Embryo colonists

If it is perceived that the human species might shortly come to an end because of some disaster, it might be possible to launch a colony ship in the hopes of saving the species at some offworld site. Such a ship would probably be put together in haste and in secret, and would likely not be able to carry many passengers. If the colony succeeds, a "bottleneck" phenomenon and inbreeding problems would likely ensue within 6 or 7 generations.

I propose that the unwanted embryos produced by in vitro fertilization clinics would be ideally suited for use by an extraterrestrial colony. These embryos could be collected centrally for this express purpose (someday sending to an extraterrestrial colony), which would be a use I would think the parents would approve. They would be assembled into a package suitable for packing away into space on short notice.

Once at the extraterrestrial colony, the embryos could be implanted into xenomothers - domestic animals (probably a cow, because of comparable gestation time). These xenomothered embryos would at birth become the "ciblings" ("hiblings" if horses are used) of conventionally conceived babies born at the same time, and raised together. Some experiments might need to be done beforehand to ensure successful xenopregnancies.

This strategy is a practical method for maximizing genetic diversity (another would be to bring no males, only banked sperm) while facilitating population expansion of the fragile new colony. It might work even better in a science fiction story.