Transcript Evolution-Fitness and Rocks

Evolution
Fitness and Rocks
Timothy G. Standish, Ph. D.
©2000 Timothy G. Standish
Evolution
At least three distinct meanings:
Change over time - The fact of
evolution
Natural selection - The theory of
evolution
No Creator/God - The belief all
organisms descended from a single
common ancestor produced by
“natural” events
©2000 Timothy G. Standish
Before Darwin Cont.
Linnaeus 1707-1778 - Swedish physician and botanist
– Sought to classify, or organize nature
– The father of taxonomy or systematics
– “Deus creavit, Linnaeus disposuit” (God creates, Linnaeus
arranges)
Lamarck 1744-1829 - Published his theory of evolution in
1809
– Proposed that organisms responded to “sentiments interieurs” (felt
needs) by evolving
Mathus 1766-1834 - Proposed the utterly dismal theorum:
– All populations of organisms grow until resources are completely
utilized so that each individual lives at the razor’s edge of
existence
©2000 Timothy G. Standish
Before Darwin, Cont.
Cuvier 1769-1832 - Father of Paleontology, the study of
fossils
– Believed fossils were a record of life over time
– Interpreted the fossil record in the context of
catastrophism where strata in the rocks represent
catastrophic events
James Hutton - Scottish geologist who, in 1795, proposed
the theory of gradualism
– Gradualism - Geological strata were laid down over a long period
of time
– Gradualism is a logical outgrowth of uniformitarianism, the
belief that the way things are now is the same as they were in the
past. As mountains are eroding slowly now and basins are filling
gradually, it follows that if the slow rate occurred in the past,
laying down the amount of sedimentary rock we now see must
have taken a long time.
©2000 Timothy G. Standish
Charles Darwin (1809-1882)
As a theology major at Cambridge
University, Darwin was taught a
variation of the Greek view of reality
Was invited to travel around the world on the HMS
Beagle surveying plant and animal life in the
southern hemisphere
Compared the theory he had been taught with
reality and could not reconcile the two
Proposed his theory of natural selection in The
Origin of Species published in 1859
©2000 Timothy G. Standish
The Voyage Of The Beagle
England
Cape Verde
Islands
Tahiti
Galapagos
Islands
South
America
Cocos
Islands
Rio de
Janeiro
Falkland
Islands
Mauritius
Sydney
Australia
New
Zealand
The object of the expedition was to complete the survey of Patagonia and Tierra del
Fuego . . . to survey the shores of Chile, Peru, and some islands in the Pacific-and to
carry a chain of chronometrical measurements round the World.
Charles Darwin in The Voyage of The Beagle
©2000 Timothy G. Standish
The Logic Of Darwin
The fossils in South America were different from
the animals that lived there now, but some seemed
to be related in some way
If fossils were a record of the past (Cuvier) then
there must have been change (evolution) between
the past an now
Change is happening slowly; thus to get change
must have taken a long time (uniformitarianism)
The rock strata took a long time to form (Hutton gradualism) thus lots of time is available for
evolution
Organisms evolved over long periods of time
©2000 Timothy G. Standish
The Mechanism Of Evolution
Darwin was not the first to propose evolution,
Lamarck and others had done it before him
Darwin’s real contribution was a credible
mechanism for evolution - Natural Selection
Natural selection is based on two points:
1 The reproductive capacity of organisms exceeds
the carrying capacity of the environment (Malthus)
2 Variation in organisms makes survival a nonrandom event - Some variants are more likely to
survive in a given environment
l Of the excess products of organisms reproductive
capacity the most fit survive - Survival of the fittest
©2000 Timothy G. Standish
Lamarck and Darwin
“Lastly, you refer repeatedly to my view as a
modification of Lamarck's doctrine of development
and progression. If this is your deliberate opinion
there is nothing to be said, but it does not seem so to
me. Plato, Buffon, my grandfather before Lamarck,
and others, propounded the ‘obvious’ view that if
species were not created separately they must have
descended from other species, and I can see nothing
else in common between the Origin and Lamarck.”
