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I'll begin this section by continuing the story of my personal odyssey in evolutionary biology and explain how I can write with some authority on the topic of this section.
While continuing my master's degree work in the then still non-existent graduate program at Southern Illinois University, Edwardsville, early in 1967 I applied to a number of universities from mediocre to the best that had evolutionary biology programs for admission as a PhD student. All but one rejected my application with no comment. The graduate admissions people at Harvard University were sufficiently interested that they engaged in some rounds of correspondence to collect additional information. In the end, before deciding to offer me a teaching fellowship, Harvard's Museum of Comparative Zoology paid my airfare and travel costs to come to Cambridge to give a seminar on the research program I had started with Sceloporus lizards. At the time, Harvard was one of the top 2-3 universities in the world in the area of evolutionary biology, with several of the authors of the mid 20th century "synthetic" theory of evolution associated with the Museum of Comparative Zoology: G.G. Simpson (Major Features of Evolution), E. Mayr (Animal Species and Evolution), A.S. Romer (The Vertebrate Body and Vertebrate Palentology). Most of the departments in the museum were also curated by leaders. My thesis committee consisted of Ernest E. Williams as my advisor, who as Curator of Herpetology had collected a particularly impressive array of students, and Ernst Mayr, then director of the Museum. I had sought to have E.O. Wilson (Sociobiology) of the Department of Biology as the third member of the committee, but Williams preferred to have one of the other (less renowned) curators to minimise friction between the two University departments.
As a complete aside, an amusing aspect of the Harvard campus is that the life sciences complex, comprising the Biology Labs, Herbaria, Museum of Comparative Zoology and the Anthropology are situated next door to the Divinity School and except for an access road completely encircle the Divinity School's dormitory.
When I was there, an important aspect of the Harvard environment was that there were no limits. The environment existed to support research with first class libraries (but not comparable to UCLA's Biomedical - biology journals were in 15-20 departmental libraries all over the campus and across the Charles River in Boston - all in separate cataloguing systems), laboratories and purchasing support. As a research student, I never had any problem purchasing any equipment or chemical justified for my work. Everywhere else I had been, external circumstances kept work to a slow pace. At Harvard, the only limit most students (including myself) encountered were our own personal limitations. Some couldn't cope with the freedom. Very few student marriages survived, and there was even a suicide or two. I myself went through a bit of a crisis when I fully realised that if I failed in my research ambitions, the only possible excuse would have been my own inadequacy.
In any event, in 1973 I completed my thesis under the title, Comparative Population Cytogenetics, Speciation and Evolution of the Iguanid Lizard Genus Sceloporus, based on three summers fieldwork in Mexico and making chromosome preparations from something like 3,000 iguanid lizards, including 1,217 from one species complex where chromosome mutations seemed to be directly involved in the development of isolating mechanisms between apparently genetically distinct species meeting geographically in hybrid zones only a few hundred meters wide. At the time this was probably the largest and most comprehensive chromosomal study of any group of closely related studies ever done. The well regarded protein geneticist, R.K. Selander, helped me in a subsidiary study where we examined protein variation for 21 different gene loci in 264 individuals in a transect across one of the hybrid zones. This work was published in the Hall and Selander (1973) paper in the journal Evolution.
The following statistics from Science Citation Index (I have on-line access through a university library) give some indication of its importance even today:
1 HALL W THESIS
HARVARD U CAM 1973
1 HALL WI THESIS HARVARD U CAM 1973
118 HALL WP EVOLUTION 27 226 1973
2 HALL WP EVOLUTION 22 226 1973
15 HALL WP THESIS HARVARD U 1973
39 HALL WP THESIS HARVARD U CAM 1973
The published Evolution article is by far the most frequently cited article by any W. Hall in 1973. The unpublished Thesis, with 56 citations, is the third most frequently cited article. Nine references to the thesis are since 1997, 24 years after it was completed. The Evolution article was referenced seven times since 1997. In most cases the same papers cite both of my works.
