By finding molecules similar to the insulin receptor in different organisms, we may be able to discern which o?

3. evolutionary relationships

this is because we all evolved from a common ancestor and following the principal of random mutations to all DNA in organisms occuring at a steady rate, the extent of difference between these proteins in different organisms (presumably just animals) can give us an indication of how long ago any two species had a common ancestor.

E.g. humans and apes' proteins are in many cases very similar, suggesting they evolved from each other 'recently', whereas humans and horses' proteins are more different in terms of structure and amino acid sequence, as we were a common species much less recently