Darwin C., letter to Charles Lyell, 12 March 1863, in Darwin
F., ed., "The Life of Charles Darwin," [1902], Senate:
London, 1995, reprint, p 256. Emphasis in original
©2000 Timothy G. Standish
Naturalism
Naturalism - The belief that
all phenomena can be
explained in a rational way
in terms of natural causes
without invoking the
supernatural
Because Darwin proposed a natural
cause (natural selection) for the origin of
organisms, his theory is considered more
scientific than religious accounts of
origins which invoke the supernatural
©2000 Timothy G. Standish
Evidence For Evolution
Biogeography - The geographical distribution of organisms
reflects their origin and isolation from other species
Fossil Record - The fossil record contains missing links
between present species and their ancestors . . . sort of . . .
maybe
Comparative Anatomy - Homologous (similar) structures
must have evolved from the same ancestral structure . . .
Except when we don’t think two organisms shared a
common ancestor with that structure.
Molecular Biology - More or less the same idea as
comparative anatomy - Similar genetic information
indicates common origin
Comparative Embryology - Similar organisms go through
similar development
©2000 Timothy G. Standish
Embryology?
"According to Darwin, it was
the similarity of embryos _in
their earliest stages_ that
provided the evidence for
common descent. The actual
pattern--early differences
followed by similarities, then
differences again--is quite
unexpected in the context of
Darwinian evolution. Instead of
providing support for Darwin's
theory, the embryological
evidence present it with a
paradox"
Jonathan Wells. 2000. Icons of Evolution: Science or
myth? Regnery Publishing, Inc. Washington, DC. p 99.
Fish
Tortoise
Hog
Rabbit
Salamander Chick
Calf
Human
Haeckel’s embryo drawings
Photos of real
embryos by M.
Richardson
zygote.swarthmore
.edu/evo5.html
©2000 Timothy G. Standish
Missing Links and the Fossil Record
"But just in proportion as this process of extermination has acted on an
enormous scale, so must the number of intermediate varieties, which
have formerly existed, be truly enormous. Why then is not every
geological formation and every stratum full of such intermediate
links? Geology assuredly does not reveal any such finely graduated
organic chain; and this, perhaps, is the most obvious and serious
objection which can be urged against the theory. The explanation lies,
as I believe, in the extreme imperfection of the geological record.”
Darwin C.R. 1872. The Origin of Species by Means of Natural Selection.
“Ancient rocks clearly preserve less information, on average, than more
recent rocks. However, if scaled to the stratigraphic level of the stage
and the taxonomic level of the family, the past 540 million years of
the fossil record provide uniformly good documentation of the life of
the past.”
M. J. Benton, M. A. Wills & R. Hitchin. 2000. Quality of the fossil record through time.
Nature 403:534-537
©2000 Timothy G. Standish
The Fact of Evolution
“When evolution is said to be a fact, not a theory, what is
actually meant? That now-living things have descended
from ancestors, with modification, over time? Or that the
modifications came by chance, not by design? Or, in
addition, that all living things ultimately had the same
ancestor? Or, still further, that the ‘first living thing’ had as
its ancestor a nonliving thing? Context indicates that when
evolution is asserted to be a fact, not a theory, the view
actually being pushed includes that of common origin,
ultimate inorganic ancestry, and modification through
nonpurposive mechanisms: a set of beliefs that goes far
beyond the mountain of fact that is actually there, which
consists largely of fossils that demonstrate some sort of
relationship and some sort of change over time.”
Bauer H.H., 1994. Scientific Literacy and the Myth of the Scientific Method. University
of Illinois Press: Urbana and Chicago IL. p 65. Emphasis in original ©2000 Timothy G. Standish
What is a Fossil?