In any event, the evolutionary hypotheses presented in the thesis have been thoroughly criticised by other scientists in the literature - see Sites et al. (1993) referenced below. Using much more sophisticated genetic and mathematical techniques than were available to me in the late 60's and early 70's, Sites and his students and colleagues extended my data on Sceloporus lizards to larger populations and more proteins over a wider geographic area with a more sophisticated analysis without refuting my hypothesis (also without finding statistically significant confirmation of some of the predictions - although even with their added data sample sizes are still too small to be very discriminatory). However, despite the facts that Sites's papers are a lot more recent and that his team members are still professionally active at major universities and museums, the 10 papers collectively received fewer citations than my one published paper plus the thesis.
The case I make here is not (just) an ego trip, but that the work has stimulated a great deal of additional research to extend or test the hypotheses presented, and that it is now inextricably woven into the overall web of science.
However, I graduated at a very bad time to find a good teaching/research job that would provide me with access to source materials for continuing my own research program. At the tail end of the baby boom, most universities still had mostly young faculty and were faced with declining enrolments and the worst days of Affirmative Action. Thanks to the growing creationist movement general appointments in the area of evolutionary biology were beginning to be seen as somewhat politically sensitive - especially in some of the lower tier state universities and Christian schools that might otherwise have offered suitable positions.
The best I could do was a tenure track appointment at the University of Puerto Rico in San Juan. (The Free and Associated State of Puerto Rico is a part of the US by decision of its people - they accept the US Constitution and welfare system but only pay local taxes.) Although UPR was established as a state university under the US Land Grant scheme that set up all of the other major state universities in the continental US, in most other regards it has more in common with Latin American schools. They were poorly resourced, things often didn't work and student/university politics tended to the extreme. I had plausible research interests in Puerto Rico and the students were the most eager to learn that I have ever worked with, but with poor library facilities, political unrest and a very heavy teaching load it was impossible to make any significant progress on the Sceloporus research. I did try to set up a a breeding experiment to test some of my hypotheses about the fertility of hybrids of chromosomally different mice, but the program and records were irreparably disrupted by student strikes and total lockouts. In general, the biology students were the best and brightest I have ever worked with, so I threw most of my efforts into my courses. However, in my third year my my mounting frustration over lack of support for my teaching efforts - to say nothing of research support lead to a public shouting match with the female department chairman [there is some irony in my use of words here, a female chairperson in a Latin American environment has to have more testosterone than any male]. She made sure that I did not pass my third year tenure review - not that I particularly wanted to anyway.
As I was finishing my thesis, my research was well regarded in the evolutionary biology and herpetology communities, but I encountered major problems with reviewers when writing up the thesis, and later when trying to prepare the work for publication. At one point where my thesis was concerned, Williams, my advisor basically told me, "I don't like it, do it over!", but he could never articulate what his problems were. Nevertheless, the thesis was accepted, even though I had explicitly argued that Ernst Mayr's published arguments to the effect that speciation could only take place through prolonged geographical isolation were wrong - at least in the case of the lizards I had studied.
Because I was well known to the department chairman, I found a one year fixed term job (not subject to Affirmative Action assessment processes) at the EPO Biology department of University of Colorado, Boulder, to reorganise the ~1,000 student first year General Biology program. Here I was responsible for 8 lecturers and around 24 teaching assistants, plus for designing new course materials for the labs. Because I needed he money, I also taught genetics in the summer sessions before and after. However, there were no openings in any of my specialties for a tenure track position. While in Colorado, my future wife's [Darwinia's] boss, the Professor of Genetics at the University of Melbourne in Australia offered me a Melbourne University Fellowship with no strings, to continue my research in Australia. Needless to say, the workload at UC provided little opportunity for writing, although I did get far enough to nearly finish a first draft of a major paper on my thesis work.
