Background Flashcards
What does evolution refer to in biology?
the process by which living species have diversified since the origin of life on Earth
What are the 4 things to considered when exploring why something evolved?
Causes
Conditions
Constraints
Consequences
What are the different evolutionary processes/mechanisms? (4)
Say whether each is targeted or random
Natural selection and sexual selection (targeted)
Genetic Drift (random)
Non assortative mating (targeted)
Migration (neither targeted nor random)
What do phylogenetic reconstructions assume?
the degree of relatedness is reflected in the number of shared characters and the similarity in structure and that those shared characters represent homologies
What is a paraphyletic taxon
a single ancestral species but does not include all species
Define polyphyletic taxon
a grade derived from more than one ancestral species
What is a clade
all monophyletic taxa
What is a monophyletic taxon
a single ancestral species including all descendants
What is Galton’s problem
the problem of drawing inferences from cross-cultural data, due to the statistical phenomenon now called autocorrelation. (the different observations are not independent of one another)
Describe Linnaean classification (4)
- A system with 7 levels
- Each level is included in the level above it
- Levels get increasingly specific from kingdom to species
- Species have a binomial
nomenclature:
Homo sapiens
What are the 4 key definitions of species? Who proposed each?
Biological Species Concept, Mayr (1942, 1963, 1970)
Mate Recognition Species Concept, Paterson (1985)
Evolutionary Species Concept, Simpson (1951, 1961)
Ecological Species Concept
Describe the Biological Species Concept
Whose idea was it
Emphasis on what separates individuals of different species, with focus on barriers to gene flow, or reproductive isolation
Mayr, 1942
Describe The Mate Recognition Species Concept
Who described it first
Emphasis on what binds individuals of a species together, rather than what separates those between species, with focus on mate recognition systems
Paterson (1985)
Who first described The Evolutionary Species Concept?
What is it
Simpson (1951, 1961)
Emphasis on the evolutionary process of speciation, rather than the maintenance of species boundaries, defining species as evolving lineages.
What is The Ecological Species Concept
Van Valen (1976) modification of Simpson’s 1961 that places emphasis on the adaptive niche shared by evolving lineages
How do animals become reproductively isolated
PRE‐ZYGOTIC MECHANISMS
• Ecological (or habitat) isolation (organisms of different species don’t meet)
• Seasonal (or temporal) isolation (organisms of different species don’t meet)
• Ethological (or sexual) isolation (organisms of different species don’t have sex)
• Mechanical isolation (organisms of different species have sex, but there’s no transfer of gamets)
• Gametic isolation (organisms of different species have sex, there’s transfer of gamets, but gamets don’t fertilise)
POST‐ZYGOTIC MECHANISMS
• Hybrid inviability (egg fertilises, but does not develop)
• Hybrid sterility (egg fertilises, embryo develops, but hybrid does not reproduce)
• Hybrid breakdown (egg fertilises, embryo develops, hybrid is viable and reproduces, but the viability and/or fertility of its offspring is much reduced)
Give 3 advantages of the Biological Species Concept
offers an elegant mechanism for the maintenance of species boundaries
it is testable on extant taxa
it is not ambiguous in application
Give 6 drawbacks of the biological species concept
o more than one reproductive barrier between species may exist
o does not apply to asexually reproducing forms
o cannot be applied to fossils
o cannot be tested (in nature) among species that are geographically isolated
o cannot easily accommodate hybrids or hybrid zones, which are not uncommon in
nature (particularly in plants!)
o disconnect between degree of reproductive isolation and amount of morphological
or genetic divergence
How did Paterson (1985) describe this theory of species
what are 2 advantages of this concept
“(Species are) that inclusive population of individual biparental organisms which share a common fertilization system” (Paterson 1985)
it is testable on extant taxa
can be applied to fossils in relation to those parts of the mating/reproductive phenotype that fossilise or leave prehistoric traces
What are 2 drawbacks of the mate recognition species concept
o cannot be applied to asexual species
o cannot easily accommodate hybrids or hybrid zones. Unclear definition and delimitation of what
constitutes a sufficiently similar mating and reproductive phenotype to warrant inclusion in the same
species
Give a quotation from Simpson and Wiley describing the Evolutionary Species concept
“A lineage (an ancestral‐descendant sequence of populations) evolving separately from others and with its own unitary evolutionary role and tendencies” (Simpson 1961)
“…a single lineage of ancestral descendant populations of organisms which maintains its identity
from other such lineages and which has its own evolutionary tendencies and historical fate” (Wiley, 1978)
Why is the evolutionary species concept
a) useful (2)
b) not useful (3)
a) it approximates to what, in practice, taxonomists and palaeontologists use
Very useful because it accommodates the persistence of species distinctiveness in the presence of interbreeding (also that asexual organisms form species).
