Kind: captions
Language: en
[Applause]
what are evolutionarily stable
strategies in many cases it's kind of
clear what's the best thing for an
individual to do the best thing it can
do to increase its survival and
reproduction but there are times when
what's the best thing to do depends upon
what other individuals in the population
are doing what in particular the
majority of individuals in the
population are doing a hypothetical
example we could call Fishers and
Pirates and but I'm talking now about
some kind of birds where there are two
ways of getting fish these are seabirds
either you can fish for fish you either
dive and the sea and catch fish or you
hang about waiting for a bird that's
caught a fish and steal it those are
pirates and these are two ways of making
a living now what's the best thing to be
a Fisher or a pirate and the answer is
that it's not obvious because it depends
what the rest of the population are
doing uh if the whole population is
fishing
then it could very well be that an
individual could mutate and become a
pirate because they're plent of fishing
going on and it's easy to steal a fish
so then you might say well a natural
selection then favors piracy the the
gene for being a pirate spread through
the population in a few Generations now
everybody's a pirate and there's no fish
so piracy is not stable it's an unstable
stable it's evolutionarily
unstable fishing might also be unstable
because if the whole population is
fishing then a mutant pirate in
invades so a a stable strategy is a
strategy such that when all the
population are doing it no mutant
individual could arise which would do
better so neither fishion or pirate in
my hypothetical sort of game is is
evolutionarily stable what might be
evolutionarily stable is some kind of
ratio it might be 80% Fishers and 20%
pis something of that sort and the
definition of stability in this case is
when they're doing equally well a
well-known example is the sex
ratio where any departure from the
stable sex ratio is uh is penalized by
natural selection if there are too many
males an individual is better off having
daughters and there very too many
females in in the population an
individual is better off of having sons
and so the the stable ratio is 50/50 or
strictly speaking it's 50% investment
economic investment in sons and economic
investment in in daughters so an
evolutionary stable strategy is a
strategy which um cannot be bettered by
any other strategy provided that
everybody else in the population is is
doing
it you know 2 years ago when this
channel reached half a million
subscribers you guys asked me who would
I like to meet and I answered Bill NY
Neil degrass Tyson Richard Dawkins and
since then Bill and NY has taught me how
to tie a bow tie I got to interview
Richard Dawkins and on August 22nd and
23rd I will be hosting Neil degrass
Tyson in Sydney and camra Link in the
description and I really want to thank
you guys because I think it is your
support that has made this all happen
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like I like to you know this week it
makes sense to share a Richard Dawkins
book my favorite is the selfish Gene
because it's not about a gene for
selfishness it's about how genes
themselves behave in selfish ways and
sometimes that means the organism that
contains those genes behaves in strange
ways ways you might not imagine that was
a real consciousness razor for me so you
should definitely check out this book if
you haven't read it already you can
actually download it for free read by
Richard Dawkins by going to
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