1.   At first, the zoo put the female chimps on birth control pills and then hormonal implants, which resulted in two births.

2.   A female chimp who died more than a decade ago turned out to be a crucial piece of the puzzle.

3.   Female chimps are extremely promiscuous and males, therefore, have little idea who their children are.

4.   In contrast, a female chimp--call her Pat Schroeder--would hew truer to her core constituency.