of altered protein and nucleic acid molecules. An abnormal protein causing molecular disease has abnormal enzymatic or other physicochemical properties. Changes in such properties are necessarily linked to changes in structure. The study of molecular diseases leads back to the study of mutations, most of which are known to be detrimental. A bacterium that loses by mutation the ability to synthesize a given enzyme has a molecular disease. The first heterotrophic organisms suffered from a molecular disease, of which they cured themselves by feeding on their fellow creatures. At the limit, life itself is a molecular disease, which it overcomes temporarily by depending on its environment.

These assertions – in particular that “life itself” was a molecular disease – were so strange and seemingly outrageous that many biologists dismissed the paper outright. However, the basic idea that the pair was considering simultaneously sparked the interest of many other scientists who willing to entertain the consequences of this mode of thinking. If Pauling and Zuckerkandl were right, then every vitamin required by human beings stood as a witness bearing testimony to the molecular diseases that our ancestors contracted hundreds of millions of years ago. These “diseases” would manifest negative symptoms only when the curative properties of the nutrients gained from our natural environment through food and drink proved insufficient to dampen their effects.

This line of reasoning provided the impetus for Pauling and Zuckerkandl to begin examining differences between the genetic code as a tool to better understand evolutionary history. Though they did not call it “the molecular clock” at the time, the concept served as the foundation for the genetic analysis of species over long periods of evolutionary history.

Fundamental to Pauling and Zuckerkandl’s argument was the notion that there was no reason to place molecules at specific points “higher” or “lower” on an evolutionary scale. Horse hemoglobin, for example, is not less organized or complex than is human hemoglobin, it is simply different. The same is true for the genetic information contained in the hemoglobin of humans as compared to other primates, such as gorillas.

As Zuckerkandl examined differences of these sorts, he was not surprised to find that the peptide sequences of a gorilla were more similar to a human’s than a horse’s were to either. He and Pauling then began to consider how these sequences must be indicative of the millions of years of separate evolution that had passed since the disappearance of the last common ancestor linking horses and primates.

While compelling in its own right, for Pauling the chief purpose of understanding these differences was to discern crucial information about the human condition and to define the parameters of optimal health. Indeed, Pauling fundamentally believed that an improved understanding of the transitions that the genetic code had undergone would ultimately reveal new and effective treatments for molecular diseases.


Table I from Pauling and Zukerkandl’s 1962 paper.

To demonstrate the efficacy of their methodology, Pauling and Zuckerkandl calculated the number of genetic differences that exist between the alpha and beta chains of hemoglobin peptide sequences in horses, humans, and gorillas, which they then used to determine the time that had elapsed since the erasure of the last common ancestor linking these species. In seeming support of their claims, the authors found that their figures matched pretty closely with data uncovered by paleontologists.

Despite this, the impact of Pauling and Zuckerkandl’s paper dissipated pretty quickly. For other established figures in the field, Pauling and Zukerkandl had failed to prove the essential assumption that evolution should proceed with relative uniformity over time. Lacking a clear reason to accept that genetic change occurs at a constant rate, there was no compelling reason to believe that Pauling and Zuckerkandl’s molecular clock should give an accurate picture of evolutionary history.

Nonetheless, the idea of the molecular clock found a degree of traction among biologists who valued its potential to corroborate and increase the accuracy of existing phylogenetic assignments. And as we’ll discuss in our next post, Pauling and Zuckerkandl continued to explore their ideas, eventually building a body of work that came into far greater favor a few decades later.

Remembering Richard Marsh


Richard Marsh, 1960. Credit: Caltech Archives.

At the beginning of this year, on Tuesday, January 3rd, the highly accomplished crystallographer Richard E. Marsh passed away at the age of 94. During his impressive sixty-six-year career at Caltech, Marsh was influenced greatly by Linus Pauling’s work in crystallography, and eventually collaborated with him throughout the 1950s and early 1960s. Colleagues and admirers alike knew Marsh for his rigorous standards in investigating atomic structure, a discipline that resulted in his determination of over one-hundred crystal structures throughout his career and the improvement of at least that many more.

In a Caltech tenure that spanned more than six decades, Marsh also inspired generations of graduates and undergrads alike, teaching valuable techniques in crystallography and instilling in his students the rigor of his own research practice. His course “Methods of Structural Determination” was among the most popular graduate offerings in the Institute’s Chemistry division for a great many years. He leaves behind an impressive legacy for the crystallographers of today.

Marsh, who went by Dick, was born in 1922 in Jackson, Michigan. By the time that he arrived at Caltech as an undergraduate in 1939, Pauling had already helped to established the Institute as among the premiere destinations for budding young crystallographers around the world. In particular, Pauling’s newly published Nature of the Chemical Bond had transformed crystallography from arcane to fundamental.

Though Pauling was certainly well known on campus when Marsh was an undergraduate, it would be another eleven years before Pauling and Marsh formally crossed paths. As a student, Marsh had identified an interest in chemistry, but hadn’t narrowed to a particular focus. He commented later that a technical drawing course at Caltech served as a precursor to his interest in crystallography. He graduated with his BS in applied chemistry in the midst of World War II (1943) and, upon graduation, enlisted in the US Navy, spending the next two years degaussing ships in New Orleans. This is where he met his wife Helena Laterriere, to whom he remained married for nearly seventy years.

