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Darwin and the biological determinant of
behaviour
Aristotle’s Natural State Model
The difference between a dachshund and a
greyhound, for Aristotle, lay only in deviations
from a true type that both kinds of dog were
unable to fully express because of interfering
forces. Variation within this framework has no
explanatory value, it is a kind of noise that has to be
seen through to arrive at the ideal type underlying the
differences between members of a species.
For Darwin, variation between!
individuals was the key to !
evolution of species.
Owing to this struggle for life, any variation, however
slight and from whatever cause proceeding, if it be in
any degree profitable to an individual of any species,
in its infinitely complex relations to other organic
beings and to external nature, will tend to the
preservation of that individual, and will generally be
inherited by its offspring ... I have called this
principle, by which each slight variation, if useful, is
preserved, by the term of Natural Selection.
Small differences can be a matter of life
or death
Darwin was influenced by Locke
Consider this remark on species by Locke (1690) in his
Essay on Human Understanding.
...the ranking of things into species (which is nothing but sorting them
under several titles) is done by us according to the ideas that we have of
them: which, though sufficient to distinguish them by names, so that we
may be able to discourse of them when we have them not present before
us; yet if we suppose it to be done by their real internal constitutions
and that things existing are distinguished by nature into species, by real
essences, according as we distinguish them into species by names, we
shall be liable to great mistakes.
Names of biological objects were invented by human
beings for the purpose of communication; they should not
be taken to refer to genuine essences that exist in the
natural world.
Erasmus Darwin was a physician and famous naturalist in his
own right, who in a two-volume book entitled Zoonomia, had
struggled to understand the nature of instincts in animals. As
he wrote, instinct ‘has been explained to be a divine something, a kind
of inspiration; whilst the poor animal, that possesses it, has been thought
little better than a machine’.
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Erasmus Darwin rejected this claim (originally linked to the
ideas of Descartes), and argued instead that what has been
referred to as instinct in animals could be understood as
arising from experience and learning.
The Origin of Instincts
Erasmus Darwin, grandfather to
Charles
‘(Instinct)...is...acquired like all other animal actions, that are
attended with consciousness, by the repeated efforts of our own
muscles under the conduct of our sensations or desires’.
:
Learning can take place in the fetal environment
prior to birth.
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For example, the pecking and swallowing of newly
hatched chick, he suggested, was the result of
repeated gaping and gulping of embryonic fluid on
the part of the fetus. The ability of a newly hatched
chicken to walk could also be accounted for by
assuming that the fetus engaged in repeated
swimming and kicking movements, so that the chicks’
have considerable practice before their birth in their
‘manner of walking....and hence accomplish it afterwards with
very few efforts’.
Lamarck’s Theory of Evolution
Jean Baptiste Lamarck
There are two reasons for paying special attention to
Lamarck. First, he emphasized the importance of
behaviour itself as the agent of evolutionary change.
Lamarck informed his students that he
‘could prove that it is neither the form of the body nor of its
parts that gives rise to the way of life of animals, but that to
the contrary, it is the habits, the way of life, and all the
influencing circumstances that have over time constituted the
form of the body and of the parts of animals’.
It is biological need, according to Lamarck, rather than will or volition
that leads to behavioral and ultimately physical changes. The term
Lamarck used for sensations of unease or need (for example, a
feeling of thirst), was sentiment interior (in French, an internal feeling)
which motivates behavior.
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Animals have sensations generated by physical needs that lead to
actions. The outcome of this behavior may be either beneficial or
harmful to the creature. Habits were acquired in the repeated
fulfillment of basic biological needs like eating, catching prey,
avoiding predators, mating and so on.
As environments changed over time, animals acquired new habits
in response to their biological needs.
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These learned behaviours resulted in animals using some organs more
and some less than they previously did.
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The acquired behaviour patterns produced small physical and cognitive
changes that were passed on to the next generation. As time progresses.
these changes accumulated over generations to result in new species.
