Final answer:
The statement is false because male and female karyotypes differ from conception, with males having XY chromosomes and females having XX chromosomes.
Step-by-step explanation:
The statement that before 8 weeks of development males and females have the same karyotypes is false. From conception, males and females have distinct karyotypes; females have a karyotype of XX chromosomes while males have a karyotype of XY chromosomes. The karyotype is the complete set of chromosomes of an organism, hence from conception, this difference is present even though the external physical characteristics may not be distinguishable until later in development.
In the initial stages post-fertilization, although the physical differences between males and females are not visible, the genetic foundation for sex differentiation is already established. The presence of a Y chromosome in males leads to the development of male sexual characteristics due to the secretion of testosterone by the genes on the Y chromosome, usually during the second month after fertilization. This developmental milestone marks the beginning of differentiation in the reproductive systems of males and females.