"Numerous writers have attempted to pinpoint what they regard as the biological substratum for personal life, with attention on development of the cerebral cortex and on identifying the first moments of conscious experience. Some have set this at 25-40 days gestation. For others, eight weeks gestation represents the point at which the brain is capable of consciousness. From this point onwards, the "biography" of the individual has begun; alternatively, this level of brain activity signifies the emergence of a person, makes possible an holistic level of life,' leads to affective recognisability by other people, or denotes the beginnings of sentience."