Jean Baptiste Lamarck
One may perceive that the bird of the shore, which does not at
all like to swim, and which however needs to draw near to
the water to find its prey, will be exposed to continual sinking
in the mud. Wishing to avoid immersing its body in the
liquid, it acquires the habit of stretching and elongating its
legs. The result of this for the generation of birds that
continue to live in this manner is that the individuals will
find themselves elevated as on stilts, on long naked legs.
Lamarck’s idea of
evolution by ‘willing’ is
absurd.
Shore birds acquire long legs
through inherited consequences
of behavior, according to
Lamarck
Darwin on Instinct
Darwin wrote in one of his notebooks:
‘Lamarck’s willing absurd…(since it is)...not
applicable to plants’. We have already seen that
Lamarck assumed nothing of the kind, though
he did assume that instincts were ‘the
consequences of emotions excited in the
sentiment intérior by each felt need’.
For
Lamarck, simple organisms (say, a jellyfish)
may be capable of learned behavior but these
responses should be distinguished from the
complex displays of instinctive behavior in
animals, which ultimately depended on
feelings of need.
The example included the reference to ‘wishing’, an
unfortunate term because it lead to the mistaken
impression that Lamarck was arguing that will
power or desire (or the intentions leading to actions)
alone were ultimately responsible for inducing
physical changes in animals.
This description of Lamarckian theorizing
is incorrect, however. It is biological need,
according to Lamarck, rather than will or
volition that leads to behavioral and
ultimately physical changes.
Habits were acquired in the repeated
fulfillment of basic biological needs like
eating, catching prey, avoiding predators,
mating and so on.
‘In every frequently repeated action, especially those that
become habitual, the subtle fluids producing it carve out and
progressively enlarge, by the repetition of particular
displacements that they undergo, the routes that they have to
pass through, and render them more and more easy’.
cells that fire together wire together.
The second part of Lamarck’s argument -- that
learned changes in behavior can be passed from
parent to offspring -- is problematic given the
modern emphasis on genetic material as the units
of evolution. Physical changes acquired during
the lifetime of the individual -- whether to the
body or the nervous system -- cannot directly
affect our genome, and therefore cannot be the
target of natural selection.
However, renewed interest in
Lamarck is that some of his
thinking is consistent with recent
developments in our understanding
of the effect of behaviour on
species change.
Darwin’s theory of how instincts develop was
based on the notion that any learned action will
become habitual with enough practice. By some
unknown mechanism (and this is the weak part of
his argument, as well as Lamarck’s), habits
‘...whether congenital or acquired by practice
often become inherited’.
For example, an instinctive action that allows an animal to escape detection by a
predator may be executed faster and more efficiently in some individuals. If
subtle differences in behavior have important consequences for survival under certain
conditions (just as subtle physical differences in beak size affect the survival of a
Galapagos finch in times of drought), behavioral variation will be operated on by
natural selection in just the same way that selection acts on physical attributes.
Over generations, Darwin inferred, ‘the most wonderful’ and complex patterns
of instinctive behavior can evolve from simpler instincts.
How might a learned behaviour
eventually become an instinct?
From “Evolution in four dimensions”
by Eva Jablonka and marion j. lamb
According to Lamarck, a learned
behaviour could gradually but
directly become an inherited behaviour.
But could instincts evolve by natural
selection?
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In other words, could learned behaviour
(acquired during the lifetime of an
individual) somehow be transferred by
natural selection to the individual’s
children?
The earliest attempt to develop such
an explanation was published by a
scottish biologist, douglas spalding in
1873.
Here is the scenario creatively
imagined by spalding.