Following his discharge, Marsh enrolled in graduate school at Tulane University so that he might remain in close proximity to his fiancée. Most of the courses that he needed were already full at the time of his enrollment, so Marsh signed up for an X-ray crystallography class at the nearby Sophie Newcomb College for women. It was there that he met the teacher who changed his life and cemented his interest in crystallography.

That teacher, Rose Mooney, had previously attempted to enroll at Caltech for graduate studies only to be turned away when she arrived in Pasadena and the administration realized that she was a female. Pauling himself stepped in at this point, giving her a temporary position in his laboratory until she was accepted into the graduate program at the University of Chicago. Her lab at Sophie Newcomb College was quite modest, containing only a Laue film holder and one x-ray tube, but for Marsh it was enough. Inspired, his course was set from then on, though he’d have to travel across the country to continue it.

After marrying Helena on August 11, 1947, Marsh enrolled at UCLA. He later called the 2,000-mile move across the southern United States the beginning of their honeymoon, joking that it was a wedding present to his new bride. At UCLA, Marsh studied crystallography under Jim McCullough and earned his Ph.D. in 1950. Caltech subsequently offered him a post-doctoral research appointment, and he remained at the Institute for his entire career, always in a non-tenured position until his retirement in 1990, when he named an emeritus professor.

In the years immediately following World War II, Caltech was still very much the place to be for crystallographers. Thanks largely to Pauling, who returned to structural chemistry after his own war projects had wrapped up, scientists from all over the world travelled to Pasadena to conduct research and solve structures.

Marsh finally became associated with Pauling in 1950, when he arrived at the Institute as a post-doc. He published his first paper with Pauling, “The Structure of Chlorine Hydrate,” in 1952. A year later, the duo published “The crystal structure of β selenium,” which marked the first time that Marsh issued a correction of someone else’s work. Indeed, over the course of his career, Marsh became increasingly focused on policing the field for errors, always striving for maximum accuracy and precision. Pauling engaged in this work himself from time to time, although the various demands on his attention kept him too busy to make a full-time habit out of it.


Marsh at the famous Caltech Proteins Conference in 1953. To his right is Francis Crick.

Pauling and Marsh continued to collaborate on a number of other publications related to atomic structure between 1952 and 1955, at which point their interests began to diverge. Nonetheless, the two retained a degree of professional closeness throughout the following decades, often writing to compliment one another on various accomplishments, solicit advice, or suggest future projects. In one instance, Pauling provided the kernel of an idea that resulted in Marsh’s 1982 paper on N, N-Dimethylglycine hydrochloride. Likewise, Marsh helped pave the way for Pauling to publish one of his own articles in Acta Crystallography, where Marsh served as an editor for seven years.

In 1975, presented with the problem of solving of a compound that generates hydrazine from molecular nitrogen, Marsh devised and shared a method for determining the structure. This solution influenced the direction of study into hydrazine formation, creating the opportunity for further study. And although Marsh continued to solve structural problems in the years that followed, he also devoted countless hours – over half his career – to the pursuit and correction of published errors, usually pertaining to inaccurate space groups in important crystal structures. Pauling later described Marsh as the “conscience of crystallography.”

With time, he gained such a reputation that his colleagues in the field were perpetually anxious that they would be “Marshed,” or taken to task, for their errors. Marsh held his colleagues accountable to their calculations and believed firmly in checking a computer’s work, rather than the other way around. He is remembered today as having been responsible for many refinements in crystallographic discipline and for the high standards that make future refinements possible.


Marsh in 2012. Photo by Rafn Stefansson.

In terms of organizational involvement, Marsh joined the American Crystallographic Association (ACA) shortly after starting at Caltech. Over the duration of his career, he became increasingly active in the group, and ultimately served as its president in 1993. He was also co-editor of Acta Crystallography from 1964-1971.

Marsh’s classroom lectures and his relationships with students were at least as influential as were his publications in crystallography. One colleague, B.C. Wang, recalled that Marsh summoned crystallographers of all stature – be they students, professors, or visiting scientists – to a group coffee at 10:30am every day, to encourage discussion and advancement within the field. Students also remembered him as critical but encouraging, his commitment to student success serving as an inspiration for their own hard work.


Marsh and Pauling in 1986. Credit: Caltech Archives.

When queried by CRC Press in the early 1990s for his input on future publications, Pauling suggested that the press solicit a monograph from Marsh on the crystal structures that he had corrected thus far, arguing that a volume of this sort might help future crystallographers to avoid these errors. Pauling then wrote to Marsh, inquiring about the total number of crystal structures that Marsh had indeed corrected. Pauling had guessed that Marsh had published fixes for 25 to 30 structures and was surprised to learn that the actual number was between 110 and 120.

Although Marsh didn’t publish this proposed monograph, Pauling’s idea evidently inspired him. In 1995, he authored a substantial article on the subject, titled “Some thoughts on choosing the correct space group.” In the piece, Marsh discussed common types of errors as well as preferable techniques and methodology, including a few tables that documented space group revisions over time.

