Human from the start
Half a century ago, Nobel Prize winning biologist Sir Peter Medawar made a startling comment. He declared that the survival of a child in a mother's womb contradicted immunological laws. Since the immune system normally detects foreign tissue and attacks it you'd expect the immune system to attack the genetically distinct child within her.
Well, we now know that it actually does but the baby survives by putting up a very specific defense. Researchers at the medical college of Georgia discovered that mammalian embryos produce a special enzyme that suppresses the mother's killer T-cell action. The human embryo starts to produce this enzyme just before it attaches to the mother's uterus.
This refutes a major argument used to support abortion that the embryo is just a part of the mother's body to do with as she pleases. The research clearly shows that the human embryo is distinct from its mother, from the beginning.