Lecture notes of the first part of the Evolutionary Developmental Biology course. This course is part of the first-year Biomedical Sciences curriculum at the Vrije Universiteit Amsterdam. Note: these notes were written based on online lectures (due to COVID-19), so the content might be different th...
To interpret and understand organismal adaptation to environmental conditions
To explain the diversity of life: the variety of organisms, their characteristics, and their
changes over time
Charles Darwin (1859) the origin of species:
Evolution is change in the heritable characteristics of biological populations over successive
generations.
Natural selection:
1. Variation in reproductive success
2. Variation in the trait of interest
3. Correlation between the trait and reproductive success
4. The trait is heritable
Survival of the fittest
- Typological thinking the “normal” or average condition is the most important aspect to
consider
- Population thinking understanding the variation in a population
Heritable traits with standing genetic variation and possibly subject to selection in humans:
- Trade-offs, random processes, mismatches, evolutionary constraints
- Claims of adaptation need examination, which can be difficult in humans
Determining if something is adaptive:
1. Observing natural selection experimental evolution in microorganisms, nematodes or
insects
2. Perturbing the trait move a trait away from its optimum
3. Trait is produced only when it serves a function
Most of these tests are not possible in humans model organisms
Tree thinking:
Understanding the position of a species or a trait in a phylogenetic tree expresses the relationship
among organisms and their evolutionary history.
,Lecture 2 – Story of our ancestors (Straalen & Roelofs 1)
Homo sapiens (knowledgeable man):
- Kingdom: animalia
- Phylum: chordata
- Subphylum: vertebrata
- Class: mammalia
- Order: primates
- Family: hominidae no tail, remarkably long periods of nursing and adolescence, sexual
dimorphism
- Subfamily: homininae bipedalism, brain size, family structure and sexuality
- Genus: homo
Anagenesis: gradual evolution of a species
The African rain forest gave to savannah (10 Mya) a new ecological niche:
Terrestrial instead of arboreal lifestyle demanded adaptation all old fossil hominins are found in
(East) Africa
Species to remember:
- Australopithecus afarensis
- Lived in Africa, ~3.5 Mya
- Ancestor of all Homo species
- Mosaic of ancestral and derived traits
- Homo erectus
- Lived in Africa and Asia, ~1.5 Mya
- African H. erectus ancestor of H. sapiens
- Homo neanderthalensis
- Lived in Europe and Asia, 600 Kya – 30 Kya
- Similarities to H. sapiens; extinct sister clade
1. Group of organisms that can produce fertile offspring
- Hybridizations between closely related species possible
2. DNA sequence similarity
3. Behaviour
4. Ecological niche
5. Morphology
- Completeness and number of specimens found important
- Variation within species versus variation between species
, Australopithecus:
- Not all humanlike traits evolved at the same time
- Apomorphic (derived) vs. plesiomorphic (ancestral)
- Skull shape and brain volume largely plesiomorphic
- The dental arcade changed from U-shaped to parabolic and became shorter
- Reduction in canine teeth size in australopithecines, but still significant sexual dimorphism
- Strong dimorphism in body size gradually disappeared6 species (4.2-2.5 Mya)
- Gradual evolution of various humanlike traits in subsequent species
- Two lineages diverged from Australopithecus
- Paranthropus (2.5-1.4 Mya), characterized by robust and muscular bodies with apelike
features of the head evolutionary dead end
- Homo (2.8 Mya - now) Homo habilis (2.8-1.4 Mya)
Lucy:
Australopithecus afarensis (3.2 Mya) excavated in 1974 in Ethiopia.
- Most complete Australopithecus fossil at that time
- First to display characteristics of bipedalism and a small brain
- Settled “brain first” versus “bipedalism first” debate
Evolution of the brain of genus Homo habilis:
Use and manufacturing of stone tools:
- Understand fracture mechanics of available stones
- Sensorimotor control over force and accuracy to strike off flakes
- Spatial understanding of where to strike
Homo rudolfensis an alternative “first” Homo species
- First appeared 2 Mya
- More humanlike features of the head
- Debated if it is a separate species or part of Homo habilis
- Few fossils remains found
Species concept problematic in genus Homo
Homo erectus (2 Mya – 108.000 Ya):
- All traits related to bipedalism well developed
- Efficient long-distance runners
- Evolution of less body hair and dark skin colour
- Brain volume (600-1000 cc) still apelike skull features
- Evolution of larger brains started ~800.000 Ya
- First species associated with hunting large animals; more sophisticated stone tool making
- First human species to migrate out of Africa
- Morphologically very diverse
Modes of speciation:
Reproductive isolation followed by local adaptation or genetic drift over time.
1. Sympatric speciation side-by-side evolution
2. Allopatric speciation a group separates and occupies a
new area
3. Parapatric speciation origin of a new species on the
border of the distribution range due to local adaptation
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