Suppose a robinson crusoe were to take after landing on an island, a
couple of parrots and to teach them to say in very good english, “How
do you do sir”? Also, suppose that the young of these birds were also
taught by mr crusoe and their parents to say, “How do you do, sir?”,
and that mr. crusoe, having little else to do, sets to work to prove the
doctrine of inherited association by direct experiment. He continues his
teaching, and every year breeds from the birds of the last and previous
years that say “how do you do, sir?” most frequently and with the best
accent. after a sufficient number of generations, his young parrots,
continually hearing their parents and a hundred other birds saying
“how do you do, sir?” begin to repeat these words so soon that an
experiment is needed to decide whether it is by instinct or by imitation;
and perhaps it is part of both. eventually, however, the instinct is
established. and though now mr crusoe dies, and leaves no record of
his work, the instinct will not die, not for a long time at least; and if
the parrots themselves have acquired a taste for good english the best
speakers will be sexually selected, and the instinct will certainly
endure to astonish and perplex mankind, though in truth we may as well
wonder at the crowing of the cock or the song of the skylark.
In this way, a learned behaviour,
initially acquired by just a few
individuals and transmitted from
parents to their offspring will become
independent of learning and cultural
transmission.
Notice two important features of this
story:
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1) Mr. crusoe selected for the best
learners -- parrots that needed to hear
the utterance fewer times than their
ancestors to learn it.
!
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So little learning was required after
many generations that behaviour was
virtually inborn.
2) Another feature of the story
is the emphasis on a second darwinian
mechanism.
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{Question to you: What was the first
Darwinian mechanism implied as part
of the first point.}
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The second feature is sexual
selection. Parrots had acquired a
taste for language utterances, and
good speakers were more likely to be
chosen as mates. A parrot could
enhance its reproductive success by
producing clear English.
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Of course, the selection of mr
crusoe’s parrots in this thought
experiment (“gedanken experiment”)
was initially artificial.
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But it is quite easy to see how an
initially learned behaviour could
become innate through natural and/or
sexual selection without an external
agent.
Imagine a population of song birds
in which the young have to learn their
song from adults.
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Now imagine that a new type of
predator emerges so that birds are
forced to sing less to avoid attracting
the attention of the predator.
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The young will now hear the song less
often and will have less chance of
learning it.
But assume that female birds continue
to prefer good singers as mates.
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This will produce a strong preference in
the population (due to sexual selection)
for birds that learn the song very
quickly.
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These birds will mate more successfully
and produce more offspring. some of
these offspring may inherit their
parent’s song learning talent.
if both predation pressure and sexual
selection persist over generations,
birds will occur many who need to hear
very little singing in order to learn
their species-specific song.
The same argument applies to
the evolution of an instinctive fear
response.
If young mammals have to learn from
gradual experience how to avoid a new
predator, and learning exposes them to
danger, the fastest learners will be
more likely to survive, and if this ability
is partly heritable, natural selection
may eventually result in a fearavoidance response that requires so
little learning as to be “instinctive” .
Darwin on the evolution of morality
Our intellect, according to Darwin, was ‘a
modification of instinct -- an unfolding and generalizing
of the means by which an instinct is transmitted’.
Human intelligence arose when the neural
systems responsible for instinctive behavior
became more flexibly capable of dealing with
aspects of our world.
Are elements of human moral reasoning instinctive
or is this cognitive domain entirely determined by
experience and instruction? Furthermore, are
animals capable of moral judgement? Darwin
viewed our moral sense as grounded in the kind of
instincts that animals display when (i) raising their
offspring, (ii) seeking and interacting with a mate or
(iii) dealing with other members of their group.
The development of conscience
‘Therefore I say, grant reason to any animal with social and sexual
instincts and yet with passion (..then...) he must have conscience -this is a capital view’
If conscience is based on instincts, our decisions may
often be determined by biological laws rather than free
will. ‘Shake ten thousand grains of sand together and one will be
uppermost, so in thoughts, one will rise according to law’, he
wrote in one of his notebooks.
The love of the mother for her offspring does not enhance
her own survival in any way, but rather the survival of her
offspring. As pointed out by the historian Robert Richards:
‘How could it explain the acquisition of instincts that not only failed
to confer an advantage on their bearers but might even be harmful to
them?’.
As Darwin wrote in frustration: ‘Neuters do not breed!