While at Caltech, Marsh worked closely with Verner Schomaker, another of Pauling’s graduate students. In 1991, the two teamed up to put together a festschrift honoring Pauling’s early work on crystallography. Pauling, a man who, by then, had received basically every award that a scientist can get, was immensely pleased and grateful for this honor.

In 2003, Marsh received the inaugural Kenneth Trueblood Award from the American Crystallographic Association for his outstanding achievements in chemical crystallography. Few other awards could be more fitting for a crystallographer of Marsh’s caliber and commitment. In announcing the prize, the chair of the selection committee identified Marsh as a “rare individual among crystallographers, an outstanding teacher and researcher who has greatly influenced so many students and faculty.” He will be remembered and missed for this indefatigable integrity, dedication, and mentorship.

John Kendrew (1917-1997)

Kendrew, John

John Kendrew building a model of myoglobin. Credit: MRC Laboratory of Molecular Biology.

[Ed Note: Today we remember Sir John Kendrew, who would have turned one-hundred years old on March 24th.]

The Cavendish Laboratory at Cambridge University was an exciting place to be in the 1950s. While James Watson and Francis Crick worked themselves into a frenzy in their race with Linus Pauling to discover the structure of DNA, lab-mate John Kendrew worked quietly alongside another future Nobel laureate, Max Perutz, as they too competed with Pauling in another arena: the molecular structure of various proteins.

For Kendrew however, this pursuit was not considered to be a competition against Pauling. Rather, he felt his corner of the laboratory to be working in tandem with researchers at Caltech in their joint pursuit of a common goal. For Kendrew, whoever got there first was beside the point. Indeed, when Perutz and Kendrew received the Nobel Prize for Chemistry – one year prior to Pauling’s receipt of his Peace Nobel – Kendrew credited Pauling as having been a source of inspiration and direction for his work on the atomic structure of myoglobin.


John Kendrew and Max Perutz, 1962.

Sixteen years Pauling’s junior, John Cowdery Kendrew was born in Oxford, England on March 24, 1917. He received an appointment for study at Cambridge in 1939 and was working on reaction kinetics before the outbreak of World War II called him away to support the Allied effort.

By the time that he had reached the rank of Wing Commander in the Air Ministry Research Establishment, Kendrew had developed relationships with several important scientific contacts. Perhaps chief among these colleagues was the crystallographer J.D. Bernal, who also influenced Pauling’s protein work in the late 1930s. Bernal encouraged Kendrew to contact Max Perutz at the Cavendish Laboratory once his military service was completed. After receiving similar advice from Pauling, Kendrew began working with Perutz in 1945. His early research at the lab was conducted in support of his Ph. D. thesis – an x-ray diffraction study of hemoglobin in fetal and adult sheep.

In the late 1940s, Kendrew and Perutz established the Cavendish MRC Unit for the Study of the Molecular Structure of Biological Systems, and together they attacked the chemical structure of proteins using X-ray crystallography, with a particular interest in whale myoglobin. Although the research excited Kendrew, he was sometimes perplexed by the cross-disciplinary nature of what he was trying to accomplish. In a later interview with the Journal of Chemical Education, he remembered, “one of the problems was the lack of professional label. By profession, I was a chemist working on a biological problem in a physics lab.”

Nonetheless, Kendrew and Perutz were avidly pursuing the structure of keratin when the Pauling family visited the Cavendish in 1948. Pauling himself had done some preliminary work on the protein about ten years earlier, but after failing to build a satisfactory chain, he had abandoned the effort and moved on to other structures. Seeing the steady progress that Kendrew and Perutz were making reignited his own interest in the structure. Not long after, while lying in bed with a severe sinus infection, he worked on a rough sketch of a keratin model, which eventually inspired his signature proteins breakthrough: the alpha-helix.

Shortly after Pauling published his landmark 1951 paper, “The Structure of Proteins: Two Hydrogen-Bonded Helical Configurations of the Polypeptide Chain,” in which he introduced the alpha and gamma helixes, Pauling invited Kendrew to visit Pasadena and lecture at Caltech. Kendrew, impressed and eager to discuss Pauling’s findings, made preparations to stop in southern California as part of an already scheduled trip to San Francisco and Seattle. The visit proved thought-provoking for both scientists, and Kendrew returned to the Cavendish brimming with fresh ideas.


Peter Pauling, 1954.

In their early exchange of correspondence, Pauling’s communications (as was typical) were usually formal and brief. On the contrary, Kendrew’s enthusiasm about both his and Pauling’s work is spelled out in long, detailed paragraphs. In due time, Pauling’s writing broadened not only in length, but in a personal dimension as well.  Importantly, between a letter dated October 8, 1956 and another written on November 22, 1957, Pauling switched from referring to his correspondent as “Dr. Kendrew” to “John,” and Kendrew responded in kind.

Without doubt, one catalyst for this shift was Kendrew’s mentorship and guidance of Linus’ second-oldest son, Peter Pauling, a budding crystallographer who was pursuing his doctorate at the Cavendish. Despite his promise and pedigree, once Peter had settled in, many scientists at Cambridge had begun to express concern about his level of commitment to and interest in his work.

