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Samenvatting Inleiding in de Antrozoologie
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Voorbeeld 4 van de 123 pagina's
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Voorbeeld van de inhoud
Thema 1 De Basis1.1 Mens-dierrelaties vanuit een evolutionair perspectief
Werkboek:
o Genetische variatie: individuele organismen verschillen in eigenschappen en de varianten van
die eigenschappen kunnen genetisch worden overgedragen van de ene op de andere generatie
o Natuurlijke selectie: eigenschappen die bijdragen aan voorbestaan en voortplanting raken
geselecteerd in de natuur, hierdoor komen die varianten in volgende generaties vaker voor
o Selectiedruk: het selectieve effect dat de natuurlijke selectie uitoefent op de genetische variatie
(bv roofdieren zijn een selectiedruk voor bruine konijnen, is medebepalend voor haarkleur
volgende generaties)
o Co-evolutie: vorm van evolutie waarbij diersoorten elkaars evolutie beïnvloeden en een
stabiele symbiose bereiken. Soorten vormen een selectiedruk voor elkaar en vinden daarin een
stabiel evenwicht. Term wordt echter meestal pas gebruikt als er sprake is van wederzijdse
samenwerking (= onbewust proces)
o Kunstmatig selectie: diersoorten die bewust elkaars evolutie beïnvloeden, intentioneel. Ene
soort beïnvloedt bewust de voortplanting van de andere soort.
o Domesticatie: specifieke vorm van kunstmatige selectie, door zorgvuldig ingrijpen in
voortplanting van dieren zorgen mensen ervoor dat diersoorten staat beter aangepast raken aan
leven nabij/in dienst van de mens
Artikel Larson and Fuller:
o Introgression: transfer of genetic information from one species to another as a result of
hybridization between them and repeated backcrossing
o Synanthropes: members of a species of wild animals and plants that live near and benefit from
an association with human beings and the somewhat artificial habits people create around
them
o Darwin (1868): 1st to recognize that domestic animals possess a wide variety of similar
morphological traits despite the lack of close evolutionary relationships between their wild
progenitors. Phenotypic convergence, animal equivalent of the domestication syndrome
recognized in plants (Harlan 1975).
o Galton (1907): suggested dogs were domesticated following the capture and nurturing of wolf
puppies in human camps. Domestication resulted as a consequence of goal-directed human
intention.
o Belyaev (1950’s): believed he could not only explain the appearance of the domestication
syndrome, but also how it could have resulted from a lack of both human intentionality and
selection pressures focused upon individual traits. Worked with a captive population of silver
foxes, selecting least aggressive individuals to breed. Resulted in acquisition of numerous
other phenotypic traits. Belyaev recreated the domestication syndrome by producing foxes
possessing traits that not only were never seen in wild foxes, but also had never been directly
selected for.
o Vigne (2011): proposed a multi staged model → gradually intensifying relationship between
humans and animals, continuum from anthropophily to commensalism, to control in the wild,
to control of captive animals, to extensive breeding and finally to pets.
o Anthropophily: preferring human beings to other animals
o Commensalism: association between 2 organisms in which 1 benefits and the other derives
neither benefits or harm
,o Zeder (2012): also a staged model approach; 3 separate pathways; commensal, prey and
directed.
o Commensal pathway: wild animals attracted to elements of human niche. Most capable of
taking advantage: tamer ones, less aggressive, shorter fight of flight distances. Referred to as
synanthropes. Most often reserved for pest species and not domestic animals. In Zeder’s
model the leap from a synanthropic population to a domestic one could only have taken place
after the animals had progressed from anthropophily to habituation, to commensalism and
partnership, at which point the establishment of a reciprocal relationship between animal and
human would have laid the foundation for domestication, including captivity and human-
controlled breeding. Responding to selective pressure while adapting to a novel niche that
includes another species. Human-directed selection associated with modern domestic
populations would only have been possible after animals adapted to take advantage of the
human environment. Absence of active human instigation.
Genetic data suggests that a long-term bidirectional gene flow between wild and domestic
stocks was common (Marshall et al, 2014). Cessation of gene flow is a recent phenomenon.
