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ARCH2108 Animals, plants and people : The process, recognition and progress of animal domestication

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Title: ARCH2108 Animals, plants and people : The process, recognition and progress of animal domestication


1
ARCH2108Animals, plants and people
The process, recognition and progress of
animal domestication
2
What is a domestic animal?
  • Domestic animals may be provisionally defined as
    those kept and bred in and around human
    habitation to be used constantly to human
    advantage.
  • Hemmer, 1983/1990
  • A domestic animal is one that has been bred in
    captivity for purposes of economic profit to a
    human community that maintains complete mastery
    over its breeding, organization of territory, and
    food supply.
  • Clutton-Brock, 1981

3
In its most developed form the domestic animal
exhibits four principal characteristics
  • 1. Its breeding is under human control.
  • 2. It provides a product or service useful to
    man.
  • 3. It is tame.
  • 4. It has been selected away from the wild type.
  • Mason, 1984
  • Zoo animals meet criterion 1, but not the others
  • Working elephants meet criteria 2 and 3, not 1
    and 4
  • Do laboratory animals meet all criteria?

4
Fully domesticated mammals have undergone
parallel changes
  • Increased colour variability
  • Paedomorphosis
  • Brain reduction
  • Docility
  • Earlier maturation
  • Verarmung der Merkwelt

5
Merkwelt
  • A concept proposed by
  • Jacob von Uexküll (1864-1944)
  • Estonian biologist, regarded by many as the
    founder of ethology.
  • - An animals world is partitioned into its
  • Umwelt - what it experiences (environment)
  • Merkwelt what it perceives (knowledge)
  • Werkwelt what it does (actions)

6
Verarmung der Merkweltcan be translated
Impoverishment of the Perceptual World
  • In Hemmers model, domestication is a process of
  • selection for docility
  • which in turn involves reduction of
  • stress, behavioural flexibility, aggression,
    activity patterns, sensory awareness
  • - in sum,
  • impoverishment of the Merkwelt.

7
  • Catecholamines
  • produced by nervous tissue and adrenal glands
  • stress hormones
  • (increase heart rate, blood pressure, muscle
    strength and alertness).
  • The most important are
  • adrenalin (epinephrine)
  • noradrenalin (norepinephrine)
  • dopamine.
  • Melanins
  • are produced by the same biochemical pathways as
    catecholamines.
  • Can we predict a link between pelage colour and
    stress susceptibility?

8
Keeler (1975)Research with colour morphs of Red
Foxes (Vulpes vulpes)
  • Wild type Silver Pearl Amber Non-agouti Non-ago
    uti/ Non-agouti/
  • black silver dilution dilution/brown

Body wt. Adrenal wt. Catecholamine products in
urine Flight distance
9
D.K.Belyaev (1917-1985)
  • Bred silver foxes (Vulpes vulpes) at the
    Institute of Cytology and Genetics in
    Novosibirsk, western Siberia, Russia
  • Selected them only for tameness
  • Phenotypic and physiological changes were
    obtained as by-products

10
Tame silver foxes
(About 18 generations)
11
Phenotypic changes
Homozygous White Spotting (SS) About F8-10
12
Belyaevs fox line also developed
  • Curly tails
  • Drooping ears
  • Out-of-season breeding activity
  • Longer moulting time

13
Paedomorphosis
  • Retention of juvenile characters into the adult
    stage
  • Short face
  • Broader skull
  • Increased kyphosis (basicranial flexion)
  • In cattle shorter, less inturned horns
  • In sheep and goats shorter horns, even absent in
    female
  • Playfulness
  • Other juvenile behaviours barking in dogs,
    kneading in cats

14
Brain reduction
  • Domestic species have brains reduced compared to
    their wild ancestral species
  • Different domestic species or even breeds have
    different degrees of size reduction
  • A few dog breeds have been selected for
    re-enlargement

15
Measuring brain size reduction
  • On whole body samples
  • Weigh body and brain
  • Graph brain weight against body weight (usually
    double logarithmic)
  • On skulls
  • Measure cranial capacity (endocranial volume
    ECV)
  • Take cube root
  • Graph it against a size standardisation measure
  • Calculate difference between intercepts of wild
    and domestic samples

16
Example camels
wild
Cube root of ECV
Domestic Bactrian
Domestic Arabian
Basal skull length
17
Percentage brain size reductions(brain vs body
weight method)according to the Kiel school
  • Laboratory mouse 0
  • Laboratory rat 8.7
  • Guinea pig 5-7 (different studies)
  • Cat 23.4
  • Ferret 32.4
  • Dog 29-34 (different studies)
  • Pig 33.6
  • Sheep ca 30
  • Llama and alpaca 19.0

18
The Kiel school(Institut für Haustierkunde,
Kiel)Herre, Röhrs, Ebinger, Kruska, Fischer
  • pool all wild specimens to calculate the
    allometric slope and intercept for the wild
    ancestral stock
  • Hemmer
  • keeps samples from different wild populations
    separate, and calculates slope and intercept for
    just the population supposed to be the source of
    the domestic form

19
hence -
  • Cat
  • 23 reduction (Herre Röhrs, 1973)
  • (recalculated as 18 by Röhrs Ebinger, 1978)
  • 10 reduction (Hemmer, 1976), using just North
    African/Middle Eastern wild cats as baseline
  • Dog
  • 234 reduction (Herre Röhrs, 1973)
  • (recalculated as 29 by Röhrs Ebinger, 1978)
  • 10 reduction (Hemmer, 1976), using just North
    Middle Eastern wolves as baseline

