This unusual head line/heart line combination occurs as a single straight line across the palm, instead of as the usual separate head and heart line. Most commonly, the owner of a Simian Crease has this Gift Marking only on one hand. But they can appear on both.
Gift Marking Purpose
The Simian Crease combines the head line and heart line. Because there is one line where normally there would be two, you experience both feelings (heart) and thoughts (head) as one energy. Often a Simian owner may not know what is meant by "feeling and thinking" as separate experiences. Simians tend to express intensely, see things in extremes, and have a lot of physical and mental stamina. On the master path they can be really strong communicators.
As a Simian, you have a lot of stamina. You may not understand why others go home when you are still working on a tight deadline. You are the one who can sustain the pressure, the intensity, and who can stay with the project. Others are not built to keep up with you so don't expect them to. This can apply to physical and mental stamina. Jerry says he can teach a class longer than students can sustain taking information. Teaching like this requires both physical and mental stamina.
You could benefit from being cautious about judging others regarding their lack of stamina.