No expert here, but in order for someone to provide an educated opinion, I think you will need some high quality and super closeups of the end of the bow and other areas as well. From the picture provided, it does not look like there is very much wear where the string is attached. If it were very old, I would expect to see more. Do you know any history behind it as to where it came from, where and how its been stored?
Also, take a powerful magnifying glass and look closely at the wood. If it has been stored away from many years, you might be able to see the tell-tell signs of insect abuse, old whitish spider droppings, etc.
Maybe putting it on the "pre-colonial" site here would provide you with more help.