---
title: "The science of embryology says a new human being exists from fertilization"
description: "Standard embryology holds that a new, living, genetically distinct human organism comes into being at fertilization. This is not a religious claim but the consensus of medical textbooks: the zygote is 'the beginning of a new human being,' and 'human development begins at fertilization.'…"
type: "argument"
id: "arg-embryology-conception"
category: "Scientific"
mode: "Offensive"
source_url: "https://www.abhortion.org/arguments/arg-embryology-conception.html"
---

# The science of embryology says a new human being exists from fertilization

**Category:** Scientific · **Mode:** Offensive · the positive case

## The argument

Standard embryology holds that a new, living, genetically distinct human organism comes into being at fertilization. This is not a religious claim but the consensus of medical textbooks: the zygote is 'the beginning of a new human being,' and 'human development begins at fertilization.' Developmental milestones (implantation, heartbeat, pain, viability, birth) mark stages in the life of a human already in existence — they do not mark the arrival of a new kind of thing. Therefore the biological human being is present the whole time abortion is performed.

## Supporting points

- Moore & Persaud, The Developing Human: the zygote is the beginning of a new human being; development begins at fertilization.
- The offspring of two humans is, from the start, a whole human organism — not an organ of the mother and not another species.
- Milestones are changes of form and degree in one continuous organism, not changes of nature or kind.
- A distinct human genome and self-directed development are present from fertilization.

## Discussion questions

1. If a distinct human organism exists from fertilization, what morally relevant change happens at any later milestone that turns a non-person into a person?
2. Why do incremental bills draw lines at heartbeat or pain if the human being is present before those markers?

## Source transcript

Drawn from The Sin of Pro-Life Incrementalism (T. Russell Hunter) — Underlies the critique of milestone-based (heartbeat/pain) bills as arbitrary..

## References

- [The Developing Human: Clinically Oriented Embryology ('a zygote is the beginning of a new human being; human development begins at fertilization')](https://www.princeton.edu/~prolife/articles/embryoquotes.html) _(embryology textbook)_
  Keith L. Moore & T.V.N. Persaud (compiled) · Saunders/Elsevier
  **Supports:** primary textbook statement that life begins at fertilization
- [When Human Life Begins — 'a whole, genetically distinct, individuated zygotic living human organism'](https://acpeds.org/when-human-life-begins/) _(medical position statement)_
  American College of Pediatricians · ACPeds
  **Supports:** 'whole, genetically distinct, individuated... living human organism' at fertilization
- [Science confirms that human life begins at fertilization](https://nrlc.org/nrlnewstoday/2017/03/science-confirms-that-human-life-begins-at-fertilization/) _(science compilation)_
  National Right to Life · NRLC
  **Supports:** additional textbook and journal statements to the same effect

## Related

**Related scriptures:**

- [Psalm 139:13-16](../scripture/psalm-139-13-16.md)
- [Psalm 51:5](../scripture/psalm-51-5.md)
- [Exodus 21:22-25](../scripture/exodus-21-22-25.md)

**Related arguments:**

- [The unborn bear the image of God, so abortion is murder — a different category than 'a hard choice'](arg-image-of-God.md)
- [“The early embryo is merely a clump of cells or a 'potential' human, not an actual human…”](def-clump-of-cells.md)
- [“The unborn is not a baby or a person until birth (or until viability); personhood is…”](def-not-a-person-until-birth.md)
- [“Bills that ban abortion at a heartbeat, at pain-capability, or after an ultrasound…”](def-milestone-bills.md)