Sexual Selection - Anthropology 116 - Anthropology 116...

Anthropology 116 – Sexual Selection
• Bad Ideas?
o Phenotypes that are detrimental to survivorship
 Seems to contradict Darwin’s idea of natural selection
 Male lifespan is significantly lower than females in mammals
• Even after “stupid behavior” is accounted for
• Function of how male bodies operate
• During mating season – exhibit a sharp increase in mortality
o For humans – mortality peaks at around 20 years
 External causes peak at 20 and then decline
 Internal cause are consistently increasing after
birth
 Ex: Ache – tribal people group in south America
• Hunt a small rodent like creature called a “kande”
o Behave like squirrels
o Go out in a semi-circle with bows and arrows and
imitate the sound of a jaguar
o Herd them into a tree
o Make lots of noise with branches and bows and arrows
o “Kande” panic and start jumping out of the trees
o Grab them by the tail while they are in the air and
swing them around and bash them into something hard
 If you don’t kill or knock him out right away
they will turn around and fight – the “kande” are
vicious
 Only the young Ache do the hunting – trying to
prove themselves
 Peak right around the same time – 20’s
• Females have a higher probability of death up until twenties
due to infanticide
o Physical characteristics
 Ex: Fiddler crab’s huge claw
• Large claw takes more energy to maintain (males have the
larger claws)
• The large claw is used as defense for females
o Increase in reproductive success but a trade of lifespan
• Gull predation
o Straight run
 Attempts are equal against both males and
females – success is about the same as well
o Angles run

 Mostly attack males and are very successful;
however completely unsuccessful against the