Quaternary

Question 1

How did Pleistocene climate affect mammal distribution

Answer 1

typified by high levels of climatic fluctuations- many mammals show fluctuations in ranges according to advancing and retreating of different vegetation types eg. cold-adapted pikas and steppe woolly rhinos
Due to niche tracking or contractions in range due to local extinction? Unsure
North American mammal families through Eocene to Pleistocene suggest that niche conservationism is ubiquitous through deep time, and that range expansions and contractions are typical (DeSantis et al., 2012)

eg. Range of Panthera leo appears to have contracted with a southwards shift, but is due to extinction of cave lion, Pathera leo spelaean

Some probably due to migration- modern elephants migrate long distances (Purdon et al., 2018), and it’s thought megafaunal migrations even more frequent in past (Harris et al., 2009)

Question 2

Climatic contributions to end Pleistocene megafaunal extinctions

Answer 2

Increased precipitation during interstadials caused a rise in dense vegetation, decreasing the quantity of forbs, much of many megafaunal diets (Willerslev et al., 2014)?
Eurasia, woolly rhino, Coelodonta antiquiatis, extinct due to increased precipitation ~13.9ka BP, herbaceous vegetation replaced by shrubs and trees (Stuart and Lister, 2012)
Repeated interstadial warming events used to explain staggered extinction patterns in Eurasia (Cooper et al., 2015)

Due to increase in stability at end of epoch? Megafauna favoured b y variable conditions of Pleistocene due to increased metabolic efficiency, starvation resistance, ability to migrate (Mann et al., 2019)
Change to climatic stability disadvantageous, leading to extinction

Question 3

Human contributions to end Pleistocene megafaunal extinctions

Answer 3

Likely no single cause and that each species’ extinction different (Lorenzen et al., 2011)- use species distribution models and aDNA to demonstrate each had own response to climatic shifts and human arrival- most cases due to combo, esp. in Holarctic
However, almost certain human role (Sandom et al., 2014)
Pattern of overlap between humans and the mammals that went extinct preclude a Blitzkreig model, of arrival and then immediate extinction- actual interaction much more complicated.

In N. America, due to top-down effects of the addition of another top predator into a predator-limited system, causing predator competition (Ripple & Van Valkenburgh, 2010)

Humans= dominant super predators, kill adult prey at higher trophic levels (Darimont et al., 2015).

Question 4

Animals preferentially killed by humans at end of Pleistocene

Answer 4

Large organisms, provide more meat for hunters and had slower reproductive rates (Lyons et al., 2009)

Slowly reproducing organisms regardless of size (those with a slow reproductive rate that survived where arboreal, nocturnal or lived in closed habitats) (Johnson et al., 2002) - ‘bradyfaunal’ extinction

Question 5

Effects of megafaunal extinctions on ecosystems

Answer 5

Widespread vegetational change
Australia, led to rise of sclerophyllous vegetation (Rule et al., 2012)
Holarctic, woody plants became dominant
Beringia, led to rise of Betula in pollen record (Doughty et al., 2010) which would have caused regional warming of up to 1 degree due to albedo effects.

Megafauna = ecosystem engineers therefore high ecosystem function (Galetti et al., 2018)
Siberia, trampling by megafauna would have exposed soil to the air, allowing it to cool. Since loss, Siberian soil has warmed, pts permafrost at risk of melting (Zimov & Zimov, 2014). Melt would release huge amount of methane, accelerating global warming and biodiversity loss.

