A single deep line running straight across the palm - instead of separate heart and head lines. If you have one, you have probably googled it and found scary medical pages. Here is the calm version: what the simian crease is, what it means medically, and what palmistry reads into it.
What the simian crease is
The technical term is single transverse palmar crease: the two large horizontal creases of the hand - heart line and head line - are fused into one line that crosses the whole palm. It can be complete or partial; many hands show transition forms where the lines touch or merge only partly.
The old name "simian crease" comes from the nineteenth century, because great apes usually have a single palmar crease. The term is considered outdated and insensitive today; medicine prefers the neutral description.
How common is it?
More common than most people think: estimates are in the low single-digit percentage range, depending on how strictly the line is defined. Many people with a single crease never notice it.
The medical context - without panic
The crease is one of the so-called soft markers: features that occur more often in some genetic conditions, including Down syndrome. That does not mean what many fear:
- The vast majority of people with a single palm crease are completely healthy.
- As a single feature it says nothing about your health - it is not a diagnosis, not even a test.
- Many people with genetic conditions do not have the crease at all.
For medical questions - especially about a child - please talk to a doctor, not to the internet and certainly not to palmistry. Nothing on this page is medical advice.
What palmistry reads into it
Traditional readings focus on what is missing: where most hands separate head and heart, here thinking and feeling run in one track. That is read as single-mindedness, strong will or "all of one piece" - and, depending on the book, as stubbornness or impulsiveness. The interpretations contradict each other, which says a lot about the system.
Variations at a glance
| Form | Description | Traditional reading |
|---|---|---|
| Complete simian crease | one line across the whole palm | strong will, single-minded, "head and heart as one" |
| Partial / transition form | lines touch or merge partly | depending on the source: either of the two types |
| Two separate lines | the usual case | heart and head read separately |
What it does not mean
It is not a warning sign, not a character certificate and not a health diagnosis. It is a fold in the skin - striking, but not fate.
Checking your own hand
Use daylight and side light; a photo from straight above helps. If you want measurements rather than stories, try the free hand check. More background: the basics and the heart line.