Secular Pro-Life
  • Home
  • About
    • Meet The Team
    • Mission and Vision
    • Stances
      • Abortion
      • Religion
      • Contraception
      • The Rape Exception
    • Frequently Asked Questions
  • Content
    • Index
    • Blog
    • Myths
    • Research
      • Abortion Law and Abortion Rates
      • Abortion Law and Pregnancy Rates
      • Later Abortion
      • Embryonic Hearts
      • Abortion Views and Gender
    • Collections
      • For the biology textbook tells me so
      • They can hear you
      • Parents can hear you
      • Our children’s heartbeats
      • Becoming Pro-Life
      • Ask An Atheist
      • Fixed that meme for you
    • Publications
      • Overview Brochure
      • Why Secular People Should Care
      • Bridges
    • Store
  • Contact
  • Get Involved
    • Why support SPL?
    • Donor Opportunities
    • Volunteer Opportunities
    • Volunteer Survey
  • Donate
  • Menu Menu

Monozygotic Twinning: Weasley brothers, flatworms, and cow clones

December 5, 2018/0 Comments/in Biology, Uncategorized /by Monica Snyder

[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 into two organisms.

Image from Gilbert & Barresi, Developmental Biology, 11th Edition
We don’t actually know why this happens. MZ twinning is more common in in vitro fertilization (IVF) than in naturally occurring pregnancies, and there is some interesting research trying to explore why that might be, but so far we haven’t got any clear answers.
 
Fred & George prove mysterious once again.

Occasionally people point to MZ twinning to undermine the claim that the human zygote is the first developmental stage of a human organism. After all, if it’s possible the early embryo can split, does that mean the zygote is actually two organisms at once? How can we say the zygote is the beginning of a single human organism when we don’t know how many organisms will be present at the end?

But we have analogous situations where a single organism can ultimately produce another, and that doesn’t undermine the fact that the original organism was and is a single organism.

For example, some people think of MZ twinning as akin to a type of asexual reproduction. Flatworms can eventually generate and split from new flatworms. That doesn’t mean the original flatworm wasn’t an individual organism.

The parent flatworm on the far left is an individual organism.
 

Others see MZ twinning as a type of natural cloning. In somatic cell nuclear transfer  (cloning), we take the DNA from Donor 1, and then we take an egg from Donor 2. We remove Donor 2’s DNA from her egg, and instead we insert Donor 1’s DNA into the egg. We stimulate that cell to grow, implant in a surrogate, and the surrogate will gestate and birth a clone of Donor 1.

Donor 1 (top left blue cow) is an individual organism.

This is a fascinating and impressive process, but it doesn’t change the fact that Donor 1 is an individual organism. We wouldn’t look at the donor cow and say “Is she an organism? Is she just one organism? If bizarre or mysterious processes happen to some of her cells, it’s possible she could generate a new organism, so how do we know how many organisms she is?” No, we know she is a single cow.

 
By analogy, the zygote may, for reasons mysterious, generate an additional organism; that doesn’t change the fact that the zygote is a single organism, and that a human zygote is the first developmental stage of a human organism.
 
Further Reading: 
Totipotency: What It Is and What It Is Not Condic, Stem Cells and Development, 2014

 

Related Posts

Tags: biology, data & studies, M
Share this entry
  • Share on Facebook
  • Share on Twitter
  • Share on Pinterest
  • Share on LinkedIn
  • Share on Reddit
  • Share by Mail
  • Link to Instagram
https://i0.wp.com/secularprolife.org/wp-content/uploads/2018/12/MZ2Btwinning.png?fit=400%2C273&ssl=1 273 400 Monica Snyder https://secularprolife.org/wp-content/uploads/2021/10/SecularProlife2.png Monica Snyder2018-12-05 12:49:002023-03-28 18:00:29Monozygotic Twinning: Weasley brothers, flatworms, and cow clones
You might also like
Speech: Monica at the Make Noise youth rally
How I see the abortion debate now that I’m pregnant.
Midweek News Item: 05/25/11
Quick News Roundup: 09/30/10
Master post: 21+ week abortions usually aren’t medically necessary
Three takeaways from Gallup abortion polling
The JFA Seminar: “Sometimes religion happens.”
Gallup Polling Data Shows Pro-Life Trend
0 replies

Leave a Reply

Want to join the discussion?
Feel free to contribute!

Leave a Reply Cancel reply

You must be logged in to post a comment.

Follow via Email

* indicates required

Categories

  • Ableism
  • Abortion pills
  • Administrative
  • Adoption & Foster Care
  • Biology
  • Bodily Rights
  • en español
  • Late-Term Abortion
  • Legislation, laws, & court cases
  • Miscarriage & Pregnancy Loss
  • Personhood
  • Philosophy
  • Pro-Life Demographics
  • Rape Exception
  • Religion
  • Research
  • Speeches, Discussions, Presentations
  • SPL Emails
  • Top SPL Articles
  • Top SPL Graphics
  • Uncategorized
  • We Asked You Answered
  • Your Stories

Archive

It’s crucial that we demonstrate that anyone can–and everyone should–oppose abortion. Thanks to you, we are working to change minds, transform our culture, and protect our prenatal children. Every donation supports our ability to provide nonsectarian, nonpartisan arguments against abortion. Read more details here. Please donate today.

DONATE
SUBSCRIBE
© Copyright 2023 Secular Pro-Life. All rights reserved. Website Design by TandarichGroup

Related Posts

Project Rosie Saves Lives in Michigan Vote for Secular Pro-Life in the Project for Awesome Video Contest
Scroll to top