Question 6

Ecometrics

Answer 6

Study of how functional traits interact with the environment over time.
eg. calcaneum gear ratio in carnivores = functional trait correlated with vegetation type
Investigating how gear ratio changes over time shows that the average gear ratio during LGM of Indiana was equivalent to that of 1800AD, whereas by 1900, had changed on average due to arrival of agriculture and extirpation of species (Polly & Head, 2015)

Question 7

The Island syndrome

Answer 7

shorten limbs
change in body mass (The Island Rule)- small become large and large become small (Foster, 1964)
shortened rostrum
reduced sexual dimorphism
increased tameness- ecological naivete may offer explanation for extinctions (End-Pleistocene? Definitely for some Holocene mammal extinctions eg. warrah killed by Gauchos for fur- extinct in 1876)

coordinated evolution of all these traits at once due to changes in neural crest pathways that affect development early in embryonic history (Sanchez-Villagra et al., 2016). Relaxation of selection pressures on islands, and their lower genetic diversity due to Founder effect means that mutation can drive rapid evolution

Question 8

Faunal turnover events

Answer 8

episodes of synchronous appearance and disappearance of species from a community, often resulting in a net change in species richness

Locally, determined by relative rates of speciation, extinction, immigration and emigration

Relative turnover = (last appearance + first appearance)/total number of species

Turnover greatest for mammals in Miocene and Pleistocene, compared to other groups

Question 9

Climatic change in Pleistocene

Answer 9

Alternating environmental change
Through large scale Milankovitch Cycles and smaller events eg. Dansgaard-Oeschger Cycles or Heinrich events
Changes were short and reversible- not really enough time for many genetic changes to accumulate in populations to drive speciation as a result of changing selection regimes— Barnosky (2001) argues that cyclical climate oscillations select against organisms that respond to them by speciation

Question 10

Sagebrush Vole changes

Answer 10

first lower molar changes from 4 triangular cusps in ancient voles to 5 or 6 currently
evo change associated with warming event during Pleistocene (Barnosky & Bell, 2003)

Question 11

Adaptations for cold

Answer 11

Fur
woolly mammoth haemoglobin could function over a wider temperature range because had more chloride binding sites, changing amount of heat released during binding

Question 12

Turnover-Pulse hypothesis

Answer 12

Vrba, 1993
climate change events drive periods of high faunal turnover
often opposed by Red Queen Hypothesis that turnover rate is constant rather than pulsed, and is controlled by biotic interactions (better fit for Pleistocene mammals, speciation rates not high enough to fit T-P hypothesis)

Question 13

Pleistocene mammal turnover

Answer 13

Higher than normal
up to 50% of divisions between extant sister taxa occurred during Pleistocene (Avise et al., 1998)
as a result of complex interactions between causal factors and responses:
-behavioural accommodation
-distributional shifts
-ecophenotypic modification (non-genetic)
-evolution (anagenesis or cladogenesis)
-extinction

Comparison between Middle to Late Miocene and Quaternary suggests an increased mammalian turnover in Europe, at least partly owing to enhanced levels of speciation and extinction
Fossil record shows that almost all modern mammal species, at least in Europe and Northern Asia are Quaternary in Origin

Question 14

Climatic oscillations favoured large-bodied organisms because

Answer 14

increased metabolic and locomotary efficiency
starvation resistance
long lifespan
ability to migrate

but have higher orientation and extinction rates than smaller mammals, perhaps because less able to ‘sleep or hide’ in response to threat (Hsiang Liow et al., 2008)

Question 15

Megafauna definition

Answer 15

Any animal above 44kg

Question 16

4 potential drivers for Pleistocene extinction

Answer 16

Overkill
Climate Change
Extraterrestrial impact
Hyperdisease

Question 17

Hyperdisease hypothesis and extraterrestrial impact hypothesis

Answer 17

Inconsistent with preferentially targeting of megafauna

Also inconsistent with asynchronous patterns of extinctions

Question 18

Generic extinction rates in each continent

Answer 18

Australia - 88% (due to isolation, naivety of native organisms, or taxonomic composition w more marsupials??)
S. America - 83%
N. America - 72%
Eurasia - 36%
Africa - 18% 
Barnosky et al., 2004

Question 19

Extinctions of megafauna in Africa

Answer 19

Lowest because location of human evolution, therefore megafauna had evolved alongside for longer and less naïve
Mammals here had earlier extinctions during Plio-Pleistocene transition and throughout Early and Middle Pleistocene
Lost its large carnivore functional diversity before 2Ma as a result of competition with human hunters (Werdelin and Lewis, 2013)
megaherbivores lost 4.6Ma before human hunting due to climate change (Faith et al., 2018)

Question 20

aDNA of sediments

Answer 20

contains plant aDNA- DNA metabarcoding of plant diversity demonstrates decline in forbs coinciding with decline in megafauna
Coprolites suggest megafaunal diets had high forb content

Question 21

Plaid-stripes model

Answer 21

Holocene is ‘striped world’ with clear latitudinal climatic bands
Pleistocene is ‘plaid world’ with dramatic fluctuations
Climate change from one to other as a driver for megafaunal extinctions?