I wrote the draft as a demonstration of how the comparative methodology (as I had learned it teaching comparative vertebrate anatomy and invertebrate biology) could be applied to less tangible processes such as the formation of new species. This was sent out for informal peer review before I left for Australia. I intended to use the time in Australia mainly for completing this and a number of related papers on my collections that had been passed over as not central to the thesis.
No sooner than I was settled in Melbourne, I received back a review of my draft paper from one of my ex research assistants who had helped with both field and lab work, who was the completing his PhD at the University of Michigan (also one of the top departments in the US in evolutionary biology) that said my writing was terrible, and that the whole thing needed to be rewritten. This was no more helpful than the similar comments that I had earlier received from my thesis advisor when I was writing up the thesis. After a couple more rounds of correspondence with my ex assistant, I basically told him that I didn't have a clue what he was complaining about and to either shut up or rewrite the paper himself. Because we were good friends, he did the latter. His covering correspondence asserted that my whole approach had been "unscientific", and his rewrite showed that he had completely failed to understand my method of argument. This was probably the greatest shock I have had in my life. Did I understand science? or was I a total failure?
The issues raised in the review went to the very core of what constitutes science, and as was the case for most scientists in the US, none of the courses in my training beyond the first introductory one (or perhaps even in high school) had even asked the question, "what is science?" After a couple of weeks to recover from the shock, I realised that before I could do any further writing on my research, I had to understand at a very deep level whether my research program was scientific and work out why my reviewers were having such difficulties understanding and accepting my method of argument. I had a vague recollection from a freshman history of civilization course that the word "epistemology" might have some bearing, and working backward from the dictionary, I finally began to find the areas of philosophy that dealt with the nature of science and what it means to say an idea is scientific. I also reinforced my conclusion that most philosophy writing is vapidly contentious posturing about the meanings of irrelevant words. However, two threads in the realm of the history and philosophy of science provided genuine guidance towards resolving my questions.
The first was T.S. Kuhn's 1970 work on scientific revolutions and the incommensurability of scientific paradigms, which has never been out of print. The second was initiated by Sir Karl Popper's books on the epistemology (theory of knowledge) of science, which more-or-less are accepted by most scientists as the bible on what represents science.
Kuhn, approaching science as a historian, introduced two seminal ideas (as elaborated in later works - See Kuhn 2000)
Kuhn's concept of incommensurability derives from the mathematical concept of incommensurability, and arises in science from the tacit [in the standard English sense of the term] nature of a paradigm. Kuhn developed the concept primarily in the framework of studying scientific "revolutions", where there was a historical progression from an earlier paradigm (disciplinary matrix) to a newer one. According to Kuhn, scientific revolutions may occur when new observations can no longer be adequately explained within an existing paradigm (the observations are anomalous). In some cases the anomalies can only be accommodated in theory based on new exemplars, models and/or symbolic generalisations. These changes often require new vocabulary and often alter the meaning and connotations of existing vocabulary. Even where the same words are used within each of the paradigms, there is often no longer a direct logical correspondence in their meanings. In other words, the world view (created by symbolic generalisations, models, exemplars and their associated theory-laden vocabulary) held by practitioners of one paradigm is logically incommensurable with that held by the alternative paradigm. Even though practitioners of both paradigms are looking at the same data, they see different worlds.
Because paradigmatic changes to vocabularies, models and exemplars are rarely discussed explicitly, and because few members of a discipline are even aware of the concept of a paradigm, Kuhn argues that the adoption of a new paradigm by an individual is a "conversion experience" (1970:151) more than it is a reasoned, logical process. Because practitioners working within the respective tacit paradigms don't know how to deal logically with their different views of the same external phenomena, discussions often become heatedly emotional, and consequently the process individuals undergo to accept a new paradigm may be more akin to religious conversion or cognitive revolution than it is to "normal" science.
Although Kuhn explored the ideas of paradigms and incommensurability primarily in the temporal process of change from one paradigm to another, two paradigms can (and often do) exist side-by-side at the same time, with the same consequences for communication between holders of the different paradigms that they have in the historical sense of a generational change.
