Dutch term – Koekoeksgraad

painting of a Dutch cuckoo

Dutch cuckoo. Credits: Jan Brandes, collection Rijksmuseum

I first heard the word Koekoeksgraad last week and liked it so much that I wanted to share it with you. Koekoeksgraad means “degree of cuckoos,” the degree of non-paternity events per generation.

I first heard the term in a presentation by forensic DNA expert Maarten Larmuseau, in a Youtube recording of his presentation about using Y-chromosomes to calculate the percentage of “cuckoos,” children whose biological father doesn’t match the documented line.

Their research found that both historically and today the degree of non-paternity events in the Netherlands and Flanders is about 0.9%, way lower than the 10% that is sometimes cited in media.

What I found interesting is that the rate didn’t change over time. Testing modern fathers and sons found the same koekoeksgraad of 0.9% as the historic rate, calculated using Y-DNA. It is remarkable that modern options like birth control and divorce haven’t had more of an impact.

It certainly is reassuring that we can be 99% sure that our paper genealogy is accurate 🙂

For those of you who understand Dutch, here is the video of the presentation:

About Yvette Hoitink

Yvette Hoitink is a professional genealogist in the Netherlands. She has been doing genealogy for almost 25 years. Her expertise is helping people from across the world find their ancestors in the Netherlands. Read about Yvette's professional genealogy services.

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