Question 22

Blitzerieg model

Answer 22

Martin, 1973
Human hunting of megafauna so quick that there was no time for archaeological evidence to accumulate

Few believe anymore, accurate radiocarbon dating demonstrates that humans and other megafauna coexisted for far too long to drive a near immediate disappearance

Question 23

Evidence of human hunting

Answer 23

On every continent
eg. killing and butchering site in Pampas of Argentina shows hunting giant ground sloth Megatherium americanum (Politis et al, 2019)

Australia, fungus Sporormiella has been used to show pattern of megafaunal decline matches spread of humans, and in Tasmania arrival of humans was v quickly followed by extirpation (Rule et al., 2012)

Question 24

Wrangel island

Answer 24

eg. extinction of mammoths, which were driven to refugia like Wrangel Island due to vegetational shifts (between 40,000 and 6000 years ago, the climatic envelope suitable for them decreased by 90%). Wrangel island separated from mainland 12,000 years ago, offered steppic refuge for those isolated with it.
Estimated to be 180cm shoulder height compared to 320cm on mainland
Final pop went extinct quickly at same time as human arrival, 4000 years ago, as demonstrated by autosomal microsatellite markers (Nystrom et al., 2012)

Range contractions increase vulnerability to extinction through decreased and restricted populations, humans finish off

Question 25

Island biogeography

Answer 25

MacArthur and Wilson (1963) Number of species on an island dependent on a balance of immigration and extinction Two critical factors controlling number of species on an island are island size and relative isolation

Question 26

Pleistocene islands

Answer 26

Sunda shelf became separate islands during Pleistocene eg. Philippines, Indonesia and Malaysia Show species-area relationship, fewer species than comparative mainland areas- effect of isolation

Question 27

Leopards on Sumatra

Answer 27

Once part of Sunda shelf Leopards were extirpated from Sumatra in the Late Pleistocene, due to competition with the Asiatic Wild Dog and other medium-sized cats (Volmer et al., 2017) Large island but its isolation restricted leopard ability to escape competition

Question 28

Tigers on Java

Answer 28

Once part of Sunda shelf Competition with Merriam's dog and Homotherium for prey during Pleistocene Greatest niche overlap between tiger and Merriam's dog Drove decrease in size of dog to reduce competition (Volmer et al., 2016)

Question 29

The Island Rule

Answer 29

Change in body size on island Has many exceptions Now believed that size of mainland population influences the size of island population Insular dwarfism of herbivores may be drive by competition and predation Insular dwarfism of carnivores may be driven y resource availability (Raia & Meiri, 2006)

Question 30

Red Deer on Jersey

Answer 30

Rapid dwarfism- island deer had 6x lower body mass than mainland relatives (Listerm 204) Isolated by a dramatic increase in sea level during Eemian- evolved in less than 6000 years Dwarfism because island resources were limited and there was no predation pressure Extinction of Jersey dwarf deer likely due to introgression from mainland populations when sea levels exposed the land bridge again

Question 31

Palaeoloxodon falconeri

Answer 31

20x lighter than modern African elephant (Larramendi and Palombo, 2015)

Question 32

Sulawesi

Answer 32

Always been isolated from mainland, therefore only inhabitants must have reached by ocean crossing May explain absence of large terrestrial carnivores (In contrast to islands previously part of Sunda shelf- influenced by mainland faunas eg. Java had orangutans, gibbons and Asian elephants by the Late Pleistocene) Continually isolated islands like this (also Crete, Madagascar, Flores) characterised by mammalian Pleistocene communities of elephants, deer and hippopotamuses- must be capable of sea faring

