How can an applicant effectively customize cover letters?

How can an applicant effectively customize cover letters? Applicants should also customize their cover letters to better serve the purpose of the job and represent themselves. Cover letters are a brief introduction into who the applicant is, what skills they possess to make them an appropriate hirer and how they can benefit the company they are applying for. 

It depends on what you believe, if you’re christian that you would have been told that the first humans were created by god and that we’re all decedent's from adam and eve but scientist say otherwise