Amidst a flurry of letters from Peter’s Cambridge professors that ranged from outright condemnation of his behavior to genuine concern for his future, a 1953 letter from Kendrew comes across as amiable but firm. In it, he expresses serious doubts about Peter’s ability to attain a Ph.D. unless he undergoes “a considerable revolution during the summer.” The message also urges the elder Pauling to alter other travel plans and come to England to address the matter in person. Ultimately, Pauling declined to do so and, fortunately, Peter initiated the revolution for which Kendrew had expressed hope. A year later, Kendrew penned another letter in which he assured Pauling that he had observed in Peter’s work both a genuine interest and a more stringent ethic.

Kendrew was not merely a fair-weather supporter of Peter’s endeavors. When Peter ran into serious personal trouble at Cambridge in 1955, Kendrew proved invaluably resourceful. Most notably, he helped Peter transfer his fellowship and remaining doctoral research to the Royal Institution of London, where former Cavendish chief Sir Lawrence Bragg was now directing the Davy-Faraday research lab.  Kendrew and Bragg later assisted Peter in moving yet again – this time to University College, London – when he could not complete his dissertation in the requisite amount of time allotted by the Royal Institution.

In a number of letters, Pauling repeatedly expressed his gratitude to Kendrew for so carefully tending to Peter’s well-being and educational progress, choppy though it was. These circumstances only served to cement a friendship between the two; one that developed alongside the great professional respect with which they had always extended to one another.


Kendrew posing at a proteins conference held at Caltech, 1953.

On the other hand, Caltech and the Cavendish regularly found themselves to be in professional competition with one other, and this did lead to occasional friction between friends. In one instance, Kendrew sought out Pauling’s assistance with a rather complicated labor shortage that had partly been caused by Pauling himself. Shortly after Peter’s departure from Cambridge and Bragg’s resignation from his leadership post in the Cavendish, Kendrew wrote to Pasadena, asking for assistance. The gravity of the moment was especially amplified for Kendrew, who was presumably a tad annoyed by Pauling’s having convinced a mutual colleague, Howard Dintzis, to leave the Cavendish for Caltech the previous year. In his letter, Kendrew made a request:

I am writing to ask whether you would be good enough to let me know if you hear of any good man who would like to come to work on the myoglobin project in the near future. As you may have heard from Howard Dintzis, owing to a continuation of unforeseen circumstances I shall be totally without collaborators from January onward.

Pauling replied kindly, but did not include any recommendations.

In 1957, Kendrew succeeded in delineating the atomic structure of myoglobin. Two years later, Max Perutz successfully mapped the structure of hemoglobin. When Lawrence Bragg approached Pauling with the idea of nominating Kendrew for the Nobel Prize in Chemistry, Pauling suggested that the award be split three ways between Kendrew, Perutz, and Robert Corey, a colleague of Pauling’s at Caltech. Bragg disagreed and instead nominated the British chemist Dorothy Crowfoot Hodgkin, a pioneer in X-ray crystallography. Ultimately, Pauling’s final nomination of Kendrew and Perutz in 1962 included Hodgkin as well. As it turned out, Kendrew and Perutz split that year’s prize, and Hodgkin took the 1964 award for herself.

The remainder of Kendrew’s career was spent working less directly on scientific research and more intently on public policy. Like Pauling, Kendrew believed that scientists bore an obligation beyond scientific research and discovery. As he expressed in a 1974 interview

[Scientists] have special knowledge, and their most important responsibility is communication; because it is bad enough to try and foresee the effects of some scientific or technological advance given all the facts, but without them it is impossible…it is all the more important for scientists to communicate and make what they are doing understood at the government level and publicly through the media.

Jojn Kendrew Award gallery, EMBL ATC 11.2016

Wall of Honor at the European Molecular Biology Laboratory.

In the same year that he gave that interview, Kendrew helped to establish the European Molecular Biology Laboratory in Heidelberg, where he acted as director until his retirement in 1981. The lab has since created the John Kendrew Award to recognize and honor outstanding contributions made by the laboratory’s alumni.

Continuing Objections to the Persian Gulf War


Linus Pauling with the Dalai Lama at a meeting of the Nuclear Age Peace Foundation, Santa Barbara, California, April 6, 1991.

[Part 2 of 2]

By spring 1991, Linus Pauling, at the age of 90, had established himself as a leading critic of the United States’ military incursion into the Persian Gulf, an engagement that had been dubbed “Operation Desert Storm.” Having already published a series of paid advertisements in national and regional media outlets urging the U.S. to pursue a diplomatic solution to Saddam Hussein’s military occupation of Kuwait, Pauling issued his most detailed argument against the conflict in a talk titled “Reflections on the Persian Gulf ‘War.'” This lecture was presented at a meeting of the Nuclear Age Peace Foundation on April 6, 1991 and attended by the Dalai Lama, among others.

Components of Pauling’s argument against the war were discussed in our previous blog post on this subject. In today’s post, we’ll dig a little bit deeper into some of the specifics conveyed by Pauling in his April speech and touch on other noteworthy activities in which Pauling engaged as he publicly argued against armed conflict in the Middle East.

Pauling began his discussion of the Gulf “War,” as he termed it, by mentioning the New York Times advertisement that he had placed in January.  He confessed that the multiple ads that he had commissioned were not likely to make a significant impact, but that he felt a moral obligation to speak out.

