Thanks, I appreciate the replies.
I should have clarified myself better. I was using longbow as a generic bow someone on foot might use. My mistake and I should have known better. The scenario I'm setting up the people are nomadic herdsmen/hunters and don't have riding animals. So I was trying to work out what their bows would look like. Sounds like a medium length bow sized to each person makes the most sense.
What is their tech level? What sort of climate do they live in? What resources do they have to make bows from? Are the bows primarily hunting or war weapons?
The Welsh/English longbow was made of one piece of wood, yew was preferred, but other woods were used as substitutes. Yew grew in England so was a local material used early on and continued to be used as the bows developed over time.
A typical Yew "war bow" would be "as tall as a man" (think 6 feet or so) and have a draw weight of 100 pounds or more.
An English longbowmen trained from youth with lighter bows and worked his way up to using the full poundage war bows.
The climate of England/Wales was suitable for one piece "self" bows. The high humidity promoted growth of the yew.
The nomadic horse archers, such as Mongols (and others) used what we call a "composite" bow today. The bow would be a combination of wood, horn, and sinew, bound together with natural glue. The bows were optimized for horse archery. They were short, with a large recurve, and had a powerful draw weight. (Although not as strong a draw weight as the Longbow).
This type of construction came about from what they had available and how they used the bow and also evolved over time. As a nomadic horse people, they had access to livestock for the horn and sinew, and some access to wood for the "core" of the bow. A longer bow, like the English longbow, wouldn't work for them, so they developed a shorter bow and figured out how to get effective draw weight from that design.
The composite horn bows wouldn't have worked as well in England. The humidity would have caused problems. And, the nomadic tribes didn't have access to the old, tall, stands of yew to make those types of bows. So you can see how each type was developed to meet the needs of their users from the materials on hand and suitable to their region and style of use.
If your characters are nomadic, and don't have horses, it sounds like we're talking about a pretty primitive culture. I'd go with a simple self-bow. Not as tall as the English longbow, due to the lack of access to suitable "sraight and tall" wood, but basically a wooden stick bow.
You could also justify some simplier composite bows. Wood core strengthened with sinew and bone, but not as fully developed as the nomadic horse archers horn bows.
As to bow length, think if it in terms of technology, not just length of the bow. The question to ask is "how sophisticated is the bow" based on their tech level and resources, not "how long is the bow."