b) has a problem of circularity in the definition of what constitutes a
common evolutionary lineage
o has a problem in defining the limits of variation within a species
o does not offer insights into either the mechanisms by which a
species evolves or is maintained
What makes primates mammals? (6)
- Thermoregulation
- Nutritional efficiency
- Locomotion and posture
- Reproduction
- Complex life history
- Behavioural flexibility
What makes a mammal a primate? (7)
Distinct hands and feet
Distinct teeth and digestive system
Greater dependence on vision than smell
Distinct peripheral auditory system
Flexible locomotor skeletal system
Reproductive and developmental
traits
Social and behavioural traits
What is special about
a) primate hands and feet (4)
b) primate teeth and gut
a) • pentadactyl (mostly) • nails instead of claws (mostly) • grasping (mostly) • opposable hallux and pollex (mostly)
b)
• Conservative dental formula (mostly)
• Molars with relatively low cusps
• Large intestines with a fermentation chamber (caecum or appendix)
How does anatomy reflect a primate’s greater dependence on vision than smell
- Shortened rostrum (mostly)
* Forward facing eyes (binocular vision), surrounded by a bony ring or wall
What is special about a primate’s
a) reproductive/ developmental traits (5)
b) locomotion anatomy
a) • Long gestations • One or two infants per birth • Long periods of dependence on mother (mostly) • Relatively slow growth • Relatively large brains
b) • Unfused and highly mobile radius and ulna in the forelimb and tibia and fibula in the hindlimb • clavicle
What 6 things make humans great apes
• Large molars with low cusps • Suspensory body proportions • No tail • Long gestation, 1 infant/birth, long reliance on mother/group, very slow growth, larger brains • Male kin‐bonding? • Use of technology
What 6 things make humans unique
• Small canines • Bipedal locomotion (and correlated adaptations) • Manufacture of technology • Extra large brains • Childhood phase in life‐history • Complex language
What are the different definitions of ‘adaptation’
Adaptation (Darwinian sense): traits that promote survival (=viability) and successful reproduction
Adaptation (Neo‐Darwinian & Fisherian sense): traits that promote reproductive success (fitness)
What is the Fisherian sense of adaptation
outcome of natural selection
What are the conditions and constraint generally when considering adaptations to diet
Conditions: what other animals are eating, how seasonal the fruiting trees are etc
Constraints: body size, can babies digest it etc
What are the 5 key differences between australopithecine bipedalism
and our own bipedal adaptations?
Orientation of shoulder joint Curvature of phalanges Shape of rib cage Shape of pelvis Relative proportions of fore and hindlimbs
What are 2 questions surrounding the length of australopithecine’s long arms
Are early hominin’s long arms an adaptation to arboreality,
signalling a mixed arboreal/terrestrial locomotion
strategy?
But since arm length is not critical for walking bipedally ‐
could it be that it was not under selection in early
hominins, even if they were no longer used for tree
climbing?
What was the first hominin fossil found
The Neanderthal child partial skull from the Grottes d’Engis, in Belgium, discovered in 1829
Who coined the term Homo neanderthalensis?
William King, 1864
What was Homo erectus first called
where/when was it discovered
Pithecanthropus erectus
from Java, discovered in 1891
What was the fossil introducing Homo heidelbergensis
mandible found in 1908 (Otto Schoetensack)
What is Eoanthropus dawsoni
fragments of a cranium and a mandible discovered in 1912 in a gravel pit at Piltdown, near Uckfield,
Sussex.
After decades of argument, it was confirmed as a hoax in 1953
Which species was introduced when a skull was found on Broken Hill, Kabwe, Zambia
Discovered: 1921?
Homo rhodesiensis (now considered by many researchers to be a population of the species Homo heidelbergensis)
Which fossil found in Taung by Dart in 1924 and was rejected for many years
Fossil from Taung, South Africa, found in 1924
Described by Raymond Dart as Australopithecus
africanus
Rejected by the major anatomists of the time,
and not acknowledged as an early hominin until the late 1940s‐50s.
