Lord of the Placenta - Part I

Answers in Genesis, our friends responsible for the Creation Museum, have now presented equally misguided evidence for scripture in their article The Placenta: A Selfless Servant. Written by David Menton, Associate Professor of Anatomy at Washington University School of Medicine, and with all the creative wit of an elementary school textbook (including a label to readers at the top of the page warning: Semi-Technical), The Placenta is your fairly typical creationist clap-trap about how such ordered perfection couldn’t possibly be other than an act of God.

While parents and loved ones lift joyful prayers of thanks for the safe arrival of their newborn, few think of thanking God for the essential services rendered by His marvelously designed creation—the placenta.

Menton then presents a fairly routine exploration of how the developing placental cells (the trophoblast) begin secreting hormones several days after fertilization (Menton specifies a Biblically-inspired three days, but the actual time can vary) that serves to enlarge the uterine lining for implantation of the egg. Following his brief discussion of how this trophoblast prepares the fertilized egg for implantation (using the inaccurate term embryo rather than blastocyst) the good doctor lays an egg of his own with the statement:

It is still a mystery how the placenta prevents the mother from rejecting it and the baby as a foreign graft without shutting down her immune system.

Now, I may not have received a PhD in cell biology from Brown, but I am capable of keeping up on the scientific literature. And, a word of advice to any creationists reading, before you start appealing to a God of the gaps you should verify that there actually is a gap to begin with. Writing in the journal Acta Paediatrica LÅ Hanson explains that:

The fetus is protected by the presence of FAS-ligand in the placenta, which can make local maternal Tc go into apoptosis. There are also T suppressor cells in the placenta which can block the activity of the Tc cells and which are tolerated during pregnancy.

Translation is in order. The mother’s body views the blastocyte as a foreign body that must be destroyed and so releases the dogs in the form of antibodies. One such antibody, the Tc cells, or Cytotoxic T cells, are especially nasty but effective in eliminating cells infected with viruses. So to protect the blastocyst a protein surrounding the placental membrane, the FAS-ligand, causes the mother’s Tc cells to die on contact (apoptosis = cell death). Secondly, a backup plan is in place by which T suppressor cells, which are usually released only after all invading organisms have been destroyed, confuse any surviving Tc cells into calling off the chase. So the placental barrier serves as a defensive wall against invading forces and, at the same time, confuses the enemy with propaganda to make additional troops think the battle is over. Naturally I’m anthropomorphizing.

Suffice it to say that Dr. Menton hasn’t been doing his homework. Had he done a brief literature review he also would have discovered that there’s an evolutionary interpretation already in hand and that appealing to divine forces strains credibility. Furthermore, this evolutionary interpretation raises additional fascinating issues about the chemical influences of why we’re attracted to the people we are. But for that you must wait for the next entry.

Click HERE for Part II

Hanson, J. (2000). The mother-offspring dyad and the immune system. Acta Paediatrica 89:252-8.