Question 33

Disadvantage of only using modern genetic data

Answer 33

Results in time averaged and biased interpretation of changes in population size, movements and selection pressures

Question 34

aDNA

Answer 34

preserved skins, mummies, archaeological bones, hair, teeth, coprolites, sediments absent from most of fossil record- instability and vulnerability to attack from water and oxygen- therefore best preserved in cold, dry, anoxic conditions eg. permafrost burials/ caves such as Vindija Cave, Croatia (where first Neanderthal genome sequence was obtained- (Green et al., 2010)). aDNA retrieved using next-generation sequencing, suitable for the small fragments usually found (previously PCR)

Question 35

Collared lemming aDNA evidence for Pleistocene extinctions

Answer 35

Brace et al., 2012 Dicronstonyx, small tundra-specialist Observed decrease in species diversity over last 50ka, and significant population size fluctuations through Late Pleistocene, representing series of extinction-recolonization events, which they link to climate fluctuations Climate associated local extinctions of keystone prey species- could have had wider reaching effects on ecological community Demonstrates role of climate change in end Pleistocene extinctions

Question 36

aDNA of steppe bison in North America

Answer 36

suggests decline was over 20ka earlier than signs of significant human presence (Willerslev & Cooper, 2005) Although absence of evidence isn't evidence of absence

Question 37

Modern human dispersal

Answer 37

genetic data favours theory that anatomically modern humans originated in Africa and later dispersed into Eurasia and Oceania to replace pre-existing archaic hominins from early migrations (rather than transition from Homo erectus to modern humans occurring in different regions of the old world)

Question 38

Split between Neanderthals and modern humans

Answer 38

ca. 550-765 kyr | based on genetic data

Question 39

Neanderthal distribution

Answer 39

based on aDNA spread into Europe and the Levant, and have been detected as far east as the Okladnikor and Denisova caves in Western Siberia (Krause et al., 2007)

Question 40

Denisovan humans

Answer 40

Finger bone discovered in Denisova Cave, Siberia (Reich et al., 2010) belonging to previously unknown hominin taxon, Denisovans Also found a molar that carries a mitochondrial genome highly similar to that of the finger bone- shares no derived morphological features with Neanderthals or modern humans, indicating that Denisovans have an evolutionary history distinct from Neanderthals and modern humans (this cave shows evidence of Neanderthals and Homo sapiens having lived in it - not necessarily at the same time) Also found evidence of fossils with mixed parentage eg. bone fragment "Denisova 11" from Denisova cave with Neanderthal mother and Denisovan father (Slon et al., 2018). mother came from a population more closely related to Neanderthals who lived later in Europe than to an earlier Neanderthal found in Denisova Cave, suggesting that migrations of Neanderthals between eastern and western Eurasia occurred sometime after 120,000 years ago & suggests that mixing was common when they met Some present day humans derive up to 5% of their ancestry from Denisovan humans, an even larger proportion than the ~2% from Neanderthals.

Question 41

European bison (wisent) origins

Answer 41

Soubrier et al. (2016) used ancient mitochondrial genomes and genome wide nuclear DNA surveys to suggest it was product of hybridization between steppe bison and aurochs 120kya Later reanalysis of the ancient mitogenomes rejected hypothesis, suggesting instead that it maintained parallel evo with the steppe bison in Eurasia, with gene flow between preventing speciation until migration of steppe bison to America (Grange et al., 2018). The set of SNPs initially used derived from modern cattle (descended from aurochs) so perhaps elevated their apparent relatedness

Question 42

Astronomical theory

Answer 42

developed by James Croll and elaborated by Milutin Milankovitch, 1920s Based on assumption that surface temps of Earth vary in response to regular and predictable changes in the Earth's orbit and axis

