Definitions of “heartbeat.” To my knowledge there’s no unifying authoritative definition of “heartbeat.” Embryology textbooks do use the term. For example: “Blood flow begins during the fourth week, and heartbeats can be visualized by Doppler ultrasonography.” – The Developing Human, Moore et al, 10th Edition (2013) “The heartbeat is initiated around the twenty-first day, and […]
Recently a FB follower shared this post to our page: (Click to enlarge) The text reads, in part: This is what an embryo at 6 weeks looks like. There is no real heart beat because it’s heart isn’t nearly complete – they’re heart “vibrations” (vibrations are caused my cellular activity where the heart WILL be. […]
The human zygote is the first developmental stage in a human life cycle. A zygote is different in kind from sperm and unfertilized eggs, which are gametes, not organisms. The zygote is different from any random cell that has human DNA, such as your skin cells (also not organisms). The zygote is a separate and […]
[Esta publicación está disponible en español aquí.] Dizygotic twinning is when two sperm fertilize two eggs and produce two zygotes which grow as two separate organisms. Not confusing, right? Monozygotic twinning is when a single sperm fertilizes a single egg and produces a single zygote, but in the earliest stages of development that embryo splits […]
[Esta publicación está disponible en español aquí.] The below blog post is also available as a recording here: The human zygote is the first developmental stage of a human organism’s life cycle. Sometimes when I state this fact, people respond by pointing out that many zygotes never implant. Bill Nye made the same point in […]
What difference is there (if any) between a human organism and a “person”? Is there such thing as a human non-person? How do we determine which human organisms have moral worth and merit social protection? People have given me a variety of suggestions for the factors human organisms need to be morally relevant, including connection […]
[This post contains photographs of infants with serious genetic abnormalities.] [Esta publicación está disponible en español aquí.] Pro-life people often say: Life begins at conception (or fertilization). At fertilization there is a new entity genetically distinct from the woman. If two humans have sex their offspring will be human (rather than a dog, a frog, […]
When we say “life begins at conception,” we mean the human life cycle begins with the zygote. But often others think we are trying to say “people [morally relevant and valuable humans] begin at conception.” This is a philosophical claim, not a scientific one. So when others counter with “science can’t tell us when life begins” […]
The fetus is a living human organism. When I state this long-standing and (at least in the field of biology) undisputed fact, pro-choicers usually have one of three reactions: Reaction 1: They argue the point based on ignorance of basic biology. “A single cell is not an organism.” “A zygote is no different than your […]
Disclaimer: This blog post is meant for biological definition purposes. It is not meant to establish or argue any moral or philosophical points. [Esta publicación está disponible en español aquí.] A zygote is a human being. 1. The zygote is an organism. Fertilization – the fusion of gametes to produce a new organism – is […]
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