Evolution, Explanation, Ethics and Aesthetics. Towards a Philosophy of Biology

400 Pages·2016·13.69 MB·English

by  Francisco J. Ayala

Evolution, Explanation,
Ethics, and Aesthetics
Towards a Philosophy of Biology
Francisco J. Ayala
University of California, Irvine, CA, United States
AMSTERDAMlBOSTONlHEIDELBERGl LONDON
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Preface
TheodosiusDobzhansky,creditedasoneofthefoundersofthemoderntheoryof
evolution, wrote in 1972 that “Nothing in Biology MakesSense Exceptin the
Light of Evolution,” the title of his address to a convention of the National
AssociationofBiologyTeachers.1Thetheoryofevolutionis,indeed,thecentral
organizing concept of modern biology. Evolution scientifically explains why
there are so many different kinds of organisms, and it accounts for their simi-
laritiesanddifferences.ItaccountsfortheappearanceofhumansonEarth,and
revealshumans’biologicalconnectionswithotherlivingbeings.Itprovidesan
understandingofconstantlyevolvingviruses,bacteria,andotherpathogensand
enablesthedevelopmentofeffectivewaystoprotectourselvesagainstthedis-
easestheycause.Knowledgeofevolutionhasmadepossibleadvancesinagri-
culture,medicine,andbiotechnology.
Michael Ruse, the distinguished and prolific philosopher of biology,
extendedDobzhansky’sstatementwithasimplemodification:“Nothingmakes
sense except in the light of evolution,” a statement he always attaches to his
signature. What does Ruse mean? Does he mean that evolution encompasses
otherscientificdisciplines,suchasastrophysics,physics,andchemistry?Does
hemeanthattheconceptofevolution goes beyond scienceandextendstoart,
literature, religion, and social and political institutions? And to human history
andfamilylife,includingloveandcare?IsuspectthatRusemeansallofthese:
indeed, that as his statementsays, “nothing makes sense except in the light of
evolution.”
Dobzhanskywouldhaveagreed. AttheveryendofhisMankindEvolving,
Dobzhansky quotes the Jesuit anthropologist Pierre Teilhard de Chardin: “Is
evolutionatheory,asystem,orahypothesis?Itismuchmoreditisageneral
postulate towhich all theories, all hypotheses, all systems must henceforward
bowandwhichtheymustsatisfyinordertobethinkableandtrue.Evolutionisa
light which illuminates all facts, a trajectory which all lines of thought must
followdthisiswhatevolutionis.”2
In the introduction to Part I of his 1988 magnificent collection of pre-
viously published papers, Toward a New Philosophy of Biology, Ernst Mayr
1.Dobzhansky,T.,1972.Nothingin biologymakessenseexceptin thelightofevolution.The
AmericanBiologyTeacher35,125e129.
2.DobzhanskyT.,1962.MankindEvolving.TheEvolutionoftheHumanSpecies.YaleUniversity
Press,NewHaven,CTandLondon.
xi
xii Preface
pointsouthis“specialconcerns”abouttheneglectofbiologyintheworksof
philosophersofscience.“Fromthe1920stothe1960s,thelogicalpositivists
and physicalists who dominated the philosophy of science had little interest
in and even less understanding of biology, because it simply did not fit their
methodology.”3 In 1961e1964, I was a PhD student at Columbia University
inNewYork,underthementorshipofDobzhansky.Earlier,Ihadthreeyears
of formal philosophical training in Spain and remained interested in the
philosophicalimplicationsofmyscientificresearch,focusedongeneticsand
evolution. I read at the time two recently published books, The Biological
Way of Thought by Morton Beckner (1959), a Ph.D. student of the eminent
philosopherofscienceErnestNagelatColumbiaUniversity,andTheAscent
of Life. A Philosophical Study of the Theory of Evolution (1961) by T. A.
Goudge, a professor of philosophy at the University of Toronto. At
Columbia, I befriended and occasionally attended the lectures of Ernest
Nagel and read the two chapters dedicated to biological issues in his
The Structure of Science. Problems in the Logic of Scientific Explanation
(1961).