He then starkly emphasized that the current war was not in fact a war, because

In a war you have opposing forces that fight and there are deaths on both sides and finally one side wins. In the old days perhaps this was a demonstration of the democratic process – the side with the biggest number of fighters won.  [Operation Desert Storm] wasn’t a war. This you could call a massacre or slaughter, perhaps even murder.

Pauling continued by querying the audience, if this is what the practice of war has become, then what shape might future wars take on? For Pauling, the US had set a dangerous precedent for the future: use force to install the government it wants and then leave.

As he dug deeper into his analysis, Pauling made connections to World War I and World War II by noting that a new generation of leaders could have ushered in World War III, but that this was averted through the development of weapons that were increasingly destructive by many orders of magnitude.

The current conflict, however, was different in how it transpired.  First, it was mostly initiated through air power – a dramatically one-sided offensive consisting of some 150,000 U.S. sorties resulting in the deaths of only about 150 American soldiers. Second, the U.S. had previously supplied Iraq with old and outdated weapons for use in its lengthy war with Iran. As a result, American military planners knew that their weaponry was far superior and would not be threatened by Iraqi stockpiles.


Pauling speaking at the Nuclear Age Peace Foundation event, Santa Barbara, California, April 6, 1991.

But the crucial question for Pauling was how many Iraqis died?  Pauling estimated the number to be around 300,000, a total which, he emphasized, included children, the elderly, and other civilians. He continued the math by pointing out that these numbers equated to a casualty ratio of 2,000 Iraqis killed for every American.

(Later analyses suggested Pauling’s numbers to be inflated. According to one, the “Gulf War Air Power Survey,” (1993) conducted by Thomas A. Keaney and Eliot A. Cohen and commissioned by the United States Air Force, about 22,000 Iraqi soldiers were killed in combat. Further, the Iraqi government estimated 2,300 civilian deaths as a result of the air campaign.)

Given casualty rates so high and so wildly out of proportion, Pauling begged the question: does a war like this make the U.S. and President Bush terrorists?  In asking this, Pauling explained

Terrorists are people who make an ultimatum, a demand of some sort in the form of an ultimatum threatening to kill hostages or other people if the demand is not met.  What did President Bush do?  He issued some ultimatums that were absolute, that by a certain date the Iraqis would have to withdraw from Kuwait, or else.  And ‘or else’ consisted in our killing 300,000 Iraqis, two thousand to one.  It seems to me that our country has become a terrorist country on a very large scale.

Instead, Pauling urged that the U.S. seek out an alternative, one that would create “a future worthy of man’s intelligence” and provide clear evidence that “we are a moral country.”


The remainder of Pauling’s activism against the Gulf War consisted primarily of co-sponsoring or otherwise participating in a variety of petitioning efforts. One of them, “The Scientists Statement of Concern,” which was initiated by Pauling, was signed by forty-seven scientists in the US, Italy, France, Germany, Sweden, Great Britain, and Switzerland. Another, “Scientists and Engineers for Peace in the Middle East,” emphasized the need to pursue social justice and economic development as a route to stability in the region.

A final piece authored by Pauling during this time period deserves mention, in part because of its unique comparison of two very high profile events that were current in March 1991. Simply titled “A Statement” and dictated on March 26, Pauling’s text began

On the 3rd of March 1991 and on many succeeding days there was shown on television a remarkable sequence of pictures of an event that occurred in Los Angeles, California. A young man, 24 years old, had been traveling at high speed in a car. He had been chased by traffic officers, and had finally been run down near Los Angeles. He got out of his car, and apparently had fallen onto the ground. He was surrounded by 15 police and traffic officers. Although he was not resisting, he was beaten by three of these officers, wielding clubs. They struck him 57 times, breaking a bone in his leg and causing many cuts and bruises. The other 12 officers, including the sergeant in charge of the three who were doing the beating, did not intervene.

People all over the world were incensed at this display of brutality. No cases of law violation were filed against the young man who had been beaten. Some of the officers were charged with having themselves violated the law. At the present time the Chief of Police of Los Angeles is under pressure to resign, because of his toleration of this case of police brutality as well as of other cases.

There is, however, another case of egregious brutality that has not been criticized in the same way, but that has instead been welcomed with approbation. This is the case of the overwhelmingly one-sided assault by the United States, abetted by other countries who were to some extent browbeaten into their attitude, against Iraq.

Describing Operation Desert Storm as being “even more one-sided than the attack of the 15 police officers” against Rodney King, Pauling continued his statement in a vein very similar to the Nuclear Age Peace Foundation talk that he would give less than two weeks later.

The First Gulf War: Pauling Speaks Out


[Part 1 of 2]

Sparked by Iraqi president Saddam Hussein’s invasion of Kuwait in August 1990, and his subsequent refusal to comply with a U.S. demand that he withdraw from the region by mid-January 1991, the first Persian Gulf War began on January 17, 1991 with an operation known as Desert Storm.