Six major types:
Preserved organisms - The most uncommon fossils, including
insects in amber, frozen mammoths, organisms preserved in peat
bogs and tar pits
Preserved hard parts - Teeth, bones, shells or other hard parts that
have been preserved over time
Impressions - Flattened outlines of the surface of an organism,
frequently carbonized
Molds - After an organism has been surrounded by mud which turns
to rock, the remains leech out of the rock, leaving only the mold
Casts - Molds that have been filled with another material after the
remains have been removed produce casts
Trace fossils - Tracks burrows and other evidence of life left in the
rock
©2000 Timothy G. Standish
Preserved Organisms
Preserved organisms - The most uncommon fossils,
including insects in amber, frozen mammoths, organisms
preserved in peat bogs and tar pits
©2000 Timothy G. Standish
Preserved Hard Parts
Process - Burial
Some hard parts may become permineralized
which involves the filling of porous areas with
mineral deposits
Examples include:
Petrified (turned to stone) wood
Teeth
Bones
Shells
©2000 Timothy G. Standish
Impressions
Impressions - Flattened outlines of the surface of
an organism, frequently carbonized
©2000 Timothy G. Standish
Molds
Molds - After an organism has been surrounded
by mud which turns to rock, the remains leech
out of the rock, leaving only the mold
1 A dead
organism is
buried
2 The remains
are dissolved
away leaving
a mold
©2000 Timothy G. Standish
A Brachiopod Mold
No part of the original brachiopod remains
Note the detail preserved in this fine-grained rock
©2000 Timothy G. Standish
Casts
Casts - Molds that have been filled with another material
after the remains have been removed produce casts
1 A dead
organism is
buried
2 The remains
are dissolved
away leaving
a mold
3 The mold fills with minerals producing a cast
©2000 Timothy G. Standish
Casts of Brachiopods
Sometimes what looks like preserved hard parts may still
be casts
Crystals
Top
Growth
lines
Bottom
©2000 Timothy G. Standish
Casts of Trilobites
Casts of many organisms are known
Trilobite casts serve as excellent examples of the detail
that can be preserved in casts.
©2000 Timothy G. Standish
Plant Fossils
Sphenophyta
©2000 Timothy G. Standish
Trace Fossils
Trace fossils - Tracks burrows and other evidence of life
left in the rock
Provide information about the behavior of organisms
©2000 Timothy G. Standish
Problems With Interpretation
Of The Fossil Record
No one was there when the fossils were
formed
Testing theories about how and when fossils
formed is difficult in many cases and
impossible in others
Multiple interpretations of data are common
Fundamentally different worldviews and lack
of rigorous testing of interpretations, leads to
interpretation driven strongly by beliefs
©2000 Timothy G. Standish
Dating Fossils
Two methods:
Relative dating - When a previously unknown fossil is
found in strata with other fossils of “known age,” the age
of the newly discovered fossil can be inferred from the
“known age” of the fossils with which it is associated.
Relative dating is done in terms of the relative
appearance of organisms in the fossil record.
(“Archaeopteryx appears after Latimeria, but before
Australopithecus.”)
Absolute dating - Involves assigning dates in terms of
years to fossils. This most frequently involves
radiometric dating techniques. (“This Archaeopteryx
fossil is 150 million years old.”)
