5. “The embryo has unequivocal human characteristics”
In 2015, in the latest edition of his book The Developing Human: Clinically Oriented Embryology (The Developing Human Being: Clinically Oriented Embryology), scientists Keith Moore, TVN Persaud and Mark Torchia stated that “human development is a continuous process that begins when an oocyte from a female is fertilized by a sperm from a male.”
“Human development begins at fertilization when a sperm fuses with an oocyte to form a single cell, the zygote,” they wrote.
The scientists further noted that “all major external and internal structures are established between the fourth and eighth week” and “upper limb sprouts are recognizable by day 26 or 27 as small swellings on the ventrolateral body walls.”