Most important were my frequent conversations with Dobzhansky, con-
cernedashewasaboutthelittleattentionphilosophersofsciencewerepayingto
themultitudeoffundamentalandever-mountingphilosophicalissuesemerging
from evolutionary biology. Dobzhansky often expressed his frustration at the
limitedinfluenceofbiologyonthethinkingofcontemporaryphilosophers.He
saw that evolutionary biology raises important new philosophical issues and
illuminatesoldones.In1971,wedecidedtoconveneaconferencewhereineight
daysofintensediscussionsuchissueswouldbejointlyexploredbyconcerned
philosophersandphilosophicallysavvyscientists.Theconferencetookplacein
Villa Serbeloni, a magnificent palace with beautiful gardens owned by the
Rockefeller Foundation, in northern Italy, overlooking Lake Como, on
September9e15,1972,includingKarlPopperamongthephilosophers,andfour
Nobel Laureates, John C. Eccles, Gerald M. Edelman, Peter Medawar, and
Jacques Monod. The papers presented at the conference were published as
Studies in the Philosophy of Biology (1974). Two relatively short books were
publishedataboutthesametimebytwoauthors,MichaelRuse(ThePhilosophy
ofBiology,1973)andDavidHull(PhilosophyofBiologicalScience,1974),who
would become over the ensuing decades two leaders among the increasing
number of philosophers dedicated to the philosophy of biology since the last
quarterofthe20thcentury.
The 17 chapters included in the present volume should be of interest to
philosophystudentsasatextbookfora universitycourseonthephilosophy of
biology,butthechaptersarenotintendedasanencompassingtreatise.Thebook
isintendedforscientistsandphilosophersconcernedwiththeissuesathand,as
3.Mayr,E.,1988.TowardaNewPhilosophyofBiology.HarvardUniversityPress,Cambridge,MA.
Preface xiii
wellasforinterestedgeneralreaders.Technicallanguagehasbeenavoidedtothe
extentpossible.Thechapterscanbereadinanysequentialorderandarelargely
self-contained,sothatanissuemostlyconsideredinaparticularchaptermaybe
brought up elsewhere, if only briefly, whenever necessary for understanding a
particulartopicunderconsideration.
There are many scientists, philosophers, and other scholars to whom I am
indebted,bothintellectuallyandpersonally.TheodosiusDobzhansky,myPh.D.
mentoratColumbiaUniversityinNewYork,deservesparticularmention.Iwant
toexpressmygratitudealsotoDeniseChilcote,myexecutiveassistant,who,for
nearlythreedecades,hasneverfailedtodowhateverneededtobedoneaswellas
it could be done. I have tremendously benefited from her dedication and
perfectionism.
FranciscoJ.Ayala
UniversityofCalifornia,Irvine,CA,UnitedStates
Chapter 1
The Darwinian Revolution
INTRODUCTION
Thepublicationin1859ofDarwin’sOriginofSpeciesopenedanewerainthe
intellectual history of mankind. The discoveries by Copernicus, Kepler,
Galileo, and Newton had gradually led to a conception of the universe as a
systemofmatterinmotiongovernedbynaturallaws.TheEarthwasfoundto
benotthecenteroftheuniversebutasmallplanetrotatingaroundanaverage
star; the universeappeared as immense in space and in time; andthe motions
of the planets around the Sun could be explained by simple lawsdthe same
laws that accounted for the motion of objects in our planet. These and many
other discoveries greatly expanded human knowledge. But the conceptual
revolutionthatwentonthroughthe17thand18thcenturieswastherealization
that the universe obeys immanent laws that can account for natural phenom-
ena. The workings of the universe were brought into the realm of scienced
explanation through natural laws. Physical phenomena could be reliably pre-
dicted whenever the causes were adequately known. Darwin completed the
CopernicanRevolutionbydrawingoutforbiologytheultimateconclusionsof
the notion of nature as a lawful system of matter in motion. The adaptations
and diversity of organisms, the origin of novel and highly organized forms,
eventhe origin ofman himself could nowbeexplainedbyanorderly process
of change governed by natural laws.
