1.   Cloning mammals is a wildly inefficient process that can require hundreds of attempts both to create an embryo and to implant it successfully.

2.   Previous efforts to clone mammals have been too chancy and inefficient to be considered practical.

3.   It was the first time scientists had used such a technique to clone a mammal.

4.   Scientists have been able to clone mammals from fetal cells for two decades.

5.   Scientists clone adult mammal, a first.

6.   The information is critical because scientists have been able to clone mammals from fetal cells for two decades.