Evolution, Primates & Behavioural Ecology – Comprehensive Lecture Notes

Types of Homology and Evolutionary Thought

Developmental Homology

Gill slits / gill pouches, post-anal tail, vertebral column appear in the embryonic stage of distantly related species (e.g.a0chick, human, cat).
Indicates common developmental pathways; answer to the sample MCQ.

Genetic Homology

Similarities in DNA/RNA sequences across species; measured directly with molecular techniques.

Structural (Morphological) Homology

Similar bone layouts used for different functions (human arm, whale fin, bat wing).

Lamarcks "Inheritance of Acquired Characteristics" (Disproven Mechanism)

Traits strengthened by use (e.g.a0giraffe neck) supposedly passed on; replaced by Darwinian natural selection in which the environment filters heritable variation.

Mass vs. Background Extinction

Mass Extinction 539 Rapid, global loss of a large proportion of taxa.
- Five recognized events; key ones covered: Permian ("Great Dying") and Late Cretaceous (non-avian dinosaurs lost).
Background Extinction 539 Normal, lowera0rate of species loss due to ordinary ecological/ evolutionary processes.

Meteor-Impact Evidence for the Late Cretaceous Event

Thin global sediment layer enriched in iridium (rare on Earth, common in meteorites) 4A5 correct answer to MCQ.
NOT: U-238 layers, complete dinosaur extinction per se, or CO₂ in glacial ice.

Core Behavioural-Ecology Terms

Concept	"How? / Why?"	Key Example(s)
Proximate causation	Mechanism (how a behaviour occurs)	Lobsters detect Earths magnetic field to navigate home at night.
Ultimate causation	Evolutionary reason (why it exists)	Navigation increases survival by returning safely to shelter.
Habituation	Decreased response after repeated benign stimulus	Nestling birds stop ducking after many overhead shadows.
Operant conditioning	Behaviour linked to reward/punishment	Skinner box: lever ⟶ food pellet or mild shock.
Fixed Action Pattern (FAP)	Innate, stereotyped, nearly unstoppable once triggered	Host yellow bird feeds oversized cuckoo chick that killed its own brood.
Reciprocal Altruism	Exchange of fitness benefits separated in time	Vampire bats regurgitate blood meals to unrelated group members.
Kin Altruism	Help directed toward relatives; modelled with Hamiltons rule	Cooperative breeding, alloparental care.

Hamiltons Rule: rB > C
(Help is favoured when the coefficient of relatedness $r$ times the benefit $B$ to the recipient exceeds the cost $C$ to the actor.)

Study Strategy Highlighted

Use MCQ stems not only to pick the right letter but to rehearse definitions, contrasts, and underlying principles.

Hybrid Case Study: The Pizzly (Grolar) Bear

Hybrid of polar bear (Ursus maritimus) 2B grizzly bear (U.a0arctos).
~8 verified individuals in the wild; fertile.
Likely arises where shrinking sea-ice pushes polar bears south and warming climate allows grizzlies north ⟶ range overlap.
Currently no self-sustaining pisley population; all hybrids traced to one female polar bear × two male grizzlies.

Adaptive Radiation of Mammals After Dinosaur Extinction

Non-avian dinosaurs vanish $ext{≈}65\text{ Mya}$ .
Vacant niches ⟶ rapid diversification (adaptive radiation) of mammals.

Earliest Primate-Like Mammals (Plesiadapiforms)

Time: just post-Cretaceous.
Traits: small brain, long muzzle, rodent-like incisors, claws (not nails), lateral eyes (poor depth perception), excellent smell, arboreal but non-leaping, low-crowned herbivorous teeth.

Primate Overview: Shared Synapomorphies

Grasping hands/feet with opposable thumbs.
Nails (not claws).
Forward-facing eyes enclosed in a post-orbital bar.
Hind-limb dominated locomotion.
Relatively large brain-to-body ratio.
Generalised heterodont dentition (incisors, canines, premolars, molars).