In the lead-up to this military engagement, Linus Pauling established himself as a prominent critic of American posturing in the Gulf.  Just shy of his ninetieth birthday, Pauling returned to the world stage first by publishing a broadly circulated statement and open letter addressed to President George H.W. Bush, and later by giving a collection of interviews and speeches excoriating American policy in the Gulf. This body of activism reflected the anti-war stance that Pauling had assumed for more than four decades and served as a final demonstration of his ambition that war be ended once and for all.

Pauling’s initial pieces included little in the way of discussion of the precise issues at hand, but instead used the Persian Gulf War as an opportunity to highlight and amplify his broader views on war and peace. Later on, as battlefield engagement became a reality, Pauling’s writing and rhetoric made greater use of concrete examples in developing a specific point of view that resisted the American military campaign.

Pauling’s opening salvo, “Stop the Rush to War,” took the form of a full-page advertisement that was published in the New York Times on January 9, 1991. In this publication, Pauling emphasized that ultimatums or deadlines issued to the Hussein regime were unlikely to prove helpful. Instead, Pauling felt that the situation called for negotiations and economic pressures, which would ultimately lead to a diplomatic solution to the conflict.

For Pauling, one thing was clear: war would not work. In the Times piece, Pauling argued against military conflict by employing the fear of the potential use of bombs, poison gas, lethal bacteria, and even nuclear weapons, which would release fallout all over the world.  He argued that no cause could ever justify this kind of war. As an alternative, Pauling encouraged the reader to take personal action to persuade their leaders and those of other nations to stop the build-up to war.

Pauling’s New York Times appeal prompted the drafting of a petition that was authored in conjunction with the Institute for Peace and International Security in the United States and Naturwissenschaftler für den Frieden (Scientists for Peace) in Germany.  Pauling also contributed a greeting message that was read at the Naturwissenschaftler für den Frieden Congress, held in Muenster on January 28, 1991. In it, Pauling emphasized that international involvement was crucial to promoting peace and ending the threat of war.

On January 17, 1991, President Bush announced that the defensive posture that had been assumed by the U.S. military since August 1990 (“Operation Desert Shield”) had shifted into a phase of active combat, the aforementioned Operation Desert Storm. The next day, Pauling authored “An Open Letter to President Bush,” which called for specific actions to be taken in order to stop the further escalation of a war that had now effectively been declared.

The open letter appeared in the January 24th and 28th editions of Roll Call, a Washington D.C.-based newspaper that claimed readership on Capitol Hill, where it was delivered twice weekly. In addition to its publication in Roll Call, a copy of the letter was sent directly to the President.


Albert Schweitzer and Linus Pauling at the Schweitzer compound, Lambéréne, Gabon. 1959.

Employing a series of concise statements, Pauling made it very clear that to kill and maim is immoral, as is war in general. He further explained that war causes human suffering and that it is our job as humans – and certainly as world leaders – to decrease the amount of suffering that exists in the world. In this, Pauling reflected the point of view of Albert Schweitzer, a philosophical role model for Pauling whose emphasis on minimizing human suffering emerged as a crucial component of Pauling’s thinking and rhetoric during his years as an activist.

Similar to the previously published “Rush to War” piece, Pauling also emphasized his fears over the unintended consequences that might arise should a collection of terrifying weapons of war be deployed. Likewise, he concluded once again that negotiation was the just and moral route to peace in the Persian Gulf.



Linus Pauling, 1991.

Pauling’s next major statement on the war came in April 1991 and was delivered in the form of a speech titled, “Reflections on the Persian Gulf ‘War.'” Pauling gave this speech in Santa Barbara, California at a meeting of the Nuclear Age Peace Foundation, which was honoring him with a lifetime achievement award. In it, he collected a series of ideas that he had been developing over the previous months, and also issued a more pointed critique of the Persian Gulf War as a specific and perilous moment in human history.

Later excerpted in an article titled “Use Strength for Morality” and published in the July-August 1991 issue of The Human Quest, Pauling’s talk began with an analysis of President Bush’s so-called “New World Order,” which Pauling defined as depending upon rule through terror and the installation of friendly governments in strategically important foreign nations.

Pauling’s lecture also reflected an earlier interview with TIME magazine in which he had questioned the concept of a “just war.” In the conversation, Pauling explained that war may be justified when the suffering brought about by the act of war yields more long-term benefit or a higher purpose than the levels of suffering already extant in a given region.

With respect to the Gulf War, Pauling was deeply concerned that the Bush administration had failed to discuss issues of human rights and democracy in the country of Kuwait. Instead, the White House had only made the case that the family of the Kuwaiti emir needed to once again be restored to power.

For Pauling, the U.S. should have been far less concerned about the emir’s circumstances and much more interested in supporting democracy for the Kuwaiti people. As in his earlier statements, Pauling reemphasized the moral imperative for the United States to apply diplomatic and economic pressures in bringing about change. The chosen alternative, military incursion, would lead only to the waste of human lives and the possibility of escalation from conventional war to nuclear engagement.

In Pauling’s view, the clearly superior route for President Bush was to align himself on the side of morality.  Were he to do so, Bush could proclaim that “I set such a high value on human life and morality that I have decided the time has come to enter into discussions about all these world problems and save tens of thousands of lives.”  Likewise, there should be no concern about losing face. Indeed, Pauling argued that the “macho” stance for President Bush would entail a shift away from his pro-war policy, because it would take far more courage to resist war than to escalate it.

