User talk:Boklage

This Wikipedia article on "Twins" is partially right.

It is only wrong about all the parts that have anything to do with the biology of twinning.

What causes all of that to be wrong is the insistence on believing that dizygotic twins arise from double ovulation. That is the "common knowledge". It is what "everybody knows". It is what very nearly everything anyone ever wrote about twins says. And it is wrong... absolutely, fundamentally, irredeemably, and always ... wrong. There is no evidence anywhere that even one naturally conceived pair of human dizygotic twins ever came from two separate, independently ovulated egg cells. But there is plenty of evidence to the contrary.

The process of building twin embryos leaves traces that are detectable even in adults, and those traces are the same in dizygotic and monozygotic twins. All twins, monozygotic and dizygotic, are more often non-righthanded than single-born individuals are. No difference in the frequency between monozygotic and dizygotic twins. Their first-degree relatives have the same excess; no difference between monozygotic & dizygotic twin families. Same with a particular bunch of malformations that are excessively frequent among twins. And there is a good deal more where that came from, all having to do with how left and right gets set up in building the embryo.

The embryonic development of twins is quite different from that of singletons. The differences between twins and singletons are the same kinds and the same sizes in monozygotic and dizygotic twins. This would not, could not, be true if dizygotic twins came from two separate and independent ovulations and therefore developed as could be expected just like singletons.

The explanation is not at all simple, and many people will find it very hard to understand and believe it. The bottom line is that all twins, both monozygotic and dizygotic, arise from within a single contiguous mass of cells derived by cell division from the substance of a single egg cell.

All twins, both monozygotic and dizygotic, arise by "splitting" an embryo, but that has nothing to do with tearing it in halves... it's more like twins "splitting" an inheritance.

As a result, dizygotic co-twins very frequently share cells of both genotypes.

You can find much of the rest of the story in the following references: The Epigenetic Environment: Secondary Sex Ratio Depends on Differential Survival in

 Embryogenesis. Human Reproduction 2005; 20(3):583-587

Embryogenesis of chimeras, twins and anterior midline asymmetries. Human Reproduction

 21(3):579-591; republished in Human Reproduction Indian Edition. May 2006; 2(6): 267-279

Traces of Embryogenesis Are the Same in Monozygotic and Dizygotic Twins: Not Compatible

 With Double Ovulation, Human Reproduction Advance Access, 2009; 1(1):1-12

Biology of Human Twinning: A Needed Change of Perspective. In Blickstein I & Keith

 LG eds)Multiple Pregnancy: Epidemiology, Gestation & Perinatal Outcome, Ch 36, pp 255-264, 2005, 
 Taylor & Francis Parthenon Publ. New York

Frequency and Survival Probability of Natural Twin Conceptions. In Keith LG, Papiernik

 E, Keith DM and Luke B (eds) Multiple Pregnancy: Epidemiology, Gestation & Perinatal Outcome, 
 1995, Parthenon Publ. New York

and there is a book, coming soon from World Scientific Publishing Co: How New Humans are Made, explaining how it actually works and how we know how it actually works. Boklage (talk) 20:32, 9 June 2009 (UTC)[reply]

Welcome!

Hello, Boklage, and welcome to Wikipedia! Thank you for your contributions. I hope you like the place and decide to stay. Here are some pages that you might find helpful:

Please remember to sign your messages on talk pages by typing four tildes (~~~~); this will automatically insert your username and the date. If you need help, check out Wikipedia:Questions, ask me on my talk page, or ask your question on this page and then place {{help me}} before the question. Again, welcome! Dawn Bard (talk) 20:01, 12 March 2013 (UTC)[reply]