Having one theory is setting a limit on your potential and the potential of the overall theory and subject you are working on. Having multiple theories gives you a broader idea and perspective of what is going on, and even though one may slightly contradict the other, it is okay because that is what theories are for.
To the point, scientists usually have more than one theory so that they can gain a broader perspective on the matter and maybe even increase the chance of being correct on the matter. 
Hope this was helpful.
Cheers,
 
        
             
        
        
        
The Egrets seem to prefer insects because they ate 66 of them, and 66 was the most visited as well.
        
                    
             
        
        
        
The answer is single nucleotide polymorphisms (SNPs)
It checks for variation in nucleotide sequences in particular genes that may be different among people, especially in different races. An example is a gene for melanin that would determine the trait for skin color. Single nucleotide changes in the gene between population can be used to differentiate populations.  
 
        
             
        
        
        
This dog already has all the answers