Transcript Physical Anthropology the nature of science

Biological
Anthropology
Darwin, Mendel, and
The Rise of the Synthetic
Theory
Three Questions to Answer
1. Where does variation come from?
2. How is variation passed on from one
generation to the next?
3. How is the variation present within a species at
any time affected by the environment?
Science as a
revolutionary process
scientific “revolution”
anomalies
“normal” science
Normal Science ca. 1600
the origin of living things
• Great Chain of Being
– Held in the hand of God
– Ranked living things as
more or less like God
• Links represent species
– Discrete
– Immutable
Carolus Linnaeus
1707-1778
• Son of a Lutheran
pastor
• Groomed to be a
pastor
• Preferred science
• Became a physician
and botanist
Carl Linneaus
by M. Hoffman in 1734.
Carolus Linnaeus
1707-1778
• Systema Naturae
(1735, with many
subsequent revisions)
• Standardized names
of plants and animals
Wedding Portrait of Linnaeus
(1739)
Binomial
nomenclature
Carolus Linnaeus
1707-1778
Before, the common
wild briar rose was
known variously as
Using binomial
nomenclature, names
were standardized:
• Rosa sylvestris
inodora seu canina
• Rosa canina
• Rosa sylvestris alba
cum robore, folio
glabro
• Coffea arabica
• Homo sapiens
Carolus Linnaeus
1707-1778
• First believed species were
immutable
• Noticed hybrids
• Observed that plant species
could change appearance as
they acclimatized to new areas
• Eventually abandoned idea of
fixity of species
Georges Cuvier
1769-1832
• “Father” of comparative
anatomy
• Studied the anatomy of
vertebrates
• Established the field of
vertebrate paleontology
Georges Cuvier
1769-1832
• Noted distinct differences
between fossil mammoth
(top) and living Indian
elephant (bottom)
• Discovered that species
could go extinct
from Cuvier's 1796 paper on
living and fossil elephants
What had happened to these
animals?
• Periodic “revolutions” or catastrophes had
befallen the earth
• These were events that had natural causes
• Although Cuvier did not identify these with
Biblical events, others would
Jean-Baptiste Lamarck
1744-1829
• Studied invertebrate anatomy
• Saw a relationship between
an animal’s form and the way
it exploited the environment
• Argued that a change in the
environment could affect the
needs of the organisms in
that environment, causing
them to alter their behavior
Lamarck said
• Altered behavior led to more
or less use of a body part,
which would therefore grow
larger or smaller
• Such changes are inherited
A great idea!
But it’s wrong!
James Hutton
1726-1797
• Scottish geologist
• A cyclical “world machine”
that exhibited “no vestige of
a beginning – no prospect
of an end.”
• This view ultimately led to
modern geological time
scales
James Hutton
1726-1797
• Pointed out role of erosion
• Earth was timeless
• A self-perpetuating place
created for humans
• No directional change, only
cycles
Charles Lyell
1797-1875
• Another Scottish geologist
• Principles of Geology
(3 Volumes; 1830-1833)
• Argued that currently
active principles were all
that was needed to explain
the geological history of
the Earth
Charles Lyell
1797-1875
“uniformitarianism”
• Excluded the use of
sudden catastrophes
when explaining fossils
• Earth was extremely old
Thomas Malthus
1766-1834
• An Essay on the
Principles of Population
(1798)
• Points out that more
individuals are born into a
species than will ever
reach maturity
• A struggle for survival
Thomas Malthus
1766-1834
"population increases in
a geometric ratio,
while the means of
subsistence increases
in an arithmetic ratio."
food supply
population
Adam Smith
1723-1790
• An Inquiry into the Nature
and Causes of the Wealth
of Nations (1776)
• Laissez-faire economics:
markets perform best if
allowed to function
according to their own
principles
Adam Smith
1723-1790
• Smith’s ideas inspired
Darwin in a more general
way:
• A system, once
established, will run itself
according to its own
principles
• A system does not
require a higher authority
to regulate a system itself
Charles Robert Darwin
Feb. 12, 1809 – April 19, 1882
• father and grandfather were
physicians
• an avid insect collector from
an early age
• December 1827
begins to study for the
clergy at Christ's College,
Cambridge
• Bachelor of Arts degree in
April, 1831
Charles Darwin
• Invited to
serve as ship’s
naturalist on
H.M.S. Beagle
The Second Voyage of the Beagle
Departs England on 27 Dec., 1831 – Returns to England on 2 October, 1836
The Post-Beagle Period
• Darwin settles into a
comfortable life
• Publishes numerous books
• Breeds pigeons
The Post-Beagle Period
• 1838-1844 – serves as
Secretary of the Geological
Society of London
• Becomes friends with
Charles Lyell
• 1837 - first mention of the
“transmutation” of species in
his notes
From Darwin’s notes – ca. 1838
Alfred Russel Wallace
• Studies the distribution
of animals in the Malay
Archipelago
Alfred Russel Wallace
(1848)
• Develops his own
ideas about natural
selection
• Sends Darwin a
manuscript in 1858
July 1, 1858
• Ideas of each presented at a meeting of the Linnean Society
• both credited with the idea of natural selection
Darwin gets Busy!