Pauling further delineated his previously expressed point of view arguing against ultimatums. In Pauling’s estimation, a series of threats were never going to prove persuasive for Saddam Hussein, whom Pauling judged to be lacking any fear over the potential deaths of soldiers or civilians. Likewise, the need to shift toward discussion was only exacerbated by the strong possibility that military conflict in the Gulf would serve to inflame the long-simmering Arab-Israeli conflict. With the end of the Cold War now at hand, the moral role of the United States as the dominant world power was to discourage regional wars rather than actively engaging in them.

The Nixon Doctrine and the End of the Vietnam War


An image of the April 24, 1971 March on Washington, as held in the Ava Helen and Linus Pauling Papers. The Paulings participated in a companion march held in San Francisco that same day.

[Pauling and the Vietnam War, Part 7 of 7]

“The American people are now learning the truth about the war…our entry into it on a great scale without even a request from South Vietnam…the corruption, the complete absence of a rational and moral goal…and the American people are now determined to bring this madness to an end.”

-Linus Pauling, 1969

In September 1969, Ho Chi Minh died at the age of seventy-nine and was replaced by Premier Pham Van Dong. At this same time, the anti-war movement was gaining considerable strength in the United States. In October, a “Vietnam Moratorium Day” was declared, during which students and faculty alike walked off of campuses across the country to talk about the war with members of their community.

At Stanford University, Linus Pauling, who had recently taken a position there as a visiting lecturer, was a central figure in this event. On the evening of the moratorium, he delivered a speech in which he proclaimed that the American people were finally learning the truth about the Vietnam War and the United States’ “cold blooded” ambition to retain control of Southeast Asia as part of a Western capitalist “economic sphere.” He delivered a similar message a month later in a talk given at Huntingdon College in Montgomery, Alabama. A story on the event, published in the Montgomery Advertiser, quoted Pauling as follows:

We – you and I and the majority of Americans – who are going to stop this war, are now face to face in opposition to the small group of rich and powerful people who are using their power to keep the war going, year after year: the people who benefit from the war, the military-industrial complex, the Pentagon and the war contractors who get the 15 billion dollars per year of excess profits on the guns, bombs, Napalm, planes and other instruments of war; and also the politicians, such as President Nixon, who are indebted to them.

The United States’ new President, Richard Nixon, had begun the troop withdrawals that he had promised on the campaign trail the year before. His plan, dubbed the
Nixon Doctrine, was to build up the Army of South Vietnam to the point where they could take over the defense of their own country. This policy came to be known as “Vietnamization.” Meanwhile, China and the Soviet Union continued to supply the North Vietnamese – and by extension the National Liberation Front – with aid. By 1970, Nixon announced that 150,000 U.S. soldiers would be withdrawn over the next year, thus reducing the American troop presence by about 265,500 people from the time when he had entered office.

However, at the same time, Nixon ordered a massive increase in bombing along the Vietnam-Cambodia border, and likewise redeployed many of the withdrawn troops to areas along the coast or just outside of Vietnam. These actions incited huge protests by those outraged by the President’s apparent subversion of his promise to de-escalate the war effort.

Pauling was among those who protested, speaking out in particular against the bombing incursions into Cambodia.  While attending a benefit in support of the McGovern-Hatfield Amendment to End the War, Pauling also declared that it had made him “sick” when Nixon stated before Congress that he would draw down troop numbers, and then, “five days later,” sent aircraft and ground troops to Cambodia. In response, Pauling suggested that everyone in the Bay Area “get sick” and take a week off of work. He explained his rationale as such:

When everyone is sick, the work stops, the economy is slowed down. If there is such an epidemic here, during the next week, it might spread over the whole country! Let our slogan be, “We’re sick of the war.”

Illness of another sort was also on Pauling’s mind. Around the same time that he proposed calling in sick to work, Pauling also recorded a radio address for KPFK-FM in Los Angeles on the subject of defoliant use in Vietnam. By 1968, he explained, 500,000 acres of cropland had been destroyed in Vietnam through the use of herbicides, some of which contained arsenic compounds. Not only did this action purposely lead to the starvation and death of civilians – especially the young and elderly – but Pauling attested that four scientists returning from South Vietnam with samples of food, hair, mother’s milk, and other substances had found them to be contaminated by these highly toxic herbicides.

Moreover, some of the herbicides being used in the war effort were not only very lethal but also very stable, and Pauling emphasized that these poisonous compounds would remain in the ecosystems of Vietnam for many years. Pauling further pointed out that several of the herbicides had been developed deliberately for the purpose of crop destruction as a tool of war by E.J. Kraus, the chairman of the Botany department at the University of Chicago. Pauling saw this as a violation of the proper role of university research, and cast aspersions upon the influence that the military and corporate war profiteers alike were gaining with respect to his academic colleagues’ research agendas.


The Paulings at an unidentified peace rally, possibly the April 24, 1971 San Francisco companion event to the March on Washington.

As these and other horrors of the Vietnam War gained increasing media traction, the anti-war movement, and the concurrent withdrawal of troops, continued. In 1971, Australia and New Zealand withdrew their complements of soldiers, and the American troop count was likewise further reduced to 196,700, with the return of an additional 45,000 troops promised for 1972. But even as this significant drawdown in ground forces was underway, significant U.S. naval and air might remained in the Gulf of Tonkin, as well as in Thailand and Guam.

