Scientists have succeeded in reconstructing the family tree of cells in a developing mouse embryo by using a new recording technology inserted into the genetic material of the fertilized egg before it started dividing. This DNA Typewriter is like a ship's logbook that keeps a history of cellular events in the order that they happen. This technology employs the cells' DNA as a recording medium. Scientsts were then able to trace cells’ relationships, starting when the fertilized egg first split in two and ending after the body with organs took shape.

Not only do big dogs die younger but they are also more susceptible to many age-related diseases. And what scientists can learn about dog aging can provide an important window into human aging too. 

Now we may know why. 

A new study led by researchers at Arizona State University offers the first compelling molecular explanation of why large dogs live shorter lives: the answer may lie in how hallmarks of aging reshape dog DNA.