What is the Gibraltar 2 fossil
Devil’s Tower Child- Neanderthal child skull
Found by Dorothy Garrod
When was the first P. boisei fossil found
What was it originally called
Discovered by Mary & Louis Leakey, 1959
Olduvai Gorge, Tanzania
Paranthropus (Australopithecus/Zinjanthropus) boisei
Discuss ramapithecus
fossil discovered in 1932 (G. Edward Lewis), Siwaliks, dating to >9 – 12 Myr
had •Parabolic dental arcade
•Small(ish) canines
•Thick enamel
thought to be very early hominid
later revealed to be Sivapithecus (including previous genus Ramapithecus): An Asian Miocene ape related to orangutans
Which hominin species have been found in Koobi Fora
P boisei
H. erectus/ ergaster
H. habilis/ rudolfensis
H. habilis/ Australopithecus sp.
What was the first afarensis fossil found
Discovered by Donald Johanson (AL 129‐1) in 1973, Middle Awash, Ethiopia
When/ where was Lucy found
‘Lucy’ (AL 288‐1) discovered in 1974, near Hadar, Ethiopia
What is the importance of the Laetoli footprints
Discovered by Mary Leakey, 1976
Dated to 3.7 million years ago, they were the oldest known evidence of hominin bipedalism at that time
Australopithecus afarensis is the species most commonly proposed.
When did the first primates appear
58-55mya
What were the first catarrhines
Where are fossils found
Where did these primates disperse to
propliopithecidae
Oman, Egypt and Angola
dispersal of apes into Eurasia in early Oligocene using a temporary land bridge
When was the Eocene-Oligocene transition
What was a key climatic change in this transition
37mya
went from very hot (hotter than any time afterwards) to much cooler
How were the continents different from now in the early Oligocene
Arabia as part of Africa
• India has joined mainland Asia
• Asia broken up into large and small island masses
• Formation of the deep circum‐Antarctic water
currents
What did the formation of deep circum-Antarctic water currents in the Eocene-Oligocene transition result in (2)
major drop in global temperatures
lowering of sea‐level as the poles begin to
glaciate
How were fauna affected by the Eocene-Oligocene transition (4)
Extinction of many large‐bodied mammals
• Disappearance of ancestral strepsirhines and tarsiers
from the norther hemisphere
• Change in relative abundance of strepsirhines and
anthropoids in Asia and Afro‐Arabia
• Primates restricted to forest patches near the
Equator
What is Saadanius (3)
What can we infer from Saadanius
• Fossil from Saudi Arabia dated to 29‐ 28 Myr (Oligocene) • Large body size (10‐20 kg) • Close to the base of the hominoid‐ cercopithecoid clade
Suggests apes have retained ancient catarrhine features to a greater extent than monkeys
What are the first fossils considered to be apes
How big are these apes considered to be
from the late Oligocene
(27‐23 Myr) from Africa and Arabia
• 3 species: 2 from Africa, 1 from Arabia
• Large body size : 12 – 35 kg
Compare the climate of the early and middle Miocene
Early Miocene (ca. 24 ‐ 17 Ma)
• warmer climate and expansion of forests
• Africa and Eurasia separated by the Tethys Sea
Middle Miocene (ca. 17 ‐ 10 Ma)
• colder climate, expansion of savannas; increased continentality
• emergence of the Arabian peninsula ‐ Afro‐Eurasian land bridge
• India continues its collision against Asia ‐ growth of the
Hymalayas
• Initiation of the Rift System
what is Proconsul
Longest lasting Miocene ape 20-12mya – partial skeleton shows no tail, similar length 4 limbs
could reach 50kg
Describe late Miocene Apes in Eurasia generally
Four major groups of Eurasian apes
• 16 genera, 24 species
• Several medium‐sized animals: 5‐15 kg
• Several large to very large: 20 ‐ >200 kg
. Of what evolutionary process are lemurs a good example?
elaborate
adaptive radiation
Invaded ecological niche
Different adaptive patterns eg blood flow to the brain (sometimes primitive as in lorises from 15mya) or aye aye with very derived traits eg 3rd digit
Absence of predators and primate competitors meant lemurs could evolve almost all the strategies seen across the world – very
define adaptive radiation
how does this apply to human evolution generally
accelerated allopatric speciation during the colonisation of new habitats, particularly if it involves empty ecological niches
Human evolution could be described as sequential adaptive radiations
What are the differences between apes in Eurasia vs Africa at the end of the Miocene?
