Evolution
A support site for modules SC0060-3 Evolution
and SCM009-M Molecular Evolution
Page last updated 29/01/02
Introductory
lecture
by Dr Kevin Reiling
These notes complement the lecture and ensure you have the main points and areas covered.
The whole
point was to reiterate topics from studies at earlier levels, if you need
more help try www.staffs.ac.uk/schools/sciences/Biological Sciences/sc0003/welcome.htm
The theory
of evolution is the only credible present-day paradigm to explain the world
around us that relies on fact rather
than faith. Faith is not an area open to scientific questioning and is therefore
an area outside the scientist's paradigm.
However, it is worth noting that there are often no real religious/ scientific
conflicts for the majority of the world's belief systems.
If
you wish to delve further into this avenue: "
DC Dennett (1995) Penguin; will help stretch the mind. There is also a reasonably
priced introductory text "Religion and
Science" M Thompson (2000) Hodder and Stoughton, which has some thought
provoking ideas.
Evolution
and Darwin are ingrained into our psyche and typified by the Haeckel-type trees
and ape-man
to modern man picture sequences, ARE OUR PERCEPTIONS BIOLOGICALLY ACCURATE?
Evolution does not work in straight lines man mind does, its
mechanisms are blind algorithms not directed anywhere
"chaos with feedback"
Questions to ponder:
Why do most people think their view of evolution is scientifically valid?
Would you expect a physicist to take your ideas of quantum
dynamics as valid?
So why should a biologist accept your ideas of a much tested biological theory
as scientific?
Remember people consider evolution as instinctive knowledge
whereas other areas of the world around us need study, why?
The phrase,
and the ideas held by most people regarding the 'Theory of Evolution' fail to
recognize that
"On the origin of species by means of natural selection or the preservation
of favoured races in the
struggle for life" Darwin 1859, had two main facets
Main mechanism? - natural selection, 'Survival of Fittest' (Spencer)
The importance of various mechanisms is where scientists disagree not with evolution itself.
Biologist use shorthand phrase, Darwinian or even evolution
in its loosest sense to represent:
Species change the mechanism is mainly natural selection but they do not strictly
mean the
content of the 1859 tome but also everything that has followed especially Mendel
(inheritance)
and Johannsen (gene concept) [technically Neo-darwinisim] and the inclusion
of all the modern
molecular/DNA evidence since Watson & Crick [Synthetic Theory].
OK, but what about these other mechanisms, they disprove Darwin
don't they? (for answer primarily
refer to what biologist mean by Darwin, above) but no, they do not. The modern
synthesis incorporates
many mechanisms, natural selection is not the only one, the commonest influences
upon evolution in
this context include genetic drift, neutralism, founder effects, the Baldwin
Effect and blind luck!
What about
other basic ideas? e.g. Lamark -
Pedantically what most people assume to be Lamark is actually close to Darwin's
wrong guess, the differences are subtle but
Lamark believed in 'inner striving', no mechanism was offered. This was the
common theory of the day not just Lamark (not just
in those times either, remember Lysenko, Stalin and communism). Genetic information
is not passed this way, changes to
soma do not affect germ line. 'Central dogma of molecular genetics' viz. "The
transfer of information from nucleic acid to nucleic acid,
or from nucleic acid to protein may be possible, but transfer from protein to
protein, or from protein to nucleic acid is impossible"
Francis Crick [it may be theoretically possible for a retrovirus in a strange
sequence of events to break this, see a molecular biologist].
Based on the idea of progress, striving, perfection. OK, progress
is
thrown up again why, is this not inherent in evolutionary thought?
It is obvious
that there is more complexity around today than at the beginning of life. Before
we return and tackle this,
which is ingrained into our culture, let us quickly mention some of the other
classics thrown at the theory.
Why no perfect
organisms? Why should there be, this is never expected within the theory, organisms
are historically based,
' descent with modification' - adaptations are compromises using what is available
the lack of perfection is actually strong
support for the theory.
Too many
things are complicated and could not arise by the process of natural selection,
the classic example is the eye.
This type of argument is simply not valid and is admirably dealt with by Dennett
("Darwin's Dangerous Idea", Ch.1,
DC Dennett (1995), Penguin). The eye is handled by Dawkins ("Climbing Mount
Improbable", Ch.5, R Dawkins (1996), Viking).
If
evolution occurs why do some things serve no purpose? Why should everything
have a purpose or design in nature (TELEOLOGY).
Some evolution is neutral, some maladaptive as environments change. There is
no reason why evolution should be long term adaptive,
natural selection responds to local and real time environmental variables. Beware
of
this idea as do earlier works "The Blind Watchmaker" Dawkins, R. (1986);
"The Panda's Thumb" Norton & Gould, S.J. (1980) and
"Plan & Purpose In Nature", Williams, G.C. (1996). These points
are all facets of a similar basic theme viz. life is designed and
evolution has progressed to produce mankind.
SO WHY, BIOLOGICALLY, NO DIRECTED PROGRESS TO PRODUCE OURSELVES?
Primitive to advanced is a deep-seated belief (arrogance?),
complexity increases leading to ourselves.
What is complexity in any than a loose instinctive sense? genome size, brain
size?
Do not confuse
inherent progress with the subtly different, but accurate statement , "the
most complex
creature on the planet has increased in complexity over time". This is
true but is it evidence for a thrust
in evolution? No, Why? [Gould, SJ, (1996),"Life's
Grandeur", Cape].
Remember 'left wall analogy'.
Bacterial
stability of life, most numerous 'individuals' on planet, over time more of
them but not really increased complexity.
So how can we assume progress if most of the life on the planet has undergone
little change in complexity?
But
may a bias exist? If new adaptation arises are the descendants
more complicated? No, most evidence is contrary
[e.g. McShea, DW (1996), "Metazoan complexity and evolution: Is there a
trend?
Parker (1975), "Causality and Cope
Complexity tends to decrease, a pure consequence of selecting for efficiency?
basically conservation of energy at
the biochemical level? If you played the
tail each time, increasingly complex but not necessarily us. (Gould, SJ, "Life's
Grandeur" [earlier] or its companion,
"Wonderful Life", 1990) or would you expect us (Replaying Life, Douglas,
New Scientist, 13/2/99).
Main Point Summary
PS The one outstanding feature of life is the stability of bacterial mode of life/complexity over billions of years!
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The content, learning and assessment of these modules, as detailed herein, may
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Page created and maintained by Drs Kevin Reiling & Andrew J White, Department
of Biological Sciences, Staffordshire University, College Road,
Stoke-on-Trent ST4 2DE, United Kingdom. Tel +44 1782 294613, email k.reiling@staffs.ac.uk
and a.j.white@staffs.ac.uk