From Pauling’s perspective, the major problem now hampering on-going peace talks in Paris was President Nixon’s continuing support of Generals Thieu and Ky of South Vietnam, political figureheads who had been put into power following a United States-sanctioned coup that had resulted in the assassination of the previous leader, President Diem. Both the North and many citizens of South Vietnam now refused to acknowledge these men as representatives of the provisional government of South Vietnam, and negotiations predictably suffered as a consequence.

In May 1972, a group based in Ann Arbor, Michigan and calling itself Hostages for Peace organized an extraordinary measure in an attempt to curb the violence in Southeast Asia. The group circulated a pledge which read as follows:

We, the undersigned American citizens, declare our willingness to go to Hanoi and Haiphong, and to declare ourselves Peace Hostages to protect Vietnamese citizens and American prisoners of war from American bombing. We each agree to spend at least two weeks in northern Vietnam until all the bombing of the area of the country stops and until all American military personnel and meteriel are removed from Indochina.

Linus and Ava Helen Pauling signed this pledge, agreeing to use themselves, effectively, as human shields against further American bombardment of North Vietnam. It was a courageous and potentially deadly commitment that the couple would, thankfully, not be called upon to realize.


“Hostages for Peace Pledge.” May 6, 1972.

On January 15, 1973, just weeks after a major bombing offensive had decimated what remained of North Vietnam’s economic and industrial capacity, President Nixon ended all military action against the North. The Paris Peace Accords were signed twelve days later, officially ending direct U.S. involvement in the Vietnam War. A cease-fire was subsequently declared across North and South Vietnam, and U.S. prisoners of war were released. The agreement guaranteed the territorial integrity of Vietnam and, like the Geneva Conference of 1954, called for national elections in the North and the South.

In other words, the conditions that Ho Chi Minh had made clear to Linus Pauling in 1965, and which Pauling had argued in favor of for the past eight years, had now been codified as an international agreement. In that time, it is estimated that anywhere from 800,000 to just over a million Vietnamese soldiers and civilians on all sides were killed, in addition to 200,000 Cambodians and 60,000 Laotians. Over 58,000 U.S. soldiers also lost their lives, with more than 1,500 still missing in action.

Tragically, like the Geneva Accords before them, the Paris Peace Accords were quickly broken. In 1974, the Viet Cong resumed military operations, and South Vietnam’s President Thieu declared that the Paris agreement was no longer in effect.

But this time, no American help arrived. In 1975, President Gerald Ford requested that Congress fund the re-supply of South Vietnam to defeat the National Liberation Front, who were now aided by a formal North Vietnamese invading force that was well-equipped, in large part, by other communist countries. Ford’s request was refused, and on April 27th, 100,000 North Vietnamese troops encircled Saigon, shelling the city while American helicopters evacuated vulnerable South Vietnamese citizens until the North’s tanks finally breached the lines of the South Vietnamese Army and captured the city.

In July 1976, North and South Vietnam were merged to form the Socialist Republic of Vietnam and, over the next ten years, more than one million South Vietnamese were sent to reeducation camps, with as many as 165,000 dying as a result.

After the war’s end, Linus Pauling carefully filed away the letters, the posters from various protests and anti-war lectures, and the memories of a long and bitter conflict. Included in these papers was correspondence concerning the Democratic Republic of Vietnam’s 26th celebration of nationhood in 1971. Though he was not in Hanoi for the event, Pauling had been in contact with a group that was, National Peace Action Coalition representatives Judy Lerner, David McReynolds, James and Patricia Lafferty, Joseph Urgo, and Ruth Colby.

The group had been met by the Peoples’ Coalition for Peace and Justice of North Vietnam, which hosted their visit. At the birthday celebration, where Premier Pham Van Dong declared the regime of the south fascist and called for the peoples of Vietnam, Cambodia, and Laos to unite to gain, “freedom, independence, peace and friendship, happiness and prosperity” for all of Indochina, the Americans were invited to make a statement of their own. Taking the stage, they articulated their feelings as best as they could:

No words of ours can fully express how deeply we have been moved by the way in which we have been received. We, citizens of a nation that has brought such terrible suffering to the peoples of Indochina, have been received as friends. The people of Vietnam understand that it is the rulers of the United States and not its citizens who are the enemy of the Vietnamese. One of our members is a veteran of the Vietnam War, and it would have been natural if he had been received with hostility. Instead, the guide in the War Museum embraced him with tears in his eyes – a simple human encounter which lifted both men above the level of being Vietnamese or American, to the level of brothers who suffered together in this, the most tragic war America has ever waged.

As North Vietnam celebrated its independence – an independence that had never been gained by South Vietnam – the American delegation in Hanoi affirmed again that, as the anti-war movement in the United States continued to swell, they would do everything in their power to end the conflict. This was a cause to which Linus and Ava Helen Pauling likewise devoted considerable energy over a full decade, and one that ultimately – through the pressure placed upon the governments involved by many such individuals throughout the world – played an important role in ending the Vietnam War.