(this)... instinct acquired?’.
How is ...
Developing queen larvae surrounded by
royal jelly
Darwin wrote in the Origin of Species:
In the eighth chapter, I have stated the fact of a neuter insect often having a
widely different structure and instinct from both parents, and never yet breeding
and so never transmitting its slowly acquired modification to its offspring, seemed
at first to me an actually fatal objection to my whole theory. But after
considering what can be done by artificial selection, I concluded that natural
selection might act on parents, and continually preserve those which produce more
and more aberrant offspring, having any structure or instinct advantageous to the
community.
Selfish genes
Who is it that benefits from certain types of
behaviour in social animals?
Are some behaviours for the ‘good of the species’
or the ‘good of the group’ when such behaviours
are not of any benefit to the individual who carries
them out?
Examples of behaviours that cannot benefit!
the individual.
Worker ants and bees work for the benefit !
of their colony and do not themselves produce!
any offspring.
Animals like birds that give alarm calls; such calls
may attract the attention of a predator and make it
less likely that the calling animal will survive to
reproduce.
The argument was that such altruistic behaviour benefits the
group rather than the individual.
Some biologists pointed out problems with this idea.
Suppose a creature in an altruistic group happens to
be born selfish.
For example, a non-caller in a group of calling birds
will be less likely to draw the attention of a predator
and so will be more likely to survive. Non-caller genes
should therefore increase in frequency, and the callers will
eventually tend to vanish.
The only way for the altruistic calling behaviour to
survive is if the group with this behaviour does much
better than individuals without such behaviour.!
One suggestion is that altruistic behaviour tends!
to benefit members of the same family of
individuals.
If altruistic behaviour tends to benefit related!
individuals, the behaviour may increase in !
frequency even if the altruistic family has!
fewer offspring than it would have produced!
without altruistic behaviour.
If there is such a thing as a genetic basis for!
altruism, the gene will increase in frequency if!
the behaviour of an individual helps his or her!
kin to survive and produce offspring, because !
kin are likely to carry copies of the gene.!
Richard Dawkins took this idea and
extended it to explain the evolution of all!
adaptive traits, including the paradox of!
altruistic behaviour.
The term “selfish gene” was developed by
Dawkins to express the idea that the survival of a
gene may not coincide with the best interests of
the individual who carries the gene.
According to Dawkins, evolution is a competition!
between rival genes rather than between other!
units of selection like the individual, a group or a
species.
According to Dawkins, the living body is merely!
a vehicle for selfish genes. !
!
Genes are “replicators”, which Dawkins defines!
as “anything in the universe of which copies are!
made”.
Bodies are not replicators because an acquired!
feature (e.g. a scar) is not copied to the next
generation.
Examples of replicators include stretches!
of DNA, or a sheet of paper that is photocopied.!
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Text on a sheet of paper will be copied to the!
next “generation” of papers, as will changes to!
a stretch of DNA (a mutation, for example will be!
transmitted to the next generation).
A vehicle, according to Dawkins, is any unit,!
discrete enough to be worth naming, which!
houses a collection of replicators and which !
works as a unit for the preservation and
propagation of those replicators.
Individual bodies are vehicles not replicators.
The distinction between replicator and vehicle!
corresponds to the distinction between genotype!
and phenotype.!
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Variations in the genome cause variations in the!
body, but the reverse is not true. Variations in the!
body due to development cannot affect variations in!
the gene.
Development is a process that concerns vehicles.!
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Genes replicate and ensure their own continuity !
over generations, sometimes at the expense of !
the vehicles that contain them.!
In addition to selfish genes, Dawkins introduced the
concept of memes or units of cultural transmission.!
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A meme is “a unit of cultural inheritance, !
hypothesized as analogous to the particulate gene,!
and as naturally selected by virtue of its
‘phenotypic’ consequences on its own survival and!
replication in the cultural environment”.
The phenotypic effect of a meme may be in the!
form of words, music, visual images, styles of
clothes, facial expressions, hand gestures, etc.