Question 43

Changes in earth's orbit affecting the amount of insolation

Answer 43

Eccentricity- how much orbit deviated from a circle to an ellipse- with the sun located at one end of the ellipse- dominant periods 100 kyr Obliquity- inclination of the Earth's axis of rotation with respect to Earth's orbital plane. Ha varied between 22 and 24.5 degrees- dominant periods 41 kyr Precession- wobble of the Earth's axis of rotation- main components around 21kyr Additional elements that moderate or amplify effects: - changes in disposition of the continental landmasses - tectonic activity - feedback mechanisms caused by oceanic circulation and changes in extent of ice cover - variation in constituents of the atmosphere (esp. CO2, CH4 and dust particles)

Question 44

Oxygen isotope records from deep sea cores

Answer 44

Sediments accumulate in relatively undisturbed manner consist party of terrigeneous sediments and biogenic sediments (calcareous and siliceous skeletal remains of small organisms that lived in ocean eg. benthic and planktonic foraminifera) Oxygen isotope analysis of microfossils tells us about global environmental change and stratigraphic record. because marine organisms secrete carbonate structures that reflect the oxygen isotope composition of the water in which they lived fractionation of water from sea surface preferential for lighter H2 16O (over 18O)- winds going towards polar ice contained more 16O In glacial stages, much H216O trapped in ice caps, so ocean 18O enriched therefore oxygen isotope ratios tell us about global ice volume produces marine isotope stages

Question 45

Marine isotope records tell us

Answer 45

cold periods much longer than warm periods asymmetrical form of each peak on the graph indicates takes longer to build an ice-sheet than to remove it climatic cycles have not been constant but have shifted from a periodicity of ~ 41ky prior to 900-800kyr to ~100kyr over last 800kyr = the mid-Pleistocene revolution/ middle Pleistocene transition (shift accompanied by intensification of glaciation)

Question 46

Loess

Answer 46

wind-blown silt deposited in cold stages containing a series of buried soils formed in temperate stages occur in central Europe and Asia, esp China Several loess sequences convincingly correlate with isotopic records from the deep sea therefore correlation between continental and isotopic records

Question 47

Maar lakes

Answer 47

long-lived lakes created in the aftermath of volcanic activity eg. in Massif central in France or lakes in Greece (Ioannia) Lake sediment contains pollen record, allowing vegetational successions to be reconstructed allows greater temporal resolution than marine sequences- accumulated more rapidly several sequences have been correlated with marine record

Question 48

Last glacial stage (Devensian)

Answer 48

began 75kyr ago 11 million square miles were ice-covered that are ice free today sea levels fell by 130m, connecting many islands to mainland vegetation= herbaceous communities, open treeless landscapes atmospheric CO2 and CH4 levels lower contained a number of short-lived warmer intervals (interstadials)- oscillation between = Dansgaard-Oeschger events, with durations of 500-2000 years energy transfer in the world's oceans driven by salt-density variations ('North Atlantic thermohaline circulation') and chemical changes resulting from biological activity believed to underlie DO events

Question 49

Ice-rafted debris & Heinrich events

Answer 49

where glaciers reach the coast, calving bays produce sediment-laden icebergs as icebergs drift south they melt and release the debris => ocean floor termed 'Heinrich layers' - record of terrestrial ice sheet instability each event accompanied by decrease in sea surface temperature and salinity

Question 50

Association hypothesis vs Individualistic view

Answer 50

AH- Clements, 1916 community = a superorganism, which remains stable through time IV- Gleason, 1926 all associations between species are the result of individuals acting in self-interest supported by pollen evidence

Question 51

Refugial locations for temperate species during cold spells in Europe

Answer 51

Peninsular regions of Iberia, Italy and the Balkans based on isopoll mapping, and from direct pollen analytical and genetic evidence as climate warmed, pops at Northern limits of refugia would have expanded North, as leading edge => founding events led to loss of alleles, increased homozygosity eg. grasshopper, bear, hedgehog Tendency for increased homozygosity may be increased by smaller climatic oscillations Therefore regions with genomic variability- greater diversity in South

