Nikolaas Tinbergen, who lived from 1907-1988, was a scientist who developed four basic questions that would explain animal behavior; he ultimately won the Nobel Prize for his work.
If you get involved in animal advocacy or rescue work, it helps to have some understanding of animal behavior. The ‘4 Questions’ help us to understand why an animal is exhibiting a behavior. Some published resources call these Questions ‘the Four Whys…’ (although the questions aren’t always phrased as a why)
1. What is the function of the trait, or why does it exist?
2. What is the phylogeny, or evolutionary history, of the trait?
3. What is the cause of the trait? Regardless of history or function, there is likely to be a physical basis for the behavior.
4. How did the trait develop? This is where you consider how the animal interacted with its environment and surroundings over time.
So, as a simple example – let’s consider barking. Barking exists as a form of communication that augments physical body language. So that’s the function question answered.
As far as evolution is concerned, it is probable that early dogs had different vocal sounds which developed into the barking we know today in the wide range of dog breeds.
The cause of barking is the passing of air through vocal chords – much like in humans.
And how the trait developed…well this is connected to domestication and how dogs could communicate with the canine and human members of their pack. Animal trainers learn to distinguish the different types of barking and help to pass this knowledge onto their clients.
Most dog owners can also understand the differences in their dog’s barking.
Kathleen Crisley, specialist in dog massage, rehabilitation and nutrition/food therapy, Canine Catering Ltd, Christchurch, New Zealand
DoggyMom.com 
Great description of how to puzzle out a behaviour!
Thank you for reading my blog.