My research on speciation in Sceloporus versus the responses from my reviewers is a classic example of paradigmatic incommensurability. As I have reconstructed my methodology, my thesis research was consciously organised along the lines of the "comparative" methodology that I had initially learned tacitly as a student in comparative ethology (animal behaviour) and comparative anatomy of the vertebrates courses. I had tested, practised and honed the methodology in my own teaching of invertebrate zoology. Basically, this is the same methodology Darwin used in his own books, as described by Ghiselin (1969) in his book, The Triumph of the Darwinian Method.
Basically, the "comparative" method is applicable and entirely appropriate to explaining scientifically, historical processes (such as the formation of new species) that are not susceptible to experimental manipulation in the lab. In the comparative method, one looks to nature for "natural experiments" where closely related species or populations are similar in most respects except for the variable one wishes to study. Darwin used it, but the concept was given a name by the Nobel prize winning Niko Tinbergen in his 1951 book The Study of Instinct. Tinbergen's research skills lay in his ability to "ask questions of nature." His four questions: immediate causation, development, evolution, and function still form the basis for modern ethological theorizing. His research with sticklebacks, herring gulls, and digger wasps are classic examples of comparative ethology, and were the prime examples of the methodology covered in one of the first two university biology courses I took at UCLA, comparative ethology. I subsequently used the concept of the natural experiment in all of my subsequent work "without question or introspection", anticipating that other "comparative" biologists would automatically understand many of the underlying assumptions of my methodology. My research extended, but did not invalidate the model of speciation described by Ernst Mayr. My unstated logical exemplars were the kinds of natural experiments performed by the co-Nobelists Tinbergen, Lorenz and von Frisch and as developed on a broader scope the comparative anatomy of the vertebrates course as taught at San Diego State. Finally, my work was framed in such a way that it related what I had done to previous work in cytogenetics as expressed in M.J.D. White's three editions of Animal Cytology and Evolution (the last published in 1973 as typed and indexed by White's secretary, my wife to be - Darwinia) and in his later (1978) book, Modes of Speciation, which cited three of my works. The value of my thesis work, in terms of the ability to be "used in judging whole theories: [where] they must, first and foremost, permit puzzle-formulation and solution; where possible they should be simple, self-consistent, and plausible, compatible, that is, with other theories currently deployed" was amply demonstrated by the use of my thesis work in Sites et al's 1992 review of phylogenetic hypotheses.
However, in the era around the time I completed my thesis, many biologists were striving to reformulate evolutionary biology as an "experimental" science by forcing their research to conform the the "hypothetico deductive" methodology [see Google for explanations - http://www.google.com/search?q=%22hypothetico+deductive%22+method+science]. The University of Michigan biology department, where my ex-assistant was working on his own doctorate, was in the forefront of this movement, and - of course - neither of us had been aware of Kuhn's concepts or that there might be different and equally valid ways of doing science.
My detailed analysis of the epistemology of the comparative method and the problems of incommensurability between it and the hypothetico deductive method are provided in the Hall (1983) paper that I have scanned, and will happily e-mail to anyone genuinely interested in the issues of what constitutes science in evolutionary biology.
To finish the autobiography, I reached my understanding of the issues surrounding my writing too late to have a realistic hope to salvage my academic career. After two years at the University of Melbourne researching epistemology and the history of science, I sent out some 200 application/resume packages - costing an average of $20-25 each to put together and post (not counting my time) to get a half-time one year term appointment to teach evolutionary biology, vertebrate biology and a seminar. [Darwinia followed me to the States and we were married there.] My office and research space was a recycled janitor closet (and I have seen larger broom closets!). Beyond this in the some 200 students that passed through the three courses I taught that year, and I didn't manage to identify one who seemed to be genuinely interested in anything that involved thinking. Needless to say, in this depressing environment I wrote nothing, and I could not face another round of applications in the still dreadful job market where the best I could reasonably hope for with my horrendously complex resume under Affirmative Action against all the bright young baby boomers was a third or fourth rank college. In disgust, I returned to Australia in late 1979 (where at least the academic market was smaller - although suffering from the same demographic problems). Here, I discovered personal computing and have retooled my analytical skills in the areas of documentation systems and organisational knowledge management, where I have reestablished a university presence in areas relating to the historical development of knowledge management technologies and the extragenetic evolution of human cognition, where I am currently writing a hypertext book on the subject.
