LEC 3 – MACROEVO AND EVO ANTHRO
•Large-scale changes at or above the special level.
•Extends over geologic era.
•Associated with research on the formation of new
EARLY SPECIES CONCEPTS
Typological species concept:
similar-looking individuals lumped into discrete categories.
Modified typological species concept: similar-looking
individuals that can successfully produce fertile offspring
lumped into discrete species categories.
(How in early taxonomy – linneaus classification –
MODERN SPECIES CONCEPTS
Biological Species Concept
Actually or potentially interbreeding populations (Mayr,
Must apply all known morphological, behavioural, and
ecological data to use as deductive proof of reproductive
isolation between species.
But, what about fossil species?
Species concept – all have underlying themes – divided into
2-3 categories –
Bio species concept – species are actually interbreeding pop
When pop not able to interbreeding – pop is reproductively
isolated (most important for bio species concept)
Not geographic iso – but reproductively iso (continuum)
Eg. iso starts w/ recognition of potential mate LEC 3 – MACROEVO AND EVO ANTHRO
Requires a lock and key mech (penis and vagina) Zygote
forming? No viable fetus? Dead new born (survival)
Selection against (reducd fitness of offspring)
Problems w/ bio species concept: Potentially interbreeding
is hard to identify
Fossils? Can’t observe fossil reproduction – don’t know if
Phylogenetic Species Concept
Smallest aggregation of sexual populations diagnosable by
unique combination of character states.
Measure and analyze variation in characters within and
Can be applied to living and fossil organisms.
Most evo anthro use this phylogenetic species concept
smallest aggreg of sexual pop diagnosable by a unique
combo of character states (phenotpic char)
At least 1 trait must be diff b/w 2 pop in order for diff
Cladistics – way of describing evo rlsps using character
states (version of diff morphological traits
focused on indiv traits
Phonetic analysis – looking at morph pattern – use idea that
simliar organism will be related
Problems: eg. birds and bats are similar – must share
common ancestor. But not the case
When trying to look at evo history – have to look at indiv
char – not the overall morphological pattern
•Evolutionary process involving the formation of new species. LEC 3 – MACROEVO AND EVO ANTHRO
•Adaptive or non-adaptive process?
•Are intermediate forms needed in speciation?
Natural sel , mutation, gene drift, gene flow(not important
component for speciation)
b/c Gene flow dec var among pop (non random) – inc w/in
pop, b/c it breaks down variation among pop – it can’t be a
part of speciation
Speciation needs a divergence or inc in genetic difference
Gene drift – inc gene var among pop (random – dec w/in
Dones’t take much gene flow to stop process of speciation –
influenced by geographic separation
If process only includes NS – adaptive process
Are intermediate forms needed in speciation – phyletic
gradualism and punctuated equil
YES – but..
Creationist used to refute the evo th – intermediate forms
leading from primitive to more derived form
Use gaps or lack of intermediate forms that evo dones’t exist
•Species formation that occurs following geographic isolation
•Isolation in terms of limited gene flow.
•Two modes of allopatric speciation: vicariant and peripatric.
Pop A and B – geo distribution – not touching = allopatry
Another scenario – A and B meet but no overlap = peripatry
sympatric – overlap
Why allopatry interesting in speciation? – reproductively
When isolation – no gene flow – LEC 3 – MACROEVO AND EVO ANTHRO
Two modes of allopatric speciation: vicariant (separate) +
peripatric speciation (involves peripatry)
•Occurs when a physical barrier creates large, geographically
•In time, populations diverge and can no longer interbreed.
•Occurs when small, peripherally isolated colony of main
population diverges to become new species.
3 ASSUMPTIONS OF CLADISTICS
1.There are changes in characteristics within lineages over
2.All organisms are descended from a common ancestor.
3.When a lineage splits, it divides into exactly two groups.
3. Doesn't necessarily have to be two groups LEC 3 – MACROEVO AND EVO ANTHRO
e.g., result of adaptive radiation
Cladistics --> also referred to as phylogenetics
CLADOGRAM OR PHYLOGENY
•A branching diagram used to illustrate phylogenetic
This examples assumes a constant rate of evolution in all
taxa and common ancestors
In other trees, branch lengths vary to reflect differences in
evolutionary time --> proportional to evolutionary
differences from each other
COMPONENTS OF INTEREST in cladograms:
- Branch Tips --> different taxa/species
- Branch Nodes --> hypothetical common ancestor
-Clades --> branch tips that share a common ancestor
- Nested clades --> share closer evolutionary relationships
READING A CLADOGRAM
•Each internal node represents a hypothetical common
•Within a cladogram may be a number of clades.
–Clade: A group of organisms that contains an ancestral
taxon (hypothetical common ancestor) and all of its
descendants. LEC 3 – MACROEVO AND EVO ANTHRO
CLADOGRAMS --> have to be viewed as hypotheses; different
data sets produce different trees
•Researchers are specifically interested in tree topology.
–Tree topology: the branching patterns of lines connecting
nodes and organisms. (internal branching pattern of nodes)
•Focus on internal branching patterns and not tips of