1. 7 billion people
Assoc Prof. Rebecca Ackermann
Department of Archaeology
Beattie Bldg, Rm 3.19
becky.ackermann@uct.ac.za
Archaeology
 Biogeography & Adaptation
 Overview of Humans/Primates
 Vision
Linguistics Anthropology Socio Cultural
Socio-Cultural  Bipedalism
Bi d li
 Brains
 Skin
 Agriculture
Biology  Domestication
 World Population Growth
 All readings are on Vula  Remain at the ENGEO Building venue for the
first practical
 Practicals and supplemental materials for the
practicals are also on Vula  Practical 1 will run Th/F (May 3 & 4) in first
/
week and M/Tu (May 7 & 8) in second week
 Bring a calculator
1

2.  Practical 2 will run Th/F of the second week (May 10 & 11)  Introduction
and M/Tu of the third week (May 14 & 15)
 Adaptation through natural selection
 Meet at the Pick-up / drop off area at the end of University
Avenue South  What is a species?
p
 13h00 – 18h00
 How does one species split into two?
 Extinction
 Wear good shoes!!! Bring appropriate clothes (e.g. rain
gear)!!!
 Bring something (e.g. clipboard) to write on
 Be sure to read background material AHEAD of time
 Biogeography = the study of the pattern of distribution of (mutation, selection, gene flow, genetic drift)
organisms (individuals, species, ecosystems) across space and
through geological time
 Patterns of distribution of organisms across geographical areas
can usually be explained through historical factors (e.g.
speciation; extinction; continental drift; glaciation, variations in
i i i i i l d if l i i i i i
sea level, river routes, habitat) in combination with geographic
constraints (landmass areas and isolation) and the available
energy supplies in the ecosystem
 Evolution (adaptation through natural selection) provides the
key explanation for the pattern of distribution of organisms
(i.e. the link between organismal variation and the
climate/environment)
 Evolution = descent with modification (i.e. change through
time) fast slow
 Adaptation of plants and animals to their environment
occurs through the process of natural selection Ship Naturalist
 Adaptation = a change of structure, form, or habits to fit
different conditions, which increases fitness 1831 1836:
1831-1836: Voyage of the
 Adaptive traits = a trait with a current functional role in Beagle
the life history of an organism that is maintained and
evolved by means of natural selection
1859: On the Origin of
 Natural selection = preservation of favorable individual Species by Means of Natural
differences and variations and the destruction of those
that are injurious Selection
2

3. 3

4. Parallel between species morphology, behaviour,
geography and adaptation (‘fit’) to environments
(the foundation of biogeography!!)
 Demonstrated FACT of evolution (and defined  Malay Archipelago:
it as descent with modification) 1848-1862
 1857: “On the
 Offered explanatory mechanism (i.e. natural
Tendency of Variation
selection… survival and mortality KEY to this
to Depart Indefinitely
definition)
from the Original Type”
 Heredity of most features  The peppered moth, Biston
 Heritable variation in the population betularia, occurs in two varieties,
melanic and non-melanic
 Variation leads to differential rates in survival &
 Non-melanic form is virtually
reproductive success among variations invisible against pale-coloured
pale coloured
 Differential survival and reproduction leads to change backgrounds, vice versa for melanic
in frequency of characters (e.g. populations will diverge form.
from one another)  Differential survival rates under
 If process goes on long enough, parent & daughter environments of different colour.
 Prior to industrial revolution,
species can no longer interbreed (e.g. they have become
lighter form dominant - a survival
too different) advantage against lichen-covered
trees.
ENVIRONMENTAL CONTEXT IS ESSENTIAL!!!
4

5.  After the industrial revolution,
more offspring of melanic form
survive to reproduce.
 Relative frequency shift: before
melanic = 5% after = 98%
l i 5%, f 98%.
 Process occurred in just 40
generations.
 Note that in this case natural
selection does not create the forms,
but rather edits the populations.
 Natural selection is ‘fine-tuning’
populations to their physical
environments.
Daubentonia
madagascariensis
Xanthopan morganii praedicta Angraecum sesquipedale
Bergmann’s Rule Allen’s Rule
Correlates between latitude (climate) and body mass / limb length
5

6.  Natural selection can act to create (or delete)  Species are uniform ‘types’ of organisms:
forms (species) when viewed over deep biogeographers classify organisms as belonging to one
(geological/evolutionary) time or other species.
 There are many different ways of defining species
 Other evolutionary forces (mutation, drift, gene
 In practice, species are generally recognised not solely
flow) also play a role in creating new forms (or even necessarily) by reproductive isolation, but by
some combination of factors such as morphology,
genetics, geographic proximity, and ecology, that
together make a species distinct even in the face of
gene flow.
Western Meadowlark Eastern Meadowlark
Modes of species change
anagenesis
cladogenesis
6

7. Tempo (pace/rate) Tempo + Mode
time
gradual gradual punctuated punctuated stasis
Phyletic gradualism Punctuated equilibrium anagenesis cladogenesis anagenesis cladogenesis
phenotype
 Speciation – e.g. diversification of lineages (lineage
splitting)
 Most important type of speciation is allopatric speciation
(although you may also encounter the terms sympatric
and parapatric speciation).
Adaptive radiation
Time 4
Differentiation (speciation)
 Species becomes geographically divided by a barrier (continental
drift, rifting, change in course of river, fire etc).
Time 3
 Separate populations are reproductively isolated from each other. Reproductive isolation
 Natural selection operates independently in each population and the
N l l i i d d tl i h l i d h
populations gradually become adapted to their own unique
Time 2
environments (divergence also occurs through genetic drift).
Physical barrier
 Reproductive isolation is initially imposed by the geographical
constraints, but eventually populations diverge too much resulting
in permanent barrier (different genomes, behaviours, etc). Time 1
Original population
 Speciation is complete; one species has become two (or more).
7

8.  If speciation occurs all the time, there should be more
species today than 10,000 years ago, and more then than
there were 10 million years ago, right?
 No, because extinction is ubiquitous.
No ubiquitous
 99% or all species that have ever existed on Earth have
gone extinct.
 Some geological periods are characterised, or dominated,
by extinction (e.g. end-Permian, end-Cretaceous).
 These are so-called mass extinction events
 Causes varied and sometimes controversial
 End-Permian event resulted in loss of 90% of all marine
species - global warming may have been the culprit (a
lesson?).
 End-Cretaceous (K-T) likely caused by asteroid impact.
Loss of large proportion of reptiles (especially the Chicxulub crater
dinosaurs).
 Causal factors may have been climate change induced by
impact: global cooling.
 Sudden disappearance ~50Ka  Climate?
 Human-induced environmental  14 genera disappear
change caused by burning before the first
p
practices
Clovis point is
 Drought-adapted flora with
palatable nutritious grasslands found
became fire-adapted desert
scrub with low-nutrition
grasses
 Stress and extinction of
megafauna
8

9.  Climate change (severe
droughts).
 Arrival of humans
(including overhunting,
introduction of alien
species, the use of
agricultural fires).
In the American South-West the dates for Clovis sites (~13Ka) coincide  Hypervirulent/hyperlethal
closely with the dates for the last appearance of the Shasta Ground Sloth. disease
 Human-induced climate change, habitat change,
and hunting are continuing to threaten megafauna
worldwide
9