• Write “short” version of his
ideas
Darwin at Down House,
ca. 1880
• Includes evidence from
– His insights into insects
and other organisms
– Distribution of organisms
– Fossil record
– Embryology
– Comparative anatomy
– Comparative behavior
– and, and, and
November 24, 1859
ON
THE ORIGIN OF SPECIES
BY MEANS OF NATURAL SELECTION,
• First edition sells out the
first day
OR THE
PRESERVATION OF FAVOURED RACES IN THE STRUGGLE
FOR LIFE.
BY CHARLES DARWIN, MA.,
FELLOW OF THE ROYAL, GEOLOGICAL, LINNAEAN, ETC., SOCIETIES;
AUTHOR OF 'JOURNAL OF RESERACHES DURING H.M.S. BEAGLE'S
VOYAGE
ROUND THE WORLD.'
LONDON :
JOHN MURRAY, ALBEMARLE STREET.
1859.
• Acceptance in scientific
circles is rapid
• Makes no reference to
evolution of humans
From the final paragraph…
“There is grandeur in this view of life, with its several
powers, having been originally breathed by the Creator
into a few forms or into one; and that, whilst this planet
has gone cycling on according to the fixed law of gravity,
from so simple a beginning endless forms most beautiful
and most wonderful have been, and are being evolved.”
Later Works
• The Descent of Man, and
Selection in Relation to
Sex (1871)
• The Formation of
Vegetable Mould through
the Action of Worms, with
Observations on Their
Habits (1881)
Natural Selection
1.
At any one time, more individuals are born into a species than will
survive
2.
Each individual is unique (that is, different from the others)
3.
Some of these differences may be advantageous in the
environment in which the individual lives, while others may
be disadvantageous
4.
The individuals with the advantages are more likely to survive and
reproduce than the individuals with the disadvantages
5.
Over time, the advantageous traits become more common, and
the disadvantageous traits become less common
Microevolution
...and there’s nothing controversial about that
Macroevolution
…if the process continues long enough, you
can end up with entirely new species
And that’s what some people object to
Two Types of Selection
Artificial
• requires
Natural
• requires
• a trait to exhibit variation
• a trait to exhibit variation
• and a selective pressure
• and a selective pressure
The selective pressure is
exerted by humans
The selective pressure is
exerted by the
environment (nature)
The Three Problems
1. How is the variation present within a species at
any time affected by the environment?
Darwin
2. How is variation passed on from one generation
to the next?
3. Where does variation come from?
The Next Piece of the Puzzle
Gregor Mendel and
The Mechanisms of Inheritance
Gregor Mendel
1822-1884
• Entered the Augustinian
monastery of St. Thomas
at Brnø at 22
• Ordained as priest in
1847
• Taught secondary school
science
Two ideas about inheritance
Particulate
Blending
If you bred a white-flowered
plant with a red-flowered
plant, you will obtain a
plant with either white or
red flowers
If you bred a white-flowered
plant with a red-flowered
plant, you will obtain a
plant with pinkish flowers
Pisum sativum
Trait
seed form
albumen color
Forms
smooth
wrinkled
yellow
green
seed coat color
gray
white
seed pod form
inflated
constricted
unripe pod color green
yellow
flower position
axial
terminal
stem length
tall
dwarf
What Mendel Discovered
• Each plant contained two
pieces of information for a
particular trait
• Some of these were
dominant, some recessive
• Each parent contributed
only one piece of
information to each of their
offspring
Some terms…
• Gene
– unit of hereditary information for
a particular trait
• Allele – alternate form of a gene
• Gamete – a sex cell (egg for females
sperm, pollen for males)
Pisum sativum
genes
alleles
Trait
seed form
albumen color
Dominant Recessive
smooth
wrinkled
yellow
green
seed coat color
gray
white
seed pod form
inflated
constricted
unripe pod color green
yellow
flower position
axial
terminal
stem length
tall
dwarf
Mendel’s First Law
The Principle of Segregation
Alleles exist in pairs
which are separated from one
another
during the production of gametes
this means that…
…the chances of any particular
outcome can be predicted!!!
Inheritance occurs according to
statistical probabilities!
Mendel’s Second Law
The Principle of Independent
Assortment
The distribution of alleles for one trait
does not affect the distribution of
alleles for another trait
Independent
Assortment
• Whether an
individual inherited
one particular trait
from its father did not
affect whether it
inherited a different
trait from the father
as well
• It’s a crapshoot!
The Synthetic Theory of
Evolution
Variation is passed down according to
Mendelian principles
and selected for or against
according to Darwinian
principles
What are the physical
mechanisms through which
traits are passed on?
Particulate or Blending?
The answer depends upon:
• the trait being studied
• the species it is being studied in
In Humans?
Over 4500 known
“particulate” traits
•
•
•
•
•
•
ABO blood group
Rh blood group
Cystic fibrosis
Cerumen
Sickle-cell
PTC tasting
Numerous
“blended” traits
•
•
•
•
•
Height
Weight
Intelligence
Skin color
Eye color
The Three Problems
1. How is the variation present within a
species at any time affected by the
environment?
Darwin
2. How is variation passed on from one
generation to the next?
Mendel
3. Where does variation come from?