All human cultures, including primitive ones, have developed their own
explanations for the origin of the world and of human beings and other
creatures. Traditional Judaism and Christianity explain the origin of living
beings and their adaptations to their environmentsdwings, gills, hands,
flowersdas the handiwork of an omniscient God. Among the Western cul-
tures, the earliest systematic attempts to account for the origin of the world,
humans, and other creatures were formulated by Greek philosophers (Mayr,
1982; Moore, 1993).
GREEK ANTIQUITY
Thales of Miletus (c.620e555 BCE) was an astronomer, geographer, and
meteorologistwhoconsideredwaterthefirstprincipleofcreation,butdidnot
Evolution,Explanation,Ethics,andAesthetics.http://dx.doi.org/10.1016/B978-0-12-803693-8.00001-3
Copyright©2016ElsevierInc.Allrightsreserved. 3
4 PART jI Evolution
advance any specific ideas about the origins of organisms. His disciple
Anaximander(c.611e547),alsoanastronomerandgeographer,proposedthat
the world is composed of four elements: earth, water, air, and fire. He spec-
ulated that the first animals were generated in an aquatic environment and
wouldlatermigratetothedryland.Humansalsowereformedfirstasfish-like
creatureswhichwouldeventuallydevelopandliveindependentlyontheland.
Anaximander’s account of human origins was not a theory about evolution in
the modern sense, but an ontogenetic account of the early stages of each in-
dividualwhowouldeventuallydevelopintoafullhuman.Thedoctrineofthe
four elementsdearth, water, air, and firedwas adopted a century later by
Empedocles (c.490e430 BCE) and, another century later, by Aristotle,
through whom it became central to Western thought for the next 2,000years.
Anaximenes (c.555e500 BCE) and Parmenides (c.515e445 BCE) accepted
similarideas,propoundingthespontaneousgenerationoforganismsfrommud
or slime.
Anaxagoras (c.500e428 BCE) and Democritus (c.460e370 BCE) were
concerned with what we now would call “adaptation” of organisms to the
environment.Theirexplanationswerethoroughlymaterialisticor,aswecould
say, physicalist: the composition and functional structures of organisms are a
necessary consequence of the properties of atoms.
More interesting in someways were the origination ideas of Empedocles,
becauseonecouldseeinthema(gross)anticipationofnaturalselection.Body
parts, such as heads, limbs, eyes, and mouths, originate spontaneously and
separately.Thesepartswouldattracteachotherinvariouscombinations,only
some of which would survive, namely those that would become functional
organisms, while all others would be eliminated.
ThethreemostimportantphilosophersofclassicalGreeceintermsoftheir
posterior influence, some extending to the present, are Socrates, Plato, and
Aristotle. Socrates (469e399 BCE), born in Athens, is known through the
writings (“dialogues”) of Plato, particularly the Apology, the Crito, and the
Phaedo, where Plato immortalized the story of Socrates’ trial and last days.
Beyond his trial and death, associated with his criticisms of the moral dis-
tortionsoftheAthenians,Socratesisparticularlyrecognizedforthe“Socratic
method”:askingfordefinitions,mostimportantlyaboutmoralvalues,suchas
piety and justice, and subjecting them to criticism and analysis, showing the
contradictions often elicited by the responses.
Plato (c.428e347 BCE) was born, probably in Athens, into awealthy and
aristocratic family. After the self-executed death sentence of his mentor Soc-
rates,PlatotraveledextensivelythroughGreece,Italy,andEgypt.Hereturned
to Athens around 387 BCE and founded the Academy, which became a
distinguished center for philosophical, mathematical, and scientific research.
Plato’s ideas are well known through his 30 dialogues, mostly philosophical.
HereplacedthespontaneousgenerationofthepreviousGreekphilosophersby
acreativepower,ordemiurge,authorofalltheidealforms,orcategoriesthat
TheDarwinianRevolution Chapter j1 5
account for all realities in the world, organisms and otherwise, which are
limited and imperfect instantiations of the ideas in the mind of the Creator
demiurge.Platowasapaganpolytheist.Hisdemiurgeisverydifferentformof
the CreatoreGod of the great monotheistic religions. According to Plato, for
example, the idea of a horse exists only in the mind of the demiurges; the
horses that exist on Earth are imperfect instantiations of the ideal horse.