20
Different regions of the brain have been
differentially reduced
  • Forebrain Corpus Midbrain Cerebellum
    Medulla
  • callosum
  • Rat 10.1 6.3 3.8 5.7 3.6
  • Cat 26.0 - - - -
  • Dog 35.0 31.0 19.0 32.0
    23.0
  • Ferret 36.8 32.7 17.4 23.9
    16.0
  • Pig 36.0 32.6 26.1 26.0
    24.6

21
So, of total brain reduction -
  • 71 (rat) to nearly 80 (others) is due to
    forebrain, mainly neocortex
  • 7 is due to corpus callosum
  • 2-3 is due to midbrain (primary sensory
    stations)
  • 13 (rat) but only 9-10 (others) is due to
    cerebellum (balance and muscular coordination)
  • 5.6 (rat) but under 4 (others) is due to
    medulla

22
Kruska (1980) measured reduction of different
sensory regions of the neocortex in pigs
  • Sensory centres reduced in the order
  • Optic
  • Acoustic
  • Olfactory
  • Amygdala (concerned with rage control) reduced by
    29 (somewhat more than olfactory bulbs)

23
Feral populations have not increased brain size
  • Cats
  • Rabbits
  • Ferrets
  • Dogs, including dingos
  • Pigs
  • Goats
  • Relative brain size can therefore be used as a
    test for whether a wild-living population is
    truly wild or feral

24
Features favouring domestication in a wild
species (Hale, 1962)
  • Group structure
  • Large social groups, hierarchical structure,
    males affiliated with female groups
  • Not territorial
  • Sexual behaviour
  • Promiscuous matings
  • Male does not have to establish dominance over
    female
  • Not monogamous
  • Sexual signals behavioural, not morphological

25
Features favouring domestication in a wild
species (continued)
  • Parent-young interaction
  • Precocial
  • Defined imprinting period
  • Female accepts other infants
  • Responses to humans
  • Short flight distance
  • Tolerant to environmental changes
  • Other
  • Adaptable
  • Unspecialised diet
  • Limited agility

26
Examples from Middle East
Why domesticate
- and why not
Goat?
Ibex?
or oryx?
or sheep?
or even gazelle?
27
Comparison between those which were domesticated
and those which were not
  • Sheep and goats
  • Group size 10-20
  • Hierarchies
  • Leadership
  • Males often part of female groups
  • Form tending bonds when mating
  • Short flight distance
  • Very environmentally tolerant
  • Generalised diet, wide adaptability
  • Fair to low agility
  • Foster abandoned infants
  • Ibex, oryx and gazelle
  • Group size 9-45
  • Non-hierarchical
  • No marked leader roles
  • Males part of female groups in ibex, oryx not
    gazelle
  • Mate in harems (ibex) or lek (oryx, gazelle)
  • Long flight distance
  • Ibex environmentally tolerant oryx, gazelle not
  • Adaptable (ibex), specialist (oryx, gazelle)
  • High agility
  • Do not foster (ibex uncertain)

28
But why the Ass and not the Onager?
Wild ass Equus africanus
Onager Equus hemionus
29
Wild asses and onager both - live in
female-young herds - males are territorial -
mate in leks - are very agile - but
  • Wild ass
  • Short flight distance
  • High environmental tolerance
  • High dietary adaptability
  • Onager
  • Long flight distance
  • Nervous, temperamental, specialized habitat
  • Dietary specialist

30
How did they come to be domesticated
anyway?Zeuners model
  • Scavengers - pig, dog, duck
  • Social parasites - reindeer, sheep, goat
  • Crop-robbers - cattle, buffalo, elephant,
    rabbit, goose
  • Pest-destroyers - cat, ferret
  • Transporters - horse, ass, camelids
  • - plus those that were systematically
    domesticated
  • fowl, hyaena, ostrich, mouse, rat, canary

31
Zeuner (1963) proposed that there were 6 stages
in the domestication of a species
  • Loose ties species is essentially wild
  • Captivity restriction of contacts with wild
    population
  • Intentional breeding for tractability
  • Planned development bred for economic and other
    characters, development of breeds
  • Elimination of the wild species as competitors

32
How can we tell if a set of remains are from wild
or domestic?
  • Size changes
  • Most domestic species are smaller than their wild
    relatives (except for some specialized breeds)
  • BUT
  • At end of Pleistocene there was a rapid size
    reduction in most large mammals anyway

33
How can we tell if a set of remains are from wild
or domestic? contd.
  • Demographic changes
  • Domesticators slaughter high proportion of
    juveniles for meat and to keep the milk for
    themselves (and most juvenile males, to select
    high-quality stud breeders), so samples will have
    a high proportion of immatures
  • BUT
  • Wild predators select their prey to much greater
    extent than is often realized, so natural kills
    may be skewed towards immatures too.

34
How can we tell if a set of remains are from wild
or domestic? contd.
  • Changes in bone structure
  • Daly, Perkins Drew (1971) claimed that, in
    metapodials, tali, phalanges and scapulae,
    domestic animals have more abrupt transition
    between compact and spongy bone -

Wild (Suberde)
Domestic (Erbaba)
Sections of distal articular surfaces of goat
metapodials
35
- and that the trabeculae are thinner, the
lacunae more rectangular.
Sheep tali
  • BUT
  • Daly et al.s material is archeological the
    model is not tested on recent samples.
  • Soil conditions might have played a part.
  • Watson, 1975

Domestic
Wild
36
Centres of Origin
6
7
9
1
8
2
3
4
5
37
Middle Eastern theatre of domestication
Cattle Sheep Goat Arabian camel? Pig Wild
ass? Cat?
Zagros
Mesopotamia
Anatolia
Levant
Lower Nile
38
Southeast Asian theatre
Buffalo Mithan? Pig
Pig
Banteng Pig
39
Central and South Asian theatres
Horse Bactrian camel
Yak
Humped cattle
40
And, presumably, Spain
Rabbit Ferret?
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