©2000 Timothy G. Standish
Formation Of
The Geologic Column
As sediment is washed away from mountains and other
zones of erosion, it is collected in depositional basins
The first sediment to settle in a basin is assumed to be the
oldest with newer strata being deposited on top
Going from the bottom to the top of the geologic column
should be a trip from the most ancient times to the present
There is no place on earth where the entire geologic
column is present; it has been pieced together using
multiple sequences of strata from multiple locations to
provide a complete sequence
Tectonic, volcanic and other geological activities may
have altered the strata sequence over time in some
locations
©2000 Timothy G. Standish
Formation Of
The Geologic Column
Zone of erosion
Deposition basin
Geological
Strata
This model makes the uniformitarian assumption that
current conditions existed in the past
©2000 Timothy G. Standish
The Geologic Column
200 -
300 -
Phanerozoic
100 -
400 500 Precambrian
Tertiary
Millions of Years Before Present
Cenozoic
Miocene
Oligocene
Eocene
Paleocene Extinction of dinosaurs and many families
Cretaceous Mammals, cycads, conifers, angiosperms
Mesozoic
Jurassic
Triassic
Permian
Carboniferous
Paleozoic Devonian
Silurian
Ordovician
Cambrian
Proterozoic
Archean
Dinosaurs
Conifers, more reptiles and amphibians
Many crinoids, amphibia and reptiles
Coal “forests” many primitive land plants
“The age of fish” small land plants
Jawless fish, strange land plants
Many marine organisms including bryozoa
Many fossils, all modern phyla ex. bryozoa
Few fossils
Ediacarian fauna (odd marine organisms)
Very few fossils, maybe none
Many pseudo fossils
©2000 Timothy G. Standish
Holocene
Pleistocene
Pliocene
Miocene
Cenozoic
Tertiary
Phanerozoic
Quaternary
The Upper Geologic Column
Oligocene
Eocene
Paleocene Extinction of dinosaurs and many families
©2000 Timothy G. Standish
Trends In
The Geologic Column
Organisms at the bottom look less like
those living today than those at the top
Moving from bottom to top, the number of
fossil species goes up
Moving from bottom to top, the number of
fossil phyla and possibly classes goes down
Moving from bottom to top, at first there
are no land-dwelling organisms, then their
numbers increase
©2000 Timothy G. Standish
Are There Missing Links In
The Geologic Column?
Not exactly, although many attempts have been
made at saying some things are
The traditional depiction of the evolution of
horses worked out by O. C. Marsh is highly
questionable:
“The most famous of all equid [horse] trends,
‘gradual reduction of the side toes,’ is flatly
fictitious.”
– Simpson G. G. 1953. The Major Features of
Evolution. New York and London: Columbia
University Press, p 263
©2000 Timothy G. Standish
More On Horses
The record of evolution is still surprisingly jerky
and, ironically, we have even fewer examples of
evolutionary transition than we had in Darwin’s
time. By this I mean that some of the classic cases of
darwinian change in the fossil record, such as the
evolution of the horse in North America have had to
be discarded or modified as a result of more detailed
information--what appeared to be a nice simple
progression when relatively few data were available
now appears to be much more complex and much
less gradualistic.
– Raup, D. M. 1979. Conflicts between Darwin and
paleontology. Field Museum of Natural History Bulletin
50:22-29
©2000 Timothy G. Standish
Young Sinosauropteryx prima
Yixian formation, lower Cretaceous, Liaoning Province, China
Found in 1996
The ruffled
dark ridge
above the
spine shows
what may
have been
feathers
Down-like
feathers?
©2000 Timothy G. Standish
Adult Sinosauropteryx prima
Yixian formation, lower Cretaceous, Liaoning Province, China
Feathers are
thought to be
on the tail
This is the
only dinosaur
ever found
with the
remains of a
small mammal
inside
Feathers?
Mammal
Jaw
©2000 Timothy G. Standish
Caudipteryx zoui
Yixian formation, lower Cretaceous, Liaoning Province, China
Feather
plume on the
short tail and
wings
Feathers and
down are
thought to
have covered
the entire
body
Only a few
hooked teeth
in the front of
its upper jaw
©2000 Timothy G. Standish
Protarchaeopteryx robusta
Yixian formation, lower Cretaceous, Liaoning Province, China
Feathers?
Did not fly
Symmetrical “feathers”
Archaeopteryx
lithographica had
asymmetrical “feathers”
©2000 Timothy G. Standish
Confuciusornis sanctus
Yixian formation, lower Cretaceous, Liaoning Province, China
A true bird
Lacks teeth in the beak
Note the forelimbs and fossil
feathers
Found in abundance the
same formation and “time”
as feathered dinosaurs!
How can Chinese feathered
dinosaurs be “missing links”
between birds and dinosaurs
when true birds were already
present?
