ANTH 311 Lecture Notes - Lecture 5: Natural Selection, Sociobiology, Primate

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Natural S e le c tio n a n d S o c io b io logy
ADAPTATION AND EVOLUTION PROCESS OF BIOLOGICAL CHANGE OVER TIME
- An a daptation (a ls o known a s microe volution) is a s hort te rm cha nge within a s pecies over a
fe w ge nera tions (e.g. moth wings change colour)
- Evolution (a ls o known a s ma croevolution) is a long term change that results in the
appea ra nce of ne w spe cies
- How do s pecies change over time ?
- Spe cies change over time through a proce s s known a s natural se lection
- Natura l s e le ction is the primary me cha nis m of biologica l change over time (ada ptation and
evolution), i.e. it produces both short and long te rm cha nges
NATURAL SELECTION
- Natura l s e le ction is the ine vitable outcome of varia tion, inherita nce, a nd overproduction be ing
true
- When there is fission in monkey groups, one of the groups will ge t to keep home turf, othe rs
will be force d out
- Kyoto s now monke y: group of 300 individuals we re give n a huge amount of resources , due to
this , one la rge group divided (fiss ion) into 2 s malle r groups s o tha t social dynamics ca n be
ma naged a nd hierarchy can be ma inta ined (difficult to do with group of 300)
- Anothe r reason why the group broke : a n increase in the ava ila bility of re sources would le a d
to fe ma le s be ing able to reproduce more often, thus , a nother way that group would ge t
bigge r. If the group grew any bigger, it would be ve ry difficult to ma intain socia l dyna mics
and hie ra rchy. The re fore, 2 s malle r groups were forme d
- Natura l s e le ction was propos e d by Da rwin (a nd Alfred Wa lla ce), a nd is ba s e d on 3
funda mental observable fa cts:
- Variation
- Lots of variation within and be twe en s pecies
- Kids had the sa me type s of varia tion a s the pa re nts did
- Inheritance (of s ome of tha t variation)
- Variation passed on from pare nts to offspring
- Ove rproduction
- All spe cies give birth to more offs pring than ca n or do s urvive to a dulthood: competition
to s urvive to a dulthood
- The environme nt naturally s e le cts s ome forms (variations ) over others
- Some individua ls have morphologica l or be havioura l varia tions /tra its tha t he lps them
survive
- Individua ls who inhe rit va ria tions are more like ly to s urvive
- Survival and then re production is the ke y to unders ta nding adapta tion, a nd evolutionary
change over time
- Fitnes s the ability to live a nd re produce
- High biological fitne s s (good ge nes ) = high re productive s ucces s (more offs pring s urvive to
adulthood)
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- Ada ptation/Evolution by Na tural S e le ction (MEMORIZE Pos s ib ly o n FINAL EXAM)
- Pos s ible e xam question: Briefly expla in e volution by na tural s e le ction.
- ANSWER: The diffe re ntia l surviva l and reproductive succes s in ea ch parental ge ne ra l
(Natura l S e le ction) le ads to a cha nge in the frequency of traits from one ge nera tion to
the next a nd to animals be ing well-suited to their e nvironme nts (Adaptation/Evolution)
one is the inevita ble outcome of the other
- Natura l s e le ction ca nnot cre a te the varia tion that its looking for
- Natura l s e le ction ca n only se le ct from the variation that alrea dy is pre s e nt, if no exis ting
variation is be neficial, e xtinction is the re s ult
- What makes a variant a good one? It ha s to he lp the individua l survive and reproduce in its
lo cal environme nt
- Variation depends on the lo c al environme nt
- Summary
- Tra its tha t are well s uite d to the environme nt:
- Give individua ls an a dva ntage in surviva l and reproductive s ucces s, and appe a r in
increased freque ncy in future generations
- Tra its tha t are not well suited to the environme nt
- Put individua ls at a dis a dvanta ge in survival a nd re productive succe s s, a nd a ppe a r in a
de creased freque ncy in future ge nerations
- This is how the popula tion cha nge s over time. This is why a nimals a re ge nera lly well
ada pted to the ir environme nts
- 4 importa nt points about na tural se le ction and e volutionary change:
- Evolution (cha nge) opera te s on the popula tion, individuals do not “evolve”. Als o, it ca n only
operate on variation tha t alre a dy e xists, does n't crea te its own
- Natura l s e le ction opera te s on the individua l. Individua ls s urvive and reproduce , or not
- There is no s uch thing a s an absolute ly better varia nt depends on the environme nt
(ofte n a s ocial a re a )
- Variation ha d to be there in the first place
SOCIOBIOLOGY
- Develope d in the 1960s a nd 1970s with the developme nt of 3 main ideas:
- Kin s e le ction
- Re ciprocal a ltruis m
- Parenta l investme nt
- What is altruis m? (P o s s ib ly on FINAL EXAM)
- Popular definition: he lping, se lfle s s , sharing behaviour opposite of s e lfish behaviour
- Biological definition: beha viour tha t potentially (not a lways) improves the surviva l a nd
re productive s ucce s s of the recipie nt while pote ntia lly e nda ngering the a ctor
- In s hort: it is the beha viour tha t be nefits the recipie nt at a cos t to the a ctor
- To wha t e xte nt is a ltruis m a bout re ciproca tion?
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