Question 52

The Baldwin effect

Answer 52

Behavioural accommodation allowing animal to remain in location and therefore subjected to natural selection to develop morphological or physiological adaptations to the new conditions

Question 53

Distributional shifts

Answer 53

Tracking preferred environment= alternative to evolution? but, change in distribution often entails selective deaths which may lead to adaptive evolution, and subdivision of populations, which may result in differentiation or even speciation. Mammals responding w range shifts: -reindeer Arctic -> southern Europe between interglacials and glacials -hippopotamus from Africa -> central Europe between glacials and interglacials distributional shifts according to temperature will expose to new changes eg. daylight conditions, substrate, competitor or predator/prey

Question 54

Ecophenotypic modification links to evolution

Answer 54

selection of animals genetically predisposed to respond ecophenotypically in adaptive morphological direction eg. island dwarfism, poor nutrition effects have become entrenched and enhanced facultative adaptation, adapted by nat. selection to respond ecophenotypically in adaptive way to environmental change eg. adaptive changes in red deer rumen morphology depending on diet raised on: on grass, open rumen with small papillae on browse, large flat papillae accommodation occurs within 2-3 weeks (red deer also has fixed but broad use adaptations eg mesodont teeth, can take in mixture of soft browse and abrasive graze)

Question 55

Bergmann's Rule

Answer 55

increased body size with latitude in modern species adapted to theory that body size responds inversely to ambient temperature as an adaptation for heat regulation by altering SA:vol ratio some contest, saying that duration and abundance of plant growing season is primary determinant of herbivore body size, which in turn selects for carnivore body size

Question 56

Polar bear evolution

Answer 56

origin linked to great expansion of ice-sheets and ice-floes | thought to be derived from a peripheral coastal population of brown bear between 0.5-0.25 My

Question 57

Musk-ox and reindeer origin

Answer 57

adapted to true tundra, a biome unknown before 2.5 My

Question 58

Woolly mammoth, woolly rhinoceros and bison origin

Answer 58

adapted to dry northern grassland known as 'tundra-steppe' or 'mammoth steppe', a Quaternary environment

Question 59

Moose (elk) evolution

Answer 59

Alces genus Largest living species of deer Early evolution in Eurasia Three chrono-species: Alces alces (0.1 Ma - present), N. Europe, Asia, N. America Alces latifrons (0.7-0.5 Ma). Early Middle Pleistocene. Eurasia and N. America Alces gallicus (2.0-1.5 Ma). Late Pliocene to early Pleistocene. Europe appear to form direct line of descent: - share a derived suite of dental and skeletal features peculiar among deer, indicating close relatedness - follow each other in time and replace each other in geographic distribution - no other presumptive ancestors known

Question 60

Morphological trends in Moose evolution

Answer 60

Body size increase from gallicus to latifrons (50% larger at shoulder), decrease to alces Skull architecture modified (facial region deepened, nostrils shortened), as ways interpreted as adaptive to a shift to boreal forest Relative length of antler beam reduced in both steps (note take into account size differences between populations to which antler size if allometrically linked, and individual ontogenetic variation- males replace every year, have to compare at similar ages)

Question 61

Adaptive explanations for reduction in moose antler length

Answer 61

gallicus to latifrons, greatly increased body size requires relative decrease in antler size to reduce mechanical stress on skull latifrons to alces, change in habitat from open steppe-grassland to coniferous woodland- 2m span as in others would impede movement

Question 62

Mammoth adaptive evolution

Answer 62

Mammuthus believed to have evolved in Africa where earliest know 56My found (Mammuthus subplanifrons). Entered Europe 3.5 My by passing through Levant into eastern Mediterranean range. Earliest known Eurasian mammoth = M. rumanus, 3 My, known from Lavant, Romania, Bulgaria, Itlay, eastern England, north-east China, appeared to be browser ``` Cold-adapted forms later, 3 chrono-species: Mammuthus primigenius (Woolly). Upper Pleistocene. 0.35-0.01 My Mammuthus trogontherii (Steppe). Middle Pleistocene. ~0.7-~0.5 My Mammuthus meridionalis (Southern). Plio-Pleistocene- Lower Pleistocene. 2.6-0.7 My. ``` appear to be direct line of descent: - no alternative progenitors - possess shared derived characters (high skull, twisted tusks) - occur in chronological succession

