Experiments Show How Neanderthals Made the First Glue

That's basically hide glue, isn't it?

Hide glues are great in low-humidity environments but can loosen in high humidity. They're useful for fixing musical instruments, for example, because hide glue joints are reversible and repairable. Hide glued joints will release easily with the application of heat and steam. I was surprised to find that most older musical instruments have been repaired to a greater/lesser degree thanks to the use of hide glue.

Bow makers (as in "bows and arrows") commonly used hide glues in regions of low humidity, but a Turkish bow composed of tendon, bone, sinew, wood, horn and hide glue likely will fail to function properly in a rainy-weather locale.

Animal glue (includes hide glue as a subtopic):

https://en.wikipedia.org/wiki/Animal_glue#Reemergence

The Mongolian bow:

http://www.coldsiberia.org/monbow.htm

The Modern Reproduction of a Mongol Era Bow based on historical facts and ancient technology research:

https://exarc.net/issue-2017-2/at/modern-reproduction-mongol...

Here's a fellow who tried both a modern glue and hide glue in making a bow:

A Note on Indian Bow Making or the Secrets of Sinew Revealed

http://www.primitiveways.com/secrets_of_sinew.html

For some use cases, you can use rice.

All you need is some leftover (cooked) white rice and a bit of water. Turn the thing into a paste of the desired consistency, and voila, a basic glue.