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HOW COULD CHIMPANZEES RECOGNIZE THEIR RELATIVES?
Animals could use one or a combination of mechanisms to recognize relatives. Whether animals recognize their kin is of interest to behavioral ecologists because if animals can recognize relatives then they could bias positive behavior towards relatives. This could explain why some individuals help each other, while others do not.
FAMILIARITY THROUGH PRIOR ASSOCIATION
How do you know you and your brother or sister are relatives? Well, if your
mother gave birth to both of you, then minimally, you are half-siblings, so
it is a pretty safe bet to treat individuals that you shared your mother with as your kin. In doing so, the shared association you and your
sisters and brothers have with your mother is used as a behavioral cue to
kinship. In chimpanzees, kids stay with their moms for many years even as
she has more kids, and so they will become familiar with those other kids
(their siblings). Also, female relatives like mothers and daughters tend to
stick together even as adults, and so kids will likely be familiar with aunts
and cousins as well. Thus, the rule of thumb for chimpanzees might be treat
those individuals who closely associated with your mother as relatives. It
is believed that familiarity is important in primate kin recognition, especially
for maternal kin (descendents of the same mom), as this example shows.
PHENOTYPE MATCHING
Have you ever had the experience of going to meet a relative that you have
never seen before for the first time, meeting them in a crowded public place
like a restaurant, and instantly knowing who in that room you are there to
meet? Why would you know which person in that room is your relative without
knowing anything about what they look or sound like? We all know that family
members often look alike – that traits are passed down through families
that many members may share. When you walk into that crowded room, you might
know immediately which person is your unfamiliar aunt because she looks just
like your dad. Well, in doing that you have identified your aunt through phenotype
matching.
Phenotypes are the observable characteristics of an individual and phenotype
matching just means that traits are being compared – but to what? Traits could be useful for phenotype matching in kin
recognition if their phenotypic similarity across individuals closely corresponds
to the genetic similarity (relatedness) of individuals. If this is the case,
then an individual can learn a trait, either their own or that of a close
relative, and use that as a template to test the similarity of others’
against. The more closely individuals are related, the more similar they will
be in that trait. In the case described above, you probably learned a phenotypic
template from your father, and your aunt and father have similar visible trait
or traits that reflect their genetic relatedness. Therefore, you can identify
her as your relative based on that trait similarity, opposed to the dissimilarity
of the rest of the unrelated people in the room.
For chimpanzees and other primates, phenotype matching may be important for paternal kin (descendents of the same father) who often do not interact in a way that would facilitate familiarity. For example, paternal half-siblings share the same father, but if they have different mothers, they are raised apart. More than visible traits could be useful for phenotype matching - other traits such as scent or vocal similarity could also be important. A note of caution, however, while we humans may be aware that someone is our relative, that does not necessarily mean kin recognition is a conscious awareness for chimpanzees and other animals. These mechanisms could allow them to bias behavior towards relatives without their actual awareness of the relationship.
You can test your abilities to match chimpanzee relatives
and see for yourself that chimpanzees, like humans, have inherited family
traits that might facilitate phenotype matching for kin recognition. To read
more about research related to kin recognition, read Emily Wroblewski’s
research description.
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