Question 63

Morphological trends in Mammoth evolution

Answer 63

Heightening and shortening of cranium and mandible Doubling number of enamel lamellae in molars Doubling of molar crown height Thinning of enamel changes effectively increase 'tooth life', thought to be adaptations to more efficient grazing of coarse vegetation of steppe tundra

Question 64

Mammoth evolution Siberia compared to Europe

Answer 64

similar morphological trends as seen in Europe occur on Siberia and Asia consistently earlier eg. meridionalis to trogontherii late Pliocene- early Pleistocene of eastern Asia trogontherii to primigenius ~800-600 kyr (several thousand years earlier) migration of these forms into Europe (not actually in situ evolution in Europe) makes sense for evolution in Siberia- permafrost environment since 2.5My (mammoth steppe)

Question 65

Water vole evolution

Answer 65

semiaquatic rodents that inhabit banks of rivers and streams fossil record covers all of Quaternary Today- Arvicola terrestris (continuously growing molars) earlier 'primitive' = Mimomys (rooted molars) transition between important biostratigraphical marker horizon in early middle Pleistocene Morphological trends: - development of enamel islet on occlusal surface (~3 My) - appearance of cement in grooves (~2.5 My) - loss of enamel islet (~1.2 My) - Loss of roots (~0.5 My) - the last Mimomys - Development of continuous growth of teeth (0.5 My)- the first Arvicola

Question 66

Arvicola molar evolution

Answer 66

Over last 0.3 My Molars consist of a series of enamel loops, each formed of a concave 'leading' edge and convex 'trailing' edge leading edges first come into play in mastication Earliest Arvicola (A. cantiana), early Middle Pleistocene inherited unusual thickening of trailing edge from ancestor Upper to middle Pleistocene, reduction in thickness of trailing edge until thinner than leading Transition quantified by calculating 'index of enamel differentiation' Unidirectional trend showed several fluctuations, eg reversal between penultimate cold stage and last interglacial)- probably represents population replacement

Question 67

Deer on Crete

Answer 67

never been connected to mainland deer arrived by sweepstake dispersal, diversifying over several thousand years of the middle and late Pleistocene into 7 or 8 endemic forms Postcranial features and unique antler morphology indicate full species status

Question 68

Homo floresiensis

Answer 68

~1m tall, small brained (380cm3) found in Liang Bua cave on Flores, 2004, though to be 60-100 kyr Partial skeletons of 9 individuals now known, with 1 complete skull No chin, more projecting face with relatively large teeth, brow ridge combination of primitive and derived features means new species Flores surrounded by deep water and never been connected to other land during quaternary, therefore must have reached by sea Likely long-term isolation with subsequent dwarfing of an ancestral H. erectus population shows that genus Homo more morphologically varied and flexible than previously thought Associated with the hominin were dwarf elephants (Stegodon) and Komodo dragons (incl. another even larger monitor lizard), giant rats and stone tools

Question 69

Humans into N. America

Answer 69

Late Pleistocene, ~ half N. America covered by ice-sheet part of Alaska remained ice free and was reached by people who had crossed from Beringia from NE Siberia- Clovis people Southern access blocked until corridor opened between shrinking ice sheets about 12,000 yr BP, entry into continent interior by 11,500 yr BP. Recent evidence suggest that humans may also have followed a coastal route that may have even reached S. America beginning of extinctions fits with arrival of humans in given region or with appearance of upper Palaeolithic hunting techniques BUT doesn't fit for Northern Eurasia, where humans had been present ~half a million years before the extinctions

Question 70

Broughton and Weitzel (2018)

Answer 70

coalescence techniques on aDNA were used to show that the arrival of Clovis people was coincident with declines in mammoths, sabre-toothed cats and horses in the USA