As a kid, did you take a stick and make it into a bow to shoot garden canes possibly at your sister? (Don’t worry, she survived and doesn’t hate me that much). If so, that’s not a million miles from what a basic primitive bow is.
Also known as the self bow (so called because its made from a single piece of wood), this type of bow has been found with indigenous peoples all over the world – in Africa, the Americas, northern Europe, and Southern Asia. The oldest bow artefacts found are all of self or primitive bows.

Rough shaping the stave
Their very lack of sophistication is their strength. A self bow can be created in less than a day from many common timbers that can be found anywhere. You just need some basic tools to aid in chopping, shaving, and scraping. A piece of wood must be long enough (approximately the height of the archer) and the grain must be pretty straight. With a little knowledge, a little effort and a few hours … you’ll get a functioning bow that while rough and ready, will be perfectly capable of throwing a pointed stick quickly and reasonably accurately at least in “hunting ranges”. Just the thing if you need a little aid in catching dinner.
You can of course spend a lot of time on your bow, and turn it into a work of art. Bowyers love to sculpt and in a self bow they have a medium that can be worked with their skill in wood alone. Exotic woods, exposing the grain, staining … using every trick in the book, bowyers have for centuries made works of art that are still functional, lets not kid ourselves, deadly weapons. However the primitive bow is really more about immediacy of construction and a total lack of sophistication in a weapon created from simple common materials in a few hours. For a 5 minute guides, just for a flavour of how its done, check out these short videos – Primitive Technology – Bow and Arrow and How to Build a Survival Bow.
Many books exist showing you how to make a primitive bow (both archer/bowyer and survivalist are fascinated by this subject for very differing reasons). A little more formal than sitting on a fallen tree in the woods making a bow, there are courses you can take from bowyers to learn how to make a bow over a weekend. A little steep cost wise as against an average weekend away but worth it I’ve been told.
For a interesting read, have a look at Stonehill Primitive and Simon Sieß. This German gentleman is very much a primitive bowyer and his website has quite a collection of bows made from what is literally scrap wood. This video from Will Lord takes things even further and creates a neolithic longbow using only historically accurate tools.
And for a discussion forum focused on such things try The Primitive Archer.