A question we're very interested in is whether family relationships
influence chimpanzee cooperation.
So we know that human cooperation often occurs among non-relatives,
and it's been thought that in all other animals that the individuals
only cooperate efficiently and well with relatives, direct kin such as brothers or parents.
We look at male chimpanzee cooperation because chimpanzee males grow up in the same group
and spend a lot of time together and engage in a lot of cooperative activities,
and see whether they prefer to interact with their maternal brothers or paternal brothers,
or if it really doesn't matter and they interact well with non-kin.
Since we're studying wild apes that are endangered and very sensitive to disturbance,
we can't just go and take blood samples like we would like to
if we were studying sheep or something like that.
So we need to rely on noninvasive samples,
things we can pick up, that might contain DNA or other interesting materials for us,
in a way that wouldn't bother the animals at all.
So we rely on samples of feces or of chewed-up fruit that contains spit
and cells from the insides of the cheeks, materials like that.
The research questions we're interested in addressing,
or many of the most stimulating ones, have to do with combining behavioral data,
data from observations of wild, living chimpanzees or gorillas or another species,
with data that we achieve in the lab through this noninvasive sampling of DNA.
So for example, we might characterize how individuals are related
and look at data from the field that consists of what cooperative activities
do individuals engage in.
Male chimpanzees hang out with one another a great deal,
live in the same group with each other all their lives
and engage in a variety of cooperative interactions.
They groom one another.
They go together on patrols of the territory boundaries.
They go on hunting parties where they go and attempt to catch monkeys.
They share the meat after they have caught these monkeys,
and it's an extremely valuable and desired resource by all the individuals.
So, researchers can count how often different pairs of individuals
engage in these cooperative interactions and come up with measures
of how cooperative different pairs are.
And then we can compare that with our data on how different individuals are related
or aren't related and start to see if being brothers makes a difference.
So what we found out is that, while individuals do interact preferentially with maternal kin,
so if individuals have a maternal brother -- and they don't always--
they do interact in a very meaningful way with those individuals.
But there are lots of other pairs of individuals that interact also very strongly
in a positive way and aren't related, so that while kinship matters,
it's not necessary for chimpanzee cooperation.
There's a lot of cooperation that occurs without any kin ties.