Aristotle(384e322BCE)wasadiscipleofPlatoandlaterateacheratthe
Academy for 20years, from 367 to 347 BCE. Aristotle, born in Stagira in
Macedon, was the son of Nichomachus, court physician to Amyntas III of
Macedonia,grandfatherofAlexandertheGreat,whowastutoredfromage13
to16(343e340BCE)byAristotle.AristotlespendthreeyearsontheAegean
island of Lesbos, close to the western coast of today’s Turkey, where he
developed his interest in and study of biology. In 335 BCE Aristotle returned
toAthens,wherehefoundedtheLyceum,hisownschool,andtaughttherefor
the next 12years.
Aristotle is fittingly recognized as one of the great philosophers of Greek
antiquity,knownforhisworksonlogic,epistemology,metaphysics,ethics,and
politics.Healsoqualifiesasagreatscientist,thefirstbiologistinthehistoryof
the world, as he dissected a variety of animals and described in detail the
development of the chicken embryo from egg to hatching. During his three
years in Lesbos he investigated all sorts of marine and lacustrine organisms,
fromcoralreefsandmolluscstofish,aswellaslandanimals.Inhisnumerous
zoological works, such as The Generation of Animals and others, Aristotle
mentions500animal species,alargenumber relativetotheknowledge ofthe
time (Leroi, 2014). Aristotle rejected the classification of animals based only
on their external structures (for example, winged or wingless), basing his
classification on the principle of organization, consisting of structure and
function (including mode of reproduction), and introduced the binomial
method of nomenclature. To define each animal, Aristotle used the genus
(which encompassed interrelated animals or organisms in general) and their
difference (the distinctive characteristics of the species or the specific organ-
ism). This binomial two-term method of identifying each particular organism
would be modified a few centuries later by Porphyry (234e305), a prolific
author, mainly of philosophical treatises, and disciple of Plotinus (considered
the father of Neoplatonism in Rome). Porphyry introduced the category of
species combined with genus to identify organisms, thus refining the combi-
nation of genus and difference used by Aristotle and thereby originating the
binomial system of nomenclature that persists to the present day and is often
erroneously credited to Linnaeus (1707e78) (Ayala, 2014).
Aristotledevelopedasystemofclassificationofanimals,recognizingnine
groupswithintwolargecategories:animalswithbloodandwithoutblood.He
classified the animals with blood into five groupsdmammals, birds, reptiles,
amphibians, and fishesdand divided the animals without blood into cepha-
lopods, crustaceans, insects, and a fourth group that would include the rest of
6 PART jI Evolution
the animals. Aristotle’s classification compares favorably with the classifica-
tionbyLinnaeus,21centurieslater,whorecognizedonlysixkindsofanimals:
mammals, birds, reptiles, fishes, insects, and worms. Aristotle considered
some animals more complex or advanced than others, but he believed in the
immutability of species, not in their evolution, and thus he did not see the
difference between lower and higher animals as the outcome of a process of
change or progress over time.
CHRISTIANITY AND EUROPE UNTIL DARWIN
Among the early Fathers of the Church, Gregory of Nyssa (335e394) and
Augustine(354e430)maintainedthatnotallofcreation,allspeciesofplants
and animals, were initially created by God; rather, some had evolved in his-
torical times from God’s creations.
According to Gregory of Nyssa, the world came about in two successive
stages. The first stage, the creative step, was instantaneous; the second stage,
the formative step, is gradual and develops through time. According to Au-
gustine, manyplant and animal species were not directly created by God, but
only indirectly, in their potentiality (their rationes seminales), so they would
come about by natural processes later in the development of the world.
Gregory’s and Augustine’s motivation was not scientific but theological. For
example,Augustinewasconcernedthatitwouldhavebeenimpossibletohold
representatives of all animal species in a single vessel, such as Noah’s Ark;
some species must have come into existence only after the Flood.
