2. Early Kalimba History
The kalimba has a rich and varied history in Africa that stretches back as much as 3000 years, but the metal tines kalimba is only about 1300 years old.

First Historical Mention of the Kalimba
First, some nomenclature: there are over 100 different types of traditional African thumb pianos, and mbira, kalimba, sansa, and karimba are among them. In 1954 Hugh Tracey chose one of those names, kalimba, for the version of the instrument he would soon ship around the world. In 1961, he also wrote an article, "The Case for the Name Mbira", suggesting that we use mbira as a generic name for any traditional African thumb piano. Today, outside of Africa, kalimba is also used generically for any non-traditional thumb piano.
The first European to record seeing the mbira was Portuguese explorer and missionary Father Dos Santos who was in present-day Mozambique in1586. He documented the playing of the 9-note iron-tined instrument he called "ambira". The players would grow their thumb nails long to play, and the instrument produced a "sweet and gentle harmony of accordant sounds". As these instruments were not very loud, they were generally played in the king's palace.
By the way, Andrew Tracey believes he knows the notes this 9-note kalimba was tuned to.

An Ancient Beginning

Bamboo Tined Kalimbas

Metal Tined Kalimbas

Growing Complexity in the Zambezi Valley

Spread Across Africa
As the mbira spread across Africa, separate clans or tribes each created their own version. As time passed, each group made modifications to the instrument design, such as how many tines the instrument had or what sort of board or gourd was used for mounting the mbira. Mbiras were also given special tunings by each group to support their unique music. The kalimba/mbira is a truly flexible instrument.
One important path of proliferation of these instruments developed when enslaved Congolese were moved around Africa and used as porters (basically, human pack animals) by their Belgian captors in the late 1800s and early 1900s. These people carried their own kalimbas and introduced them to many new groups of Africans who had never seen them. The Bushmen of the Kalahari Desert, isolated and nomadic, were not exposed to the kalimba until the 1950s.
Diverse Cultural Uses
In addition to wide variation in design and sound of the instrument, each group of people used the mbira differently in their social lives. In some African cultures, the mbira (and its modern descendant the kalimba) is the personal instrument of choice, something to take with you to help you pass the time tending cattle or riding the bus. In some places, it is an instrument of celebration for weddings, or an instrument to play for kings. It is used widely as an instrument to accompany the voice. One saying goes: "Kalimba without singing is like rice without beans". And in some societies, it is a tool to attract the spirits of ancestors, to bring them back for a time so that their advice might be heard.
The history and pre-history of the kalimba/mbira are diverse and rich. Standing in the 21st century, we can choose to look into the past and learn the traditional songs, or we can choose to look forward and invent something new, just as the Africans have done all along. I choose to look both forward and backward, and I have found that it makes my kalimba experience that much richer.