Major Primate Branches

Prosimians ("before monkeys")

Lemurs, bush babies, lorises.
Often nocturnal; huge eyes.
Endemic/isolated (e.g.a0Madagascar) ⟶ unique evolutionary paths.

New World Monkeys (Platyrrhines)

Geography: Central & South America.
Small–medium; broad lateral nostrils; prehensile tail; no buttocks pads/cheek pouches.
Examples: squirrel monkey, golden lion tamarin.

Old World Monkeys (Cercopithecoids)

Geography: Africa & Asia.
Larger; downward nostrils; longer hind-limbs; flat nails; sitting pads; non-prehensile tails.
Examples: macaques, baboons.

Apes

Shared trait with Old World monkeys: closely spaced nostrils.
Lesser Apes – gibbons; extreme brachiation.
Great Apes (Hominidae) – orangutans, gorillas, humans, chimpanzees, bonobos.
- No tail, long arms, short legs, broad chest & shoulders, large brain-body ratio.

Molecular Evidence of Human–Chimp Relationship

DNA double helix melts at $95^\circ\text{C}$ when perfectly matched.
King & Wilson (1975) created human–chimp hybrid DNA; melted at $94^\circ\text{C}$ ⟶ ~1 % sequence divergence.
Full genomes: Human (2003), Chimpanzee (2005) confirm $\approx99\%$ similarity; divergence $5\text{–}7\text{ Mya}$ .

Hominins: Definition & Earliest Member

Hominins = modern humans (Homo sapiens) + all extinct, bipedal ancestors; excludes chimpanzees & bonobos.
Earliest specimen: Sahelanthropus tchadensis (discovered 2002).
- Age: $6\text{–}7\text{ Mya}$ .
- Chimp-sized brain, prominent brow ridge.

Skeletal Adaptations for Habitual Bipedalism

Foramen Magnum Position – hole for spinal cord under centre of skull keeps head balanced over body.
S-shaped Vertebral Column – weight centred above pelvis.
Short, Broad Pelvis – supports internal organs; aligns femurs.
Long Legs / Valgus Knee – stride efficiency; knees angled inward to keep feet under centre of gravity.
Arched Foot & Non-Opposable Big Toe (not detailed in transcript but integral) – spring & shock absorption.

Modern slump (hunched over laptops) counteracts evolved posture – periodic movement recommended!

Fossil Teeth as Evolutionary Clues

Teeth & enamel fossilise readily (hard tissues).
Wear patterns, crown height, and micro-damage reveal diet and habitat.
Aid in placing extinct taxa on phylogenetic trees.

Key Numerical / Statistical Points

Iridium layer dating late Cretaceous: $\sim65\text{ Mya}$ .
Background extinction rate ≪ mass-extinction pulse.
Human–chimp DNA difference: $\sim1\%$ (melting temp 1 °C lower).
Earliest hominin: $6\text{–}7\text{ Mya}$ .
Number of verified pizzlies: $\text{≈}8$ .

Timeline Snapshot

$65\text{ Mya}$ – Asteroid impact ⟶ dinosaur extinction ⟶ mammal radiation.
$\sim60\text{–}50\text{ Mya}$ – Plesiadapiforms (primate-like).
$\sim40\text{–}30\text{ Mya}$ – Split of New vs.a0Old World monkeys.
$\sim20\text{ Mya}$ – Early apes diversify.
$6\text{–}7\text{ Mya}$ – First hominins.
$2003$ – Human genome.
$2005$ – Chimp genome.

Quick Glossary

Agnostic (in quiz) – merely a distractor; not used in behavioural ecology.
Iridium – extraterrestrial metal marking impact layer.
Prehensile – capable of grasping.
Brachiation – arm-over-arm tree locomotion (gibbons).
Monophyletic Group – clade containing ancestor & all descendants.
Synapomorphy – shared, derived trait defining a clade.