The Simian Line
You can also read about what is the meaning of simian line in Indian Palmistry
This line can appear on one or both hands. The simian line is often heavy and chain like. In many cases, there are semi-simian formations where there are vestigial pieces of head and heart lines left on the hand.
The word "simian' meaning "monkey like" is used because early palmists thought that monkeys had this formation on their hands.
I have visited zoos and studied the hands of many apes and monkeys, even going as far as taking hand prints from a baby Barbary ape when I was in Gibraltar.
I discovered that the lines on any monkey or ape hand are the same as human ones and that these creatures do not have a "simian" line formation. The skin ridge pat-terns are quite different from those of humans though.
The Semi-Simian Line
People with simian lines find it difficult to lead a normal, balanced life. They focus entirely on either their work or their relationship, or on something else in a one-sided manner.
They hold on to resentments and then explode in a tantrum or floods of tears. These people can be very obstinate.
Semi-simian lines are also uncommon. They mean much the same as a simian line, but the person is likely to develop a more balanced attitude with time and experience.