The establishment of domestic populations following a commensal route requires 2 criteria:
a) Mechanism that genetically differentiates nascent domestic population from its wild
progenitor
b) Evidence that gene flow between 2 populations would not break down the differences
essentials to maintaining a domesticated status
Speciation in an allopatric (separated geographically) context is easily conceived. Sympatric
(evolution of a new species from a surviving ancestral species while both continue to inhabit
the same geographic region) speciation requires a reduction of gene flow through another
method than geography. The differing selection regimes experienced by one species living in
2 habitats (1 anthropogenic) would promote distinct constellations of adaptions through
destabilizing (or disruptive) selection. Habitat shifts may explain the emergence of domestic
animals following the commensal pathway. Example; dogs were derived exclusively from
gray wolves. First domestic animal, only domestication before agriculture. Domesticated by
mobile hunter-gatherers. Recent gray wolves studies: presence of significant genetic and
morphological differences in sympatric populations. Similar with arctic foxes. If the 2
populations continue to concentrate on different resource strategies for a sufficient period of
time, the 2 ecotypes could evolve sufficient genetic and/or behavioural differences and
become classified as a separate species. Differences significant enough → elevation from
ecotypes to full species. Different ecotypes can maintain their integrity despite significant
gene flow. Thus, anthropophilic animals could have evolved a synanthropic ecotype
characterized by adaptions to the human niche. Having initiated and sustained the divergence,
they could have then become domesticated through more intensive human selection.
o Prey pathway: begins with human action. Primary motive was however not to domesticate but
to increase efficiency of resource management. Medium to large herbivores targeted as prey.
They were wary of humans and not attracted to the human niche. Humans likely altered
hunting strategies to maximize availability. Associated with more settles human communities
that cultivated plants. Changes in management strategies of hunted sheep, goats, pigs and
cows starting early Holocene, about 11.7 kya. By 10 kya people were preferentially killing
young males, allowing females to live to produce more offspring. Cow and pig species were
severely overhunted before domestication. Led to management strategies that ultimately led to
domestication flowing the prey pathway.
Suggests this pathway was as accidental and unintentional as the commensal pathway. No
desire to completely control the animal, but to increase the supply of vanishing resources.
Evolutionary pressures for a lack of aggression would have led (as Belyaev demonstrated) to
, an acquisition of the same domestication syndrome traits found in the commensal
domesticates despite having entered the human niche through completely separate trajectories.
o Directed pathway: only pathway that began with a deliberate objective to domesticate a
species. Before these taxa were targeted, humans already possessed and were reliant upon
domestic plants and animals. Animals such as horses, donkeys and camels → brought into the
human niche for reasons such as transport. Domestication was a multigenerational adaption to
human selection pressures, including tameness (for instance; neither gazelles nor zebras
possess the necessary prerequisites and were never domesticated). Majority of modern
domestic animals have arisen in the past few hundred years because of the directed pathway
(including most small pets).
o Zeders pathways is the first framework that allows for a comprehensive consideration of
accidental and intentional selective pressures associated with the context of how separate
species entered the human niche.
o Early animal domestication is associated with perhaps only 3 regions; Near East, central China
and the Andes. Animal domestication was relatively rare not only on a global scale, but also
within the area traversed by the wild species. Many more animals were domesticated after the
establishment of agricultural societies and often in regions distant from centres of pant
domestication.
o Commensal pathway taxa: earliest domestic animals all followed the commensal pathway,
although processes did not take place simultaneously. Dogs were first, across Eurasia before
the end of Pleistocene. Cats also followed the commensal pathway ~11.000 years BP
(attracted to pests, including mice that colonized early grain stores). Pigeon keeping first
appears in Mesopotamia and Egypt. Guinea pigs in the Ades took advantage of kitchen waste,
~5 kya. Polynesian rat may have also followed this pathway
Pathway of pigs is less clear. They were hunted, but may also have followed the commensal
route (consuming human waste), at least ~ 3.000 years. Chickens were attracted to kitchen
scraps, animal dung and crop-processing waste, by at least 4.500-4.000 years BP. Duck and
geese were possibly attracted to rice paddies. Carp similarly. `
o Prey pathway taxa: larger meat animals more often followed this pathway. Likely hunted first,
more intensive strategies were necessary to mitigate the effects of overhunting. Sheep, goats
and cattle in western Eurasia between 10.500-10.000 years BP. There is no clear evidence for
the domestication of a herder prey animal in Africa. This suggests that domesticated cattle
were introduced from western Eurasia and subsequently interbred with Saharan wild
populations. Reindeer also followed this pathway but were domesticated by nomadic hunting
societies, not sedentary cultivators. Early attempts in Norway from 6.700-6.200 years BP,
sledge runners from 6.000-5.000 years BP. Herding is thought to have begun 3.000-2.000
years BP. In the Americas: llamas, alpacas, turkeys and Muscovy ducks followed this
pathway. Llamas and alpacas 6.000-5.000 years BP, turkeys 2 kya, Muscovy ducks about 4
kya.