African Apes in late Miocene are very rare and all 6 genera known are represented by 1 species each and include earliest hominids
Very diverse apes in Asia eg Gigantopithecus
What is Gigantopithecus
co‐existed with H. erectus in China
Some individuals may have been up to 300 kg!
Name a representative of the orangutan lineage from the Miocene
When/ where did it live
Sivapithecus
~12.5‐7 Myr
India, Nepal
What is the difference between climate change and environmental change
Climate change: affects species through environmental change
Environmental change: may be local, regional, continental, but rarely
global in scale
What are the conditions, causes, constraints and consequences of timing of environmental change leading to primate evolution
conditions: timing of environmental change
causes: biological/ behavioural innovations
constraints: adjacent empty niches
consequences: evolutionary transition
How did the climatic change in the Eocene - Oligocene transition affect different primate populations
Africa:
decrease in number and size of lemur-like primates
increase in number and size of anthropoids
Asia:
Decrease in size and number of anthropoids
increase in size and number of lemur like primates
What are prevailing and dominant winds
Where does the ITCZ flow
Prevailing winds: winds that blow from a particular direction
Dominant winds: trends in winds with high speeds
ITCZ – flows through Sahara
Give some examples of how varied lemurs are
some are nocturnal, some diurnal
varied diets (some frugivores, some flexible etc)
some produce triplets or twins while others only have single births
True or false
Evolution happens only in the spatial realm
false
The evolutionary history of a lineage is a history of expansions and contractions of its
geographical range – evolution happens in time and space
What is expansion and dispersal potential a function of?
What happens if the costs of predation and competition are reduced
a lineage’s ecological traits
if the costs of
predation and competition are reduced, it can lead to adaptive radiations.
How can we infer the sequence of radiations of a lineage
from the relative distribution of descendant clades.
What do Stewart and Disotell have to say about the LCA of living African apes?
3 candidates:
Samburupithecus [9.5 Myr, Kenya]: 1 sp, 60 kg
Nakalipithecus [9.9‐9.8 Myr, Kenya]: 1 sp, 40 kg
Chororapithecus [10 Myr, Ethiopia]: 1 sp, 25+ kg
How did Disotell and Stewart explain the absence of fossils of African apes in Miocene
Argued that it was a dispersal of Asian apes into Africa which explains why there are no fossils of apes in the late Miocene as old African apes went extinct
When did gorillas, chimps, and humans diverge from each other
Genetic phylogenies suggest orangutans diverged from rest of African apes 10mya while LCA of gorillas, chimps, bonobos and humans lived 7-5 mya
Gorilla diverged ~5mya
What were the 2 scenarios suggested by Stewart and Disotell for African ape dispersal in to eurasia
A; ancestor to all African apes disperses into Eurasia ~20mya and a second related ape disperses out of Africa 15mya
B: 1 dispersal out of Africa which is the ancestor of all apes in Eurasia, one of which disperses back into Africa ~10mya – this is much more likely as many many dispersals would be needed for A to explain the fossil patterns
Is there a fossil suggested to be a hominin older than Sahalenthropus
Yes
Graecopithecus
7.175-7.24mya
Vassilissis (Greece)
has been suggested Graecopithecus maybe the oldest known hominin based on dental morphology
Is there a suggestion of a biped in Greece 5.7mya?
Yes
fossil footprints
bipedal? – narrow heel and non-opposed hallux suggest this to be the case
How do the ancient Greek fossils suggested to be hominins (footprints and Graecopithecus) suggest about forest adaptations of chimps and gorillas?
If these fossils are part of the apes that dispersed back to Africa 10-7mya then it would suggest terrestriality and perhaos bipedality based on geography which would mean forest adaptations of gorillas and chimps are convergent rather than a ancestral trait
Are we sure about the date of the LCA of orangutans, gorillas, chimps, bonobos and humans?
Disputes about mutation rate may mean LCA was older – sequence of divergence in phylogenetic tree likely to be correct but dates maybe incorrect
Moorjani 2016 suggests LCA with orangutans is 15mya and with gorillas 10.8mya
From the fossil evidence when were apes in Africa
before 10mya
after 7mya
