In philosophy and bioethics, potential (future) person (in plural, sometimes termed potential people) has been defined as an entity which is not currently a person but which is capable of developing into a person, given certain biologically and/or technically possible conditions. The term unconceived has also been used in a similar sense, but does not necessarily include the capability of being conceived or developing into a person. In 1977, Canadian Philosopher Mary Anne Warren discussed various definitions for potential people. Most simply, a potential person could be defined as the currently existing genetic material that will constitute them, such as a sexually viable egg and sperm cell taken together, also when still being located in separate places. Potential people may also be defined from reproductive capability, which also includes the presence of other necessary factors for becoming a person, such as the availability of a womb to grow in, the will and means of parents to conceive, or even the care after birth to raise the individual into a complete sentient being. Thus the progression towards existence of a potential person usually lies mainly in the maturation of previous people to develop the will and ability to become potential parents. In this sense, destroying sperm cells, for instance, does not significantly reduce the number of potential persons, because, provided the will and other means to conceive a person remains the same, there is still the possibility to extract the genetic information from remaining sperm cells or, theoretically, even from somatic cells such as skin cells (by somatic cell nuclear transfer). Actually, in this sense, for a man that intends to conceive only two children, the billions of sperm cells he produces throughout his lifetime may, taken together, still only be regarded as a contributing factor to a maximum of two potential persons.