Week 4: Cultural transmission Flashcards
Social learning (Imo the monkey)
a Japanese macaque monkey that lived on Koshima Islet, Japan, in the 1950s.
When Imo was a year old, she began to wash the sweet potatoes in water before she ate them.
This behavior is novel and creative, removing all the sand from the sweet potatoes before eating.
Many of Imo’s peers and relatives learned the skill of potato washing from Imo.
By 1959, most infant macaques in Imo’s troop intently watched their mothers, many of whom had acquired Imo’s habit.
The infants learned to wash their own sweet potatoes at early ages.
Evolution by natural selection
variation: Members of a species differ in some of their characteristics
inheritance: Parents are able to pass on some of their distinctive characteristics to their offspring
differential reproductive success: Some individuals have more surviving offspring than others in their population, thanks to their distinctive characteristics
For natural selection to act on a behavior, a mechanism of transmitting that behavior across generations is required.
DNA
A means of transmitting traits across generation
Enabling natural selection to act on genetically encoded traits
Modes of inheritance
Genetic transmission:
- Until recently, this mode was regarded as the only way to transmit information across generations
Cultural transmission:
- The transfer of information from individual to individual through social learning - both within and between generations of animals
- potato washing in Japanese macaque is an example of cultural transmission
What is important about cultural transmission?
transmission across generations:
- individual learning disappears when that individual dies
- When cultural transmission is in play, what is learned by one individual may be passed down through generations
the speed of transmission:
- cultural transmission of information operates much faster, and can cause important changes in the behavior seen in populations in just a few generations
- natural selection acting on the gene frequency changes: a few dozen generations
- natural selection acting on major morphological changes: much longer
Galapagos Islands
an archipelago of volcanic islands on either side of the Equator in the Pacific ocean, about 1000 km west of continental Ecuador.
Noteworthy species:
- Galápagos land iguanas
- Marine iguana
- Galápagos tortoise
- Flightless cormorant
- Blue-footed booby
- Galápagos penguin
- Waved albatross
- 4 endemic species of Galápagos mockingbirds
- 13 endemic species of Darwin’s finches
- Galápagos sea lions
Darwin finches
at least 13 species of finches on the Galápagos Islands.
each filling a different niche on different islands.
All of them evolved from one ancestral species, which colonized the islands only a few million years ago.
This process, whereby species evolve rapidly to exploit empty eco space, is know as adaptive radiation
Medium ground finch and cactus finch
Peter and Rosemary Grant studied the role of cultural transmission in the evolution of finch song.
the medium ground finch (Geospiza fortis; left) and the cactus finch (G. scandens; right)
both live on the Galápagos Islands of Daphne Major
some cases of interbreeding between two finch species, but no fitness penalty for hybridization
Although there seems to be no cost for hybridization, two finch species rarely interbreed. Why?
In finches, male birdsong plays a prominent role in the mating success.
As in all songbirds, male finches learn the songs they sing.
The Grants found that these songs were transmitted across generations via cultural transmission.
Fathers and songs have very similar songs.
The Grants also found that the songs of these two species were quite different from one another.
Of 482 females sampled, 95 % of females mated with males who sang the song appropriate to their own species.
Females tend to avoid males who sing songs that are similar to the songs that their own fathers sang, which suggests that song also plays a role in preventing inbreeding.
It seems that cultural transmission of song allows females to recognize individuals of their own species as well as to reduce the chance of inbreeding.
Cultural transmission of male song
genetic transmission: the songs of songs are similar to the songs of both their paternal and maternal grandfathers.
cultural transmission: the songs of the songs should resemble those of their paternal grandfather, but not those of their maternal grandfather.
Components of male finch song are positively correlated with those of their father and their paternal grandfather, but not their maternal grandfather. This is consistent with cultural transmission of male song.
Cultural transmission and bran size
E. O. Wilson suggested that in a population of large-brained animals, new innovations might arise and spread more often than would happen in a population of small-brain animals.
There is a significant positive correlation between brain size and both innovation and social learning frequency.
A similar trend between large brain size and an increased propensity toward innovation was found for birds.