o Secondary products diversification: many prey pathway animals underwent diversification for
additional uses, including textile fibres, egg, milk and traction. Each of these adaptions (or
‘improvement traits’) occurred as part of post domestication diversification processes often
associated with economic specialization in the context of emerging complex societies. Only
regional populations were involved. Some secondary products, like eggs or milk, are
metabolically expensive and, under wild conditions without the aid of human food provision,
likely to be limited in production.
o Directed pathway taxa: usually postdating secondary products revolution, often occurred in
regions peripheral to those where early animal domestication took place. Domestication of
animals like donkeys and camels, which provided more efficient transport than cattle carts, is
, entangled with the expansion of trade and agriculture into new regions. Horses may have been
tamed and ridden firstly as an efficient means to hunt (7.000 years BP). Intensive breeding
(5.500-4.000 years BP) → used for trade transport, warfare and horse milking. Insects also
followed this pathway. Artificial honey bee hives 3.000 years BP in Jordan. Saturnid moths
for silk from about 6.000 BP, but domestication evidence 3.500 years BP. Secondary food
animals, generally much smaller than the early herded food animals, include rabbits, birds and
fish.
First domesticated animals in each region followed either a commensal or prey pathway.
Neither of these began with the intention to create a domestic animal. Integration of
domesticated animals in human societies created a model and a goal that people could
envision when considering other animals. Total umber of domesticated animals doubled in
middle Holocene (8.000-4.000 years BP), the majority however have been domesticated in the
past few centuries, including numerous small pets, fresh water fish and marine species. All
recent domestications were the result of a directed pathway, this has corrupted our impression
of the initial evolutionary process of animal domestication. People could not begin
intentionally domesticating animals until they had procured them through entirely
unintentional means.
o Conclusions: Many domestication episodes are genetically and archaeologically poorly
documented. Clearer framework is emerging. Initial pulse occurred during early Holocene,
after that animals were domesticated with increasing frequency, entangling numerous species
into human environments and economies. Beginnings of animal domestication involved a
protracted co-evolutionary process with multiple stages along different pathways. Humans
became entangled with these species as the relationship between them, and the human role in
their survival and reproduction, intensified.
The necessary circumstances appear to have coincided rarely. Gene flow (or introgressive
capture) between domesticated animals and other populations occurred frequently, often
significantly affecting the genomes and phenotypes of the domestic animals.
Once domestication became established, a relaxation of natural selective pressure allowed for
the appearance of mutations related to novel traits. By recognizing and selecting for these
changes, the genomes of domestic animals became even more differentiated from their wild
ancestors. Some of these traits were linked to fashion (coat colour), others economically
motivated (milk, wool, egg-laying). Many of these traits were exaptations (shift in the function
of a trait during evolution) or rather emergent accidental properties that resulted as the
domestication process shifted from unconsciousness to increasingly conscious selection.
Werkboek:
o Domesticatiesyndroom: set eigenschappen die in alle gedomesticeerde diersoorten lijkt voor te
komen, vaak gaat het om eigenschappen die de dieren in onze ogen schattiger of kinderlijker
doen voorkomen (grotere variatie in kleur en textuur van vacht, hangoren, volgzaamheid,
verschuivingen in ontwikkelingscyclus, variaties in schedelvorming en plaatsen van tanden,
dwerg- en reuzenvarianten).
o Belyaev: selecteerde zilvervossen op slechts 1 eigenschap: tolerantie voor menselijke
aanwezigheid. Ondanks een gebrek aan andere selectiedrukken trad het domesticatiesyndroom
binnen enkele generaties op. Conclusie: domesticatiesyndroom hoeft niet te ontstaan door
kunstmatige selectie, maar kan bijproduct zijn van een natuurlijk selectie op tolerantie van de
dieren voor menselijke aanwezigheid. Dus het gevolg van een authentiek evolutionair proces,
niet van intentioneel ingrijpen
o Mogelijk gaat het een combinatie van beide; waarschijnlijk neemt in 1 e instantie (door
vreedzaam samenleven met mensen) de natuurlijke selectiedruk af, waardoor meer variatie
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