My next section explores the concepts of knowledge and truth, as elucidated on Sir Karl Popper's writings and as attempted
As a documentation systems and knowledge management analyst, I have again had to confront in very pragmatic terms the questions "What is knowledge?", "Why do we need to know" and "How can we tell what someone's claim to knowledge is likely to be worth anything?"
In 1983 most scientists simply assumed that knowledge was what their work generated. Philosophers of science weren't so sure. A wide range of opinions were surveyed and reviewed in Suppe's (1977), second edition of what started as the proceedings of a conference. This should still be required reading today for anyone wanting to understand the epistemological foundations of science. Basically there were two schools (major paradigmatic differences with associated communication problems were apparent amongst the contributors):
In my opinion, the two groups basically sit at right angles to one another. The first group is concerned with the question "why and how scientists come to think they know the truth", the second group with "what methods of research and argument are most likely to reveal objective truth". Except for Kuhn, who had very important things to say about paradigms and interparadigmatic communication as discussed above, and Polanyi, who highlighted personal aspects of the search for knowledge that Popper never discussed, the first group have little to say that bears on the subject of this essay.
Popper's epistemology rests on the fundamental premise that there is a genuine objective reality that exists, and that what a human claims to know may actually be true according to this objective reality. In other words "John's claim may be true, is there any way we can prove its truth?"
Science seeks to understand the laws governing nature. Scientists' claims to have a true understanding of a natural law are claiming much more than John saying, "I know there is a rock sitting on that table because I can see it". If John is a scientist making scientific claims, these will relate to multiple instances of a supposed process or action perform in the same way in the past, now and in the future. Popper was very much concerned with the epistemology of this kind of science.
In his (1934 and 1959) book, The Logic of Scientific Discovery [which really had nothing to do with processes by which knowledge might actually be discovered], Popper argued that in formal logic, no matter how many times some prediction claimed to represent true knowledge was repeated and confirmed, this did not prove that the next iteration of the experiment would yield the predicted result. Conversely, in formal logic, a single failure of the experiment to behave as predicted would deductively "falsify" the prediction (i.e., prove it to be wrong). Popper then argued from this dichotomy that the best way to differentiate between an hypothesis that deserved to be called scientific versus a fantasy or unsupported belief was (1) the capacity of the hypothesis to be tested in ways that had the potential falsified and (2) on the robustness of the attempts to actually perform these tests.
This is more-or-less the basis for the hypothetico-deductive method of science. A hypothesis is constructed that makes deductively testable predictions. An experiment is designed to test the predictions. The hypothesis stands or falls depending on whether the results conform to the predictions or refutes them. It is considered to be bad science to always reformulate the hypothesis every time it fails to make it predict the results observed because this potentially leads to increasingly narrow and ad hoc explanations rather than comprehensive explanations.
On the other hand, if the claim to know truth is stated in such a way that it makes no predictions subject to falsification, there no way to test its connections to objective reality. In other words, both the claims that "God exists" and "There is no God" are equally unscientific beliefs, as all the proposed proofs and falsifications are equally subjective to the person making the claims. Neither claim makes any tangible claims that are susceptible to falsification. For example, I am well known to be an atheist, and claim that my reasons for thinking there is no God are rational and defensible; but I will be the first to admit that these reasons are not scientific in the sense that they can be deductively falsified.
