Mummified baby mammoth at the Field Museum (Wikipedia Commons)
National Geographic’s cover story, “Reviving Extinct Species,” has garnered much media attention as well as serious debate (e.g. here). I was struck by the apparent assumption that an ovum with a reconstructed mammoth genome could be gestated in an elephant uterus. Experience with embryo transfer between closely related species is not encouraging. 70% of donkey-in-horse pregnancies ended in abortion after 80-85 days because of defective placental development (reference here).
Perhaps less spectacular but nonetheless impressive is the resurrection of mammoth hemoglobin achieved 3 years ago by a team led by Kevin Campbell of the University of Manitoba (here). They were able to make functional analyses that revealed adaptations for cold tolerance.
Primates and some other mammals have a fetal hemoglobin with high oxygen affinity that aids oxygen transfer across the placenta. Many mammals use a different trick to raise the oxygen affinity of fetal blood. The fetal red cells have a low content of the hemoglobin ligand DPG thereby increasing the molecule's affinity for oxygen (explained here). DPG certainly binds to mammoth DPG, raising the possibility that mammoth fetuses, too, had red cells with a low DPG content.