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Think basics, not exotics

It’s one of the most basic tenets of medicine.

When you hear hoofbeats, think horses, not zebras.

Often ascribed to Dr. Theodore Woodward, a professor at the University of Maryland School of Medicine in the 1940s, what it means in essence is that when a doctor encounters a basic set of symptoms that look like the common cold, the doctor should think that it is the common cold and — unless there’s good reason to think otherwise — not some exotic illness that appears in that time and place only in the pages of a textbook.1

In other words, we should look for the most likely, most common explanation for what we’re seeing first before heading off to consider the far-fetched exotic possibilities.

horses not zebras

And it’s as applicable to genealogy as it is to diagnosing disease.

We go with the probable solution and try to rule it out before we go on to the less likely possibilities.

Probability theory is behind most of what we do in using DNA evidence, for example. It’s the whole basis for the Shared cM Project tool that gives us 99% odds that a person with whom we share 2000 centimorgans of autosomal DNA will be a grandparent/grandchild, aunt/uncle, niece/nephew or half-sibling — and 0.90% odds that the person could be a full sibling.2 And our job is to rule out all those likely relationships — the horses — before we consider the unlikely one — the zebra.

And probabilities are something we should consider in more prosaic genealogical situations.

We need to look for the horses before we conclude our case is the zebra.

Case in point: I was updating my genealogy database and my Ancestry tree last night with information located for me last week as I was honored to be one of the guests in the 2021 WikiTree Challenge. And I was double-checking what the challenge participants had found versus what I had.

And when I got to the entry in my Ancestry tree for the youngest child of my paternal third great grandparents, Friedrich and Johanne Sophia (Schumann) Geissler in the area of Germany that is now the state of Sachsen-Anhalt, a hint popped up. And it was to a family tree linking a woman named Johanne Rosine Geissler to the baptismal record for my second great grand-aunt, Johanne Rosine Geissler.

And it then goes on to link to an image of a church baptismal record for her child, Johann Julius Kirsch.

Oh boy… possible cousins, right?3

Um… wrong.

You see, that child’s baptismal record says the mother in that case — Johanne Rosine (Geissler) Kirsch — bore that son, Johann Julius Kirsch, in Rehehausen on 3 April 1845 — and he was her third child and first son.4

There are only two problems with concluding that that mother is the same person as my second great grand-aunt.

First off, my Johanne Rosine Geissler was born on 24 December 1833 and baptized 1 January 1834.5

That would make her just a bit more than 12 years and four months old in April of 1845.

That’s a little young to be having her first child. It’s ridiculously young to be turning out her third child.

When we spot an age issue like that, we should immediately stop and think: “When you hear hoofbeats, think horses, not zebras.”

A 12-year-old mother of three?

That’s not a horse.

That’s a zebra.

That alone should tell us that my second great grand-aunt is not the Johanne Rosine Geissler who gave birth to her third child in 1845.

Oh, and the second reason why I’m really sure this isn’t my Johanne Rosine Geissler producing this third child in 1845?

My second great grand-aunt Johanne Rosine Geissler died on 3 August 1834 at the age of seven months, one week and three days. She was buried at the same church where she was baptized.6

The horse here is another — a different — Johanne Rosine Geissler.

Anything else is a zebra.

Cite/link to this post: Judy G. Russell, “Think horses, not zebras,” The Legal Genealogist ( : posted 20 Feb 2021).


  1. See “When You Hear Hoofbeats Look for Horses Not Zebras,” Quote Investigator, posted 26 Nov 2017 ( : accessed 20 Feb 2021).
  2. See “The Shared cM Project 4.0 tool v4,” March 2020, DNA Painter, filtered at 2000 cm ( : accessed 20 Feb 2021).
  3. No, I’m not going to identify the tree. The point isn’t to embarrass anybody. It’s just to give a concrete example.
  4. Evangelische Kirche Rehmsdorf (Kr. Weißenfels), Tauf-Nachrichten, Nr. 4/1845, Johann Julius Kirsch; digital images, “Saxony, Anhalt, Anhalt-Bernburg, Anhalt-Dessau and Anhalt-Köthen, Germany, Lutheran Baptisms, Marriages, and Burials, 1760-1890,” ( : accessed 20 Feb 2021).
  5. Evangelische Kirche Ossig (Kr. Zeitz), Taufregister Nr. 22 1833/34, Johanne Rosine Geissler; digital images, “Saxony, Anhalt, Anhalt-Bernburg, Anhalt-Dessau and Anhalt-Köthen, Germany, Lutheran Baptisms, Marriages, and Burials, 1760-1890,” ( : accessed 20 Feb 2021).
  6. Ibid., Todten-Anzeigen Nr. 7 1834, Johanne Rosine Geissler.
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