Popper had many critics who claimed that his principle of falsification and concept of demarcation (i.e., how to differentiate between science and non-science) were overly simplistic and did not correspond to the real world, where experiments involved all kinds of accessory processes, including human error and the fact that many processes were not completely deterministic anyway. Popper eventually accepted that falsification of the prediction of an hypothesis did not prove absolutely its falsity.
However, in Conjectures and Refutations, Popper(1963) was still concerned to develop an epistemology that would help explain how scientific endeavour could lead to the growth of true knowledge through time. Certainly our experience with the results scientific methods is that we know vastly more about how the details of how the world works at the beginning of the 21st Century than we did at the beginning of the 20th Century. Basically his approach was to propose increasingly bold hypotheses that make as many predictions as possible about how reality should perform and to strenuously test the predictions in attempts to falsify them. Confirmatory tests do not prove the truth of the hypothesis and falsifications do not prove the falsity of the hypothesis, however it is rational to believe that a bold hypothesis that has successfully made many different kinds predictions that passed their tests without falsification is in some way closer to the real truth (i.e., is more realistic) than an idea which has not been tested at all or that has demonstrated its failure to predict the observed results.
In Objective Knowledge (1972) Popper focuses on the question of how science should proceed through time to ensure that the truth content in our knowledge grows in time (without ever giving us the ability to say that the knowledge so generated is actually true), i.e., to formlate an Evolutionary Theory of Knowledge. Basically the idea is to develop increasingly bold conjectures that offer increasing scope and number of connections to reality and to constantly test and criticise these connections and to selectively eliminate those conjectures that whose predictions regularly fail their tests. The claims to knowledge that are left are demonstrably robust and more accurate depictions of reality than the ones replaced.
For example, modern astrophysical data are telling us that something is wrong with either gravitational or relativity theories (actually the two are closely intertwined). Nevertheless, we continue to use these theories as if they were true because no other explanation has come along that explains more things about reality in testable ways than do gravity and relativity. When a more comprehensive theory is proposed that explains more of the observations and predicts some previously unknown properties of the universe that are confirmed, then it will be accepted in place of the existing theories.
I will now argue that the Darwinian comparative method conforms as well to Popper's criteria for what constitutes scientific explanation as does the hypothetico-deductive method.
Historical processes that have a stochastic basis (i.e., that are neither completely random nor deterministically predictable) and take place over times are not amenable to classical hypothetico-deductive testing in the laboratory. On the other hand it may be possible to identify natural experiments that are in similar in most respects but vary in the features of interest. An epistemically valuable or "bold" conjecture will not only explain (ad hoc) the features observed but will also predict other aspects of the biology which have not yet been observed or considered in the original conjecture. These predictions are subject to testing in the same way that predictions made via an hypothetico-deductive method would be.
For example, my thesis on chromosome evolution and speciation in Sceloporus presented conjectures within a framework of theory that made many predictions about aspects of biology of the various species that I did not have the time, specimens or technologies to actually test. These predictions have informed a great deal of additional research by many scientists. Irrespective of whether this additional work has confirmed or refuted the predictions, the comparative methodology I followed was undeniably scientific by Popper's criteria.
As Gould (2002) so lucidly explains in Chapter 2 of his The Structure of Evolutionary Theory, Darwin's theory makes a vast array of implicit and explicit predictions about the kinds of diversity and similarities we might expect to see which have informed and suggested research and testing across the full gamut of biological sciences from molecular genetics and biophysics through to ethology and community ecology. After nearly a century and a half of strenuous scientific investigation the core of the theory remains massively intact. The best would-be revolutionaries like Gould and myself can do is offer a few tweaks and tucks around the periphery.
Behe's attempts to offer a counter theory is pathetic by comparison. His theory is that because he cannot offer an explanation for how they might have evolved, cellular structures like the bacterial flagellum are so "irreducibly" complex that they must have been "designed", thereby refuting the theory of evolution.