They are the outward and visible manifestations!
of the memes within the brain. They may be
perceived by the sense organs of other individuals!
and they may so imprint themselves on the brains!
of the receiving individuals that a copy (not
necessarily exact) of the original meme is graven!
in the receiving brain.
Just as a “selfish gene” can undermine the!
survival and reproductive success of its vehicle (as
in the case of altruistic behaviour that leads to
increased likelihood of falling victim to a predator)
so “selfish memes” can increase in frequency yet!
compromise the welfare of their vehicles (e.g. the
meme for smoking continues to proliferate in!
teenagers).!
!
Memes are described as “viruses of the mind”.
In their book “Evolution in Four Dimensions”,
Eva Jablonka and Marion Lamb are critical of!
the notion of memes as functioning analogously
to genes.
Recall that genes, according to Dawkins
are held to be replicators that are distinct
from their vehicles, just the way a recipe
for a cake is distinct from the actual
cake that is baked.!
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The problem is this: variations in ideas (memes) are
constructed by individuals through learning and
these individuals are themselves vehicles.!
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If a meme is like a gene, then in each instance it
should be possible to identify a replicator, or
something that can be copied.!
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But learning is not just copying. It is a developmental!
process whose outcome depends on meaning and!
performance.
What is being copied is the “phenotype” of!
the meme, they way it is being expressed by the!
individual.!
!
This is very different to DNA replication or
photocopying, where what is being copied is
irrelevant to the copying process itself. A digital
scanner, the camera of an Iphone, or a Xerox
machine will all serve as different ways to copy the
same written paper.
By contrast, the form of a meme depends on
factors like context, social transmission and
culture.
For example, Mickey Mouse in 1928 was a decidedly rat-like figure with no white gloves.
Over the years, he has become progressively cuter and more juvenile, with baggy pants.!
!
It is surely not the case that the durability and transformation of this cartoon figure can
simply be understood in terms of an ability of a meme to replicate over generations better
than other competing memes that have disappeared. The transformation in Mickey
Mouse has to do with complex societal interactions (including the advent of television)
that combined to produce a form appealing to both adults and children.
Six universally expressed emotions
It fortunately occurred to me to show several of the best plates,
without a word of explanation, to above twenty educated persons of
various ages and both sexes, asking them, in each case, ... what
emotion or feeling the ....(photograph depicted...); and I recorded
their answers in the words which they used. Several of the
expressions were instantly recognized by almost everyone, though
described in not exactly the same terms; and these may, I think, be
relied on as truthful, and will hereafter be specified. On the other
hand, the most widely different judgments were pronounced in regard
to some of them. This exhibition was of use in another way, by
convincing me how easily we may be misguided by our imagination;
for when I first looked through Dr. Duchenne's photographs, reading
at the same time the text, and thus learning what was intended, I
was struck with admiration at the truthfulness of all, with only a
few exceptions. Nevertheless, if I had examined them without any
explanation, no doubt I should have been as much perplexed, in some
cases, as other persons have been.
In Darwin’s book on emotional expression, he
applied Lamarckian ideas to developing an account of
how expressions evolved. There are no arguments of
the evolution of emotional expressions based on
natural selection, consistent with Darwin’s
assumption that expressions have no function and so
confer no advantage to the survival of an animal or
its community.
The principle of associated habits.
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Actions intentionally carried out, especially to stop an unpleasant sensation, may become routinely associated with an emotional
state. The action might then be automatically triggered when the emotion is experienced.
The principle of antithesis
When certain actions were linked to a particular internal state, the contrasting mental state would tend
to evoke behavior that was also opposite.
Spilling over
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The idea is that certain emotional expressions are the result of powerful nervous energy overflowing into and thereby influencing the
activity of other neural pathways. For example, trembling produced by fear. According to Darwin, this kind of emotional response is
‘..of no service, often of much disservice, and cannot have been at first acquired through the will, and then rendered habitual in association with any
emotion’.