Feathers
©2000 Timothy G. Standish
Sinornithosaurus millenii
or How Science Can Fail
According to the National Geographic,
Sinornithosaurus millenii is a “125-million-yearold feathered dinosaur”
This feathered dinosaur showed that feathers
were widespread in dinosaurs and were present
in “Tyrannosaurus rex and velociraptors”
In addition, the fossil had “a highly advanced
shoulder girdle that allowed for flapping arms”
In other words, this is a missing link between
dinosaurs and birds!
©2000 Timothy G. Standish
Sinornithosaurus millenii
or How Science Can Fail
©2000 Timothy G. Standish
Natural Selection
Natural selection is thought to be the most common cause
of changes in allelic frequencies and thus populations
being out of equilibrium
It is important to note that for the effect of natural
selection to be detected on the basis of violation of
Hardy-Weinburg, selection would have to be fairly
stringent at the point in time data were collected
Hardy-Weinburg can be used to compare populations of
the same species and may infer that selection has
occurred, assuming the other factors previously
mentioned are not at play
©2000 Timothy G. Standish
Natural Selection
p= 0.1
q= 0.9
©2000 Timothy G. Standish
Natural Selection
p= 0.1
q= 0.9
If selection (s)
is 0.5 against aa
and fitness = W=1-s
©2000 Timothy G. Standish
Natural Selection
Second Generation
p= 0.17
q= 0.83
AA=2
Aa =30
aa =68
©2000 Timothy G. Standish
Natural Selection
Third Generation
p= 0.25
q= 0.75
AA=3
Aa =46
aa =51
©2000 Timothy G. Standish
Natural Selection
Fourth Generation
p= 0.34
q= 0.66
AA=3
Aa =62
aa =35
©2000 Timothy G. Standish
Natural Selection
Fifth Generation
p= 0.42
q= 0.58
AA=4
Aa =75
aa =21
©2000 Timothy G. Standish
Natural Selection
Sixth Generation
p= 0.46
q= 0.54
AA=5
Aa =83
aa =12
©2000 Timothy G. Standish
Natural Selection
Sixth Generation
After 6 generations, the population is not in equilibrium:
p= 0.46 q= 0.54
p2 + 2pq + q2 = 0.212 + 0.497 + 0.292 =1.001
Expected genotype numbers:
AA = 21 (Actual =5)
Aa = 50 (Actual = 83)
aa = 29 (Actual = 12)
No need to do a Chi square on this one!
©2000 Timothy G. Standish
Rate of Change With
Selection
Even with heavy selection (s=0.5) the rate of
change in allele frequency declines rapidly
after a few generations
Frequency
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1
q
2
3
4
5
6
p
7
Generations
8
9
Alleles
10
©2000 Timothy G. Standish
Rate of Change With Selection
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1
2
3
q
4
5
6
7
8
Generations
p
9
10
Alleles
Frequency
Frequency
The heavier the selection, the faster the
change and the quicker the decline in
rate of change.
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1
s = 0.9
q
2
3
4
5
6
p
7
8
Generations
s = 0.1
9
Alleles
10
©2000 Timothy G. Standish
Types of Selection
Selection
Selection
Frequency
Frequency
Stabilizing
Selection
Frequency
Pseudopterix
pleiorostrum
(many beaked
fake bird)
Directional
Diversifying
©2000 Timothy G. Standish
How Species Evolve
T
i
m
e
T
i
m
e
D Morphology
Anagenesis
D Morphology
Cladogenesis
©2000 Timothy G. Standish
Tempo Of Evolution
T
i
m
e
T
i
m
e
D Morphology
Gradualism
D Morphology
Punctuated
Equilibrium
©2000 Timothy G. Standish
Human Phylogeny
0
Adapted from: Tattersal, I. 2000. Once We were Not Alone.
Homo sapiens
Scientific American. January.
H. neanderthalensis
Millions of years before present
H. heidelbergensis
H. erectus
1
2
3
P. robustus P. boisei
H. ergaster
H. habilis
H. rudolfensis
Panthropus aethiopicus
A. garhi
A. africanus
A. bahrelghazali
A. afarensis
4
5
Australopithicus anamensis
Ardipithecus ramidus
©2000 Timothy G. Standish
©2000 Timothy G. Standish