A truly scientific theory would make some predictions as to how this design process actually worked, to guide research to test the predictions. Basically he says the only way his "theory" can be refuted is by demonstrating he evolution of the bacterial flagellum in the lab. Based on the epistemology discussed above, he is making a travesty of the scientific method. Natural experiments based on analogously complex organelles will suffice to demonstrate the vacuousness of Behe's argument.
Some of the background for these experiments will be laid in the next installment.
Edmonds, D. & Eidinow, J. 2001. Wittgenstein's Poker: The Story of a Ten-Minute Argument Between Two Great Philosophers. HarperCollins Publishers, New York
Fumerton, R., 2000. Foundationalist Theories of Epistemic Justification in - Zalta, E.N. ed. Stanford Encyclopedia of Philosoply - http://setis.library.usyd.edu.au/stanford/entries/justep-foundational/
Ghiselin, M.T. 1969. The Triumph of the Darwinian Method. Univ. Calif. Press, Berkeley. [now lost]
Gould, S.J. 2002. The Structure of Evolutionary Theory. Belknap Press, Harvard University Press, Cambridge, Mass.
Hall, W.P. 1973. Comparative population cytogenetics, speciation and evolution of the iguanid lizard genus Sceloporus. PhD Thesis, Harvard University
_____. 1983. Modes of speciation and evolution in the sceloporine iguanid lizards. I. Epistemology of the comparative approach and introduction to the problem. (in) A.G.J. Rhodin and K. Miyata, eds. Advances in Herpetology and Evolutionary Biology - Essays in Honor of Ernest E Williams. Museum of Comparative Zoology, Cambridge Mass. pp.643-679
_____. & Selander, R.K. 1973. Hybridization of karyotypically differentiated populations in the Sceloporus grammicus complex (Iguanidae). Evolution 27: 226-242
Kuhn, T.S. 1970. The Structure of Scientific Revolutions, 2nd. Ed. Enlarged. International Encyclopedia of Unified Science 2(2). University of Chicago Press, Chicago.
_____. 2000. The Road Since Structure: Philosophical Essays, 1970-1993, with an Autobiographical Interview. J. Conant and J. Haugeland [eds.]. The University of Chicago Press, Chicago.
Polanyi Michael 1958. Personal Knowledge: Towards a Post-Critical Philosophy. University of Chicago Press.
_____. 1966. The Tacit Dimension. Doubleday & Co.
Popper, K.R. 1934, 1959. The Logic of Scientific Discovery, Sixth Impression (Revised) [First English Ed., Hutchinson, 1959. First published as Logik Der Forschung in Vienna: Springer, 1934]. London, Hutchinson & Co., Ltd., 480 pp.
____. 1963, 1972a. Conjectures and Refutations: The Growth of Scientific Knowledge, 4th Ed. (Revised) [1st Ed., 1963]. London, Routledge and Kegan Paul, 431 pp.
____. 1972b. Objective Knowledge: An Evolutionary Approach. London, Oxford Univ. Press, 380 pp.
Sites, J.W., et. al. 1992. A review of phylogenetic hypotheses for lizards of the genus Sceloporus (Phrynosomatidae): Implications for ecological and evolutionary studies. Bull. Am. Mus. Nat. Hist., No. 213, 110 pp.
Suppe, F. 1977. [Editor] The Structure of Scientific Theories. 2nd Ed., University of Illinois Press.
Thornton, S. 2000. Karl Popper. in The Stanford Encyclopedia of Philosophy (Winter 2001 Edition), Edward N. Zalta (ed.), . - http://plato.stanford.edu/archives/win2001/entries/popper
Tinbergen, N. 1951. The Study of Instinct. Clarendon Press, Oxford.
White, M.J.D. 1973. Animal Cytology and Evolution. 3rd. Ed. Cambridge University Press, London.
_____. 1978. Modes of Speciation. W.H. Freeman and Company, San Francisco.