The notion that organisms may change by natural processes was not
investigated as a biological subject by Christian theologians of the Middle
Ages, but it was, usually incidentally, considered as a possibility by many,
including Albertus Magnus (1200e80) and his student Thomas Aquinas
(1224e74).Aquinas concluded, after consideration ofthe arguments, thatthe
development of living creatures, such as maggots and flies, from nonliving
matter, such as decaying meat, was not incompatible with Christian faith or
philosophy,butheleftittoothers(scientists,incurrentparlance)todetermine
whether this actually happened.
Theissueofwhetherlivingorganismscouldspontaneouslyarisefromdead
matter was not settled until four centuries later by the Italian Francesco Redi
(1626e97), one of the first scientists to conduct biological experiments with
propercontrols.Redisetupflaskswithvariouskindsoffreshmeat:somewere
sealed, others covered with gauze so that air but not flies could enter, and
others left uncovered. The meat putrefied in all flasks, but maggots appeared
onlyintheuncoveredflaskswhichflieshadenteredfreely.Rediwasapoetas
wellasaphysician,chieflyknownforhisBaccoinToscana(1685,Bacchusin
Tuscany).
The cause of putrefaction was discovered two centuries later by Dar-
win’s younger contemporary, the French chemist Louis Pasteur (1822e95),
TheDarwinianRevolution Chapter j1 7
one of the greatest scientists of all time. Pasteur demonstrated that
fermentation and putrefaction were caused by minute organisms that could
be destroyed by heat. Food decomposes when placed in contact with germs
presentintheair.Thegermsdonotarisespontaneouslywithinthefood.We
owe to Pasteur the process of pasteurization, the destruction by heat of
microorganisms in milk, wine, and beer, which can thus be preserved if
kept out of contact with the microorganisms in the air. Pasteur also
demonstrated that cholera and rabies are caused by microorganisms, and he
invented vaccination, treatment with attenuated (or killed) infective agents
that would stimulate the immune system of animals and humans, thus
protecting them against infection.
In the 18th century Pierre-Louis Moreau de Maupertuis (1698e1759)
proposedthespontaneousgenerationandextinctionoforganismsaspartofhis
theoryoforigins,butheadvancednotheoryaboutthepossibletransformation
of one species into another through knowable natural causes. One of the
greatest naturalists of the time, Georges-Louis Leclerc, Comte de Buffon
(1707e78), explicitly considereddand rejecteddthe possible descent of
several distinct kinds of organisms from a common ancestor. However, he
made the claim that organisms arise from organic molecules by spontaneous
generation,sotherecouldbeasmanykindsofanimalsandplantsasthereare
viable combinations of molecules.
The Swedish botanist Carolus Linnaeus (1707e88) devised the hierar-
chical system of plant and animal classification that is still in use in a
modernized form. Although he insisted on the fixity of species, his classifi-
cationsystemeventuallycontributedmuchtotheacceptanceoftheconceptof
evolution by common descent.
The first broad theory of evolution was proposed by the French naturalist
Jean-Baptiste de Monet, Chevalier de Lamarck (1744e1829). In his Philos-
ophie zoologique (1809, Zoological Philosophy), Lamarck held the enlight-
ened view, shared by the intellectuals of his age, that living organisms
representaprogression,withhumansasthehighestform.Lamarck’stheoryof
evolution asserts that organisms evolve through eons of time from lower to
higher forms, a process still going on, always culminating in human beings.
The remote ancestors of humans were worms and other inferior creatures,
which gradually evolved into more and more advanced organisms, ultimately
humans.
The “inheritance of acquired characters” is the theory most often associ-
atedwithLamarck’sname.Yetthistheorywasactuallyasubsidiaryconstruct
of his theory of evolution: that evolution is a continuous process, and that
today’swormswillyieldhumansastheirremotedescendants.Itstatedthatas
animals become adapted to their environments through their habits, modifi-
cations in their body plans occur by “use and disuse.” Use of an organ or
structure reinforces it; disuse leads to obliteration. Lamarck’s theory further
assertedthatthecharacteristicsacquiredbyuseanddisusewouldbeinherited.